$ curl https://mirror.openshift.com/pub/openshift-v4/clients/butane/latest/butane --output butane
OpenShift Container Platform supports both cluster-wide and per-machine configuration via Ignition, which allows arbitrary partitioning and file content changes to the operating system. In general, if a configuration file is documented in Red Hat Enterprise Linux (RHEL), then modifying it via Ignition is supported.
There are two ways to deploy machine config changes:
Creating machine configs that are included in manifest files
to start up a cluster during openshift-install
.
Creating machine configs that are passed to running OpenShift Container Platform nodes via the Machine Config Operator.
Additionally, modifying the reference config, such as
the Ignition config that is passed to coreos-installer
when installing bare-metal nodes
allows per-machine configuration. These changes are currently not visible
to the Machine Config Operator.
The following sections describe features that you might want to configure on your nodes in this way.
Machine configs are used to configure control plane and worker machines by instructing machines how to create users and file systems, set up the network, install systemd units, and more.
Because modifying machine configs can be difficult, you can use Butane configs to create machine configs for you, thereby making node configuration much easier.
Butane is a command-line utility that OpenShift Container Platform uses to provide convenient, short-hand syntax for writing machine configs, as well as for performing additional validation of machine configs. The format of the Butane config file that Butane accepts is defined in the OpenShift Butane config spec.
You can install the Butane tool (butane
) to create OpenShift Container Platform machine configs from a command-line interface. You can install butane
on Linux, Windows, or macOS by downloading the corresponding binary file.
Butane releases are backwards-compatible with older releases and with the Fedora CoreOS Config Transpiler (FCCT). |
Navigate to the Butane image download page at https://mirror.openshift.com/pub/openshift-v4/clients/butane/.
Get the butane
binary:
For the newest version of Butane, save the latest butane
image to your current directory:
$ curl https://mirror.openshift.com/pub/openshift-v4/clients/butane/latest/butane --output butane
Optional: For a specific type of architecture you are installing Butane on, such as aarch64 or ppc64le, indicate the appropriate URL. For example:
$ curl https://mirror.openshift.com/pub/openshift-v4/clients/butane/latest/butane-aarch64 --output butane
Make the downloaded binary file executable:
$ chmod +x butane
Move the butane
binary file to a directory on your PATH
.
To check your PATH
, open a terminal and execute the following command:
$ echo $PATH
You can now use the Butane tool by running the butane
command:
$ butane <butane_file>
You can use Butane to produce a MachineConfig
object so that you can configure worker or control plane nodes at installation time or via the Machine Config Operator.
You have installed the butane
utility.
Create a Butane config file. The following example creates a file named 99-worker-custom.bu
that configures the system console to show kernel debug messages and specifies custom settings for the chrony time service:
variant: openshift
version: 4.15.0
metadata:
name: 99-worker-custom
labels:
machineconfiguration.openshift.io/role: worker
openshift:
kernel_arguments:
- loglevel=7
storage:
files:
- path: /etc/chrony.conf
mode: 0644
overwrite: true
contents:
inline: |
pool 0.rhel.pool.ntp.org iburst
driftfile /var/lib/chrony/drift
makestep 1.0 3
rtcsync
logdir /var/log/chrony
The |
Create a MachineConfig
object by giving Butane the file that you created in the previous step:
$ butane 99-worker-custom.bu -o ./99-worker-custom.yaml
A MachineConfig
object YAML file is created for you to finish configuring your machines.
Save the Butane config in case you need to update the MachineConfig
object in the future.
If the cluster is not running yet, generate manifest files and add the MachineConfig
object YAML file to the openshift
directory. If the cluster is already running, apply the file as follows:
$ oc create -f 99-worker-custom.yaml
Although it is often preferable to modify kernel arguments as a day-2 activity, you might want to add kernel arguments to all master or worker nodes during initial cluster installation. Here are some reasons you might want to add kernel arguments during cluster installation so they take effect before the systems first boot up:
You need to do some low-level network configuration before the systems start.
You want to disable a feature, such as SELinux, so it has no impact on the systems when they first come up.
Disabling SELinux on RHCOS in production is not supported. Once SELinux has been disabled on a node, it must be re-provisioned before re-inclusion in a production cluster. |
To add kernel arguments to master or worker nodes, you can create a MachineConfig
object
and inject that object into the set of manifest files used by Ignition during
cluster setup.
For a listing of arguments you can pass to a RHEL 8 kernel at boot time, see Kernel.org kernel parameters. It is best to only add kernel arguments with this procedure if they are needed to complete the initial OpenShift Container Platform installation.
Change to the directory that contains the installation program and generate the Kubernetes manifests for the cluster:
$ ./openshift-install create manifests --dir <installation_directory>
Decide if you want to add kernel arguments to worker or control plane nodes.
In the openshift
directory, create a file (for example,
99-openshift-machineconfig-master-kargs.yaml
) to define a MachineConfig
object to add the kernel settings.
This example adds a loglevel=7
kernel argument to control plane nodes:
$ cat << EOF > 99-openshift-machineconfig-master-kargs.yaml
apiVersion: machineconfiguration.openshift.io/v1
kind: MachineConfig
metadata:
labels:
machineconfiguration.openshift.io/role: master
name: 99-openshift-machineconfig-master-kargs
spec:
kernelArguments:
- loglevel=7
EOF
You can change master
to worker
to add kernel arguments to worker nodes instead.
Create a separate YAML file to add to both master and worker nodes.
You can now continue on to create the cluster.
For most common hardware, the Linux kernel includes the device driver modules needed to use that hardware when the computer starts up. For some hardware, however, modules are not available in Linux. Therefore, you must find a way to provide those modules to each host computer. This procedure describes how to do that for nodes in an OpenShift Container Platform cluster.
When a kernel module is first deployed by following these instructions, the module is made available for the current kernel. If a new kernel is installed, the kmods-via-containers software will rebuild and deploy the module so a compatible version of that module is available with the new kernel.
The way that this feature is able to keep the module up to date on each node is by:
Adding a systemd service to each node that starts at boot time to detect if a new kernel has been installed and
If a new kernel is detected, the service rebuilds the module and installs it to the kernel
For information on the software needed for this procedure, see the kmods-via-containers github site.
A few important issues to keep in mind:
This procedure is Technology Preview.
Software tools and examples are not yet available in official RPM form
and can only be obtained for now from unofficial github.com
sites noted in the procedure.
Third-party kernel modules you might add through these procedures are not supported by Red Hat.
In this procedure, the software needed to build your kernel modules is
deployed in a RHEL 8 container. Keep in mind that modules are rebuilt
automatically on each node when that node gets a new kernel. For that
reason, each node needs access to a yum
repository that contains the
kernel and related packages needed to rebuild the module. That content
is best provided with a valid RHEL subscription.
Before deploying kernel modules to your OpenShift Container Platform cluster, you can test the process on a separate RHEL system. Gather the kernel module’s source code, the KVC framework, and the kmod-via-containers software. Then build and test the module. To do that on a RHEL 8 system, do the following:
Register a RHEL 8 system:
# subscription-manager register
Attach a subscription to the RHEL 8 system:
# subscription-manager attach --auto
Install software that is required to build the software and container:
# yum install podman make git -y
Clone the kmod-via-containers
repository:
Create a folder for the repository:
$ mkdir kmods; cd kmods
Clone the repository:
$ git clone https://github.com/kmods-via-containers/kmods-via-containers
Install a KVC framework instance on your RHEL 8 build host to test the module.
This adds a kmods-via-container
systemd service and loads it:
Change to the kmod-via-containers
directory:
$ cd kmods-via-containers/
Install the KVC framework instance:
$ sudo make install
Reload the systemd manager configuration:
$ sudo systemctl daemon-reload
Get the kernel module source code. The source code might be used to
build a third-party module that you do not
have control over, but is supplied by others. You will need content
similar to the content shown in the kvc-simple-kmod
example that can
be cloned to your system as follows:
$ cd .. ; git clone https://github.com/kmods-via-containers/kvc-simple-kmod
Edit the configuration file, simple-kmod.conf
file, in this example, and
change the name of the Dockerfile to Dockerfile.rhel
:
Change to the kvc-simple-kmod
directory:
$ cd kvc-simple-kmod
Rename the Dockerfile:
$ cat simple-kmod.conf
KMOD_CONTAINER_BUILD_CONTEXT="https://github.com/kmods-via-containers/kvc-simple-kmod.git"
KMOD_CONTAINER_BUILD_FILE=Dockerfile.rhel
KMOD_SOFTWARE_VERSION=dd1a7d4
KMOD_NAMES="simple-kmod simple-procfs-kmod"
Create an instance of kmods-via-containers@.service
for your kernel module,
simple-kmod
in this example:
$ sudo make install
Enable the kmods-via-containers@.service
instance:
$ sudo kmods-via-containers build simple-kmod $(uname -r)
Enable and start the systemd service:
$ sudo systemctl enable kmods-via-containers@simple-kmod.service --now
Review the service status:
$ sudo systemctl status kmods-via-containers@simple-kmod.service
● kmods-via-containers@simple-kmod.service - Kmods Via Containers - simple-kmod
Loaded: loaded (/etc/systemd/system/kmods-via-containers@.service;
enabled; vendor preset: disabled)
Active: active (exited) since Sun 2020-01-12 23:49:49 EST; 5s ago...
To confirm that the kernel modules are loaded, use the lsmod
command to list the modules:
$ lsmod | grep simple_
simple_procfs_kmod 16384 0
simple_kmod 16384 0
Optional. Use other methods to check that the simple-kmod
example is working:
Look for a "Hello world" message in the kernel ring buffer with dmesg
:
$ dmesg | grep 'Hello world'
[ 6420.761332] Hello world from simple_kmod.
Check the value of simple-procfs-kmod
in /proc
:
$ sudo cat /proc/simple-procfs-kmod
simple-procfs-kmod number = 0
Run the spkut
command to get more information from the module:
$ sudo spkut 44
KVC: wrapper simple-kmod for 4.18.0-147.3.1.el8_1.x86_64
Running userspace wrapper using the kernel module container...
+ podman run -i --rm --privileged
simple-kmod-dd1a7d4:4.18.0-147.3.1.el8_1.x86_64 spkut 44
simple-procfs-kmod number = 0
simple-procfs-kmod number = 44
Going forward, when the system boots this service will check if a new kernel is running. If there is a new kernel, the service builds a new version of the kernel module and then loads it. If the module is already built, it will just load it.
Depending on whether or not you must have the kernel module in place when OpenShift Container Platform cluster first boots, you can set up the kernel modules to be deployed in one of two ways:
Provision kernel modules at cluster install time (day-1):
You can create the content as a MachineConfig
object and provide it to openshift-install
by including it with a set of manifest files.
Provision kernel modules via Machine Config Operator (day-2): If you can wait until the cluster is up and running to add your kernel module, you can deploy the kernel module software via the Machine Config Operator (MCO).
In either case, each node needs to be able to get the kernel packages and related software packages at the time that a new kernel is detected. There are a few ways you can set up each node to be able to obtain that content.
Provide RHEL entitlements to each node.
Get RHEL entitlements from an existing RHEL host, from the /etc/pki/entitlement
directory
and copy them to the same location as the other files you provide
when you build your Ignition config.
Inside the Dockerfile, add pointers to a yum
repository containing the kernel and other packages.
This must include new kernel packages as they are needed to match newly installed kernels.
By packaging kernel module software with a MachineConfig
object, you can
deliver that software to worker or control plane nodes at installation time
or via the Machine Config Operator.
Register a RHEL 8 system:
# subscription-manager register
Attach a subscription to the RHEL 8 system:
# subscription-manager attach --auto
Install software needed to build the software:
# yum install podman make git -y
Create a directory to host the kernel module and tooling:
$ mkdir kmods; cd kmods
Get the kmods-via-containers
software:
Clone the kmods-via-containers
repository:
$ git clone https://github.com/kmods-via-containers/kmods-via-containers
Clone the kvc-simple-kmod
repository:
$ git clone https://github.com/kmods-via-containers/kvc-simple-kmod
Get your module software. In this example, kvc-simple-kmod
is used.
Create a fakeroot directory and populate it with files that you want to deliver via Ignition, using the repositories cloned earlier:
Create the directory:
$ FAKEROOT=$(mktemp -d)
Change to the kmod-via-containers
directory:
$ cd kmods-via-containers
Install the KVC framework instance:
$ make install DESTDIR=${FAKEROOT}/usr/local CONFDIR=${FAKEROOT}/etc/
Change to the kvc-simple-kmod
directory:
$ cd ../kvc-simple-kmod
Create the instance:
$ make install DESTDIR=${FAKEROOT}/usr/local CONFDIR=${FAKEROOT}/etc/
Clone the fakeroot directory, replacing any symbolic links with copies of their targets, by running the following command:
$ cd .. && rm -rf kmod-tree && cp -Lpr ${FAKEROOT} kmod-tree
Create a Butane config file, 99-simple-kmod.bu
, that embeds the kernel module tree and enables the systemd service.
See "Creating machine configs with Butane" for information about Butane. |
variant: openshift
version: 4.15.0
metadata:
name: 99-simple-kmod
labels:
machineconfiguration.openshift.io/role: worker (1)
storage:
trees:
- local: kmod-tree
systemd:
units:
- name: kmods-via-containers@simple-kmod.service
enabled: true
1 | To deploy on control plane nodes, change worker to master . To deploy on both control plane and worker nodes, perform the remainder of these instructions once for each node type. |
Use Butane to generate a machine config YAML file, 99-simple-kmod.yaml
, containing the files and configuration to be delivered:
$ butane 99-simple-kmod.bu --files-dir . -o 99-simple-kmod.yaml
If the cluster is not up yet, generate manifest files and add this file to the
openshift
directory. If the cluster is already running, apply the file as follows:
$ oc create -f 99-simple-kmod.yaml
Your nodes will start the kmods-via-containers@simple-kmod.service
service and the kernel modules will be loaded.
To confirm that the kernel modules are loaded, you can log in to a node
(using oc debug node/<openshift-node>
, then chroot /host
).
To list the modules, use the lsmod
command:
$ lsmod | grep simple_
simple_procfs_kmod 16384 0
simple_kmod 16384 0
During an OpenShift Container Platform installation, you can enable boot disk encryption and mirroring on the cluster nodes.
You can enable encryption for the boot disks on the control plane and compute nodes at installation time. OpenShift Container Platform supports the Trusted Platform Module (TPM) v2 and Tang encryption modes.
This is the preferred mode. TPM v2 stores passphrases in a secure cryptoprocessor on the server. You can use this mode to prevent decryption of the boot disk data on a cluster node if the disk is removed from the server.
Tang and Clevis are server and client components that enable network-bound disk encryption (NBDE). You can bind the boot disk data on your cluster nodes to one or more Tang servers. This prevents decryption of the data unless the nodes are on a secure network where the Tang servers are accessible. Clevis is an automated decryption framework used to implement decryption on the client side.
The use of the Tang encryption mode to encrypt your disks is only supported for bare metal and vSphere installations on user-provisioned infrastructure. |
In earlier versions of Red Hat Enterprise Linux CoreOS (RHCOS), disk encryption was configured by specifying /etc/clevis.json
in the Ignition config.
That file is not supported in clusters created with OpenShift Container Platform 4.7 or later.
Configure disk encryption by using the following procedure.
When the TPM v2 or Tang encryption modes are enabled, the RHCOS boot disks are encrypted using the LUKS2 format.
This feature:
Is available for installer-provisioned infrastructure, user-provisioned infrastructure, and Assisted Installer deployments
For Assisted installer deployments:
Each cluster can only have a single encryption method, Tang or TPM
Encryption can be enabled on some or all nodes
There is no Tang threshold; all servers must be valid and operational
Encryption applies to the installation disks only, not to the workload disks
Is supported on Red Hat Enterprise Linux CoreOS (RHCOS) systems only
Sets up disk encryption during the manifest installation phase, encrypting all data written to disk, from first boot forward
Requires no user intervention for providing passphrases
Uses AES-256-XTS encryption, or AES-256-CBC if FIPS mode is enabled
In OpenShift Container Platform, you can specify a requirement for more than one Tang server. You can also configure the TPM v2 and Tang encryption modes simultaneously. This enables boot disk data decryption only if the TPM secure cryptoprocessor is present and the Tang servers are accessible over a secure network.
You can use the threshold
attribute in your Butane configuration to define the minimum number of TPM v2 and Tang encryption conditions required for decryption to occur.
The threshold is met when the stated value is reached through any combination of the declared conditions. In the case of offline provisioning, the offline server is accessed using an included advertisement, and only uses that supplied advertisement if the number of online servers do not meet the set threshold.
For example, the threshold
value of 2
in the following configuration can be reached by accessing two Tang servers, with the offline server available as a backup, or by accessing the TPM secure cryptoprocessor and one of the Tang servers:
variant: openshift
version: 4.15.0
metadata:
name: worker-storage
labels:
machineconfiguration.openshift.io/role: worker
boot_device:
layout: x86_64 (1)
luks:
tpm2: true (2)
tang: (3)
- url: http://tang1.example.com:7500
thumbprint: jwGN5tRFK-kF6pIX89ssF3khxxX
- url: http://tang2.example.com:7500
thumbprint: VCJsvZFjBSIHSldw78rOrq7h2ZF
- url: http://tang3.example.com:7500
thumbprint: PLjNyRdGw03zlRoGjQYMahSZGu9
advertisement: "{\"payload\": \"...\", \"protected\": \"...\", \"signature\": \"...\"}" (4)
threshold: 2 (5)
openshift:
fips: true
1 | Set this field to the instruction set architecture of the cluster nodes.
Some examples include, x86_64 , aarch64 , or ppc64le . |
2 | Include this field if you want to use a Trusted Platform Module (TPM) to encrypt the root file system. |
3 | Include this section if you want to use one or more Tang servers. |
4 | Optional: Include this field for offline provisioning. Ignition will provision the Tang server binding rather than fetching the advertisement from the server at runtime. This lets the server be unavailable at provisioning time. |
5 | Specify the minimum number of TPM v2 and Tang encryption conditions required for decryption to occur. |
The default |
If you require TPM v2 and Tang for decryption, the value of the |
During OpenShift Container Platform installation on control plane and worker nodes, you can enable mirroring of the boot and other disks to two or more redundant storage devices. A node continues to function after storage device failure provided one device remains available.
Mirroring does not support replacement of a failed disk. Reprovision the node to restore the mirror to a pristine, non-degraded state.
For user-provisioned infrastructure deployments, mirroring is available only on RHCOS systems.
Support for mirroring is available on |
You can enable and configure encryption and mirroring during an OpenShift Container Platform installation.
You have downloaded the OpenShift Container Platform installation program on your installation node.
You installed Butane on your installation node.
Butane is a command-line utility that OpenShift Container Platform uses to offer convenient, short-hand syntax for writing and validating machine configs. For more information, see "Creating machine configs with Butane". |
You have access to a Red Hat Enterprise Linux (RHEL) 8 machine that can be used to generate a thumbprint of the Tang exchange key.
If you want to use TPM v2 to encrypt your cluster, check to see if TPM v2 encryption needs to be enabled in the host firmware for each node. This is required on most Dell systems. Check the manual for your specific system.
If you want to use Tang to encrypt your cluster, follow these preparatory steps:
Set up a Tang server or access an existing one. See Network-bound disk encryption for instructions.
Install the clevis
package on a RHEL 8 machine, if it is not already installed:
$ sudo yum install clevis
On the RHEL 8 machine, run the following command to generate a thumbprint of the exchange key.
Replace http://tang1.example.com:7500
with the URL of your Tang server:
$ clevis-encrypt-tang '{"url":"http://tang1.example.com:7500"}' < /dev/null > /dev/null (1)
1 | In this example, tangd.socket is listening on port 7500 on the Tang server. |
The |
The advertisement contains the following signing keys:
PLjNyRdGw03zlRoGjQYMahSZGu9 (1)
1 | The thumbprint of the exchange key. |
When the Do you wish to trust these keys? [ynYN]
prompt displays, type Y
.
Optional: For offline Tang provisioning:
Obtain the advertisement from the server using the curl
command. Replace http://tang2.example.com:7500
with the URL of your Tang server:
$ curl -f http://tang2.example.com:7500/adv > adv.jws && cat adv.jws
{"payload": "eyJrZXlzIjogW3siYWxnIjogIkV", "protected": "eyJhbGciOiJFUzUxMiIsImN0eSI", "signature": "ADLgk7fZdE3Yt4FyYsm0pHiau7Q"}
Provide the advertisement file to Clevis for encryption:
$ clevis-encrypt-tang '{"url":"http://tang2.example.com:7500","adv":"adv.jws"}' < /dev/null > /dev/null
If the nodes are configured with static IP addressing, run coreos-installer iso customize --dest-karg-append
or use the coreos-installer
--append-karg
option when installing RHCOS nodes to set the IP address of the installed system.
Append the ip=
and other arguments needed for your network.
Some methods for configuring static IPs do not affect the initramfs after the first boot and will not work with Tang encryption.
These include the |
On your installation node, change to the directory that contains the installation program and generate the Kubernetes manifests for the cluster:
$ ./openshift-install create manifests --dir <installation_directory> (1)
1 | Replace <installation_directory> with the path to the directory that you want to store the installation files in. |
Create a Butane config that configures disk encryption, mirroring, or both.
For example, to configure storage for compute nodes, create a $HOME/clusterconfig/worker-storage.bu
file.
variant: openshift
version: 4.15.0
metadata:
name: worker-storage (1)
labels:
machineconfiguration.openshift.io/role: worker (1)
boot_device:
layout: x86_64 (2)
luks: (3)
tpm2: true (4)
tang: (5)
- url: http://tang1.example.com:7500 (6)
thumbprint: PLjNyRdGw03zlRoGjQYMahSZGu9 (7)
- url: http://tang2.example.com:7500
thumbprint: VCJsvZFjBSIHSldw78rOrq7h2ZF
advertisement: "{"payload": "eyJrZXlzIjogW3siYWxnIjogIkV", "protected": "eyJhbGciOiJFUzUxMiIsImN0eSI", "signature": "ADLgk7fZdE3Yt4FyYsm0pHiau7Q"}" (8)
threshold: 1 (9)
mirror: (10)
devices: (11)
- /dev/sda
- /dev/sdb
openshift:
fips: true (12)
1 | For control plane configurations, replace worker with master in both of these locations. |
2 | Set this field to the instruction set architecture of the cluster nodes.
Some examples include, x86_64 , aarch64 , or ppc64le . |
3 | Include this section if you want to encrypt the root file system. For more details, see "About disk encryption". |
4 | Include this field if you want to use a Trusted Platform Module (TPM) to encrypt the root file system. |
5 | Include this section if you want to use one or more Tang servers. |
6 | Specify the URL of a Tang server.
In this example, tangd.socket is listening on port 7500 on the Tang server. |
7 | Specify the exchange key thumbprint, which was generated in a preceding step. |
8 | Optional: Specify the advertisement for your offline Tang server in valid JSON format. |
9 | Specify the minimum number of TPM v2 and Tang encryption conditions that must be met for decryption to occur.
The default value is 1 .
For more information about this topic, see "Configuring an encryption threshold". |
10 | Include this section if you want to mirror the boot disk. For more details, see "About disk mirroring". |
11 | List all disk devices that should be included in the boot disk mirror, including the disk that RHCOS will be installed onto. |
12 | Include this directive to enable FIPS mode on your cluster. |
To enable FIPS mode for your cluster, you must run the installation program from a Red Hat Enterprise Linux (RHEL) computer configured to operate in FIPS mode. For more information about configuring FIPS mode on RHEL, see Installing the system in FIPS mode. If you are configuring nodes to use both disk encryption and mirroring, both features must be configured in the same Butane configuration file.
If you are configuring disk encryption on a node with FIPS mode enabled, you must include the |
Create a control plane or compute node manifest from the corresponding Butane configuration file and save it to the <installation_directory>/openshift
directory.
For example, to create a manifest for the compute nodes, run the following command:
$ butane $HOME/clusterconfig/worker-storage.bu -o <installation_directory>/openshift/99-worker-storage.yaml
Repeat this step for each node type that requires disk encryption or mirroring.
Save the Butane configuration file in case you need to update the manifests in the future.
Continue with the remainder of the OpenShift Container Platform installation.
You can monitor the console log on the RHCOS nodes during installation for error messages relating to disk encryption or mirroring. |
If you configure additional data partitions, they will not be encrypted unless encryption is explicitly requested. |
After installing OpenShift Container Platform, you can verify if boot disk encryption or mirroring is enabled on the cluster nodes.
From the installation host, access a cluster node by using a debug pod:
Start a debug pod for the node, for example:
$ oc debug node/compute-1
Set /host
as the root directory within the debug shell.
The debug pod mounts the root file system of the node in /host
within the pod.
By changing the root directory to /host
, you can run binaries contained in the executable paths on the node:
# chroot /host
OpenShift Container Platform cluster nodes running Red Hat Enterprise Linux CoreOS (RHCOS) are immutable and rely on Operators to apply cluster changes.
Accessing cluster nodes using SSH is not recommended.
However, if the OpenShift Container Platform API is not available, or |
If you configured boot disk encryption, verify if it is enabled:
From the debug shell, review the status of the root mapping on the node:
# cryptsetup status root
/dev/mapper/root is active and is in use.
type: LUKS2 (1)
cipher: aes-xts-plain64 (2)
keysize: 512 bits
key location: keyring
device: /dev/sda4 (3)
sector size: 512
offset: 32768 sectors
size: 15683456 sectors
mode: read/write
1 | The encryption format. When the TPM v2 or Tang encryption modes are enabled, the RHCOS boot disks are encrypted using the LUKS2 format. |
2 | The encryption algorithm used to encrypt the LUKS2 volume.
The aes-cbc-essiv:sha256 cipher is used if FIPS mode is enabled. |
3 | The device that contains the encrypted LUKS2 volume.
If mirroring is enabled, the value will represent a software mirror device, for example /dev/md126 . |
List the Clevis plugins that are bound to the encrypted device:
# clevis luks list -d /dev/sda4 (1)
1 | Specify the device that is listed in the device field in the output of the preceding step. |
1: sss '{"t":1,"pins":{"tang":[{"url":"http://tang.example.com:7500"}]}}' (1)
1 | In the example output, the Tang plugin is used by the Shamir’s Secret Sharing (SSS) Clevis plugin for the /dev/sda4 device. |
If you configured mirroring, verify if it is enabled:
From the debug shell, list the software RAID devices on the node:
# cat /proc/mdstat
Personalities : [raid1]
md126 : active raid1 sdb3[1] sda3[0] (1)
393152 blocks super 1.0 [2/2] [UU]
md127 : active raid1 sda4[0] sdb4[1] (2)
51869632 blocks super 1.2 [2/2] [UU]
unused devices: <none>
1 | The /dev/md126 software RAID mirror device uses the /dev/sda3 and /dev/sdb3 disk devices on the cluster node. |
2 | The /dev/md127 software RAID mirror device uses the /dev/sda4 and /dev/sdb4 disk devices on the cluster node. |
Review the details of each of the software RAID devices listed in the output of the preceding command.
The following example lists the details of the /dev/md126
device:
# mdadm --detail /dev/md126
/dev/md126:
Version : 1.0
Creation Time : Wed Jul 7 11:07:36 2021
Raid Level : raid1 (1)
Array Size : 393152 (383.94 MiB 402.59 MB)
Used Dev Size : 393152 (383.94 MiB 402.59 MB)
Raid Devices : 2
Total Devices : 2
Persistence : Superblock is persistent
Update Time : Wed Jul 7 11:18:24 2021
State : clean (2)
Active Devices : 2 (3)
Working Devices : 2 (3)
Failed Devices : 0 (4)
Spare Devices : 0
Consistency Policy : resync
Name : any:md-boot (5)
UUID : ccfa3801:c520e0b5:2bee2755:69043055
Events : 19
Number Major Minor RaidDevice State
0 252 3 0 active sync /dev/sda3 (6)
1 252 19 1 active sync /dev/sdb3 (6)
1 | Specifies the RAID level of the device.
raid1 indicates RAID 1 disk mirroring. |
2 | Specifies the state of the RAID device. |
3 | States the number of underlying disk devices that are active and working. |
4 | States the number of underlying disk devices that are in a failed state. |
5 | The name of the software RAID device. |
6 | Provides information about the underlying disk devices used by the software RAID device. |
List the file systems mounted on the software RAID devices:
# mount | grep /dev/md
/dev/md127 on / type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md127 on /etc type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md127 on /usr type xfs (ro,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md127 on /sysroot type xfs (ro,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md127 on /var type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md127 on /var/lib/containers/storage/overlay type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md127 on /var/lib/kubelet/pods/e5054ed5-f882-4d14-b599-99c050d4e0c0/volume-subpaths/etc/tuned/1 type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md127 on /var/lib/kubelet/pods/e5054ed5-f882-4d14-b599-99c050d4e0c0/volume-subpaths/etc/tuned/2 type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md127 on /var/lib/kubelet/pods/e5054ed5-f882-4d14-b599-99c050d4e0c0/volume-subpaths/etc/tuned/3 type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md127 on /var/lib/kubelet/pods/e5054ed5-f882-4d14-b599-99c050d4e0c0/volume-subpaths/etc/tuned/4 type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md127 on /var/lib/kubelet/pods/e5054ed5-f882-4d14-b599-99c050d4e0c0/volume-subpaths/etc/tuned/5 type xfs (rw,relatime,seclabel,attr2,inode64,logbufs=8,logbsize=32k,prjquota)
/dev/md126 on /boot type ext4 (rw,relatime,seclabel)
In the example output, the /boot
file system is mounted on the /dev/md126
software RAID device and the root file system is mounted on /dev/md127
.
Repeat the verification steps for each OpenShift Container Platform node type.
For more information about the TPM v2 and Tang encryption modes, see Configuring automated unlocking of encrypted volumes using policy-based decryption.
You can enable software RAID partitioning to provide an external data volume. OpenShift Container Platform supports RAID 0, RAID 1, RAID 4, RAID 5, RAID 6, and RAID 10 for data protection and fault tolerance. See "About disk mirroring" for more details.
You have downloaded the OpenShift Container Platform installation program on your installation node.
You have installed Butane on your installation node.
Butane is a command-line utility that OpenShift Container Platform uses to provide convenient, short-hand syntax for writing machine configs, as well as for performing additional validation of machine configs. For more information, see the Creating machine configs with Butane section. |
Create a Butane config that configures a data volume by using software RAID.
To configure a data volume with RAID 1 on the same disks that are used for a mirrored boot disk, create a $HOME/clusterconfig/raid1-storage.bu
file, for example:
variant: openshift
version: 4.15.0
metadata:
name: raid1-storage
labels:
machineconfiguration.openshift.io/role: worker
boot_device:
mirror:
devices:
- /dev/disk/by-id/scsi-3600508b400105e210000900000490000
- /dev/disk/by-id/scsi-SSEAGATE_ST373453LW_3HW1RHM6
storage:
disks:
- device: /dev/disk/by-id/scsi-3600508b400105e210000900000490000
partitions:
- label: root-1
size_mib: 25000 (1)
- label: var-1
- device: /dev/disk/by-id/scsi-SSEAGATE_ST373453LW_3HW1RHM6
partitions:
- label: root-2
size_mib: 25000 (1)
- label: var-2
raid:
- name: md-var
level: raid1
devices:
- /dev/disk/by-partlabel/var-1
- /dev/disk/by-partlabel/var-2
filesystems:
- device: /dev/md/md-var
path: /var
format: xfs
wipe_filesystem: true
with_mount_unit: true
1 | When adding a data partition to the boot disk, a minimum value of 25000 mebibytes is recommended. If no 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. |
To configure a data volume with RAID 1 on secondary disks, create a $HOME/clusterconfig/raid1-alt-storage.bu
file, for example:
variant: openshift
version: 4.15.0
metadata:
name: raid1-alt-storage
labels:
machineconfiguration.openshift.io/role: worker
storage:
disks:
- device: /dev/sdc
wipe_table: true
partitions:
- label: data-1
- device: /dev/sdd
wipe_table: true
partitions:
- label: data-2
raid:
- name: md-var-lib-containers
level: raid1
devices:
- /dev/disk/by-partlabel/data-1
- /dev/disk/by-partlabel/data-2
filesystems:
- device: /dev/md/md-var-lib-containers
path: /var/lib/containers
format: xfs
wipe_filesystem: true
with_mount_unit: true
Create a RAID manifest from the Butane config you created in the previous step and save it to the <installation_directory>/openshift
directory. For example, to create a manifest for the compute nodes, run the following command:
$ butane $HOME/clusterconfig/<butane_config>.bu -o <installation_directory>/openshift/<manifest_name>.yaml (1)
1 | Replace <butane_config> and <manifest_name> with the file names from the previous step. For example, raid1-alt-storage.bu and raid1-alt-storage.yaml for secondary disks. |
Save the Butane config in case you need to update the manifest in the future.
Continue with the remainder of the OpenShift Container Platform installation.
Intel® VROC is a type of hybrid RAID, where some of the maintenance is offloaded to the hardware, but appears as software RAID to the operating system.
Support for Intel® VROC 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. |
The following procedure configures an Intel® VROC-enabled RAID1.
You have a system with Intel® Volume Management Device (VMD) enabled.
Create the Intel® Matrix Storage Manager (IMSM) RAID container by running the following command:
$ mdadm -CR /dev/md/imsm0 -e \
imsm -n2 /dev/nvme0n1 /dev/nvme1n1 (1)
1 | The RAID device names. In this example, there are two devices listed. If you provide more than two device names, you must adjust the -n flag. For example, listing three devices would use the flag -n3 . |
Create the RAID1 storage inside the container:
Create a dummy RAID0 volume in front of the real RAID1 volume by running the following command:
$ mdadm -CR /dev/md/dummy -l0 -n2 /dev/imsm0 -z10m --assume-clean
Create the real RAID1 array by running the following command:
$ mdadm -CR /dev/md/coreos -l1 -n2 /dev/imsm0
Stop both RAID0 and RAID1 member arrays and delete the dummy RAID0 array with the following commands:
$ mdadm -S /dev/md/dummy \
mdadm -S /dev/md/coreos \
mdadm --kill-subarray=0 /dev/md/imsm0
Restart the RAID1 arrays by running the following command:
$ mdadm -A /dev/md/coreos /dev/md/imsm0
Install RHCOS on the RAID1 device:
Get the UUID of the IMSM container by running the following command:
$ mdadm --details --export /dev/md/imsm0
Install RHCOS and include the rd.md.uuid
kernel argument by running the following command:
$ coreos-installer install /dev/md/coreos \
--append-karg rd.md.uuid=<md_UUID> (1)
...
1 | The UUID of the IMSM container. |
Include any additional coreos-installer
arguments you need to install RHCOS.
You
can
set the time server and related settings used by the chrony time service (chronyd
)
by modifying the contents of the chrony.conf
file and passing those contents
to your nodes as a machine config.
Create a Butane config including the contents of the chrony.conf
file. For example, to configure chrony on worker nodes, create a 99-worker-chrony.bu
file.
See "Creating machine configs with Butane" for information about Butane. |
variant: openshift
version: 4.15.0
metadata:
name: 99-worker-chrony (1)
labels:
machineconfiguration.openshift.io/role: worker (1)
storage:
files:
- path: /etc/chrony.conf
mode: 0644 (2)
overwrite: true
contents:
inline: |
pool 0.rhel.pool.ntp.org iburst (3)
driftfile /var/lib/chrony/drift
makestep 1.0 3
rtcsync
logdir /var/log/chrony
1 | On control plane nodes, substitute master for worker in both of these locations. |
2 | Specify an octal value mode for the mode field in the machine config file. After creating the file and applying the changes, the mode is converted to a decimal value. You can check the YAML file with the command oc get mc <mc-name> -o yaml . |
3 | Specify any valid, reachable time source, such as the one provided by your DHCP server.
Alternately, you can specify any of the following NTP servers: 1.rhel.pool.ntp.org , 2.rhel.pool.ntp.org , or 3.rhel.pool.ntp.org . |
Use Butane to generate a MachineConfig
object file, 99-worker-chrony.yaml
, containing the configuration to be delivered to the nodes:
$ butane 99-worker-chrony.bu -o 99-worker-chrony.yaml
Apply the configurations in one of two ways:
If the cluster is not running yet, after you generate manifest files, add the MachineConfig
object file to the <installation_directory>/openshift
directory, and then continue to create the cluster.
If the cluster is already running, apply the file:
$ oc apply -f ./99-worker-chrony.yaml
For information on Butane, see Creating machine configs with Butane.
For information on FIPS support, see Support for FIPS cryptography.