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Installing a user-provisioned bare metal cluster with network customizations

In OpenShift Container Platform 4.13, you can install a cluster on bare metal infrastructure that you provision with customized network configuration options. By customizing your network configuration, your cluster can coexist with existing IP address allocations in your environment and integrate with existing MTU and VXLAN configurations.

When you customize OpenShift Container Platform networking, you must set most of the network configuration parameters during installation. You can modify only kubeProxy network configuration parameters in a running cluster.

Prerequisites

Internet access for OpenShift Container Platform

In OpenShift Container Platform 4.13, you require access to the internet to install your cluster.

You must have internet access to:

  • Access OpenShift Cluster Manager Hybrid Cloud Console to download the installation program and perform subscription management. If the cluster has internet access and you do not disable Telemetry, that service automatically entitles your cluster.

  • Access Quay.io to obtain the packages that are required to install your cluster.

  • Obtain the packages that are required to perform cluster updates.

If your cluster cannot have direct internet access, you can perform a restricted network installation on some types of infrastructure that you provision. During that process, you download the required content and use it to populate a mirror registry with the installation packages. With some installation types, the environment that you install your cluster in will not require internet access. Before you update the cluster, you update the content of the mirror registry.
Additional resources

Requirements for a cluster with user-provisioned infrastructure

For a cluster that contains user-provisioned infrastructure, you must deploy all of the required machines.

This section describes the requirements for deploying OpenShift Container Platform on user-provisioned infrastructure.

Required machines for cluster installation

The smallest OpenShift Container Platform clusters require the following hosts:

Table 1. Minimum required hosts
Hosts Description

One temporary bootstrap machine

The cluster requires the bootstrap machine to deploy the OpenShift Container Platform cluster on the three control plane machines. You can remove the bootstrap machine after you install the cluster.

Three control plane machines

The control plane machines run the Kubernetes and OpenShift Container Platform services that form the control plane.

At least two compute machines, which are also known as worker machines.

The workloads requested by OpenShift Container Platform users run on the compute machines.

As an exception, you can run zero compute machines in a bare metal cluster that consists of three control plane machines only. This provides smaller, more resource efficient clusters for cluster administrators and developers to use for testing, development, and production. Running one compute machine is not supported.

To maintain high availability of your cluster, use separate physical hosts for these cluster machines.

The bootstrap and control plane machines must use Red Hat Enterprise Linux CoreOS (RHCOS) as the operating system. However, the compute machines can choose between Red Hat Enterprise Linux CoreOS (RHCOS), Red Hat Enterprise Linux (RHEL) 8.6 and later.

Note that RHCOS is based on Red Hat Enterprise Linux (RHEL) 9.2 and inherits all of its hardware certifications and requirements. See Red Hat Enterprise Linux technology capabilities and limits.

Minimum resource requirements for cluster installation

Each cluster machine must meet the following minimum requirements:

Table 2. Minimum resource requirements
Machine Operating System CPU [1] RAM Storage Input/Output Per Second (IOPS)[2]

Bootstrap

RHCOS

4

16 GB

100 GB

300

Control plane

RHCOS

4

16 GB

100 GB

300

Compute

RHCOS, RHEL 8.6 and later [3]

2

8 GB

100 GB

300

  1. One CPU is equivalent to one physical core when simultaneous multithreading (SMT), or Hyper-Threading, is not enabled. When enabled, use the following formula to calculate the corresponding ratio: (threads per core × cores) × sockets = CPUs.

  2. OpenShift Container Platform and Kubernetes are sensitive to disk performance, and faster storage is recommended, particularly for etcd on the control plane nodes which require a 10 ms p99 fsync duration. Note that on many cloud platforms, storage size and IOPS scale together, so you might need to over-allocate storage volume to obtain sufficient performance.

  3. As with all user-provisioned installations, if you choose to use RHEL compute machines in your cluster, you take responsibility for all operating system life cycle management and maintenance, including performing system updates, applying patches, and completing all other required tasks. Use of RHEL 7 compute machines is deprecated and has been removed in OpenShift Container Platform 4.10 and later.

As of OpenShift Container Platform version 4.13, RHCOS is based on RHEL version 9.2, which updates the micro-architecture requirements. The following list contains the minimum instruction set architectures (ISA) that each architecture requires:

  • x86-64 architecture requires x86-64-v2 ISA

  • ARM64 architecture requires ARMv8.0-A ISA

  • IBM Power architecture requires Power 9 ISA

  • s390x architecture requires z14 ISA

For more information, see RHEL Architectures.

If an instance type for your platform meets the minimum requirements for cluster machines, it is supported to use in OpenShift Container Platform.

Additional resources

Certificate signing requests management

Because your cluster has limited access to automatic machine management when you use infrastructure that you provision, you must provide a mechanism for approving cluster certificate signing requests (CSRs) after installation. The kube-controller-manager only approves the kubelet client CSRs. The machine-approver cannot guarantee the validity of a serving certificate that is requested by using kubelet credentials because it cannot confirm that the correct machine issued the request. You must determine and implement a method of verifying the validity of the kubelet serving certificate requests and approving them.

Additional resources

Networking requirements for user-provisioned infrastructure

All the Red Hat Enterprise Linux CoreOS (RHCOS) machines require networking to be configured in initramfs during boot to fetch their Ignition config files.

During the initial boot, the machines require an IP address configuration that is set either through a DHCP server or statically by providing the required boot options. After a network connection is established, the machines download their Ignition config files from an HTTP or HTTPS server. The Ignition config files are then used to set the exact state of each machine. The Machine Config Operator completes more changes to the machines, such as the application of new certificates or keys, after installation.

It is recommended to use a DHCP server for long-term management of the cluster machines. Ensure that the DHCP server is configured to provide persistent IP addresses, DNS server information, and hostnames to the cluster machines.

If a DHCP service is not available for your user-provisioned infrastructure, you can instead provide the IP networking configuration and the address of the DNS server to the nodes at RHCOS install time. These can be passed as boot arguments if you are installing from an ISO image. See the Installing RHCOS and starting the OpenShift Container Platform bootstrap process section for more information about static IP provisioning and advanced networking options.

The Kubernetes API server must be able to resolve the node names of the cluster machines. If the API servers and worker nodes are in different zones, you can configure a default DNS search zone to allow the API server to resolve the node names. Another supported approach is to always refer to hosts by their fully-qualified domain names in both the node objects and all DNS requests.

Setting the cluster node hostnames through DHCP

On Red Hat Enterprise Linux CoreOS (RHCOS) machines, the hostname is set through NetworkManager. By default, the machines obtain their hostname through DHCP. If the hostname is not provided by DHCP, set statically through kernel arguments, or another method, it is obtained through a reverse DNS lookup. Reverse DNS lookup occurs after the network has been initialized on a node and can take time to resolve. Other system services can start prior to this and detect the hostname as localhost or similar. You can avoid this by using DHCP to provide the hostname for each cluster node.

Additionally, setting the hostnames through DHCP can bypass any manual DNS record name configuration errors in environments that have a DNS split-horizon implementation.

Network connectivity requirements

You must configure the network connectivity between machines to allow OpenShift Container Platform cluster components to communicate. Each machine must be able to resolve the hostnames of all other machines in the cluster.

This section provides details about the ports that are required.

In connected OpenShift Container Platform environments, all nodes are required to have internet access to pull images for platform containers and provide telemetry data to Red Hat.
Table 3. Ports used for all-machine to all-machine communications
Protocol Port Description

ICMP

N/A

Network reachability tests

TCP

1936

Metrics

9000-9999

Host level services, including the node exporter on ports 9100-9101 and the Cluster Version Operator on port 9099.

10250-10259

The default ports that Kubernetes reserves

10256

openshift-sdn

UDP

4789

VXLAN

6081

Geneve

9000-9999

Host level services, including the node exporter on ports 9100-9101.

500

IPsec IKE packets

4500

IPsec NAT-T packets

123

Network Time Protocol (NTP) on UDP port 123

If an external NTP time server is configured, you must open UDP port 123.

TCP/UDP

30000-32767

Kubernetes node port

ESP

N/A

IPsec Encapsulating Security Payload (ESP)
Table 4. Ports used for all-machine to control plane communications
Protocol Port Description

TCP

6443

Kubernetes API
Table 5. Ports used for control plane machine to control plane machine communications
Protocol Port Description

TCP

2379-2380

etcd server and peer ports

NTP configuration for user-provisioned infrastructure

OpenShift Container Platform clusters are configured to use a public Network Time Protocol (NTP) server by default. If you want to use a local enterprise NTP server, or if your cluster is being deployed in a disconnected network, you can configure the cluster to use a specific time server. For more information, see the documentation for Configuring chrony time service.

If a DHCP server provides NTP server information, the chrony time service on the Red Hat Enterprise Linux CoreOS (RHCOS) machines read the information and can sync the clock with the NTP servers.

Additional resources

User-provisioned DNS requirements

In OpenShift Container Platform deployments, DNS name resolution is required for the following components:

  • The Kubernetes API

  • The OpenShift Container Platform application wildcard

  • The bootstrap, control plane, and compute machines

Reverse DNS resolution is also required for the Kubernetes API, the bootstrap machine, the control plane machines, and the compute machines.

DNS A/AAAA or CNAME records are used for name resolution and PTR records are used for reverse name resolution. The reverse records are important because Red Hat Enterprise Linux CoreOS (RHCOS) uses the reverse records to set the hostnames for all the nodes, unless the hostnames are provided by DHCP. Additionally, the reverse records are used to generate the certificate signing requests (CSR) that OpenShift Container Platform needs to operate.

It is recommended to use a DHCP server to provide the hostnames to each cluster node. See the DHCP recommendations for user-provisioned infrastructure section for more information.

The following DNS records are required for a user-provisioned OpenShift Container Platform cluster and they must be in place before installation. In each record, <cluster_name> is the cluster name and <base_domain> is the base domain that you specify in the install-config.yaml file. A complete DNS record takes the form: <component>.<cluster_name>.<base_domain>..

Table 6. Required DNS records
Component Record Description

Kubernetes API

api.<cluster_name>.<base_domain>.

A DNS A/AAAA or CNAME record, and a DNS PTR record, to identify the API load balancer. These records must be resolvable by both clients external to the cluster and from all the nodes within the cluster.

api-int.<cluster_name>.<base_domain>.

A DNS A/AAAA or CNAME record, and a DNS PTR record, to internally identify the API load balancer. These records must be resolvable from all the nodes within the cluster.

The API server must be able to resolve the worker nodes by the hostnames that are recorded in Kubernetes. If the API server cannot resolve the node names, then proxied API calls can fail, and you cannot retrieve logs from pods.

Routes

*.apps.<cluster_name>.<base_domain>.

A wildcard DNS A/AAAA or CNAME record that refers to the application ingress load balancer. The application ingress load balancer targets the machines that run the Ingress Controller pods. The Ingress Controller pods run on the compute machines by default. These records must be resolvable by both clients external to the cluster and from all the nodes within the cluster.

For example, console-openshift-console.apps.<cluster_name>.<base_domain> is used as a wildcard route to the OpenShift Container Platform console.

Bootstrap machine

bootstrap.<cluster_name>.<base_domain>.

A DNS A/AAAA or CNAME record, and a DNS PTR record, to identify the bootstrap machine. These records must be resolvable by the nodes within the cluster.

Control plane machines

<control_plane><n>.<cluster_name>.<base_domain>.

DNS A/AAAA or CNAME records and DNS PTR records to identify each machine for the control plane nodes. These records must be resolvable by the nodes within the cluster.

Compute machines

<compute><n>.<cluster_name>.<base_domain>.

DNS A/AAAA or CNAME records and DNS PTR records to identify each machine for the worker nodes. These records must be resolvable by the nodes within the cluster.

In OpenShift Container Platform 4.4 and later, you do not need to specify etcd host and SRV records in your DNS configuration.

You can use the dig command to verify name and reverse name resolution. See the section on Validating DNS resolution for user-provisioned infrastructure for detailed validation steps.

Example DNS configuration for user-provisioned clusters

This section provides A and PTR record configuration samples that meet the DNS requirements for deploying OpenShift Container Platform on user-provisioned infrastructure. The samples are not meant to provide advice for choosing one DNS solution over another.

In the examples, the cluster name is ocp4 and the base domain is example.com.

Example DNS A record configuration for a user-provisioned cluster

The following example is a BIND zone file that shows sample A records for name resolution in a user-provisioned cluster.

Sample DNS zone database 
$TTL 1W
@	IN	SOA	ns1.example.com.	root (
			2019070700	; serial
			3H		; refresh (3 hours)
			30M		; retry (30 minutes)
			2W		; expiry (2 weeks)
			1W )		; minimum (1 week)
	IN	NS	ns1.example.com.
	IN	MX 10	smtp.example.com.
;
;
ns1.example.com.		IN	A	192.168.1.5
smtp.example.com.		IN	A	192.168.1.5
;
helper.example.com.		IN	A	192.168.1.5
helper.ocp4.example.com.	IN	A	192.168.1.5
;
api.ocp4.example.com.		IN	A	192.168.1.5 (1)
api-int.ocp4.example.com.	IN	A	192.168.1.5 (2)
;
*.apps.ocp4.example.com.	IN	A	192.168.1.5 (3)
;
bootstrap.ocp4.example.com.	IN	A	192.168.1.96 (4)
;
control-plane0.ocp4.example.com.	IN	A	192.168.1.97 (5)
control-plane1.ocp4.example.com.	IN	A	192.168.1.98 (5)
control-plane2.ocp4.example.com.	IN	A	192.168.1.99 (5)
;
compute0.ocp4.example.com.	IN	A	192.168.1.11 (6)
compute1.ocp4.example.com.	IN	A	192.168.1.7 (6)
;
;EOF
1 Provides name resolution for the Kubernetes API. The record refers to the IP address of the API load balancer.
2 Provides name resolution for the Kubernetes API. The record refers to the IP address of the API load balancer and is used for internal cluster communications.
3 Provides name resolution for the wildcard routes. The record refers to the IP address of the application ingress load balancer. The application ingress load balancer targets the machines that run the Ingress Controller pods. The Ingress Controller pods run on the compute machines by default.

In the example, the same load balancer is used for the Kubernetes API and application ingress traffic. In production scenarios, you can deploy the API and application ingress load balancers separately so that you can scale the load balancer infrastructure for each in isolation.
4 Provides name resolution for the bootstrap machine.
5 Provides name resolution for the control plane machines.
6 Provides name resolution for the compute machines.
Example DNS PTR record configuration for a user-provisioned cluster

The following example BIND zone file shows sample PTR records for reverse name resolution in a user-provisioned cluster.

Sample DNS zone database for reverse records 
$TTL 1W
@	IN	SOA	ns1.example.com.	root (
			2019070700	; serial
			3H		; refresh (3 hours)
			30M		; retry (30 minutes)
			2W		; expiry (2 weeks)
			1W )		; minimum (1 week)
	IN	NS	ns1.example.com.
;
5.1.168.192.in-addr.arpa.	IN	PTR	api.ocp4.example.com. (1)
5.1.168.192.in-addr.arpa.	IN	PTR	api-int.ocp4.example.com. (2)
;
96.1.168.192.in-addr.arpa.	IN	PTR	bootstrap.ocp4.example.com. (3)
;
97.1.168.192.in-addr.arpa.	IN	PTR	control-plane0.ocp4.example.com. (4)
98.1.168.192.in-addr.arpa.	IN	PTR	control-plane1.ocp4.example.com. (4)
99.1.168.192.in-addr.arpa.	IN	PTR	control-plane2.ocp4.example.com. (4)
;
11.1.168.192.in-addr.arpa.	IN	PTR	compute0.ocp4.example.com. (5)
7.1.168.192.in-addr.arpa.	IN	PTR	compute1.ocp4.example.com. (5)
;
;EOF
1 Provides reverse DNS resolution for the Kubernetes API. The PTR record refers to the record name of the API load balancer.
2 Provides reverse DNS resolution for the Kubernetes API. The PTR record refers to the record name of the API load balancer and is used for internal cluster communications.
3 Provides reverse DNS resolution for the bootstrap machine.
4 Provides reverse DNS resolution for the control plane machines.
5 Provides reverse DNS resolution for the compute machines.

A PTR record is not required for the OpenShift Container Platform application wildcard.

Load balancing requirements for user-provisioned infrastructure

Before you install OpenShift Container Platform, you must provision the API and application Ingress load balancing infrastructure. In production scenarios, you can deploy the API and application Ingress load balancers separately so that you can scale the load balancer infrastructure for each in isolation.

If you want to deploy the API and application Ingress load balancers with a Red Hat Enterprise Linux (RHEL) instance, you must purchase the RHEL subscription separately.

The load balancing infrastructure must meet the following requirements:

  1. API load balancer: Provides a common endpoint for users, both human and machine, to interact with and configure the platform. Configure the following conditions:

    • Layer 4 load balancing only. This can be referred to as Raw TCP or SSL Passthrough mode.

    • A stateless load balancing algorithm. The options vary based on the load balancer implementation.

    Do not configure session persistence for an API load balancer. Configuring session persistence for a Kubernetes API server might cause performance issues from excess application traffic for your OpenShift Container Platform cluster and the Kubernetes API that runs inside the cluster.

    Configure the following ports on both the front and back of the load balancers:

    Table 7. API load balancer
    Port Back-end machines (pool members) Internal External Description

    6443

    Bootstrap and control plane. You remove the bootstrap machine from the load balancer after the bootstrap machine initializes the cluster control plane. You must configure the /readyz endpoint for the API server health check probe.

    X

    X

    Kubernetes API server

    22623

    Bootstrap and control plane. You remove the bootstrap machine from the load balancer after the bootstrap machine initializes the cluster control plane.

    X

    Machine config server

    The load balancer must be configured to take a maximum of 30 seconds from the time the API server turns off the /readyz endpoint to the removal of the API server instance from the pool. Within the time frame after /readyz returns an error or becomes healthy, the endpoint must have been removed or added. Probing every 5 or 10 seconds, with two successful requests to become healthy and three to become unhealthy, are well-tested values.

  2. Application Ingress load balancer: Provides an ingress point for application traffic flowing in from outside the cluster. A working configuration for the Ingress router is required for an OpenShift Container Platform cluster.

    Configure the following conditions:

    • Layer 4 load balancing only. This can be referred to as Raw TCP or SSL Passthrough mode.

    • A connection-based or session-based persistence is recommended, based on the options available and types of applications that will be hosted on the platform.

    If the true IP address of the client can be seen by the application Ingress load balancer, enabling source IP-based session persistence can improve performance for applications that use end-to-end TLS encryption.

    Configure the following ports on both the front and back of the load balancers:

    Table 8. Application Ingress load balancer
    Port Back-end machines (pool members) Internal External Description

    443

    The machines that run the Ingress Controller pods, compute, or worker, by default.

    X

    X

    HTTPS traffic

    80

    The machines that run the Ingress Controller pods, compute, or worker, by default.

    X

    X

    HTTP traffic

    If you are deploying a three-node cluster with zero compute nodes, the Ingress Controller pods run on the control plane nodes. In three-node cluster deployments, you must configure your application Ingress load balancer to route HTTP and HTTPS traffic to the control plane nodes.

Example load balancer configuration for user-provisioned clusters

This section provides an example API and application Ingress load balancer configuration that meets the load balancing requirements for user-provisioned clusters. The sample is an /etc/haproxy/haproxy.cfg configuration for an HAProxy load balancer. The example is not meant to provide advice for choosing one load balancing solution over another.

In the example, the same load balancer is used for the Kubernetes API and application ingress traffic. In production scenarios, you can deploy the API and application ingress load balancers separately so that you can scale the load balancer infrastructure for each in isolation.

If you are using HAProxy as a load balancer and SELinux is set to enforcing, you must ensure that the HAProxy service can bind to the configured TCP port by running setsebool -P haproxy_connect_any=1.
Sample API and application Ingress load balancer configuration 
global
  log         127.0.0.1 local2
  pidfile     /var/run/haproxy.pid
  maxconn     4000
  daemon
defaults
  mode                    http
  log                     global
  option                  dontlognull
  option http-server-close
  option                  redispatch
  retries                 3
  timeout http-request    10s
  timeout queue           1m
  timeout connect         10s
  timeout client          1m
  timeout server          1m
  timeout http-keep-alive 10s
  timeout check           10s
  maxconn                 3000
listen api-server-6443 (1)
  bind *:6443
  mode tcp
  option  httpchk GET /readyz HTTP/1.0
  option  log-health-checks
  balance roundrobin
  server bootstrap bootstrap.ocp4.example.com:6443 verify none check check-ssl inter 10s fall 2 rise 3 backup (2)
  server master0 master0.ocp4.example.com:6443 weight 1 verify none check check-ssl inter 10s fall 2 rise 3
  server master1 master1.ocp4.example.com:6443 weight 1 verify none check check-ssl inter 10s fall 2 rise 3
  server master2 master2.ocp4.example.com:6443 weight 1 verify none check check-ssl inter 10s fall 2 rise 3
listen machine-config-server-22623 (3)
  bind *:22623
  mode tcp
  server bootstrap bootstrap.ocp4.example.com:22623 check inter 1s backup (2)
  server master0 master0.ocp4.example.com:22623 check inter 1s
  server master1 master1.ocp4.example.com:22623 check inter 1s
  server master2 master2.ocp4.example.com:22623 check inter 1s
listen ingress-router-443 (4)
  bind *:443
  mode tcp
  balance source
  server worker0 worker0.ocp4.example.com:443 check inter 1s
  server worker1 worker1.ocp4.example.com:443 check inter 1s
listen ingress-router-80 (5)
  bind *:80
  mode tcp
  balance source
  server worker0 worker0.ocp4.example.com:80 check inter 1s
  server worker1 worker1.ocp4.example.com:80 check inter 1s
1 Port 6443 handles the Kubernetes API traffic and points to the control plane machines.
2 The bootstrap entries must be in place before the OpenShift Container Platform cluster installation and they must be removed after the bootstrap process is complete.
3 Port 22623 handles the machine config server traffic and points to the control plane machines.
4 Port 443 handles the HTTPS traffic and points to the machines that run the Ingress Controller pods. The Ingress Controller pods run on the compute machines by default.
5 Port 80 handles the HTTP traffic and points to the machines that run the Ingress Controller pods. The Ingress Controller pods run on the compute machines by default.

If you are deploying a three-node cluster with zero compute nodes, the Ingress Controller pods run on the control plane nodes. In three-node cluster deployments, you must configure your application Ingress load balancer to route HTTP and HTTPS traffic to the control plane nodes.

If you are using HAProxy as a load balancer, you can check that the haproxy process is listening on ports 6443, 22623, 443, and 80 by running netstat -nltupe on the HAProxy node.

Preparing the user-provisioned infrastructure

Before you install OpenShift Container Platform on user-provisioned infrastructure, you must prepare the underlying infrastructure.

This section provides details about the high-level steps required to set up your cluster infrastructure in preparation for an OpenShift Container Platform installation. This includes configuring IP networking and network connectivity for your cluster nodes, enabling the required ports through your firewall, and setting up the required DNS and load balancing infrastructure.

After preparation, your cluster infrastructure must meet the requirements outlined in the Requirements for a cluster with user-provisioned infrastructure section.

Prerequisites
Procedure

  1. If you are using DHCP to provide the IP networking configuration to your cluster nodes, configure your DHCP service.

    1. Add persistent IP addresses for the nodes to your DHCP server configuration. In your configuration, match the MAC address of the relevant network interface to the intended IP address for each node.

    2. When you use DHCP to configure IP addressing for the cluster machines, the machines also obtain the DNS server information through DHCP. Define the persistent DNS server address that is used by the cluster nodes through your DHCP server configuration.

      If you are not using a DHCP service, you must provide the IP networking configuration and the address of the DNS server to the nodes at RHCOS install time. These can be passed as boot arguments if you are installing from an ISO image. See the Installing RHCOS and starting the OpenShift Container Platform bootstrap process section for more information about static IP provisioning and advanced networking options.

    3. Define the hostnames of your cluster nodes in your DHCP server configuration. See the Setting the cluster node hostnames through DHCP section for details about hostname considerations.

      If you are not using a DHCP service, the cluster nodes obtain their hostname through a reverse DNS lookup.

  2. Ensure that your network infrastructure provides the required network connectivity between the cluster components. See the Networking requirements for user-provisioned infrastructure section for details about the requirements.

  3. Configure your firewall to enable the ports required for the OpenShift Container Platform cluster components to communicate. See Networking requirements for user-provisioned infrastructure section for details about the ports that are required.

    By default, port 1936 is accessible for an OpenShift Container Platform cluster, because each control plane node needs access to this port.

    Avoid using the Ingress load balancer to expose this port, because doing so might result in the exposure of sensitive information, such as statistics and metrics, related to Ingress Controllers.

  4. Setup the required DNS infrastructure for your cluster.

    1. Configure DNS name resolution for the Kubernetes API, the application wildcard, the bootstrap machine, the control plane machines, and the compute machines.

    2. Configure reverse DNS resolution for the Kubernetes API, the bootstrap machine, the control plane machines, and the compute machines.

      See the User-provisioned DNS requirements section for more information about the OpenShift Container Platform DNS requirements.

  5. Validate your DNS configuration.

    1. From your installation node, run DNS lookups against the record names of the Kubernetes API, the wildcard routes, and the cluster nodes. Validate that the IP addresses in the responses correspond to the correct components.

    2. From your installation node, run reverse DNS lookups against the IP addresses of the load balancer and the cluster nodes. Validate that the record names in the responses correspond to the correct components.

      See the Validating DNS resolution for user-provisioned infrastructure section for detailed DNS validation steps.

  6. Provision the required API and application ingress load balancing infrastructure. See the Load balancing requirements for user-provisioned infrastructure section for more information about the requirements.

Some load balancing solutions require the DNS name resolution for the cluster nodes to be in place before the load balancing is initialized.
Additional resources

Validating DNS resolution for user-provisioned infrastructure

You can validate your DNS configuration before installing OpenShift Container Platform on user-provisioned infrastructure.

The validation steps detailed in this section must succeed before you install your cluster.
Prerequisites

  • You have configured the required DNS records for your user-provisioned infrastructure.

Procedure

  1. From your installation node, run DNS lookups against the record names of the Kubernetes API, the wildcard routes, and the cluster nodes. Validate that the IP addresses contained in the responses correspond to the correct components.

    1. Perform a lookup against the Kubernetes API record name. Check that the result points to the IP address of the API load balancer:

      $ dig +noall +answer @<nameserver_ip> api.<cluster_name>.<base_domain> (1)
      1 Replace <nameserver_ip> with the IP address of the nameserver, <cluster_name> with your cluster name, and <base_domain> with your base domain name.
      Example output
      api.ocp4.example.com.		604800	IN	A	192.168.1.5

    2. Perform a lookup against the Kubernetes internal API record name. Check that the result points to the IP address of the API load balancer:

      $ dig +noall +answer @<nameserver_ip> api-int.<cluster_name>.<base_domain>
      Example output
      api-int.ocp4.example.com.		604800	IN	A	192.168.1.5

    3. Test an example *.apps.<cluster_name>.<base_domain> DNS wildcard lookup. All of the application wildcard lookups must resolve to the IP address of the application ingress load balancer:

      $ dig +noall +answer @<nameserver_ip> random.apps.<cluster_name>.<base_domain>
      Example output
      random.apps.ocp4.example.com.		604800	IN	A	192.168.1.5

      In the example outputs, the same load balancer is used for the Kubernetes API and application ingress traffic. In production scenarios, you can deploy the API and application ingress load balancers separately so that you can scale the load balancer infrastructure for each in isolation.

      You can replace random with another wildcard value. For example, you can query the route to the OpenShift Container Platform console:

      $ dig +noall +answer @<nameserver_ip> console-openshift-console.apps.<cluster_name>.<base_domain>
      Example output
      console-openshift-console.apps.ocp4.example.com. 604800 IN	A 192.168.1.5

    4. Run a lookup against the bootstrap DNS record name. Check that the result points to the IP address of the bootstrap node:

      $ dig +noall +answer @<nameserver_ip> bootstrap.<cluster_name>.<base_domain>
      Example output
      bootstrap.ocp4.example.com.		604800	IN	A	192.168.1.96

    5. Use this method to perform lookups against the DNS record names for the control plane and compute nodes. Check that the results correspond to the IP addresses of each node.

  2. From your installation node, run reverse DNS lookups against the IP addresses of the load balancer and the cluster nodes. Validate that the record names contained in the responses correspond to the correct components.

    1. Perform a reverse lookup against the IP address of the API load balancer. Check that the response includes the record names for the Kubernetes API and the Kubernetes internal API:

      $ dig +noall +answer @<nameserver_ip> -x 192.168.1.5
      Example output
      5.1.168.192.in-addr.arpa. 604800	IN	PTR	api-int.ocp4.example.com. (1)
5.1.168.192.in-addr.arpa. 604800	IN	PTR	api.ocp4.example.com. (2)
      1 Provides the record name for the Kubernetes internal API.
      2 Provides the record name for the Kubernetes API.

      A PTR record is not required for the OpenShift Container Platform application wildcard. No validation step is needed for reverse DNS resolution against the IP address of the application ingress load balancer.

    2. Perform a reverse lookup against the IP address of the bootstrap node. Check that the result points to the DNS record name of the bootstrap node:

      $ dig +noall +answer @<nameserver_ip> -x 192.168.1.96
      Example output
      96.1.168.192.in-addr.arpa. 604800	IN	PTR	bootstrap.ocp4.example.com.

    3. Use this method to perform reverse lookups against the IP addresses for the control plane and compute nodes. Check that the results correspond to the DNS record names of each node.

Additional resources

Generating a key pair for cluster node SSH access

During an OpenShift Container Platform installation, you can provide an SSH public key to the installation program. The key is passed to the Red Hat Enterprise Linux CoreOS (RHCOS) nodes through their Ignition config files and is used to authenticate SSH access to the nodes. The key is added to the ~/.ssh/authorized_keys list for the core user on each node, which enables password-less authentication.

After the key is passed to the nodes, you can use the key pair to SSH in to the RHCOS nodes as the user core. To access the nodes through SSH, the private key identity must be managed by SSH for your local user.

If you want to SSH in to your cluster nodes to perform installation debugging or disaster recovery, you must provide the SSH public key during the installation process. The ./openshift-install gather command also requires the SSH public key to be in place on the cluster nodes.

Do not skip this procedure in production environments, where disaster recovery and debugging is required.

You must use a local key, not one that you configured with platform-specific approaches such as AWS key pairs.
Procedure

  1. If you do not have an existing SSH key pair on your local machine to use for authentication onto your cluster nodes, create one. For example, on a computer that uses a Linux operating system, run the following command:

    $ ssh-keygen -t ed25519 -N '' -f <path>/<file_name> (1)
    1 Specify the path and file name, such as ~/.ssh/id_ed25519, of the new SSH key. If you have an existing key pair, ensure your public key is in the your ~/.ssh directory.

  2. View the public SSH key:

    $ cat <path>/<file_name>.pub

    For example, run the following to view the ~/.ssh/id_ed25519.pub public key:

    $ cat ~/.ssh/id_ed25519.pub

  3. Add the SSH private key identity to the SSH agent for your local user, if it has not already been added. SSH agent management of the key is required for password-less SSH authentication onto your cluster nodes, or if you want to use the ./openshift-install gather command.

    On some distributions, default SSH private key identities such as ~/.ssh/id_rsa and ~/.ssh/id_dsa are managed automatically.

    1. If the ssh-agent process is not already running for your local user, start it as a background task:

      $ eval "$(ssh-agent -s)"
      Example output
      Agent pid 31874

  4. Add your SSH private key to the ssh-agent:

    $ ssh-add <path>/<file_name> (1)
    1 Specify the path and file name for your SSH private key, such as ~/.ssh/id_ed25519
    Example output
    Identity added: /home/<you>/<path>/<file_name> (<computer_name>)
Next steps

  • When you install OpenShift Container Platform, provide the SSH public key to the installation program.

Additional resources

Obtaining the installation program

Before you install OpenShift Container Platform, download the installation file on the host you are using for installation.

Prerequisites

  • You have a computer that runs Linux or macOS, with 500 MB of local disk space.

Procedure

  1. Access the Infrastructure Provider page on the OpenShift Cluster Manager site. If you have a Red Hat account, log in with your credentials. If you do not, create an account.

  2. Select your infrastructure provider.

  3. Navigate to the page for your installation type, download the installation program that corresponds with your host operating system and architecture, and place the file in the directory where you will store the installation configuration files.

    The installation program creates several files on the computer that you use to install your cluster. You must keep the installation program and the files that the installation program creates after you finish installing the cluster. Both files are required to delete the cluster.

    Deleting the files created by the installation program does not remove your cluster, even if the cluster failed during installation. To remove your cluster, complete the OpenShift Container Platform uninstallation procedures for your specific cloud provider.

  4. Extract the installation program. For example, on a computer that uses a Linux operating system, run the following command:

    $ tar -xvf openshift-install-linux.tar.gz

  5. Download your installation pull secret from the Red Hat OpenShift Cluster Manager. This pull secret allows you to authenticate with the services that are provided by the included authorities, including Quay.io, which serves the container images for OpenShift Container Platform components.

Installing the OpenShift CLI by downloading the binary

You can install the OpenShift CLI (oc) to interact with OpenShift Container Platform from a command-line interface. You can install oc on Linux, Windows, or macOS.

If you installed an earlier version of oc, you cannot use it to complete all of the commands in OpenShift Container Platform 4.13. Download and install the new version of oc.

Installing the OpenShift CLI on Linux

You can install the OpenShift CLI (oc) binary on Linux by using the following procedure.

Procedure

  1. Navigate to the OpenShift Container Platform downloads page on the Red Hat Customer Portal.

  2. Select the architecture from the Product Variant drop-down list.

  3. Select the appropriate version from the Version drop-down list.

  4. Click Download Now next to the OpenShift v4.13 Linux Client entry and save the file.

  5. Unpack the archive:

    $ tar xvf <file>

  6. Place the oc binary in a directory that is on your PATH.

    To check your PATH, execute the following command:

    $ echo $PATH
Verification

  • After you install the OpenShift CLI, it is available using the oc command:

    $ oc <command>

Installing the OpenShift CLI on Windows

You can install the OpenShift CLI (oc) binary on Windows by using the following procedure.

Procedure

  1. Navigate to the OpenShift Container Platform downloads page on the Red Hat Customer Portal.

  2. Select the appropriate version from the Version drop-down list.

  3. Click Download Now next to the OpenShift v4.13 Windows Client entry and save the file.

  4. Unzip the archive with a ZIP program.

  5. Move the oc binary to a directory that is on your PATH.

    To check your PATH, open the command prompt and execute the following command:

    C:\> path
Verification

  • After you install the OpenShift CLI, it is available using the oc command:

    C:\> oc <command>

Installing the OpenShift CLI on macOS

You can install the OpenShift CLI (oc) binary on macOS by using the following procedure.

Procedure

  1. Navigate to the OpenShift Container Platform downloads page on the Red Hat Customer Portal.

  2. Select the appropriate version from the Version drop-down list.

  3. Click Download Now next to the OpenShift v4.13 macOS Client entry and save the file.

    For macOS arm64, choose the OpenShift v4.13 macOS arm64 Client entry.

  4. Unpack and unzip the archive.

  5. Move the oc binary to a directory on your PATH.

    To check your PATH, open a terminal and execute the following command:

    $ echo $PATH
Verification

  • After you install the OpenShift CLI, it is available using the oc command:

    $ oc <command>

Manually creating the installation configuration file

Installing the cluster requires that you manually create the installation configuration file.

Prerequisites

  • You have an SSH public key on your local machine to provide to the installation program. The key will be used for SSH authentication onto your cluster nodes for debugging and disaster recovery.

  • You have obtained the OpenShift Container Platform installation program and the pull secret for your cluster.

Procedure

  1. Create an installation directory to store your required installation assets in:

    $ mkdir <installation_directory>

    You must create a directory. Some installation assets, like bootstrap X.509 certificates have short expiration intervals, so you must not reuse an installation directory. If you want to reuse individual files from another cluster installation, you can copy them into your directory. However, the file names for the installation assets might change between releases. Use caution when copying installation files from an earlier OpenShift Container Platform version.

  2. Customize the sample install-config.yaml file template that is provided and save it in the <installation_directory>.

    You must name this configuration file install-config.yaml.

  3. Back up the install-config.yaml file so that you can use it to install multiple clusters.

    The install-config.yaml file is consumed during the next step of the installation process. You must back it up now.

Installation configuration parameters

Before you deploy an OpenShift Container Platform cluster, you provide a customized install-config.yaml installation configuration file that describes the details for your environment.

After installation, you cannot modify these parameters in the install-config.yaml file.

Required configuration parameters

Required installation configuration parameters are described in the following table:

Table 9. Required parameters
Parameter Description Values

apiVersion

The API version for the install-config.yaml content. The current version is v1. The installation program may also support older API versions.

String

baseDomain

The base domain of your cloud provider. The base domain is used to create routes to your OpenShift Container Platform cluster components. The full DNS name for your cluster is a combination of the baseDomain and metadata.name parameter values that uses the <metadata.name>.<baseDomain> format.

A fully-qualified domain or subdomain name, such as example.com.

metadata

Kubernetes resource ObjectMeta, from which only the name parameter is consumed.

Object

metadata.name

The name of the cluster. DNS records for the cluster are all subdomains of {{.metadata.name}}.{{.baseDomain}}.

String of lowercase letters and hyphens (-), such as dev.

platform

The configuration for the specific platform upon which to perform the installation: alibabacloud, aws, baremetal, azure, gcp, ibmcloud, nutanix, openstack, ovirt, powervs, vsphere, or {}. For additional information about platform.<platform> parameters, consult the table for your specific platform that follows.

Object

pullSecret

Get a pull secret from the Red Hat OpenShift Cluster Manager to authenticate downloading container images for OpenShift Container Platform components from services such as Quay.io.

 
{
   "auths":{
      "cloud.openshift.com":{
         "auth":"b3Blb=",
         "email":"you@example.com"
      },
      "quay.io":{
         "auth":"b3Blb=",
         "email":"you@example.com"
      }
   }
}

Network configuration parameters

You can customize your installation configuration based on the requirements of your existing network infrastructure. For example, you can expand the IP address block for the cluster network or provide different IP address blocks than the defaults.

  • If you use the Red Hat OpenShift Networking OVN-Kubernetes network plugin, both IPv4 and IPv6 address families are supported.

  • If you use the Red Hat OpenShift Networking OpenShift SDN network plugin, only the IPv4 address family is supported.

If you configure your cluster to use both IP address families, review the following requirements:

  • Both IP families must use the same network interface for the default gateway.

  • Both IP families must have the default gateway.

  • You must specify IPv4 and IPv6 addresses in the same order for all network configuration parameters. For example, in the following configuration IPv4 addresses are listed before IPv6 addresses.

networking:
  clusterNetwork:
  - cidr: 10.128.0.0/14
    hostPrefix: 23
  - cidr: fd00:10:128::/56
    hostPrefix: 64
  serviceNetwork:
  - 172.30.0.0/16
  - fd00:172:16::/112

Globalnet is not supported with Red Hat OpenShift Data Foundation disaster recovery solutions. For regional disaster recovery scenarios, ensure that you use a nonoverlapping range of private IP addresses for the cluster and service networks in each cluster.
Table 10. Network parameters
Parameter Description Values

networking

The configuration for the cluster network.

Object

You cannot modify parameters specified by the networking object after installation.

networking.networkType

The Red Hat OpenShift Networking network plugin to install.

Either OpenShiftSDN or OVNKubernetes. OpenShiftSDN is a CNI plugin for all-Linux networks. OVNKubernetes is a CNI plugin for Linux networks and hybrid networks that contain both Linux and Windows servers. The default value is OVNKubernetes.

networking.clusterNetwork

The IP address blocks for pods.

The default value is 10.128.0.0/14 with a host prefix of /23.

If you specify multiple IP address blocks, the blocks must not overlap.

An array of objects. For example:

networking:
  clusterNetwork:
  - cidr: 10.128.0.0/14
    hostPrefix: 23
  - cidr: fd01::/48
    hostPrefix: 64

networking.clusterNetwork.cidr

Required if you use networking.clusterNetwork. An IP address block.

If you use the OpenShift SDN network plugin, specify an IPv4 network. If you use the OVN-Kubernetes network plugin, you can specify IPv4 and IPv6 networks.

An IP address block in Classless Inter-Domain Routing (CIDR) notation. The prefix length for an IPv4 block is between 0 and 32. The prefix length for an IPv6 block is between 0 and 128. For example, 10.128.0.0/14 or fd01::/48.

networking.clusterNetwork.hostPrefix

The subnet prefix length to assign to each individual node. For example, if hostPrefix is set to 23 then each node is assigned a /23 subnet out of the given cidr. A hostPrefix value of 23 provides 510 (2^(32 - 23) - 2) pod IP addresses.

A subnet prefix.

For an IPv4 network the default value is 23. For an IPv6 network the default value is 64. The default value is also the minimum value for IPv6.

networking.serviceNetwork

The IP address block for services. The default value is 172.30.0.0/16.

The OpenShift SDN and OVN-Kubernetes network plugins support only a single IP address block for the service network.

If you use the OVN-Kubernetes network plugin, you can specify an IP address block for both of the IPv4 and IPv6 address families.

An array with an IP address block in CIDR format. For example:

networking:
  serviceNetwork:
   - 172.30.0.0/16
   - fd02::/112

networking.machineNetwork

The IP address blocks for machines.

If you specify multiple IP address blocks, the blocks must not overlap.

An array of objects. For example:

networking:
  machineNetwork:
  - cidr: 10.0.0.0/16

networking.machineNetwork.cidr

Required if you use networking.machineNetwork. An IP address block. The default value is 10.0.0.0/16 for all platforms other than libvirt and IBM Power Virtual Server. For libvirt, the default value is 192.168.126.0/24. For IBM Power Virtual Server, the default value is 192.168.0.0/24.

An IP network block in CIDR notation.

For example, 10.0.0.0/16 or fd00::/48.

Set the networking.machineNetwork to match the CIDR that the preferred NIC resides in.

Optional configuration parameters

Optional installation configuration parameters are described in the following table:

Table 11. Optional parameters
Parameter Description Values

additionalTrustBundle

A PEM-encoded X.509 certificate bundle that is added to the nodes' trusted certificate store. This trust bundle may also be used when a proxy has been configured.

String

capabilities

Controls the installation of optional core cluster components. You can reduce the footprint of your OpenShift Container Platform cluster by disabling optional components. For more information, see the "Cluster capabilities" page in Installing.

String array

capabilities.baselineCapabilitySet

Selects an initial set of optional capabilities to enable. Valid values are None, v4.11, v4.12 and vCurrent. The default value is vCurrent.

String

capabilities.additionalEnabledCapabilities

Extends the set of optional capabilities beyond what you specify in baselineCapabilitySet. You may specify multiple capabilities in this parameter.

String array

cpuPartitioningMode

Enables workload partitioning, which isolates OpenShift Container Platform services, cluster management workloads, and infrastructure pods to run on a reserved set of CPUs. Workload partitioning can only be enabled during installation and cannot be disabled after installation. While this field enables workload partitioning, it does not configure workloads to use specific CPUs. For more information, see the Workload partitioning page in the Scalability and Performance section.

None or AllNodes. None is the default value.

compute

The configuration for the machines that comprise the compute nodes.

Array of MachinePool objects.

compute.architecture

Determines the instruction set architecture of the machines in the pool. Currently, clusters with varied architectures are not supported. All pools must specify the same architecture. Valid values are amd64 and arm64.

String

compute: hyperthreading:

Whether to enable or disable simultaneous multithreading, or hyperthreading, on compute machines. By default, simultaneous multithreading is enabled to increase the performance of your machines' cores.

If you disable simultaneous multithreading, ensure that your capacity planning accounts for the dramatically decreased machine performance.

Enabled or Disabled

compute.name

Required if you use compute. The name of the machine pool.

worker

compute.platform

Required if you use compute. Use this parameter to specify the cloud provider to host the worker machines. This parameter value must match the controlPlane.platform parameter value.

alibabacloud, aws, azure, gcp, ibmcloud, nutanix, openstack, ovirt, powervs, vsphere, or {}

compute.replicas

The number of compute machines, which are also known as worker machines, to provision.

A positive integer greater than or equal to 2. The default value is 3.

featureSet

Enables the cluster for a feature set. A feature set is a collection of OpenShift Container Platform features that are not enabled by default. For more information about enabling a feature set during installation, see "Enabling features using feature gates".

String. The name of the feature set to enable, such as TechPreviewNoUpgrade.

controlPlane

The configuration for the machines that comprise the control plane.

Array of MachinePool objects.

controlPlane.architecture

Determines the instruction set architecture of the machines in the pool. Currently, clusters with varied architectures are not supported. All pools must specify the same architecture. Valid values are amd64 and arm64.

String

controlPlane: hyperthreading:

Whether to enable or disable simultaneous multithreading, or hyperthreading, on control plane machines. By default, simultaneous multithreading is enabled to increase the performance of your machines' cores.

If you disable simultaneous multithreading, ensure that your capacity planning accounts for the dramatically decreased machine performance.

Enabled or Disabled

controlPlane.name

Required if you use controlPlane. The name of the machine pool.

master

controlPlane.platform

Required if you use controlPlane. Use this parameter to specify the cloud provider that hosts the control plane machines. This parameter value must match the compute.platform parameter value.

alibabacloud, aws, azure, gcp, ibmcloud, nutanix, openstack, ovirt, powervs, vsphere, or {}

controlPlane.replicas

The number of control plane machines to provision.

The only supported value is 3, which is the default value.

credentialsMode

The Cloud Credential Operator (CCO) mode. If no mode is specified, the CCO dynamically tries to determine the capabilities of the provided credentials, with a preference for mint mode on the platforms where multiple modes are supported.

Not all CCO modes are supported for all cloud providers. For more information about CCO modes, see the Cloud Credential Operator entry in the Cluster Operators reference content.

If your AWS account has service control policies (SCP) enabled, you must configure the credentialsMode parameter to Mint, Passthrough or Manual.

Mint, Passthrough, Manual or an empty string ("").

imageContentSources

Sources and repositories for the release-image content.

Array of objects. Includes a source and, optionally, mirrors, as described in the following rows of this table.

imageContentSources.source

Required if you use imageContentSources. Specify the repository that users refer to, for example, in image pull specifications.

String

imageContentSources.mirrors

Specify one or more repositories that may also contain the same images.

Array of strings

publish

How to publish or expose the user-facing endpoints of your cluster, such as the Kubernetes API, OpenShift routes.

Internal or External. The default value is External.

Setting this field to Internal is not supported on non-cloud platforms.

If the value of the field is set to Internal, the cluster will become non-functional. For more information, refer to BZ#1953035.

sshKey

The SSH key to authenticate access to your cluster machines.

For production OpenShift Container Platform clusters on which you want to perform installation debugging or disaster recovery, specify an SSH key that your ssh-agent process uses.

For example, sshKey: ssh-ed25519 AAAA...

  1. Not all CCO modes are supported for all cloud providers. For more information about CCO modes, see the "Managing cloud provider credentials" entry in the Authentication and authorization content.

Sample install-config.yaml file for bare metal

You can customize the install-config.yaml file to specify more details about your OpenShift Container Platform cluster’s platform or modify the values of the required parameters.

apiVersion: v1
baseDomain: example.com (1)
compute: (2)
- hyperthreading: Enabled (3)
  name: worker
  replicas: 0 (4)
controlPlane: (2)
  hyperthreading: Enabled (3)
  name: master
  replicas: 3 (5)
metadata:
  name: test (6)
networking:
  clusterNetwork:
  - cidr: 10.128.0.0/14 (7)
    hostPrefix: 23 (8)
  networkType: OVNKubernetes (9)
  serviceNetwork: (10)
  - 172.30.0.0/16
platform:
  none: {} (11)
fips: false (12)
pullSecret: '{"auths": ...}' (13)
sshKey: 'ssh-ed25519 AAAA...' (14)
1 The base domain of the cluster. All DNS records must be sub-domains of this base and include the cluster name.
2 The controlPlane section is a single mapping, but the compute section is a sequence of mappings. To meet the requirements of the different data structures, the first line of the compute section must begin with a hyphen, -, and the first line of the controlPlane section must not. Only one control plane pool is used.
3 Specifies whether to enable or disable simultaneous multithreading (SMT), or hyperthreading. By default, SMT is enabled to increase the performance of the cores in your machines. You can disable it by setting the parameter value to Disabled. If you disable SMT, you must disable it in all cluster machines; this includes both control plane and compute machines.

Simultaneous multithreading (SMT) is enabled by default. If SMT is not enabled in your BIOS settings, the hyperthreading parameter has no effect.

If you disable hyperthreading, whether in the BIOS or in the install-config.yaml file, ensure that your capacity planning accounts for the dramatically decreased machine performance.
4 You must set this value to 0 when you install OpenShift Container Platform on user-provisioned infrastructure. In installer-provisioned installations, the parameter controls the number of compute machines that the cluster creates and manages for you. In user-provisioned installations, you must manually deploy the compute machines before you finish installing the cluster.

If you are installing a three-node cluster, do not deploy any compute machines when you install the Red Hat Enterprise Linux CoreOS (RHCOS) machines.
5 The number of control plane machines that you add to the cluster. Because the cluster uses these values as the number of etcd endpoints in the cluster, the value must match the number of control plane machines that you deploy.
6 The cluster name that you specified in your DNS records.
7 A block of IP addresses from which pod IP addresses are allocated. This block must not overlap with existing physical networks. These IP addresses are used for the pod network. If you need to access the pods from an external network, you must configure load balancers and routers to manage the traffic.

Class E CIDR range is reserved for a future use. To use the Class E CIDR range, you must ensure your networking environment accepts the IP addresses within the Class E CIDR range.
8 The subnet prefix length to assign to each individual node. For example, if hostPrefix is set to 23, then each node is assigned a /23 subnet out of the given cidr, which allows for 510 (2^(32 - 23) - 2) pod IP addresses. If you are required to provide access to nodes from an external network, configure load balancers and routers to manage the traffic.
9 The cluster network plugin to install. The supported values are OVNKubernetes and OpenShiftSDN. The default value is OVNKubernetes.
10 The IP address pool to use for service IP addresses. You can enter only one IP address pool. This block must not overlap with existing physical networks. If you need to access the services from an external network, configure load balancers and routers to manage the traffic.
11 You must set the platform to none. You cannot provide additional platform configuration variables for your platform.

Clusters that are installed with the platform type none are unable to use some features, such as managing compute machines with the Machine API. This limitation applies even if the compute machines that are attached to the cluster are installed on a platform that would normally support the feature. This parameter cannot be changed after installation.
12 Whether to enable or disable FIPS mode. By default, FIPS mode is not enabled.

OpenShift Container Platform 4.13 is based on Red Hat Enterprise Linux (RHEL) 9.2. RHEL 9.2 cryptographic modules have not yet been submitted for FIPS validation. For more information, see "About this release" in the 4.13 OpenShift Container Platform Release Notes.
13 The pull secret from the Red Hat OpenShift Cluster Manager. This pull secret allows you to authenticate with the services that are provided by the included authorities, including Quay.io, which serves the container images for OpenShift Container Platform components.
14 The SSH public key for the core user in Red Hat Enterprise Linux CoreOS (RHCOS).

For production OpenShift Container Platform clusters on which you want to perform installation debugging or disaster recovery, specify an SSH key that your ssh-agent process uses.
Additional resources

Network configuration phases

There are two phases prior to OpenShift Container Platform installation where you can customize the network configuration.

Phase 1

You can customize the following network-related fields in the install-config.yaml file before you create the manifest files:

  • networking.networkType

  • networking.clusterNetwork

  • networking.serviceNetwork

  • networking.machineNetwork

    For more information on these fields, refer to Installation configuration parameters.

    Set the networking.machineNetwork to match the CIDR that the preferred NIC resides in.

    The CIDR range 172.17.0.0/16 is reserved by libVirt. You cannot use this range or any range that overlaps with this range for any networks in your cluster.
Phase 2

After creating the manifest files by running openshift-install create manifests, you can define a customized Cluster Network Operator manifest with only the fields you want to modify. You can use the manifest to specify advanced network configuration.

You cannot override the values specified in phase 1 in the install-config.yaml file during phase 2. However, you can further customize the network plugin during phase 2.

Specifying advanced network configuration

You can use advanced network configuration for your network plugin to integrate your cluster into your existing network environment. You can specify advanced network configuration only before you install the cluster.

Customizing your network configuration by modifying the OpenShift Container Platform manifest files created by the installation program is not supported. Applying a manifest file that you create, as in the following procedure, is supported.
Prerequisites

  • You have created the install-config.yaml file and completed any modifications to it.

Procedure

  1. Change to the directory that contains the installation program and create the manifests:

    $ ./openshift-install create manifests --dir <installation_directory> (1)
    1 <installation_directory> specifies the name of the directory that contains the install-config.yaml file for your cluster.

  2. Create a stub manifest file for the advanced network configuration that is named cluster-network-03-config.yml in the <installation_directory>/manifests/ directory:

    apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:

  3. Specify the advanced network configuration for your cluster in the cluster-network-03-config.yml file, such as in the following examples:

    Specify a different VXLAN port for the OpenShift SDN network provider
    apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:
  defaultNetwork:
    openshiftSDNConfig:
      vxlanPort: 4800
    Enable IPsec for the OVN-Kubernetes network provider
    apiVersion: operator.openshift.io/v1
kind: Network
metadata:
  name: cluster
spec:
  defaultNetwork:
    ovnKubernetesConfig:
      ipsecConfig: {}

  4. Optional: Back up the manifests/cluster-network-03-config.yml file. The installation program consumes the manifests/ directory when you create the Ignition config files.

Cluster Network Operator configuration

The configuration for the cluster network is specified as part of the Cluster Network Operator (CNO) configuration and stored in a custom resource (CR) object that is named cluster. The CR specifies the fields for the Network API in the operator.openshift.io API group.

The CNO configuration inherits the following fields during cluster installation from the Network API in the Network.config.openshift.io API group and these fields cannot be changed:

clusterNetwork

IP address pools from which pod IP addresses are allocated.

serviceNetwork

IP address pool for services.

defaultNetwork.type

Cluster network plugin, such as OpenShift SDN or OVN-Kubernetes.

You can specify the cluster network plugin configuration for your cluster by setting the fields for the defaultNetwork object in the CNO object named cluster.

Cluster Network Operator configuration object

The fields for the Cluster Network Operator (CNO) are described in the following table:

Table 12. Cluster Network Operator configuration object
Field Type Description

metadata.name

string

The name of the CNO object. This name is always cluster.

spec.clusterNetwork

array

A list specifying the blocks of IP addresses from which pod IP addresses are allocated and the subnet prefix length assigned to each individual node in the cluster. For example:

spec:
  clusterNetwork:
  - cidr: 10.128.0.0/19
    hostPrefix: 23
  - cidr: 10.128.32.0/19
    hostPrefix: 23

You can customize this field only in the install-config.yaml file before you create the manifests. The value is read-only in the manifest file.

spec.serviceNetwork

array

A block of IP addresses for services. The OpenShift SDN and OVN-Kubernetes network plugins support only a single IP address block for the service network. For example:

spec:
  serviceNetwork:
  - 172.30.0.0/14

You can customize this field only in the install-config.yaml file before you create the manifests. The value is read-only in the manifest file.

spec.defaultNetwork

object

Configures the network plugin for the cluster network.

spec.kubeProxyConfig

object

The fields for this object specify the kube-proxy configuration. If you are using the OVN-Kubernetes cluster network plugin, the kube-proxy configuration has no effect.

defaultNetwork object configuration

The values for the defaultNetwork object are defined in the following table:

Table 13. defaultNetwork object
Field Type Description

type

string

Either OpenShiftSDN or OVNKubernetes. The Red Hat OpenShift Networking network plugin is selected during installation. This value cannot be changed after cluster installation.

OpenShift Container Platform uses the OVN-Kubernetes network plugin by default.

openshiftSDNConfig

object

This object is only valid for the OpenShift SDN network plugin.

ovnKubernetesConfig

object

This object is only valid for the OVN-Kubernetes network plugin.
Configuration for the OpenShift SDN network plugin

The following table describes the configuration fields for the OpenShift SDN network plugin:

Table 14. openshiftSDNConfig object
Field Type Description

mode

string

Configures the network isolation mode for OpenShift SDN. The default value is NetworkPolicy.

The values Multitenant and Subnet are available for backwards compatibility with OpenShift Container Platform 3.x but are not recommended. This value cannot be changed after cluster installation.

mtu

integer

The maximum transmission unit (MTU) for the VXLAN overlay network. This is detected automatically based on the MTU of the primary network interface. You do not normally need to override the detected MTU.

If the auto-detected value is not what you expect it to be, confirm that the MTU on the primary network interface on your nodes is correct. You cannot use this option to change the MTU value of the primary network interface on the nodes.

If your cluster requires different MTU values for different nodes, you must set this value to 50 less than the lowest MTU value in your cluster. For example, if some nodes in your cluster have an MTU of 9001, and some have an MTU of 1500, you must set this value to 1450.

This value cannot be changed after cluster installation.

vxlanPort

integer

The port to use for all VXLAN packets. The default value is 4789. This value cannot be changed after cluster installation.

If you are running in a virtualized environment with existing nodes that are part of another VXLAN network, then you might be required to change this. For example, when running an OpenShift SDN overlay on top of VMware NSX-T, you must select an alternate port for the VXLAN, because both SDNs use the same default VXLAN port number.

On Amazon Web Services (AWS), you can select an alternate port for the VXLAN between port 9000 and port 9999.
Example OpenShift SDN configuration
defaultNetwork:
  type: OpenShiftSDN
  openshiftSDNConfig:
    mode: NetworkPolicy
    mtu: 1450
    vxlanPort: 4789
Configuration for the OVN-Kubernetes network plugin

The following table describes the configuration fields for the OVN-Kubernetes network plugin:

Table 15. ovnKubernetesConfig object
Field Type Description

mtu

integer

The maximum transmission unit (MTU) for the Geneve (Generic Network Virtualization Encapsulation) overlay network. This is detected automatically based on the MTU of the primary network interface. You do not normally need to override the detected MTU.

If the auto-detected value is not what you expect it to be, confirm that the MTU on the primary network interface on your nodes is correct. You cannot use this option to change the MTU value of the primary network interface on the nodes.

If your cluster requires different MTU values for different nodes, you must set this value to 100 less than the lowest MTU value in your cluster. For example, if some nodes in your cluster have an MTU of 9001, and some have an MTU of 1500, you must set this value to 1400.

genevePort

integer

The port to use for all Geneve packets. The default value is 6081. This value cannot be changed after cluster installation.

ipsecConfig

object

Specify an empty object to enable IPsec encryption.

policyAuditConfig

object

Specify a configuration object for customizing network policy audit logging. If unset, the defaults audit log settings are used.

gatewayConfig

object

Optional: Specify a configuration object for customizing how egress traffic is sent to the node gateway.

While migrating egress traffic, you can expect some disruption to workloads and service traffic until the Cluster Network Operator (CNO) successfully rolls out the changes.

v4InternalSubnet

If your existing network infrastructure overlaps with the 100.64.0.0/16 IPv4 subnet, you can specify a different IP address range for internal use by OVN-Kubernetes. You must ensure that the IP address range does not overlap with any other subnet used by your OpenShift Container Platform installation. The IP address range must be larger than the maximum number of nodes that can be added to the cluster. For example, if the clusterNetwork.cidr value is 10.128.0.0/14 and the clusterNetwork.hostPrefix value is /23, then the maximum number of nodes is 2^(23-14)=512.

This field cannot be changed after installation.

The default value is 100.64.0.0/16.

v6InternalSubnet

If your existing network infrastructure overlaps with the fd98::/48 IPv6 subnet, you can specify a different IP address range for internal use by OVN-Kubernetes. You must ensure that the IP address range does not overlap with any other subnet used by your OpenShift Container Platform installation. The IP address range must be larger than the maximum number of nodes that can be added to the cluster.

This field cannot be changed after installation.

The default value is fd98::/48.
Table 16. policyAuditConfig object
Field Type Description

rateLimit

integer

The maximum number of messages to generate every second per node. The default value is 20 messages per second.

maxFileSize

integer

The maximum size for the audit log in bytes. The default value is 50000000 or 50 MB.

maxLogFiles

integer

The maximum number of log files that are retained.

destination

string

One of the following additional audit log targets:

libc

The libc syslog() function of the journald process on the host.

udp:<host>:<port>

A syslog server. Replace <host>:<port> with the host and port of the syslog server.

unix:<file>

A Unix Domain Socket file specified by <file>.

null

Do not send the audit logs to any additional target.

syslogFacility

string

The syslog facility, such as kern, as defined by RFC5424. The default value is local0.
Table 17. gatewayConfig object
Field Type Description

routingViaHost

boolean

Set this field to true to send egress traffic from pods to the host networking stack. For highly-specialized installations and applications that rely on manually configured routes in the kernel routing table, you might want to route egress traffic to the host networking stack. By default, egress traffic is processed in OVN to exit the cluster and is not affected by specialized routes in the kernel routing table. The default value is false.

This field has an interaction with the Open vSwitch hardware offloading feature. If you set this field to true, you do not receive the performance benefits of the offloading because egress traffic is processed by the host networking stack.
Example OVN-Kubernetes configuration with IPSec enabled
defaultNetwork:
  type: OVNKubernetes
  ovnKubernetesConfig:
    mtu: 1400
    genevePort: 6081
    ipsecConfig: {}

kubeProxyConfig object configuration

The values for the kubeProxyConfig object are defined in the following table:

Table 18. kubeProxyConfig object
Field Type Description

iptablesSyncPeriod

string

The refresh period for iptables rules. The default value is 30s. Valid suffixes include s, m, and h and are described in the Go time package documentation.

Because of performance improvements introduced in OpenShift Container Platform 4.3 and greater, adjusting the iptablesSyncPeriod parameter is no longer necessary.

proxyArguments.iptables-min-sync-period

array

The minimum duration before refreshing iptables rules. This field ensures that the refresh does not happen too frequently. Valid suffixes include s, m, and h and are described in the Go time package. The default value is:

kubeProxyConfig:
  proxyArguments:
    iptables-min-sync-period:
    - 0s

Creating the Ignition config files

Because you must manually start the cluster machines, you must generate the Ignition config files that the cluster needs to make its machines.

  • The Ignition config files that the installation program generates contain certificates that expire after 24 hours, which are then renewed at that time. If the cluster is shut down before renewing the certificates and the cluster is later restarted after the 24 hours have elapsed, the cluster automatically recovers the expired certificates. The exception is that you must manually approve the pending node-bootstrapper certificate signing requests (CSRs) to recover kubelet certificates. See the documentation for Recovering from expired control plane certificates for more information.

  • It is recommended that you use Ignition config files within 12 hours after they are generated because the 24-hour certificate rotates from 16 to 22 hours after the cluster is installed. By using the Ignition config files within 12 hours, you can avoid installation failure if the certificate update runs during installation.
Prerequisites

  • Obtain the OpenShift Container Platform installation program and the pull secret for your cluster.

Procedure

  • Obtain the Ignition config files:

    $ ./openshift-install create ignition-configs --dir <installation_directory> (1)
    1 For <installation_directory>, specify the directory name to store the files that the installation program creates.

    If you created an install-config.yaml file, specify the directory that contains it. Otherwise, specify an empty directory. Some installation assets, like bootstrap X.509 certificates have short expiration intervals, so you must not reuse an installation directory. If you want to reuse individual files from another cluster installation, you can copy them into your directory. However, the file names for the installation assets might change between releases. Use caution when copying installation files from an earlier OpenShift Container Platform version.

    The following files are generated in the directory:

    .
├── auth
│   ├── kubeadmin-password
│   └── kubeconfig
├── bootstrap.ign
├── master.ign
├── metadata.json
└── worker.ign

Installing RHCOS and starting the OpenShift Container Platform bootstrap process

To install OpenShift Container Platform on bare metal infrastructure that you provision, you must install Red Hat Enterprise Linux CoreOS (RHCOS) on the machines. When you install RHCOS, you must provide the Ignition config file that was generated by the OpenShift Container Platform installation program for the type of machine you are installing. If you have configured suitable networking, DNS, and load balancing infrastructure, the OpenShift Container Platform bootstrap process begins automatically after the RHCOS machines have rebooted.

To install RHCOS on the machines, follow either the steps to use an ISO image or network PXE booting.

The compute node deployment steps included in this installation document are RHCOS-specific. If you choose instead to deploy RHEL-based compute nodes, you take responsibility for all operating system life cycle management and maintenance, including performing system updates, applying patches, and completing all other required tasks. Only RHEL 8 compute machines are supported.

You can configure RHCOS during ISO and PXE installations by using the following methods:

  • Kernel arguments: You can use kernel arguments to provide installation-specific information. For example, you can specify the locations of the RHCOS installation files that you uploaded to your HTTP server and the location of the Ignition config file for the type of node you are installing. For a PXE installation, you can use the APPEND parameter to pass the arguments to the kernel of the live installer. For an ISO installation, you can interrupt the live installation boot process to add the kernel arguments. In both installation cases, you can use special coreos.inst.* arguments to direct the live installer, as well as standard installation boot arguments for turning standard kernel services on or off.

  • Ignition configs: OpenShift Container Platform Ignition config files (*.ign) are specific to the type of node you are installing. You pass the location of a bootstrap, control plane, or compute node Ignition config file during the RHCOS installation so that it takes effect on first boot. In special cases, you can create a separate, limited Ignition config to pass to the live system. That Ignition config could do a certain set of tasks, such as reporting success to a provisioning system after completing installation. This special Ignition config is consumed by the coreos-installer to be applied on first boot of the installed system. Do not provide the standard control plane and compute node Ignition configs to the live ISO directly.

  • coreos-installer: You can boot the live ISO installer to a shell prompt, which allows you to prepare the permanent system in a variety of ways before first boot. In particular, you can run the coreos-installer command to identify various artifacts to include, work with disk partitions, and set up networking. In some cases, you can configure features on the live system and copy them to the installed system.

Whether to use an ISO or PXE install depends on your situation. A PXE install requires an available DHCP service and more preparation, but can make the installation process more automated. An ISO install is a more manual process and can be inconvenient if you are setting up more than a few machines.

As of OpenShift Container Platform 4.6, the RHCOS ISO and other installation artifacts provide support for installation on disks with 4K sectors.

Installing RHCOS by using an ISO image

You can use an ISO image to install RHCOS on the machines.

Prerequisites

  • You have created the Ignition config files for your cluster.

  • You have configured suitable network, DNS and load balancing infrastructure.

  • You have an HTTP server that can be accessed from your computer, and from the machines that you create.

  • You have reviewed the Advanced RHCOS installation configuration section for different ways to configure features, such as networking and disk partitioning.

Procedure

  1. Obtain the SHA512 digest for each of your Ignition config files. For example, you can use the following on a system running Linux to get the SHA512 digest for your bootstrap.ign Ignition config file:

    $ sha512sum <installation_directory>/bootstrap.ign

    The digests are provided to the coreos-installer in a later step to validate the authenticity of the Ignition config files on the cluster nodes.

  2. Upload the bootstrap, control plane, and compute node Ignition config files that the installation program created to your HTTP server. Note the URLs of these files.

    You can add or change configuration settings in your Ignition configs before saving them to your HTTP server. If you plan to add more compute machines to your cluster after you finish installation, do not delete these files.

  3. From the installation host, validate that the Ignition config files are available on the URLs. The following example gets the Ignition config file for the bootstrap node:

    $ curl -k http://<HTTP_server>/bootstrap.ign (1)
    Example output
      % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0{"ignition":{"version":"3.2.0"},"passwd":{"users":[{"name":"core","sshAuthorizedKeys":["ssh-rsa...

    Replace bootstrap.ign with master.ign or worker.ign in the command to validate that the Ignition config files for the control plane and compute nodes are also available.

  4. Although it is possible to obtain the RHCOS images that are required for your preferred method of installing operating system instances from the RHCOS image mirror page, the recommended way to obtain the correct version of your RHCOS images are from the output of openshift-install command:

    $ openshift-install coreos print-stream-json | grep '\.iso[^.]'
    Example output
    "location": "<url>/art/storage/releases/rhcos-4.13-aarch64/<release>/aarch64/rhcos-<release>-live.aarch64.iso",
"location": "<url>/art/storage/releases/rhcos-4.13-ppc64le/<release>/ppc64le/rhcos-<release>-live.ppc64le.iso",
"location": "<url>/art/storage/releases/rhcos-4.13-s390x/<release>/s390x/rhcos-<release>-live.s390x.iso",
"location": "<url>/art/storage/releases/rhcos-4.13/<release>/x86_64/rhcos-<release>-live.x86_64.iso",

    The RHCOS images might not change with every release of OpenShift Container Platform. You must download images with the highest version that is less than or equal to the OpenShift Container Platform version that you install. Use the image versions that match your OpenShift Container Platform version if they are available. Use only ISO images for this procedure. RHCOS qcow2 images are not supported for this installation type.

    ISO file names resemble the following example:

    rhcos-<version>-live.<architecture>.iso

  5. Use the ISO to start the RHCOS installation. Use one of the following installation options:

    • Burn the ISO image to a disk and boot it directly.

    • Use ISO redirection by using a lights-out management (LOM) interface.

  6. Boot the RHCOS ISO image without specifying any options or interrupting the live boot sequence. Wait for the installer to boot into a shell prompt in the RHCOS live environment.

    It is possible to interrupt the RHCOS installation boot process to add kernel arguments. However, for this ISO procedure you should use the coreos-installer command as outlined in the following steps, instead of adding kernel arguments.

  7. Run the coreos-installer command and specify the options that meet your installation requirements. At a minimum, you must specify the URL that points to the Ignition config file for the node type, and the device that you are installing to:

    $ sudo coreos-installer install --ignition-url=http://<HTTP_server>/<node_type>.ign <device> --ignition-hash=sha512-<digest> (1) (2)
    1 You must run the coreos-installer command by using sudo, because the core user does not have the required root privileges to perform the installation.
    2 The --ignition-hash option is required when the Ignition config file is obtained through an HTTP URL to validate the authenticity of the Ignition config file on the cluster node. <digest> is the Ignition config file SHA512 digest obtained in a preceding step.

    If you want to provide your Ignition config files through an HTTPS server that uses TLS, you can add the internal certificate authority (CA) to the system trust store before running coreos-installer.

    The following example initializes a bootstrap node installation to the /dev/sda device. The Ignition config file for the bootstrap node is obtained from an HTTP web server with the IP address 192.168.1.2:

    $ sudo coreos-installer install --ignition-url=http://192.168.1.2:80/installation_directory/bootstrap.ign /dev/sda --ignition-hash=sha512-a5a2d43879223273c9b60af66b44202a1d1248fc01cf156c46d4a79f552b6bad47bc8cc78ddf0116e80c59d2ea9e32ba53bc807afbca581aa059311def2c3e3b

  8. Monitor the progress of the RHCOS installation on the console of the machine.

    Be sure that the installation is successful on each node before commencing with the OpenShift Container Platform installation. Observing the installation process can also help to determine the cause of RHCOS installation issues that might arise.

  9. After RHCOS installs, you must reboot the system. During the system reboot, it applies the Ignition config file that you specified.

  10. Check the console output to verify that Ignition ran.

    Example command
    Ignition: ran on 2022/03/14 14:48:33 UTC (this boot)
Ignition: user-provided config was applied

  11. Continue to create the other machines for your cluster.

    You must create the bootstrap and control plane machines at this time. If the control plane machines are not made schedulable, also create at least two compute machines before you install OpenShift Container Platform.

    If the required network, DNS, and load balancer infrastructure are in place, the OpenShift Container Platform bootstrap process begins automatically after the RHCOS nodes have rebooted.

    RHCOS nodes do not include a default password for the core user. You can access the nodes by running ssh core@<node>.<cluster_name>.<base_domain> as a user with access to the SSH private key that is paired to the public key that you specified in your install_config.yaml file. OpenShift Container Platform 4 cluster nodes running RHCOS are immutable and rely on Operators to apply cluster changes. Accessing cluster nodes by using SSH is not recommended. However, when investigating installation issues, if the OpenShift Container Platform API is not available, or the kubelet is not properly functioning on a target node, SSH access might be required for debugging or disaster recovery.

Installing RHCOS by using PXE or iPXE booting

You can use PXE or iPXE booting to install RHCOS on the machines.

Prerequisites

  • You have created the Ignition config files for your cluster.

  • You have configured suitable network, DNS and load balancing infrastructure.

  • You have configured suitable PXE or iPXE infrastructure.

  • You have an HTTP server that can be accessed from your computer, and from the machines that you create.

  • You have reviewed the Advanced RHCOS installation configuration section for different ways to configure features, such as networking and disk partitioning.

Procedure

  1. Upload the bootstrap, control plane, and compute node Ignition config files that the installation program created to your HTTP server. Note the URLs of these files.

    You can add or change configuration settings in your Ignition configs before saving them to your HTTP server. If you plan to add more compute machines to your cluster after you finish installation, do not delete these files.

  2. From the installation host, validate that the Ignition config files are available on the URLs. The following example gets the Ignition config file for the bootstrap node:

    $ curl -k http://<HTTP_server>/bootstrap.ign (1)
    Example output
      % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0{"ignition":{"version":"3.2.0"},"passwd":{"users":[{"name":"core","sshAuthorizedKeys":["ssh-rsa...

    Replace bootstrap.ign with master.ign or worker.ign in the command to validate that the Ignition config files for the control plane and compute nodes are also available.

  3. Although it is possible to obtain the RHCOS kernel, initramfs and rootfs files that are required for your preferred method of installing operating system instances from the RHCOS image mirror page, the recommended way to obtain the correct version of your RHCOS files are from the output of openshift-install command:

    $ openshift-install coreos print-stream-json | grep -Eo '"https.*(kernel-|initramfs.|rootfs.)\w+(\.img)?"'
    Example output
    "<url>/art/storage/releases/rhcos-4.13-aarch64/<release>/aarch64/rhcos-<release>-live-kernel-aarch64"
"<url>/art/storage/releases/rhcos-4.13-aarch64/<release>/aarch64/rhcos-<release>-live-initramfs.aarch64.img"
"<url>/art/storage/releases/rhcos-4.13-aarch64/<release>/aarch64/rhcos-<release>-live-rootfs.aarch64.img"
"<url>/art/storage/releases/rhcos-4.13-ppc64le/49.84.202110081256-0/ppc64le/rhcos-<release>-live-kernel-ppc64le"
"<url>/art/storage/releases/rhcos-4.13-ppc64le/<release>/ppc64le/rhcos-<release>-live-initramfs.ppc64le.img"
"<url>/art/storage/releases/rhcos-4.13-ppc64le/<release>/ppc64le/rhcos-<release>-live-rootfs.ppc64le.img"
"<url>/art/storage/releases/rhcos-4.13-s390x/<release>/s390x/rhcos-<release>-live-kernel-s390x"
"<url>/art/storage/releases/rhcos-4.13-s390x/<release>/s390x/rhcos-<release>-live-initramfs.s390x.img"
"<url>/art/storage/releases/rhcos-4.13-s390x/<release>/s390x/rhcos-<release>-live-rootfs.s390x.img"
"<url>/art/storage/releases/rhcos-4.13/<release>/x86_64/rhcos-<release>-live-kernel-x86_64"
"<url>/art/storage/releases/rhcos-4.13/<release>/x86_64/rhcos-<release>-live-initramfs.x86_64.img"
"<url>/art/storage/releases/rhcos-4.13/<release>/x86_64/rhcos-<release>-live-rootfs.x86_64.img"

    The RHCOS artifacts might not change with every release of OpenShift Container Platform. You must download images with the highest version that is less than or equal to the OpenShift Container Platform version that you install. Only use the appropriate kernel, initramfs, and rootfs artifacts described below for this procedure. RHCOS QCOW2 images are not supported for this installation type.

    The file names contain the OpenShift Container Platform version number. They resemble the following examples:

    • kernel: rhcos-<version>-live-kernel-<architecture>

    • initramfs: rhcos-<version>-live-initramfs.<architecture>.img

    • rootfs: rhcos-<version>-live-rootfs.<architecture>.img

  4. Upload the rootfs, kernel, and initramfs files to your HTTP server.

    If you plan to add more compute machines to your cluster after you finish installation, do not delete these files.

  5. Configure the network boot infrastructure so that the machines boot from their local disks after RHCOS is installed on them.

  6. Configure PXE or iPXE installation for the RHCOS images and begin the installation.

    Modify one of the following example menu entries for your environment and verify that the image and Ignition files are properly accessible:

    • For PXE (x86_64):

      DEFAULT pxeboot
TIMEOUT 20
PROMPT 0
LABEL pxeboot
    KERNEL http://<HTTP_server>/rhcos-<version>-live-kernel-<architecture> (1)
    APPEND initrd=http://<HTTP_server>/rhcos-<version>-live-initramfs.<architecture>.img coreos.live.rootfs_url=http://<HTTP_server>/rhcos-<version>-live-rootfs.<architecture>.img coreos.inst.install_dev=/dev/sda coreos.inst.ignition_url=http://<HTTP_server>/bootstrap.ign (2) (3)
      1 Specify the location of the live kernel file that you uploaded to your HTTP server. The URL must be HTTP, TFTP, or FTP; HTTPS and NFS are not supported.
      2 If you use multiple NICs, specify a single interface in the ip option. For example, to use DHCP on a NIC that is named eno1, set ip=eno1:dhcp.
      3 Specify the locations of the RHCOS files that you uploaded to your HTTP server. The initrd parameter value is the location of the initramfs file, the coreos.live.rootfs_url parameter value is the location of the rootfs file, and the coreos.inst.ignition_url parameter value is the location of the bootstrap Ignition config file. You can also add more kernel arguments to the APPEND line to configure networking or other boot options.

      This configuration does not enable serial console access on machines with a graphical console. To configure a different console, add one or more console= arguments to the APPEND line. For example, add console=tty0 console=ttyS0 to set the first PC serial port as the primary console and the graphical console as a secondary console. For more information, see How does one set up a serial terminal and/or console in Red Hat Enterprise Linux? and "Enabling the serial console for PXE and ISO installation" in the "Advanced RHCOS installation configuration" section.

    • For iPXE (x86_64 + aarch64 ):

      kernel http://<HTTP_server>/rhcos-<version>-live-kernel-<architecture> initrd=main coreos.live.rootfs_url=http://<HTTP_server>/rhcos-<version>-live-rootfs.<architecture>.img coreos.inst.install_dev=/dev/sda coreos.inst.ignition_url=http://<HTTP_server>/bootstrap.ign (1) (2)
initrd --name main http://<HTTP_server>/rhcos-<version>-live-initramfs.<architecture>.img (3)
boot
      1 Specify the locations of the RHCOS files that you uploaded to your HTTP server. The kernel parameter value is the location of the kernel file, the initrd=main argument is needed for booting on UEFI systems, the coreos.live.rootfs_url parameter value is the location of the rootfs file, and the coreos.inst.ignition_url parameter value is the location of the bootstrap Ignition config file.
      2 If you use multiple NICs, specify a single interface in the ip option. For example, to use DHCP on a NIC that is named eno1, set ip=eno1:dhcp.
      3 Specify the location of the initramfs file that you uploaded to your HTTP server.

      This configuration does not enable serial console access on machines with a graphical console. To configure a different console, add one or more console= arguments to the kernel line. For example, add console=tty0 console=ttyS0 to set the first PC serial port as the primary console and the graphical console as a secondary console. For more information, see How does one set up a serial terminal and/or console in Red Hat Enterprise Linux? and "Enabling the serial console for PXE and ISO installation" in the "Advanced RHCOS installation configuration" section.

      To network boot the CoreOS kernel on aarch64 architecture, you need to use a version of iPXE build with the IMAGE_GZIP option enabled. See IMAGE_GZIP option in iPXE.

    • For PXE (with UEFI and Grub as second stage) on aarch64:

      menuentry 'Install CoreOS' {
    linux rhcos-<version>-live-kernel-<architecture>  coreos.live.rootfs_url=http://<HTTP_server>/rhcos-<version>-live-rootfs.<architecture>.img coreos.inst.install_dev=/dev/sda coreos.inst.ignition_url=http://<HTTP_server>/bootstrap.ign (1) (2)
    initrd rhcos-<version>-live-initramfs.<architecture>.img (3)
}
      1 Specify the locations of the RHCOS files that you uploaded to your HTTP/TFTP server. The kernel parameter value is the location of the kernel file on your TFTP server. The coreos.live.rootfs_url parameter value is the location of the rootfs file, and the coreos.inst.ignition_url parameter value is the location of the bootstrap Ignition config file on your HTTP Server.
      2 If you use multiple NICs, specify a single interface in the ip option. For example, to use DHCP on a NIC that is named eno1, set ip=eno1:dhcp.
      3 Specify the location of the initramfs file that you uploaded to your TFTP server.

  7. Monitor the progress of the RHCOS installation on the console of the machine.

    Be sure that the installation is successful on each node before commencing with the OpenShift Container Platform installation. Observing the installation process can also help to determine the cause of RHCOS installation issues that might arise.

  8. After RHCOS installs, the system reboots. During reboot, the system applies the Ignition config file that you specified.

  9. Check the console output to verify that Ignition ran.

    Example command
    Ignition: ran on 2022/03/14 14:48:33 UTC (this boot)
Ignition: user-provided config was applied

  10. Continue to create the machines for your cluster.

    You must create the bootstrap and control plane machines at this time. If the control plane machines are not made schedulable, also create at least two compute machines before you install the cluster.

    If the required network, DNS, and load balancer infrastructure are in place, the OpenShift Container Platform bootstrap process begins automatically after the RHCOS nodes have rebooted.

    RHCOS nodes do not include a default password for the core user. You can access the nodes by running ssh core@<node>.<cluster_name>.<base_domain> as a user with access to the SSH private key that is paired to the public key that you specified in your install_config.yaml file. OpenShift Container Platform 4 cluster nodes running RHCOS are immutable and rely on Operators to apply cluster changes. Accessing cluster nodes by using SSH is not recommended. However, when investigating installation issues, if the OpenShift Container Platform API is not available, or the kubelet is not properly functioning on a target node, SSH access might be required for debugging or disaster recovery.

Advanced RHCOS installation configuration

A key benefit for manually provisioning the Red Hat Enterprise Linux CoreOS (RHCOS) nodes for OpenShift Container Platform is to be able to do configuration that is not available through default OpenShift Container Platform installation methods. This section describes some of the configurations that you can do using techniques that include:

  • Passing kernel arguments to the live installer

  • Running coreos-installer manually from the live system

  • Customizing a live ISO or PXE boot image

The advanced configuration topics for manual Red Hat Enterprise Linux CoreOS (RHCOS) installations detailed in this section relate to disk partitioning, networking, and using Ignition configs in different ways.

Using advanced networking options for PXE and ISO installations

Networking for OpenShift Container Platform nodes uses DHCP by default to gather all necessary configuration settings. To set up static IP addresses or configure special settings, such as bonding, you can do one of the following:

  • Pass special kernel parameters when you boot the live installer.

  • Use a machine config to copy networking files to the installed system.

  • Configure networking from a live installer shell prompt, then copy those settings to the installed system so that they take effect when the installed system first boots.

To configure a PXE or iPXE installation, use one of the following options:

  • See the "Advanced RHCOS installation reference" tables.

  • Use a machine config to copy networking files to the installed system.

To configure an ISO installation, use the following procedure.

Procedure

  1. Boot the ISO installer.

  2. From the live system shell prompt, configure networking for the live system using available RHEL tools, such as nmcli or nmtui.

  3. Run the coreos-installer command to install the system, adding the --copy-network option to copy networking configuration. For example:

    $ sudo coreos-installer install --copy-network \
     --ignition-url=http://host/worker.ign /dev/disk/by-id/scsi-<serial_number>

    The --copy-network option only copies networking configuration found under /etc/NetworkManager/system-connections. In particular, it does not copy the system hostname.

  4. Reboot into the installed system.

Additional resources

Disk partitioning

Disk partitions are created on OpenShift Container Platform cluster nodes during the Red Hat Enterprise Linux CoreOS (RHCOS) installation. Each RHCOS node of a particular architecture uses the same partition layout, unless you override the default partitioning configuration. During the RHCOS installation, the size of the root file system is increased to use any remaining available space on the target device.

The use of a custom partition scheme on your node might result in OpenShift Container Platform not monitoring or alerting on some node partitions. If you override the default partitioning, see Understanding OpenShift File System Monitoring (eviction conditions) for more information about how OpenShift Container Platform monitors your host file systems.

OpenShift Container Platform monitors the following two filesystem identifiers:

  • nodefs, which is the filesystem that contains /var/lib/kubelet

  • imagefs, which is the filesystem that contains /var/lib/containers

For the default partition scheme, nodefs and imagefs monitor the same root filesystem, /.

To override the default partitioning when installing RHCOS on an OpenShift Container Platform cluster node, you must create separate partitions.

For disk sizes larger than 100GB, and especially disk sizes larger than 1TB, create a separate /var partition. See "Creating a separate /var partition" and this Red Hat Knowledgebase article for more information.

Consider a situation where you want to add a separate storage partition for your containers and container images. For example, by mounting /var/lib/containers in a separate partition, the kubelet separately monitors /var/lib/containers as the imagefs directory and the root file system as the nodefs directory.

If you have resized your disk size to host a larger file system, consider creating a separate /var/lib/containers partition. Consider resizing a disk that has an xfs format to reduce CPU time issues caused by a high number of allocation groups.
Creating a separate /var partition

In general, you should use the default disk partitioning that is created during the RHCOS installation. However, there are cases where you might want to create a separate partition for a directory that you expect to grow.

OpenShift Container Platform supports the addition of a single partition to attach storage to either the /var directory or a subdirectory of /var. For example:

  • /var/lib/containers: Holds container-related content that can grow as more images and containers are added to a system.

  • /var/lib/etcd: Holds data that you might want to keep separate for purposes such as performance optimization of etcd storage.

  • /var: Holds data that you might want to keep separate for purposes such as auditing.

    For disk sizes larger than 100GB, and especially larger than 1TB, create a separate /var partition.

Storing the contents of a /var directory separately makes it easier to grow storage for those areas as needed and reinstall OpenShift Container Platform at a later date and keep that data intact. With this method, you will not have to pull all your containers again, nor will you have to copy massive log files when you update systems.

The use of a separate partition for the /var directory or a subdirectory of /var also prevents data growth in the partitioned directory from filling up the root file system.

The following procedure sets up a separate /var partition by adding a machine config manifest that is wrapped into the Ignition config file for a node type during the preparation phase of an installation.

Procedure

  1. On your installation host, change to the directory that contains the OpenShift Container Platform installation program and generate the Kubernetes manifests for the cluster:

    $ openshift-install create manifests --dir <installation_directory>

  2. Create a Butane config that configures the additional partition. For example, name the file $HOME/clusterconfig/98-var-partition.bu, change the disk device name to the name of the storage device on the worker systems, and set the storage size as appropriate. This example places the /var directory on a separate partition:

    variant: openshift
version: 4.13.0
metadata:
  labels:
    machineconfiguration.openshift.io/role: worker
  name: 98-var-partition
storage:
  disks:
  - device: /dev/disk/by-id/<device_name> (1)
    partitions:
    - label: var
      start_mib: <partition_start_offset> (2)
      size_mib: <partition_size> (3)
      number: 5
  filesystems:
    - device: /dev/disk/by-partlabel/var
      path: /var
      format: xfs
      mount_options: [defaults, prjquota] (4)
      with_mount_unit: true
    1 The storage device name of the disk that you want to partition.
    2 When adding a data partition to the boot disk, a minimum offset value of 25000 mebibytes is recommended. The root file system is automatically resized to fill all available space up to the specified offset. If no offset value is specified, or if the specified value is smaller than the recommended minimum, the resulting root file system will be too small, and future reinstalls of RHCOS might overwrite the beginning of the data partition.
    3 The size of the data partition in mebibytes.
    4 The prjquota mount option must be enabled for filesystems used for container storage.

    When creating a separate /var partition, you cannot use different instance types for compute nodes, if the different instance types do not have the same device name.

  3. Create a manifest from the Butane config and save it to the clusterconfig/openshift directory. For example, run the following command:

    $ butane $HOME/clusterconfig/98-var-partition.bu -o $HOME/clusterconfig/openshift/98-var-partition.yaml

  4. Create the Ignition config files:

    $ openshift-install create ignition-configs --dir <installation_directory> (1)
    1 For <installation_directory>, specify the same installation directory.

    Ignition config files are created for the bootstrap, control plane, and compute nodes in the installation directory:

    .
├── auth
│   ├── kubeadmin-password
│   └── kubeconfig
├── bootstrap.ign
├── master.ign
├── metadata.json
└── worker.ign

    The files in the <installation_directory>/manifest and <installation_directory>/openshift directories are wrapped into the Ignition config files, including the file that contains the 98-var-partition custom MachineConfig object.

Next steps

  • You can apply the custom disk partitioning by referencing the Ignition config files during the RHCOS installations.

Retaining existing partitions

For an ISO installation, you can add options to the coreos-installer command that cause the installer to maintain one or more existing partitions. For a PXE installation, you can add coreos.inst.* options to the APPEND parameter to preserve partitions.

Saved partitions might be data partitions from an existing OpenShift Container Platform system. You can identify the disk partitions you want to keep either by partition label or by number.

If you save existing partitions, and those partitions do not leave enough space for RHCOS, the installation will fail without damaging the saved partitions.
Retaining existing partitions during an ISO installation

This example preserves any partition in which the partition label begins with data (data*):

# coreos-installer install --ignition-url http://10.0.2.2:8080/user.ign \
        --save-partlabel 'data*' /dev/disk/by-id/scsi-<serial_number>

The following example illustrates running the coreos-installer in a way that preserves the sixth (6) partition on the disk:

# coreos-installer install --ignition-url http://10.0.2.2:8080/user.ign \
        --save-partindex 6 /dev/disk/by-id/scsi-<serial_number>

This example preserves partitions 5 and higher:

# coreos-installer install --ignition-url http://10.0.2.2:8080/user.ign
        --save-partindex 5- /dev/disk/by-id/scsi-<serial_number>

In the previous examples where partition saving is used, coreos-installer recreates the partition immediately.

Retaining existing partitions during a PXE installation

This APPEND option preserves any partition in which the partition label begins with 'data' ('data*'):

coreos.inst.save_partlabel=data*

This APPEND option preserves partitions 5 and higher:

coreos.inst.save_partindex=5-

This APPEND option preserves partition 6:

coreos.inst.save_partindex=6

Identifying Ignition configs

When doing an RHCOS manual installation, there are two types of Ignition configs that you can provide, with different reasons for providing each one:

  • Permanent install Ignition config: Every manual RHCOS installation needs to pass one of the Ignition config files generated by openshift-installer, such as bootstrap.ign, master.ign and worker.ign, to carry out the installation.

    It is not recommended to modify these Ignition config files directly. You can update the manifest files that are wrapped into the Ignition config files, as outlined in examples in the preceding sections.

    For PXE installations, you pass the Ignition configs on the APPEND line using the coreos.inst.ignition_url= option. For ISO installations, after the ISO boots to the shell prompt, you identify the Ignition config on the coreos-installer command line with the --ignition-url= option. In both cases, only HTTP and HTTPS protocols are supported.

  • Live install Ignition config: This type can be created by using the coreos-installer customize subcommand and its various options. With this method, the Ignition config passes to the live install medium, runs immediately upon booting, and performs setup tasks before or after the RHCOS system installs to disk. This method should only be used for performing tasks that must be done once and not applied again later, such as with advanced partitioning that cannot be done using a machine config.

    For PXE or ISO boots, you can create the Ignition config and APPEND the ignition.config.url= option to identify the location of the Ignition config. You also need to append ignition.firstboot ignition.platform.id=metal or the ignition.config.url option will be ignored.

Default console configuration

Red Hat Enterprise Linux CoreOS (RHCOS) nodes installed from an OpenShift Container Platform 4.13 boot image use a default console that is meant to accomodate most virtualized and bare metal setups. Different cloud and virtualization platforms may use different default settings depending on the chosen architecture. Bare metal installations use the kernel default settings which typically means the graphical console is the primary console and the serial console is disabled.

The default consoles may not match your specific hardware configuration or you might have specific needs that require you to adjust the default console. For example:

  • You want to access the emergency shell on the console for debugging purposes.

  • Your cloud platform does not provide interactive access to the graphical console, but provides a serial console.

  • You want to enable multiple consoles.

Console configuration is inherited from the boot image. This means that new nodes in existing clusters are unaffected by changes to the default console.

You can configure the console for bare metal installations in the following ways:

  • Using coreos-installer manually on the command line.

  • Using the coreos-installer iso customize or coreos-installer pxe customize subcommands with the --dest-console option to create a custom image that automates the process.

For advanced customization, perform console configuration using the coreos-installer iso or coreos-installer pxe subcommands, and not kernel arguments.

Enabling the serial console for PXE and ISO installations

By default, the Red Hat Enterprise Linux CoreOS (RHCOS) serial console is disabled and all output is written to the graphical console. You can enable the serial console for an ISO installation and reconfigure the bootloader so that output is sent to both the serial console and the graphical console.

Procedure

  1. Boot the ISO installer.

  2. Run the coreos-installer command to install the system, adding the --console option once to specify the graphical console, and a second time to specify the serial console:

    $ coreos-installer install \
  --console=tty0 \(1)
  --console=ttyS0,<options> \(2)
  --ignition-url=http://host/worker.ign /dev/disk/by-id/scsi-<serial_number>
    1 The desired secondary console. In this case, the graphical console. Omitting this option will disable the graphical console.
    2 The desired primary console. In this case the serial console. The options field defines the baud rate and other settings. A common value for this field is 11520n8. If no options are provided, the default kernel value of 9600n8 is used. For more information on the format of this option, see Linux kernel serial console documentation.

  3. Reboot into the installed system.

    A similar outcome can be obtained by using the coreos-installer install --append-karg option, and specifying the console with console=. However, this will only set the console for the kernel and not the bootloader.

To configure a PXE installation, make sure the coreos.inst.install_dev kernel command line option is omitted, and use the shell prompt to run coreos-installer manually using the above ISO installation procedure.

Customizing a live RHCOS ISO or PXE install

You can use the live ISO image or PXE environment to install RHCOS by injecting an Ignition config file directly into the image. This creates a customized image that you can use to provision your system.

For an ISO image, the mechanism to do this is the coreos-installer iso customize subcommand, which modifies the .iso file with your configuration. Similarly, the mechanism for a PXE environment is the coreos-installer pxe customize subcommand, which creates a new initramfs file that includes your customizations.

The customize subcommand is a general purpose tool that can embed other types of customizations as well. The following tasks are examples of some of the more common customizations:

  • Inject custom CA certificates for when corporate security policy requires their use.

  • Configure network settings without the need for kernel arguments.

  • Embed arbitrary preinstall and post-install scripts or binaries.

Customizing a live RHCOS ISO image

You can customize a live RHCOS ISO image directly with the coreos-installer iso customize subcommand. When you boot the ISO image, the customizations are applied automatically.

You can use this feature to configure the ISO image to automatically install RHCOS.

Procedure

  1. Download the coreos-installer binary from the coreos-installer image mirror page.

  2. Retrieve the RHCOS ISO image from the RHCOS image mirror page and the Ignition config file, and then run the following command to inject the Ignition config directly into the ISO image:

    $ coreos-installer iso customize rhcos-<version>-live.x86_64.iso \
    --dest-ignition bootstrap.ign \ (1)
    --dest-device /dev/disk/by-id/scsi-<serial_number> (2)
    1 The Ignition config file that is generated from the openshift-installer installation program.
    2 When you specify this option, the ISO image automatically runs an installation. Otherwise, the image remains configured for installation, but does not install automatically unless you specify the coreos.inst.install_dev kernel argument.

  3. Optional: To remove the ISO image customizations and return the image to its pristine state, run:

    $ coreos-installer iso reset rhcos-<version>-live.x86_64.iso

    You can now re-customize the live ISO image or use it in its pristine state.

Applying your customizations affects every subsequent boot of RHCOS.

Modifying a live install ISO image to enable the serial console

On clusters installed with OpenShift Container Platform 4.12 and above, the serial console is disabled by default and all output is written to the graphical console. You can enable the serial console with the following procedure.

Procedure

  1. Download the coreos-installer binary from the coreos-installer image mirror page.

  2. Retrieve the RHCOS ISO image from the RHCOS image mirror page and run the following command to customize the ISO image to enable the serial console to receive output:

    $ coreos-installer iso customize rhcos-<version>-live.x86_64.iso \
  --dest-ignition <path> \(1)
  --dest-console tty0 \(2)
  --dest-console ttyS0,<options> \(3)
  --dest-device /dev/disk/by-id/scsi-<serial_number> (4)
    1 The location of the Ignition config to install.
    2 The desired secondary console. In this case, the graphical console. Omitting this option will disable the graphical console.
    3 The desired primary console. In this case, the serial console. The options field defines the baud rate and other settings. A common value for this field is 115200n8. If no options are provided, the default kernel value of 9600n8 is used. For more information on the format of this option, see the Linux kernel serial console documentation.
    4 The specified disk to install to. If you omit this option, the ISO image automatically runs the installation program which will fail unless you also specify the coreos.inst.install_dev kernel argument.

    The --dest-console option affects the installed system and not the live ISO system. To modify the console for a live ISO system, use the --live-karg-append option and specify the console with console=.

    Your customizations are applied and affect every subsequent boot of the ISO image.

  3. Optional: To remove the ISO image customizations and return the image to its original state, run the following command:

    $ coreos-installer iso reset rhcos-<version>-live.x86_64.iso

    You can now recustomize the live ISO image or use it in its original state.

Modifying a live install ISO image to use a custom certificate authority

You can provide certificate authority (CA) certificates to Ignition with the --ignition-ca flag of the customize subcommand. You can use the CA certificates during both the installation boot and when provisioning the installed system.

Custom CA certificates affect how Ignition fetches remote resources but they do not affect the certificates installed onto the system.
Procedure

  1. Download the coreos-installer binary from the coreos-installer image mirror page.

  2. Retrieve the RHCOS ISO image from the RHCOS image mirror page and run the following command to customize the ISO image for use with a custom CA:

    $ coreos-installer iso customize rhcos-<version>-live.x86_64.iso --ignition-ca cert.pem

The coreos.inst.ignition_url kernel parameter does not work with the --ignition-ca flag. You must use the --dest-ignition flag to create a customized image for each cluster.

Applying your custom CA certificate affects every subsequent boot of RHCOS.

Modifying a live install ISO image with customized network settings

You can embed a NetworkManager keyfile into the live ISO image and pass it through to the installed system with the --network-keyfile flag of the customize subcommand.

When creating a connection profile, you must use a .nmconnection filename extension in the filename of the connection profile. If you do not use a .nmconnection filename extension, the cluster will apply the connection profile to the live environment, but it will not apply the configuration when the cluster first boots up the nodes, resulting in a setup that does not work.
Procedure

  1. Download the coreos-installer binary from the coreos-installer image mirror page.

  2. Create a connection profile for a bonded interface. For example, create the bond0.nmconnection file in your local directory with the following content:

    [connection]
id=bond0
type=bond
interface-name=bond0
multi-connect=1

[bond]
miimon=100
mode=active-backup

[ipv4]
method=auto

[ipv6]
method=auto

  3. Create a connection profile for a secondary interface to add to the bond. For example, create the bond0-proxy-em1.nmconnection file in your local directory with the following content:

    [connection]
id=em1
type=ethernet
interface-name=em1
master=bond0
multi-connect=1
slave-type=bond

  4. Create a connection profile for a secondary interface to add to the bond. For example, create the bond0-proxy-em2.nmconnection file in your local directory with the following content:

    [connection]
id=em2
type=ethernet
interface-name=em2
master=bond0
multi-connect=1
slave-type=bond

  5. Retrieve the RHCOS ISO image from the RHCOS image mirror page and run the following command to customize the ISO image with your configured networking:

    $ coreos-installer iso customize rhcos-<version>-live.x86_64.iso \
    --network-keyfile bond0.nmconnection \
    --network-keyfile bond0-proxy-em1.nmconnection \
    --network-keyfile bond0-proxy-em2.nmconnection

    Network settings are applied to the live system and are carried over to the destination system.

Customizing a live RHCOS PXE environment

You can customize a live RHCOS PXE environment directly with the coreos-installer pxe customize subcommand. When you boot the PXE environment, the customizations are applied automatically.

You can use this feature to configure the PXE environment to automatically install RHCOS.

Procedure

  1. Download the coreos-installer binary from the coreos-installer image mirror page.

  2. Retrieve the RHCOS kernel, initramfs and rootfs files from the RHCOS image mirror page and the Ignition config file, and then run the following command to create a new initramfs file that contains the customizations from your Ignition config:

    $ coreos-installer pxe customize rhcos-<version>-live-initramfs.x86_64.img \
    --dest-ignition bootstrap.ign \ (1)
    --dest-device /dev/disk/by-id/scsi-<serial_number> \ (2)
    -o rhcos-<version>-custom-initramfs.x86_64.img (3)
    1 The Ignition config file that is generated from openshift-installer.
    2 When you specify this option, the PXE environment automatically runs an install. Otherwise, the image remains configured for installing, but does not do so automatically unless you specify the coreos.inst.install_dev kernel argument.
    3 Use the customized initramfs file in your PXE configuration. Add the ignition.firstboot and ignition.platform.id=metal kernel arguments if they are not already present.

Applying your customizations affects every subsequent boot of RHCOS.

Modifying a live install PXE environment to enable the serial console

On clusters installed with OpenShift Container Platform 4.12 and above, the serial console is disabled by default and all output is written to the graphical console. You can enable the serial console with the following procedure.

Procedure

  1. Download the coreos-installer binary from the coreos-installer image mirror page.

  2. Retrieve the RHCOS kernel, initramfs and rootfs files from the RHCOS image mirror page and the Ignition config file, and then run the following command to create a new customized initramfs file that enables the serial console to receive output:

    $ coreos-installer pxe customize rhcos-<version>-live-initramfs.x86_64.img \
  --dest-ignition <path> \(1)
  --dest-console tty0 \(2)
  --dest-console ttyS0,<options> \(3)
  --dest-device /dev/disk/by-id/scsi-<serial_number> \(4)
  -o rhcos-<version>-custom-initramfs.x86_64.img (5)
    1 The location of the Ignition config to install.
    2 The desired secondary console. In this case, the graphical console. Omitting this option will disable the graphical console.
    3 The desired primary console. In this case, the serial console. The options field defines the baud rate and other settings. A common value for this field is 115200n8. If no options are provided, the default kernel value of 9600n8 is used. For more information on the format of this option, see the Linux kernel serial console documentation.
    4 The specified disk to install to. If you omit this option, the PXE environment automatically runs the installer which will fail unless you also specify the coreos.inst.install_dev kernel argument.
    5 Use the customized initramfs file in your PXE configuration. Add the ignition.firstboot and ignition.platform.id=metal kernel arguments if they are not already present.

    Your customizations are applied and affect every subsequent boot of the PXE environment.

Modifying a live install PXE environment to use a custom certificate authority

You can provide certificate authority (CA) certificates to Ignition with the --ignition-ca flag of the customize subcommand. You can use the CA certificates during both the installation boot and when provisioning the installed system.

Custom CA certificates affect how Ignition fetches remote resources but they do not affect the certificates installed onto the system.
Procedure

  1. Download the coreos-installer binary from the coreos-installer image mirror page.

  2. Retrieve the RHCOS kernel, initramfs and rootfs files from the RHCOS image mirror page and run the following command to create a new customized initramfs file for use with a custom CA:

    $ coreos-installer pxe customize rhcos-<version>-live-initramfs.x86_64.img \
    --ignition-ca cert.pem \
    -o rhcos-<version>-custom-initramfs.x86_64.img

  3. Use the customized initramfs file in your PXE configuration. Add the ignition.firstboot and ignition.platform.id=metal kernel arguments if they are not already present.

The coreos.inst.ignition_url kernel parameter does not work with the --ignition-ca flag. You must use the --dest-ignition flag to create a customized image for each cluster.

Applying your custom CA certificate affects every subsequent boot of RHCOS.

Modifying a live install PXE environment with customized network settings

You can embed a NetworkManager keyfile into the live PXE environment and pass it through to the installed system with the --network-keyfile flag of the customize subcommand.

When creating a connection profile, you must use a .nmconnection filename extension in the filename of the connection profile. If you do not use a .nmconnection filename extension, the cluster will apply the connection profile to the live environment, but it will not apply the configuration when the cluster first boots up the nodes, resulting in a setup that does not work.
Procedure

  1. Download the coreos-installer binary from the coreos-installer image mirror page.

  2. Create a connection profile for a bonded interface. For example, create the bond0.nmconnection file in your local directory with the following content:

    [connection]
id=bond0
type=bond
interface-name=bond0
multi-connect=1

[bond]
miimon=100
mode=active-backup

[ipv4]
method=auto

[ipv6]
method=auto

  3. Create a connection profile for a secondary interface to add to the bond. For example, create the bond0-proxy-em1.nmconnection file in your local directory with the following content:

    [connection]
id=em1
type=ethernet
interface-name=em1
master=bond0
multi-connect=1
slave-type=bond

  4. Create a connection profile for a secondary interface to add to the bond. For example, create the bond0-proxy-em2.nmconnection file in your local directory with the following content:

    [connection]
id=em2
type=ethernet
interface-name=em2
master=bond0
multi-connect=1
slave-type=bond

  5. Retrieve the RHCOS kernel, initramfs and rootfs files from the RHCOS image mirror page and run the following command to create a new customized initramfs file that contains your configured networking:

    $ coreos-installer pxe customize rhcos-<version>-live-initramfs.x86_64.img \
    --network-keyfile bond0.nmconnection \
    --network-keyfile bond0-proxy-em1.nmconnection \
    --network-keyfile bond0-proxy-em2.nmconnection \
    -o rhcos-<version>-custom-initramfs.x86_64.img

  6. Use the customized initramfs file in your PXE configuration. Add the ignition.firstboot and ignition.platform.id=metal kernel arguments if they are not already present.

    Network settings are applied to the live system and are carried over to the destination system.

Advanced RHCOS installation reference

This section illustrates the networking configuration and other advanced options that allow you to modify the Red Hat Enterprise Linux CoreOS (RHCOS) manual installation process. The following tables describe the kernel arguments and command-line options you can use with the RHCOS live installer and the coreos-installer command.

Networking and bonding options for ISO installations

If you install RHCOS from an ISO image, you can add kernel arguments manually when you boot the image to configure networking for a node. If no networking arguments are specified, DHCP is activated in the initramfs when RHCOS detects that networking is required to fetch the Ignition config file.

When adding networking arguments manually, you must also add the rd.neednet=1 kernel argument to bring the network up in the initramfs.

The following information provides examples for configuring networking and bonding on your RHCOS nodes for ISO installations. The examples describe how to use the ip=, nameserver=, and bond= kernel arguments.

Ordering is important when adding the kernel arguments: ip=, nameserver=, and then bond=.

The networking options are passed to the dracut tool during system boot. For more information about the networking options supported by dracut, see the dracut.cmdline manual page.

The following examples are the networking options for ISO installation.

Configuring DHCP or static IP addresses

To configure an IP address, either use DHCP (ip=dhcp) or set an individual static IP address (ip=<host_ip>). If setting a static IP, you must then identify the DNS server IP address (nameserver=<dns_ip>) on each node. The following example sets:

  • The node’s IP address to 10.10.10.2

  • The gateway address to 10.10.10.254

  • The netmask to 255.255.255.0

  • The hostname to core0.example.com

  • The DNS server address to 4.4.4.41

  • The auto-configuration value to none. No auto-configuration is required when IP networking is configured statically.

ip=10.10.10.2::10.10.10.254:255.255.255.0:core0.example.com:enp1s0:none
nameserver=4.4.4.41

When you use DHCP to configure IP addressing for the RHCOS machines, the machines also obtain the DNS server information through DHCP. For DHCP-based deployments, you can define the DNS server address that is used by the RHCOS nodes through your DHCP server configuration.
Configuring an IP address without a static hostname

You can configure an IP address without assigning a static hostname. If a static hostname is not set by the user, it will be picked up and automatically set by a reverse DNS lookup. To configure an IP address without a static hostname refer to the following example:

  • The node’s IP address to 10.10.10.2

  • The gateway address to 10.10.10.254

  • The netmask to 255.255.255.0

  • The DNS server address to 4.4.4.41

  • The auto-configuration value to none. No auto-configuration is required when IP networking is configured statically.

ip=10.10.10.2::10.10.10.254:255.255.255.0::enp1s0:none
nameserver=4.4.4.41
Specifying multiple network interfaces

You can specify multiple network interfaces by setting multiple ip= entries.

ip=10.10.10.2::10.10.10.254:255.255.255.0:core0.example.com:enp1s0:none
ip=10.10.10.3::10.10.10.254:255.255.255.0:core0.example.com:enp2s0:none
Configuring default gateway and route

Optional: You can configure routes to additional networks by setting an rd.route= value.

When you configure one or multiple networks, one default gateway is required. If the additional network gateway is different from the primary network gateway, the default gateway must be the primary network gateway.

  • Run the following command to configure the default gateway:

    ip=::10.10.10.254::::

  • Enter the following command to configure the route for the additional network:

    rd.route=20.20.20.0/24:20.20.20.254:enp2s0
Disabling DHCP on a single interface

You can disable DHCP on a single interface, such as when there are two or more network interfaces and only one interface is being used. In the example, the enp1s0 interface has a static networking configuration and DHCP is disabled for enp2s0, which is not used:

ip=10.10.10.2::10.10.10.254:255.255.255.0:core0.example.com:enp1s0:none
ip=::::core0.example.com:enp2s0:none
Combining DHCP and static IP configurations

You can combine DHCP and static IP configurations on systems with multiple network interfaces, for example:

ip=enp1s0:dhcp
ip=10.10.10.2::10.10.10.254:255.255.255.0:core0.example.com:enp2s0:none
Configuring VLANs on individual interfaces

Optional: You can configure VLANs on individual interfaces by using the vlan= parameter.

  • To configure a VLAN on a network interface and use a static IP address, run the following command:

    ip=10.10.10.2::10.10.10.254:255.255.255.0:core0.example.com:enp2s0.100:none
vlan=enp2s0.100:enp2s0

  • To configure a VLAN on a network interface and to use DHCP, run the following command:

    ip=enp2s0.100:dhcp
vlan=enp2s0.100:enp2s0
Providing multiple DNS servers

You can provide multiple DNS servers by adding a nameserver= entry for each server, for example:

nameserver=1.1.1.1
nameserver=8.8.8.8
Bonding multiple network interfaces to a single interface

Optional: You can bond multiple network interfaces to a single interface by using the bond= option. Refer to the following examples:

  • The syntax for configuring a bonded interface is: bond=<name>[:<network_interfaces>][:options]

    <name> is the bonding device name (bond0), <network_interfaces> represents a comma-separated list of physical (ethernet) interfaces (em1,em2), and options is a comma-separated list of bonding options. Enter modinfo bonding to see available options.

  • When you create a bonded interface using bond=, you must specify how the IP address is assigned and other information for the bonded interface.

    • To configure the bonded interface to use DHCP, set the bond’s IP address to dhcp. For example:

      bond=bond0:em1,em2:mode=active-backup
ip=bond0:dhcp

    • To configure the bonded interface to use a static IP address, enter the specific IP address you want and related information. For example:

      bond=bond0:em1,em2:mode=active-backup
ip=10.10.10.2::10.10.10.254:255.255.255.0:core0.example.com:bond0:none
Bonding multiple SR-IOV network interfaces to a dual port NIC interface

Support for Day 1 operations associated with enabling NIC partitioning for SR-IOV devices is a Technology Preview feature only. Technology Preview features are not supported with Red Hat production service level agreements (SLAs) and might not be functionally complete. Red Hat does not recommend using them in production. These features provide early access to upcoming product features, enabling customers to test functionality and provide feedback during the development process.

For more information about the support scope of Red Hat Technology Preview features, see Technology Preview Features Support Scope.

Optional: You can bond multiple SR-IOV network interfaces to a dual port NIC interface by using the bond= option.

On each node, you must perform the following tasks:

  1. Create the SR-IOV virtual functions (VFs) following the guidance in Managing SR-IOV devices. Follow the procedure in the "Attaching SR-IOV networking devices to virtual machines" section.

  2. Create the bond, attach the desired VFs to the bond and set the bond link state up following the guidance in Configuring network bonding. Follow any of the described procedures to create the bond.

The following examples illustrate the syntax you must use:

  • The syntax for configuring a bonded interface is bond=<name>[:<network_interfaces>][:options].

    <name> is the bonding device name (bond0), <network_interfaces> represents the virtual functions (VFs) by their known name in the kernel and shown in the output of the ip link command(eno1f0, eno2f0), and options is a comma-separated list of bonding options. Enter modinfo bonding to see available options.

  • When you create a bonded interface using bond=, you must specify how the IP address is assigned and other information for the bonded interface.

    • To configure the bonded interface to use DHCP, set the bond’s IP address to dhcp. For example:

      bond=bond0:eno1f0,eno2f0:mode=active-backup
ip=bond0:dhcp

    • To configure the bonded interface to use a static IP address, enter the specific IP address you want and related information. For example:

      bond=bond0:eno1f0,eno2f0:mode=active-backup
ip=10.10.10.2::10.10.10.254:255.255.255.0:core0.example.com:bond0:none
Using network teaming

Optional: You can use a network teaming as an alternative to bonding by using the team= parameter:

  • The syntax for configuring a team interface is: team=name[:network_interfaces]

    name is the team device name (team0) and network_interfaces represents a comma-separated list of physical (ethernet) interfaces (em1, em2).

Teaming is planned to be deprecated when RHCOS switches to an upcoming version of RHEL. For more information, see this Red Hat Knowledgebase Article.

Use the following example to configure a network team:

team=team0:em1,em2
ip=team0:dhcp
coreos-installer options for ISO and PXE installations

You can install RHCOS by running coreos-installer install <options> <device> at the command prompt, after booting into the RHCOS live environment from an ISO image.

The following table shows the subcommands, options, and arguments you can pass to the coreos-installer command.

Table 19. coreos-installer subcommands, command-line options, and arguments

coreos-installer install subcommand

Subcommand

Description

$ coreos-installer install <options> <device>

Embed an Ignition config in an ISO image.

coreos-installer install subcommand options

Option

Description

-u, --image-url <url>

Specify the image URL manually.

-f, --image-file <path>

Specify a local image file manually. Used for debugging.

-i, --ignition-file <path>

Embed an Ignition config from a file.

-I, --ignition-url <URL>

Embed an Ignition config from a URL.

--ignition-hash <digest>

Digest type-value of the Ignition config.

-p, --platform <name>

Override the Ignition platform ID for the installed system.

--console <spec>

Set the kernel and bootloader console for the installed system. For more information about the format of <spec>, see the Linux kernel serial console documentation.

--append-karg <arg>…​

Append a default kernel argument to the installed system.

--delete-karg <arg>…​

Delete a default kernel argument from the installed system.

-n, --copy-network

Copy the network configuration from the install environment.

The --copy-network option only copies networking configuration found under /etc/NetworkManager/system-connections. In particular, it does not copy the system hostname.

--network-dir <path>

For use with -n. Default is /etc/NetworkManager/system-connections/.

--save-partlabel <lx>..

Save partitions with this label glob.

--save-partindex <id>…​

Save partitions with this number or range.

--insecure

Skip RHCOS image signature verification.

--insecure-ignition

Allow Ignition URL without HTTPS or hash.

--architecture <name>

Target CPU architecture. Valid values are x86_64 and aarch64.

--preserve-on-error

Do not clear partition table on error.

-h, --help

Print help information.

coreos-installer install subcommand argument

Argument

Description

<device>

The destination device.

coreos-installer ISO subcommands

Subcommand

Description

$ coreos-installer iso customize <options> <ISO_image>

Customize a RHCOS live ISO image.

coreos-installer iso reset <options> <ISO_image>

Restore a RHCOS live ISO image to default settings.

coreos-installer iso ignition remove <options> <ISO_image>

Remove the embedded Ignition config from an ISO image.

coreos-installer ISO customize subcommand options

Option

Description

--dest-ignition <path>

Merge the specified Ignition config file into a new configuration fragment for the destination system.

--dest-console <spec>

Specify the kernel and bootloader console for the destination system.

--dest-device <path>

Install and overwrite the specified destination device.

--dest-karg-append <arg>

Add a kernel argument to each boot of the destination system.

--dest-karg-delete <arg>

Delete a kernel argument from each boot of the destination system.

--network-keyfile <path>

Configure networking by using the specified NetworkManager keyfile for live and destination systems.

--ignition-ca <path>

Specify an additional TLS certificate authority to be trusted by Ignition.

--pre-install <path>

Run the specified script before installation.

--post-install <path>

Run the specified script after installation.

--installer-config <path>

Apply the specified installer configuration file.

--live-ignition <path>

Merge the specified Ignition config file into a new configuration fragment for the live environment.

--live-karg-append <arg>

Add a kernel argument to each boot of the live environment.

--live-karg-delete <arg>

Delete a kernel argument from each boot of the live environment.

--live-karg-replace <k=o=n>

Replace a kernel argument in each boot of the live environment, in the form key=old=new.

-f, --force

Overwrite an existing Ignition config.

-o, --output <path>

Write the ISO to a new output file.

-h, --help

Print help information.

coreos-installer PXE subcommands

Subcommand

Description

Note that not all of these options are accepted by all subcommands.

coreos-installer pxe customize <options> <path>

Customize a RHCOS live PXE boot config.

coreos-installer pxe ignition wrap <options>

Wrap an Ignition config in an image.

coreos-installer pxe ignition unwrap <options> <image_name>

Show the wrapped Ignition config in an image.

coreos-installer PXE customize subcommand options

Option

Description

Note that not all of these options are accepted by all subcommands.

--dest-ignition <path>

Merge the specified Ignition config file into a new configuration fragment for the destination system.

--dest-console <spec>

Specify the kernel and bootloader console for the destination system.

--dest-device <path>

Install and overwrite the specified destination device.

--network-keyfile <path>

Configure networking by using the specified NetworkManager keyfile for live and destination systems.

--ignition-ca <path>

Specify an additional TLS certificate authority to be trusted by Ignition.

--pre-install <path>

Run the specified script before installation.

post-install <path>

Run the specified script after installation.

--installer-config <path>

Apply the specified installer configuration file.

--live-ignition <path>

Merge the specified Ignition config file into a new configuration fragment for the live environment.

-o, --output <path>

Write the initramfs to a new output file.

This option is required for PXE environments.

-h, --help

Print help information.
coreos.inst boot options for ISO or PXE installations

You can automatically invoke coreos-installer options at boot time by passing coreos.inst boot arguments to the RHCOS live installer. These are provided in addition to the standard boot arguments.

  • For ISO installations, the coreos.inst options can be added by interrupting the automatic boot at the bootloader menu. You can interrupt the automatic boot by pressing TAB while the RHEL CoreOS (Live) menu option is highlighted.

  • For PXE or iPXE installations, the coreos.inst options must be added to the APPEND line before the RHCOS live installer is booted.

The following table shows the RHCOS live installer coreos.inst boot options for ISO and PXE installations.

Table 20. coreos.inst boot options
Argument Description

coreos.inst.install_dev

Required. The block device on the system to install to. It is recommended to use the full path, such as /dev/sda, although sda is allowed.

coreos.inst.ignition_url

Optional: The URL of the Ignition config to embed into the installed system. If no URL is specified, no Ignition config is embedded. Only HTTP and HTTPS protocols are supported.

coreos.inst.save_partlabel

Optional: Comma-separated labels of partitions to preserve during the install. Glob-style wildcards are permitted. The specified partitions do not need to exist.

coreos.inst.save_partindex

Optional: Comma-separated indexes of partitions to preserve during the install. Ranges m-n are permitted, and either m or n can be omitted. The specified partitions do not need to exist.

coreos.inst.insecure

Optional: Permits the OS image that is specified by coreos.inst.image_url to be unsigned.

coreos.inst.image_url

Optional: Download and install the specified RHCOS image.

  • This argument should not be used in production environments and is intended for debugging purposes only.

  • While this argument can be used to install a version of RHCOS that does not match the live media, it is recommended that you instead use the media that matches the version you want to install.

  • If you are using coreos.inst.image_url, you must also use coreos.inst.insecure. This is because the bare-metal media are not GPG-signed for OpenShift Container Platform.

  • Only HTTP and HTTPS protocols are supported.

coreos.inst.skip_reboot

Optional: The system will not reboot after installing. After the install finishes, you will receive a prompt that allows you to inspect what is happening during installation. This argument should not be used in production environments and is intended for debugging purposes only.

coreos.inst.platform_id

Optional: The Ignition platform ID of the platform the RHCOS image is being installed on. Default is metal. This option determines whether or not to request an Ignition config from the cloud provider, such as VMware. For example: coreos.inst.platform_id=vmware.

ignition.config.url

Optional: The URL of the Ignition config for the live boot. For example, this can be used to customize how coreos-installer is invoked, or to run code before or after the installation. This is different from coreos.inst.ignition_url, which is the Ignition config for the installed system.

Enabling multipathing with kernel arguments on RHCOS

RHCOS supports multipathing on the primary disk, allowing stronger resilience to hardware failure to achieve higher host availability.

You can enable multipathing at installation time for nodes that were provisioned in OpenShift Container Platform 4.8 or later. While postinstallation support is available by activating multipathing via the machine config, enabling multipathing during installation is recommended.

In setups where any I/O to non-optimized paths results in I/O system errors, you must enable multipathing at installation time.

On IBM Z and IBM® LinuxONE, you can enable multipathing only if you configured your cluster for it during installation. For more information, see "Installing RHCOS and starting the OpenShift Container Platform bootstrap process" in Installing a cluster with z/VM on IBM Z and IBM® LinuxONE.

The following procedure enables multipath at installation time and appends kernel arguments to the coreos-installer install command so that the installed system itself will use multipath beginning from the first boot.

OpenShift Container Platform does not support enabling multipathing as a day-2 activity on nodes that have been upgraded from 4.6 or earlier.
Prerequisites

  • You have created the Ignition config files for your cluster.

  • You have reviewed Installing RHCOS and starting the OpenShift Container Platform bootstrap process.

Procedure

  1. To enable multipath and start the multipathd daemon, run the following command on the installation host:

    $ mpathconf --enable && systemctl start multipathd.service

    • Optional: If booting the PXE or ISO, you can instead enable multipath by adding rd.multipath=default from the kernel command line.

  2. Append the kernel arguments by invoking the coreos-installer program:

    • If there is only one multipath device connected to the machine, it should be available at path /dev/mapper/mpatha. For example:

      $ coreos-installer install /dev/mapper/mpatha \(1)
--ignition-url=http://host/worker.ign \
--append-karg rd.multipath=default \
--append-karg root=/dev/disk/by-label/dm-mpath-root \
--append-karg rw
      1 Indicates the path of the single multipathed device.

    • If there are multiple multipath devices connected to the machine, or to be more explicit, instead of using /dev/mapper/mpatha, it is recommended to use the World Wide Name (WWN) symlink available in /dev/disk/by-id. For example:

      $ coreos-installer install /dev/disk/by-id/wwn-<wwn_ID> \(1)
--ignition-url=http://host/worker.ign \
--append-karg rd.multipath=default \
--append-karg root=/dev/disk/by-label/dm-mpath-root \
--append-karg rw
      1 Indicates the WWN ID of the target multipathed device. For example, 0xx194e957fcedb4841.

      This symlink can also be used as the coreos.inst.install_dev kernel argument when using special coreos.inst.* arguments to direct the live installer. For more information, see "Installing RHCOS and starting the OpenShift Container Platform bootstrap process".

  3. Reboot into the installed system.

  4. Check that the kernel arguments worked by going to one of the worker nodes and listing the kernel command line arguments (in /proc/cmdline on the host):

    $ oc debug node/ip-10-0-141-105.ec2.internal
    Example output
    Starting pod/ip-10-0-141-105ec2internal-debug ...
To use host binaries, run `chroot /host`

sh-4.2# cat /host/proc/cmdline
...
rd.multipath=default root=/dev/disk/by-label/dm-mpath-root
...

sh-4.2# exit

    You should see the added kernel arguments.

Enabling multipathing on secondary disks

RHCOS also supports multipathing on a secondary disk. Instead of kernel arguments, you use Ignition to enable multipathing for the secondary disk at installation time.

Prerequisites

  • You have read the section Disk partitioning.

  • You have read Enabling multipathing with kernel arguments on RHCOS.

  • You have installed the Butane utility.

Procedure

  1. Create a Butane config with information similar to the following:

    Example multipath-config.bu
    variant: openshift
version: {product-version}.0
systemd:
  units:
    - name: mpath-configure.service
      enabled: true
      contents: |
        [Unit]
        Description=Configure Multipath on Secondary Disk
        ConditionFirstBoot=true
        ConditionPathExists=!/etc/multipath.conf
        Before=multipathd.service (1)
        DefaultDependencies=no

        [Service]
        Type=oneshot
        ExecStart=/usr/sbin/mpathconf --enable (2)

        [Install]
        WantedBy=multi-user.target
    - name: mpath-var-lib-container.service
      enabled: true
      contents: |
        [Unit]
        Description=Set Up Multipath On /var/lib/containers
        ConditionFirstBoot=true (3)
        Requires=dev-mapper-mpatha.device
        After=dev-mapper-mpatha.device
        After=ostree-remount.service
        Before=kubelet.service
        DefaultDependencies=no

        [Service] (4)
        Type=oneshot
        ExecStart=/usr/sbin/mkfs.xfs -L containers -m reflink=1 /dev/mapper/mpatha
        ExecStart=/usr/bin/mkdir -p /var/lib/containers

        [Install]
        WantedBy=multi-user.target
    - name: var-lib-containers.mount
      enabled: true
      contents: |
        [Unit]
        Description=Mount /var/lib/containers
        After=mpath-var-lib-containers.service
        Before=kubelet.service (5)

        [Mount] (6)
        What=/dev/disk/by-label/dm-mpath-containers
        Where=/var/lib/containers
        Type=xfs

        [Install]
        WantedBy=multi-user.target
    1 The configuration must be set before launching the multipath daemon.
    2 Starts the mpathconf utility.
    3 This field must be set to the value true.
    4 Creates the filesystem and directory /var/lib/containers.
    5 The device must be mounted before starting any nodes.
    6 Mounts the device to the /var/lib/containers mount point. This location cannot be a symlink.

  2. Create the Ignition configuration by running the following command:

    $ butane --pretty --strict multipath-config.bu > multipath-config.ign

  3. Continue with the rest of the first boot RHCOS installation process.

    Do not add the rd.multipath or root kernel arguments on the command-line during installation unless the primary disk is also multipathed.

Waiting for the bootstrap process to complete

The OpenShift Container Platform bootstrap process begins after the cluster nodes first boot into the persistent RHCOS environment that has been installed to disk. The configuration information provided through the Ignition config files is used to initialize the bootstrap process and install OpenShift Container Platform on the machines. You must wait for the bootstrap process to complete.

Prerequisites

  • You have created the Ignition config files for your cluster.

  • You have configured suitable network, DNS and load balancing infrastructure.

  • You have obtained the installation program and generated the Ignition config files for your cluster.

  • You installed RHCOS on your cluster machines and provided the Ignition config files that the OpenShift Container Platform installation program generated.

  • Your machines have direct internet access or have an HTTP or HTTPS proxy available.

Procedure

  1. Monitor the bootstrap process:

    $ ./openshift-install --dir <installation_directory> wait-for bootstrap-complete \ (1)
    --log-level=info (2)
    1 For <installation_directory>, specify the path to the directory that you stored the installation files in.
    2 To view different installation details, specify warn, debug, or error instead of info.
    Example output
    INFO Waiting up to 30m0s for the Kubernetes API at https://api.test.example.com:6443...
INFO API v1.26.0 up
INFO Waiting up to 30m0s for bootstrapping to complete...
INFO It is now safe to remove the bootstrap resources

    The command succeeds when the Kubernetes API server signals that it has been bootstrapped on the control plane machines.

  2. After the bootstrap process is complete, remove the bootstrap machine from the load balancer.

    You must remove the bootstrap machine from the load balancer at this point. You can also remove or reformat the bootstrap machine itself.
Additional resources

Logging in to the cluster by using the CLI

You can log in to your cluster as a default system user by exporting the cluster kubeconfig file. The kubeconfig file contains information about the cluster that is used by the CLI to connect a client to the correct cluster and API server. The file is specific to a cluster and is created during OpenShift Container Platform installation.

Prerequisites

  • You deployed an OpenShift Container Platform cluster.

  • You installed the oc CLI.

Procedure

  1. Export the kubeadmin credentials:

    $ export KUBECONFIG=<installation_directory>/auth/kubeconfig (1)
    1 For <installation_directory>, specify the path to the directory that you stored the installation files in.

  2. Verify you can run oc commands successfully using the exported configuration:

    $ oc whoami
    Example output
    system:admin

Approving the certificate signing requests for your machines

When you add machines to a cluster, two pending certificate signing requests (CSRs) are generated for each machine that you added. You must confirm that these CSRs are approved or, if necessary, approve them yourself. The client requests must be approved first, followed by the server requests.

Prerequisites

  • You added machines to your cluster.

Procedure

  1. Confirm that the cluster recognizes the machines:

    $ oc get nodes
    Example output
    NAME      STATUS    ROLES   AGE  VERSION
master-0  Ready     master  63m  v1.26.0
master-1  Ready     master  63m  v1.26.0
master-2  Ready     master  64m  v1.26.0

    The output lists all of the machines that you created.

    The preceding output might not include the compute nodes, also known as worker nodes, until some CSRs are approved.

  2. Review the pending CSRs and ensure that you see the client requests with the Pending or Approved status for each machine that you added to the cluster:

    $ oc get csr
    Example output
    NAME        AGE     REQUESTOR                                                                   CONDITION
csr-8b2br   15m     system:serviceaccount:openshift-machine-config-operator:node-bootstrapper   Pending
csr-8vnps   15m     system:serviceaccount:openshift-machine-config-operator:node-bootstrapper   Pending
...

    In this example, two machines are joining the cluster. You might see more approved CSRs in the list.

  3. If the CSRs were not approved, after all of the pending CSRs for the machines you added are in Pending status, approve the CSRs for your cluster machines:

    Because the CSRs rotate automatically, approve your CSRs within an hour of adding the machines to the cluster. If you do not approve them within an hour, the certificates will rotate, and more than two certificates will be present for each node. You must approve all of these certificates. After the client CSR is approved, the Kubelet creates a secondary CSR for the serving certificate, which requires manual approval. Then, subsequent serving certificate renewal requests are automatically approved by the machine-approver if the Kubelet requests a new certificate with identical parameters.

    For clusters running on platforms that are not machine API enabled, such as bare metal and other user-provisioned infrastructure, you must implement a method of automatically approving the kubelet serving certificate requests (CSRs). If a request is not approved, then the oc exec, oc rsh, and oc logs commands cannot succeed, because a serving certificate is required when the API server connects to the kubelet. Any operation that contacts the Kubelet endpoint requires this certificate approval to be in place. The method must watch for new CSRs, confirm that the CSR was submitted by the node-bootstrapper service account in the system:node or system:admin groups, and confirm the identity of the node.

    • To approve them individually, run the following command for each valid CSR:

      $ oc adm certificate approve <csr_name> (1)
      1 <csr_name> is the name of a CSR from the list of current CSRs.

    • To approve all pending CSRs, run the following command:

      $ oc get csr -o go-template='{{range .items}}{{if not .status}}{{.metadata.name}}{{"\n"}}{{end}}{{end}}' | xargs --no-run-if-empty oc adm certificate approve

      Some Operators might not become available until some CSRs are approved.

  4. Now that your client requests are approved, you must review the server requests for each machine that you added to the cluster:

    $ oc get csr
    Example output
    NAME        AGE     REQUESTOR                                                                   CONDITION
csr-bfd72   5m26s   system:node:ip-10-0-50-126.us-east-2.compute.internal                       Pending
csr-c57lv   5m26s   system:node:ip-10-0-95-157.us-east-2.compute.internal                       Pending
...

  5. If the remaining CSRs are not approved, and are in the Pending status, approve the CSRs for your cluster machines:

    • To approve them individually, run the following command for each valid CSR:

      $ oc adm certificate approve <csr_name> (1)
      1 <csr_name> is the name of a CSR from the list of current CSRs.

    • To approve all pending CSRs, run the following command:

      $ oc get csr -o go-template='{{range .items}}{{if not .status}}{{.metadata.name}}{{"\n"}}{{end}}{{end}}' | xargs oc adm certificate approve

  6. After all client and server CSRs have been approved, the machines have the Ready status. Verify this by running the following command:

    $ oc get nodes
    Example output
    NAME      STATUS    ROLES   AGE  VERSION
master-0  Ready     master  73m  v1.26.0
master-1  Ready     master  73m  v1.26.0
master-2  Ready     master  74m  v1.26.0
worker-0  Ready     worker  11m  v1.26.0
worker-1  Ready     worker  11m  v1.26.0

    It can take a few minutes after approval of the server CSRs for the machines to transition to the Ready status.
Additional information

Initial Operator configuration

After the control plane initializes, you must immediately configure some Operators so that they all become available.

Prerequisites

  • Your control plane has initialized.

Procedure

  1. Watch the cluster components come online:

    $ watch -n5 oc get clusteroperators
    Example output
    NAME                                       VERSION   AVAILABLE   PROGRESSING   DEGRADED   SINCE
authentication                             4.13.0    True        False         False      19m
baremetal                                  4.13.0    True        False         False      37m
cloud-credential                           4.13.0    True        False         False      40m
cluster-autoscaler                         4.13.0    True        False         False      37m
config-operator                            4.13.0    True        False         False      38m
console                                    4.13.0    True        False         False      26m
csi-snapshot-controller                    4.13.0    True        False         False      37m
dns                                        4.13.0    True        False         False      37m
etcd                                       4.13.0    True        False         False      36m
image-registry                             4.13.0    True        False         False      31m
ingress                                    4.13.0    True        False         False      30m
insights                                   4.13.0    True        False         False      31m
kube-apiserver                             4.13.0    True        False         False      26m
kube-controller-manager                    4.13.0    True        False         False      36m
kube-scheduler                             4.13.0    True        False         False      36m
kube-storage-version-migrator              4.13.0    True        False         False      37m
machine-api                                4.13.0    True        False         False      29m
machine-approver                           4.13.0    True        False         False      37m
machine-config                             4.13.0    True        False         False      36m
marketplace                                4.13.0    True        False         False      37m
monitoring                                 4.13.0    True        False         False      29m
network                                    4.13.0    True        False         False      38m
node-tuning                                4.13.0    True        False         False      37m
openshift-apiserver                        4.13.0    True        False         False      32m
openshift-controller-manager               4.13.0    True        False         False      30m
openshift-samples                          4.13.0    True        False         False      32m
operator-lifecycle-manager                 4.13.0    True        False         False      37m
operator-lifecycle-manager-catalog         4.13.0    True        False         False      37m
operator-lifecycle-manager-packageserver   4.13.0    True        False         False      32m
service-ca                                 4.13.0    True        False         False      38m
storage                                    4.13.0    True        False         False      37m

  2. Configure the Operators that are not available.

Additional resources

Image registry removed during installation

On platforms that do not provide shareable object storage, the OpenShift Image Registry Operator bootstraps itself as Removed. This allows openshift-installer to complete installations on these platform types.

After installation, you must edit the Image Registry Operator configuration to switch the managementState from Removed to Managed. When this has completed, you must configure storage.

Image registry storage configuration

The Image Registry Operator is not initially available for platforms that do not provide default storage. After installation, you must configure your registry to use storage so that the Registry Operator is made available.

Instructions are shown for configuring a persistent volume, which is required for production clusters. Where applicable, instructions are shown for configuring an empty directory as the storage location, which is available for only non-production clusters.

Additional instructions are provided for allowing the image registry to use block storage types by using the Recreate rollout strategy during upgrades.

Configuring block registry storage for bare metal

To allow the image registry to use block storage types during upgrades as a cluster administrator, you can use the Recreate rollout strategy.

Block storage volumes, or block persistent volumes, are supported but not recommended for use with the image registry on production clusters. An installation where the registry is configured on block storage is not highly available because the registry cannot have more than one replica.

If you choose to use a block storage volume with the image registry, you must use a filesystem persistent volume claim (PVC).
Procedure

  1. Enter the following command to set the image registry storage as a block storage type, patch the registry so that it uses the Recreate rollout strategy, and runs with only one (1) replica:

    $ oc patch config.imageregistry.operator.openshift.io/cluster --type=merge -p '{"spec":{"rolloutStrategy":"Recreate","replicas":1}}'

  2. Provision the PV for the block storage device, and create a PVC for that volume. The requested block volume uses the ReadWriteOnce (RWO) access mode.

    1. Create a pvc.yaml file with the following contents to define a VMware vSphere PersistentVolumeClaim object:

      kind: PersistentVolumeClaim
apiVersion: v1
metadata:
  name: image-registry-storage (1)
  namespace: openshift-image-registry (2)
spec:
  accessModes:
  - ReadWriteOnce (3)
  resources:
    requests:
      storage: 100Gi (4)
      1 A unique name that represents the PersistentVolumeClaim object.
      2 The namespace for the PersistentVolumeClaim object, which is openshift-image-registry.
      3 The access mode of the persistent volume claim. With ReadWriteOnce, the volume can be mounted with read and write permissions by a single node.
      4 The size of the persistent volume claim.

    2. Enter the following command to create the PersistentVolumeClaim object from the file:

      $ oc create -f pvc.yaml -n openshift-image-registry

  3. Enter the following command to edit the registry configuration so that it references the correct PVC:

    $ oc edit config.imageregistry.operator.openshift.io -o yaml
    Example output
    storage:
  pvc:
    claim: (1)
    1 By creating a custom PVC, you can leave the claim field blank for the default automatic creation of an image-registry-storage PVC.

Completing installation on user-provisioned infrastructure

After you complete the Operator configuration, you can finish installing the cluster on infrastructure that you provide.

Prerequisites

  • Your control plane has initialized.

  • You have completed the initial Operator configuration.

Procedure

  1. Confirm that all the cluster components are online with the following command:

    $ watch -n5 oc get clusteroperators
    Example output
    NAME                                       VERSION   AVAILABLE   PROGRESSING   DEGRADED   SINCE
authentication                             4.13.0    True        False         False      19m
baremetal                                  4.13.0    True        False         False      37m
cloud-credential                           4.13.0    True        False         False      40m
cluster-autoscaler                         4.13.0    True        False         False      37m
config-operator                            4.13.0    True        False         False      38m
console                                    4.13.0    True        False         False      26m
csi-snapshot-controller                    4.13.0    True        False         False      37m
dns                                        4.13.0    True        False         False      37m
etcd                                       4.13.0    True        False         False      36m
image-registry                             4.13.0    True        False         False      31m
ingress                                    4.13.0    True        False         False      30m
insights                                   4.13.0    True        False         False      31m
kube-apiserver                             4.13.0    True        False         False      26m
kube-controller-manager                    4.13.0    True        False         False      36m
kube-scheduler                             4.13.0    True        False         False      36m
kube-storage-version-migrator              4.13.0    True        False         False      37m
machine-api                                4.13.0    True        False         False      29m
machine-approver                           4.13.0    True        False         False      37m
machine-config                             4.13.0    True        False         False      36m
marketplace                                4.13.0    True        False         False      37m
monitoring                                 4.13.0    True        False         False      29m
network                                    4.13.0    True        False         False      38m
node-tuning                                4.13.0    True        False         False      37m
openshift-apiserver                        4.13.0    True        False         False      32m
openshift-controller-manager               4.13.0    True        False         False      30m
openshift-samples                          4.13.0    True        False         False      32m
operator-lifecycle-manager                 4.13.0    True        False         False      37m
operator-lifecycle-manager-catalog         4.13.0    True        False         False      37m
operator-lifecycle-manager-packageserver   4.13.0    True        False         False      32m
service-ca                                 4.13.0    True        False         False      38m
storage                                    4.13.0    True        False         False      37m

    Alternatively, the following command notifies you when all of the clusters are available. It also retrieves and displays credentials:

    $ ./openshift-install --dir <installation_directory> wait-for install-complete (1)
    1 For <installation_directory>, specify the path to the directory that you stored the installation files in.
    Example output
    INFO Waiting up to 30m0s for the cluster to initialize...

    The command succeeds when the Cluster Version Operator finishes deploying the OpenShift Container Platform cluster from Kubernetes API server.

    • The Ignition config files that the installation program generates contain certificates that expire after 24 hours, which are then renewed at that time. If the cluster is shut down before renewing the certificates and the cluster is later restarted after the 24 hours have elapsed, the cluster automatically recovers the expired certificates. The exception is that you must manually approve the pending node-bootstrapper certificate signing requests (CSRs) to recover kubelet certificates. See the documentation for Recovering from expired control plane certificates for more information.

    • It is recommended that you use Ignition config files within 12 hours after they are generated because the 24-hour certificate rotates from 16 to 22 hours after the cluster is installed. By using the Ignition config files within 12 hours, you can avoid installation failure if the certificate update runs during installation.

  2. Confirm that the Kubernetes API server is communicating with the pods.

    1. To view a list of all pods, use the following command:

      $ oc get pods --all-namespaces
      Example output
      NAMESPACE                         NAME                                            READY   STATUS      RESTARTS   AGE
openshift-apiserver-operator      openshift-apiserver-operator-85cb746d55-zqhs8   1/1     Running     1          9m
openshift-apiserver               apiserver-67b9g                                 1/1     Running     0          3m
openshift-apiserver               apiserver-ljcmx                                 1/1     Running     0          1m
openshift-apiserver               apiserver-z25h4                                 1/1     Running     0          2m
openshift-authentication-operator authentication-operator-69d5d8bf84-vh2n8        1/1     Running     0          5m
...

    2. View the logs for a pod that is listed in the output of the previous command by using the following command:

      $ oc logs <pod_name> -n <namespace> (1)
      1 Specify the pod name and namespace, as shown in the output of the previous command.

      If the pod logs display, the Kubernetes API server can communicate with the cluster machines.

  3. For an installation with Fibre Channel Protocol (FCP), additional steps are required to enable multipathing. Do not enable multipathing during installation.

    See "Enabling multipathing with kernel arguments on RHCOS" in the Post-installation machine configuration tasks documentation for more information.

Telemetry access for OpenShift Container Platform

In OpenShift Container Platform 4.13, the Telemetry service, which runs by default to provide metrics about cluster health and the success of updates, requires internet access. If your cluster is connected to the internet, Telemetry runs automatically, and your cluster is registered to OpenShift Cluster Manager Hybrid Cloud Console.

After you confirm that your OpenShift Cluster Manager Hybrid Cloud Console inventory is correct, either maintained automatically by Telemetry or manually by using OpenShift Cluster Manager, use subscription watch to track your OpenShift Container Platform subscriptions at the account or multi-cluster level.

Additional resources

Next steps