About OpenShift Container Registry

OpenShift Container Platform is a fully-featured enterprise solution that includes an integrated container registry called OpenShift Container Registry (OCR). Alternatively, instead of deploying OpenShift Container Platform as a full PaaS environment for developers, you can install OCR as a stand-alone container registry to run on-premise or in the cloud.

When installing a stand-alone deployment of OCR, a cluster of masters and nodes is still installed, similar to a typical OpenShift Container Platform installation. Then, the container registry is deployed to run on the cluster. This stand-alone deployment option is useful for administrators that want a container registry, but do not require the full OpenShift Container Platform environment that includes the developer-focused web console and application build and deployment tools.

OCR has replaced the upstream Atomic Registry project, which was a different implementation that used a non-Kubernetes deployment method that leveraged systemd and local configuration files to manage services.

OCR provides the following capabilities:

Administrators may want to deploy a stand-alone OCR to manage a registry separately that supports multiple OpenShift Container Platform clusters. A stand-alone OCR also enables administrators to separate their registry to satisfy their own security or compliance requirements.

Minimum Hardware Requirements

Installing a stand-alone OCR has the following hardware requirements:

  • Physical or virtual system, or an instance running on a public or private IaaS.

  • Base OS: RHEL 7.3 or 7.4 with the "Minimal" installation option and the latest packages from the RHEL 7 Extras channel, or RHEL Atomic Host 7.4.2 or later.

  • NetworkManager 1.0 or later

  • 2 vCPU.

  • Minimum 16 GB RAM.

  • Minimum 15 GB hard disk space for the file system containing /var/.

  • An additional minimum 15 GB unallocated space to be used for Docker’s storage back end; see Configuring Docker Storage for details.

OpenShift Container Platform only supports servers with x86_64 architecture.

Meeting the /var/ file system sizing requirements in RHEL Atomic Host requires making changes to the default configuration. See Managing Storage in Red Hat Enterprise Linux Atomic Host for instructions on configuring this during or after installation.

Supported System Topologies

The following system topologies are supported for stand-alone OCR:


A single host that includes the master, node, etcd, and registry components.

Multiple Masters (Highly-Available)

Three hosts with all components included on each (master, node, etcd, and registry), with the masters configured for native high-availability.

Host Preparation

Before installing stand-alone OCR, all of the same steps detailed in the Host Preparation topic for installing a full OpenShift Container Platform PaaS must be performed. This includes registering and subscribing the host(s) to the proper repositories, installing or updating certain packages, and setting up Docker and its storage requirements.

Follow the steps in the Host Preparation topic, then continue to Installation Methods.

Installation Methods

To install a stand-alone registry, use either of the standard installation methods (quick or advanced) used to install any variant of OpenShift Container Platform.

Quick Installation for Stand-alone OpenShift Container Registry

The following shows the step-by-step process for running the quick install tool to install an OpenShift Container Registry, instead of the full OpenShift Container Platform install.

  1. Start the interactive installation:

    $ atomic-openshift-installer install
  2. Follow the on-screen instructions to install a new registry. The installation questions will be largely the same as if you were installing a full OpenShift Container Platform PaaS. When you reach the following screen, choose 2 to follow the registry installation path:

    Which variant would you like to install?
    (1) OpenShift Container Platform
    (2) Registry
  3. Specify the hosts that make up your cluster:

    Enter hostname or IP address:
    Will this host be an OpenShift master? [y/N]:
    Will this host be RPM or Container based (rpm/container)? [rpm]:

    See the Installing on Containerized Hosts topic for information about RPM versus containerized hosts.

  4. Change the cluster host name, if desired:

    Enter hostname or IP address [None]:
  5. Choose the host to act as the storage host (the master host by default):

    Enter hostname or IP address [master.host.example.com]:
  6. Change the default subdomain, if desired:

    New default subdomain (ENTER for none) []:

    All certificates and routes are created with this subdomain. Ensure this is set to the correct desired subdomain to avoid having to change the configuration after installation.

  7. Specify a HTTP or HTTPS proxy, if needed:

    Specify your http proxy ? (ENTER for none) []:
    Specify your https proxy ? (ENTER for none) []:

After the previous has been entered, the next page summarizes your install and starts to gather the host information.

For further usage details on the quick installer in general, including next steps, see the full topic at Quick Installation.

Advanced Installation for Stand-alone OpenShift Container Registry

When using the advanced installation method to install stand-alone OCR, use the same steps for installing a full OpenShift Container Platform PaaS using Ansible described in the full Advanced Installation topic. The main difference is that you must set deployment_subtype=registry in the inventory file within the [OSEv3:vars] section for the playbooks to follow the registry installation path.

See the following example inventory files for the different supported system topologies:

All-in-one Stand-alone OpenShift Container Registry Inventory File
# Create an OSEv3 group that contains the masters and nodes groups

# Set variables common for all OSEv3 hosts
# SSH user, this user should allow ssh based auth without requiring a password


# If ansible_ssh_user is not root, ansible_become must be set to true

deployment_subtype=registry (1)

# uncomment the following to enable htpasswd authentication; defaults to DenyAllPasswordIdentityProvider
#openshift_master_identity_providers=[{'name': 'htpasswd_auth', 'login': 'true', 'challenge': 'true', 'kind': 'HTPasswdPasswordIdentityProvider', 'filename': '/etc/origin/master/htpasswd'}]

# host group for masters

# host group for nodes, includes region info
registry.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}" openshift_schedulable=true (2)
1 Set deployment_subtype=registry to ensure installation of stand-alone OCR and not a full OpenShift Container Platform environment.
2 Set openshift_schedulable=true on the node entry to make the single node schedulable for pod placement.
Multiple Masters (Highly-Available) Stand-alone OpenShift Container Registry Inventory File
# Create an OSEv3 group that contains the master, nodes, etcd, and lb groups.
# The lb group lets Ansible configure HAProxy as the load balancing solution.
# Comment lb out if your load balancer is pre-configured.

# Set variables common for all OSEv3 hosts
deployment_subtype=registry (1)


# Uncomment the following to enable htpasswd authentication; defaults to
# DenyAllPasswordIdentityProvider.
#openshift_master_identity_providers=[{'name': 'htpasswd_auth', 'login': 'true', 'challenge': 'true', 'kind': 'HTPasswdPasswordIdentityProvider', 'filename': '/etc/origin/master/htpasswd'}]

# Native high availability cluster method with optional load balancer.
# If no lb group is defined installer assumes that a load balancer has
# been preconfigured. For installation the value of
# openshift_master_cluster_hostname must resolve to the load balancer
# or to one or all of the masters defined in the inventory if no load
# balancer is present.

# apply updated node defaults
openshift_node_kubelet_args={'pods-per-core': ['10'], 'max-pods': ['250'], 'image-gc-high-threshold': ['90'], 'image-gc-low-threshold': ['80']}

# override the default controller lease ttl

# enable ntp on masters to ensure proper failover

# host group for masters

# host group for etcd

# Specify load balancer host

# host group for nodes, includes region info
master[1:3].example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}" openshift_schedulable=true
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"
1 Set deployment_subtype=registry to ensure installation of stand-alone OCR and not a full OpenShift Container Platform environment.

After you have configured Ansible by defining an inventory file in /etc/ansible/hosts, you can run the advanced installation using the following playbook:

# ansible-playbook /usr/share/ansible/openshift-ansible/playbooks/byo/config.yml

For more detailed usage information on the advanced installation method, including a comprehensive list of available Ansible variables, see the full topic at Advanced Installation.