Chapter 2. Installing a Cluster

OpenShift Container Platform can be installed on a single system for a development environment only. An all-in-one environment is not considered a production environment.

The following table describes an example environment for a single master (with etcd installed on the same host) and two nodes:

The following table describes an example environment for a single master, three etcd hosts, and two nodes:

The following describes an example environment for three masters with co-located clustered etcd, one HAProxy load balancer, and two nodes using the native HA method:

The following describes an example environment for three masters, one HAProxy load balancer, three external clustered etcd hosts, and two nodes using the native HA method:

You can also install OpenShift Container Platform to act as a stand-alone registry using the OpenShift Container Platform’s integrated registry. See Installing a Stand-alone Registry for details on this scenario.

You must have an active OpenShift Container Platform subscription on your Red Hat account to proceed. If you do not, contact your sales representative for more information.

The system requirements vary per host type:

Meeting the /var/ file system sizing requirements in RHEL Atomic Host requires making changes to the default configuration. See Managing Storage with Docker-formatted Containers for instructions on configuring this during or after installation.

The system’s temporary directory is determined according to the rules defined in the tempfile module in Python’s standard library.

You must configure storage for each system that runs a container daemon. For containerized installations, you need storage on masters. Also, by default, the web console is run in containers on masters, and storage is needed on masters to run the web console. Containers are run on nodes, so storage is always required on the nodes. The size of storage depends on workload, number of containers, the size of the containers being run, and the containers' storage requirements. Containerized etcd also needs container storage configured.

Test or sample environments function with the minimum requirements. For production environments, the following recommendations apply:

A minimum of three etcd hosts and a load-balancer between the master hosts are required.

See Recommended Practices for OpenShift Container Platform Master Hosts for performance guidance.

For more information, see Sizing Considerations and Cluster Limits.

Any nodes used in a Container-Native Storage or Container-Ready Storage cluster are considered storage nodes. Storage nodes can be grouped into distinct cluster groups, though a single node can not be in multiple groups. For each group of storage nodes:

By default, OpenShift Container Platform masters and nodes use all available cores in the system they run on. You can choose the number of cores you want OpenShift Container Platform to use by setting the GOMAXPROCS environment variable. See the Go Language documentation for more information, including how the GOMAXPROCS environment variable works.

For example, run the following before starting the server to make OpenShift Container Platform only run on one core:

# export GOMAXPROCS=1

Security-Enhanced Linux (SELinux) must be enabled on all of the servers before installing OpenShift Container Platform or the installer will fail. Also, configure SELINUX=enforcing and SELINUXTYPE=targeted in the /etc/selinux/config file:

# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#     enforcing - SELinux security policy is enforced.
#     permissive - SELinux prints warnings instead of enforcing.
#     disabled - No SELinux policy is loaded.
SELINUX=enforcing
# SELINUXTYPE= can take one of these three values:
#     targeted - Targeted processes are protected,
#     minimum - Modification of targeted policy. Only selected processes are protected.
#     mls - Multi Level Security protection.
SELINUXTYPE=targeted

To access GlusterFS volumes, the mount.glusterfs command must be available on all schedulable nodes. For RPM-based systems, the glusterfs-fuse package must be installed:

# yum install glusterfs-fuse

This package comes installed on every RHEL system. However, it is recommended to update to the latest available version from Red Hat Gluster Storage. To do this, the following RPM repository must be enabled:

# subscription-manager repos --enable=rh-gluster-3-client-for-rhel-7-server-rpms

If glusterfs-fuse is already installed on the nodes, ensure that the latest version is installed:

# yum update glusterfs-fuse

Optional: Using OverlayFS

OverlayFS is a union file system that allows you to overlay one file system on top of another.

As of Red Hat Enterprise Linux 7.4, you have the option to configure your OpenShift Container Platform environment to use OverlayFS. The overlay2 graph driver is fully supported in addition to the older overlay driver. However, Red Hat recommends using overlay2 instead of overlay, because of its speed and simple implementation.

Comparing the Overlay Versus Overlay2 Graph Drivers has more information about the overlay and overlay2 drivers.

See the Overlay Graph Driver section of the Atomic Host documentation for instructions on how to enable the overlay2 graph driver for the Docker service.

OpenShift Container Platform runs containers on hosts in the cluster, and in some cases, such as build operations and the registry service, it does so using privileged containers. Furthermore, those containers access the hosts' Docker daemon and perform docker build and docker push operations. As such, cluster administrators should be aware of the inherent security risks associated with performing docker run operations on arbitrary images as they effectively have root access. This is particularly relevant for docker build operations.

Exposure to harmful containers can be limited by assigning specific builds to nodes so that any exposure is limited to those nodes. To do this, see the Assigning Builds to Specific Nodes section of the Developer Guide. For cluster administrators, see the Configuring Global Build Defaults and Overrides section of the Installation and Configuration Guide.

You can also use security context constraints to control the actions that a pod can perform and what it has the ability to access. For instructions on how to enable images to run with USER in the Dockerfile, see Managing Security Context Constraints (requires a user with cluster-admin privileges).

For more information, see these articles:

OpenShift Container Platform requires a fully functional DNS server in the environment. This is ideally a separate host running DNS software and can provide name resolution to hosts and containers running on the platform.

Key components of OpenShift Container Platform run themselves inside of containers and use the following process for name resolution:

As of OpenShift Container Platform 3.2, dnsmasq is automatically configured on all masters and nodes. The pods use the nodes as their DNS, and the nodes forward the requests. By default, dnsmasq is configured on the nodes to listen on port 53, therefore the nodes cannot run any other type of DNS application.

The following is an example set of DNS records:

master1    A   10.64.33.100
master2    A   10.64.33.103
node1      A   10.64.33.101
node2      A   10.64.33.102

If you do not have a properly functioning DNS environment, you could experience failure with:

*.cloudapps.example.com. 300 IN  A 192.168.133.2

A shared network must exist between the master and node hosts. If you plan to configure multiple masters for high-availability using the advanced installation method, you must also select an IP to be configured as your virtual IP (VIP) during the installation process. The IP that you select must be routable between all of your nodes, and if you configure using a FQDN it should resolve on all nodes.

[OSEv3:vars]
os_firewall_use_firewalld=True

The Kubernetes persistent volume framework allows you to provision an OpenShift Container Platform cluster with persistent storage using networked storage available in your environment. This can be done after completing the initial OpenShift Container Platform installation depending on your application needs, giving users a way to request those resources without having any knowledge of the underlying infrastructure.

The Installation and Configuration Guide provides instructions for cluster administrators on provisioning an OpenShift Container Platform cluster with persistent storage using NFS, GlusterFS, Ceph RBD, OpenStack Cinder, AWS Elastic Block Store (EBS), GCE Persistent Disks, and iSCSI.

There are certain aspects to take into consideration if installing OpenShift Container Platform on a cloud provider.

# ansible-playbook  [-i /path/to/inventory] \
    /usr/share/ansible/openshift-ansible/playbooks/byo/openshift_facts.yml

OverlayFS is a type of union file system. It allows you to overlay one file system on top of another. Changes are recorded in the upper file system, while the lower file system remains unmodified.

Comparing the Overlay Versus Overlay2 Graph Drivers has more information about the overlay and overlay2 drivers.

For information on enabling the OverlayFS storage driver for the Docker service, see the Red Hat Enterprise Linux Atomic Host documentation.

You can use the docker-storage-setup script included with Docker to create a thin pool device and configure Docker’s storage driver. This can be done after installing Docker and should be done before creating images or containers. The script reads configuration options from the /etc/sysconfig/docker-storage-setup file and supports three options for creating the logical volume:

Option A is the most robust option, however it requires adding an additional block device to your host before configuring Docker storage. Options B and C both require leaving free space available when provisioning your host. Option C is known to cause issues with some applications, for example Red Hat Mobile Application Platform (RHMAP).

Should you need to reconfigure Docker storage after having created the docker-pool, you should first remove the docker-pool logical volume. If you are using a dedicated volume group, you should also remove the volume group and any associated physical volumes before reconfiguring docker-storage-setup according to the instructions above.

See Logical Volume Manager Administration for more detailed information on LVM management.

OpenShift Container Platform is capable of cryptographically verifying images are from trusted sources. The Container Security Guide provides a high-level description of how image signing works.

You can configure image signature verification using the atomic command line interface (CLI), version 1.12.5 or greater. The atomic CLI is pre-installed on RHEL Atomic Host systems.

Install the atomic package if it is not installed on the host system:

$ yum install atomic

The atomic trust sub-command manages trust configuration. The default configuration is to whitelist all registries. This means no signature verification is configured.

$ atomic trust show
* (default)                         accept

A reasonable configuration might be to whitelist a particular registry or namespace, blacklist (reject) untrusted registries, and require signature verification on a vendor registry. The following set of commands performs this example configuration:

$ atomic trust add --type insecureAcceptAnything 172.30.1.1:5000

$ atomic trust add --sigstoretype atomic \
  --pubkeys pub@example.com \
  172.30.1.1:5000/production

$ atomic trust add --sigstoretype atomic \
  --pubkeys /etc/pki/example.com.pub \
  172.30.1.1:5000/production

$ atomic trust add --sigstoretype web \
  --sigstore https://access.redhat.com/webassets/docker/content/sigstore \
  --pubkeys /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release \
  registry.access.redhat.com

# atomic trust show
* (default)                         accept
172.30.1.1:5000                     accept
172.30.1.1:5000/production          signed security@example.com
registry.access.redhat.com          signed security@redhat.com,security@redhat.com

When all the signed sources are verified, nodes may be further hardened with a global reject default:

$ atomic trust default reject

$ atomic trust show
* (default)                         reject
172.30.1.1:5000                     accept
172.30.1.1:5000/production          signed security@example.com
registry.access.redhat.com          signed security@redhat.com,security@redhat.com

Use the atomic man page man atomic-trust for additional examples.

The following files and directories comprise the trust configuration of a host:

The trust configuration may be managed directly on each node or the generated files managed on a separate host and distributed to the appropriate nodes using Ansible, for example. See the Container Image Signing Integration Guide for an example of automating file distribution with Ansible.

Sometimes a container’s log file (the /var/lib/docker/containers/<hash>/<hash>-json.log file on the node where the container is running) can increase to a problematic size. You can manage this by configuring Docker’s json-file logging driver to restrict the size and number of log files.

For example, to set the maximum file size to 1MB and always keep the last three log files, edit the /etc/sysconfig/docker file to configure max-size=1M and max-file=3, ensuring that the values maintain the single quotation mark formatting:

OPTIONS='--insecure-registry=172.30.0.0/16 --selinux-enabled --log-opt  max-size=1M --log-opt max-file=3'

Next, restart the Docker service:

# systemctl restart docker

Container logs are stored in the /var/lib/docker/containers/<hash>/ directory on the node where the container is running. For example:

# ls -lh /var/lib/docker/containers/f088349cceac173305d3e2c2e4790051799efe363842fdab5732f51f5b001fd8/
total 2.6M
-rw-r--r--. 1 root root 5.6K Nov 24 00:12 config.json
-rw-r--r--. 1 root root 649K Nov 24 00:15 f088349cceac173305d3e2c2e4790051799efe363842fdab5732f51f5b001fd8-json.log
-rw-r--r--. 1 root root 977K Nov 24 00:15 f088349cceac173305d3e2c2e4790051799efe363842fdab5732f51f5b001fd8-json.log.1
-rw-r--r--. 1 root root 977K Nov 24 00:15 f088349cceac173305d3e2c2e4790051799efe363842fdab5732f51f5b001fd8-json.log.2
-rw-r--r--. 1 root root 1.3K Nov 24 00:12 hostconfig.json
drwx------. 2 root root    6 Nov 24 00:12 secrets

See Docker’s documentation for additional information on how to configure logging drivers.

When a volume is provisioned using the VOLUME instruction in a Dockerfile or using the docker run -v <volumename> command, a host’s storage space is used. Using this storage can lead to an unexpected out of space issue and could bring down the host.

In OpenShift Container Platform, users trying to run their own images risk filling the entire storage space on a node host. One solution to this issue is to prevent users from running images with volumes. This way, the only storage a user has access to can be limited, and the cluster administrator can assign storage quota.

Using docker-novolume-plugin solves this issue by disallowing starting a container with local volumes defined. In particular, the plug-in blocks docker run commands that contain:

The plug-in does not block references to bind mounts.

To enable docker-novolume-plugin, perform the following steps on each node host:

After you enable this plug-in, containers with local volumes defined fail to start and show the following error message:

runContainer: API error (500): authorization denied by plugin
docker-novolume-plugin: volumes are not allowed

To assign environment variables during the Ansible install that apply more globally to your OpenShift Container Platform cluster overall, indicate the desired variables in the /etc/ansible/hosts file on separate, single lines within the [OSEv3:vars] section. For example:

[OSEv3:vars]

openshift_master_identity_providers=[{'name': 'htpasswd_auth',
'login': 'true', 'challenge': 'true',
'kind': 'HTPasswdPasswordIdentityProvider',
'filename': '/etc/origin/master/htpasswd'}]

openshift_master_default_subdomain=apps.test.example.com

The following tables describe variables for use with the Ansible installer that can be assigned cluster-wide:

openshift_master_admission_plugin_config={"ClusterResourceOverride":{"configuration":{"apiVersion":"v1","kind":"ClusterResourceOverrideConfig","memoryRequestToLimitPercent":"25","cpuRequestToLimitPercent":"25","limitCPUToMemoryPercent":"200"}}}

openshift_master_cluster_public_hostname=openshift-ansible.public.example.com

openshift_docker_additional_registries=example.com:443

Various defaults used throughout the playbooks and roles used by the installer are based on the deployment type configuration (usually defined in an Ansible inventory file).

Ensure the openshift_deployment_type parameter in your inventory file’s [OSEv3:vars] section is set to openshift-enterprise to install the OpenShift Container Platform variant:

[OSEv3:vars]
openshift_deployment_type=openshift-enterprise

To assign environment variables to hosts during the Ansible installation, indicate the desired variables in the /etc/ansible/hosts file after the host entry in the [masters] or [nodes] sections. For example:

[masters]
ec2-52-6-179-239.compute-1.amazonaws.com openshift_public_hostname=ose3-master.public.example.com

The following table describes variables for use with the Ansible installer that can be assigned to individual host entries:

OPTIONS='--log-driver json-file --insecure-registry=172.30.0.0/16 --selinux-enabled --log-opt max-size=1M --log-opt max-file=3'

To configure the default project settings, configure the following variables in the /etc/ansible/hosts file:

To configure the default ports used by the master API, configure the following variables in the /etc/ansible/hosts file:

For example:

openshift_master_api_port=3443

The web console port setting (openshift_master_console_port) must match the API server port (openshift_master_api_port).

Pre-install checks are a set of diagnostic tasks that run as part of the openshift_health_checker Ansible role. They run prior to an Ansible installation of OpenShift Container Platform, ensure that required inventory values are set, and identify potential issues on a host that can prevent or interfere with a successful installation.

The following table describes available pre-install checks that will run before every Ansible installation of OpenShift Container Platform:

To disable specific pre-install checks, include the variable openshift_disable_check with a comma-delimited list of check names in your inventory file. For example:

openshift_disable_check=memory_availability,disk_availability

System containers provide a way to containerize services that need to run before the docker daemon is running. They are Docker-formatted containers that use:

System containers are therefore stored and run outside of the traditional docker service. For more details on system container technology, see Running System Containers in the Red Hat Enterprise Linux Atomic Host: Managing Containers documentation.

You can configure your OpenShift Container Platform installation to run certain components as system containers instead of their RPM or standard containerized methods. Currently, the docker and etcd components can be run as system containers in OpenShift Container Platform.

openshift_docker_systemcontainer_image_override="<registry>/<user>/<image>:<tag>"

openshift_use_etcd_system_container=True

If you are using an image registry other than the default at registry.access.redhat.com, specify the desired registry within the /etc/ansible/hosts file.

oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true

For example:

oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true
openshift_docker_additional_registries=example.com:443
+openshift_crio_systemcontainer_image_override=<registry>/<repo>/<image>:<tag>
openshift_cockpit_deployer_prefix='registry.example.com/openshift3/'
openshift_web_console_prefix='registry.example.com/openshift3/ose-
openshift_service_catalog_image_prefix='registry.example.com/openshift3/ose-'
ansible_service_broker_image_prefix='registry.example.com/openshift3/ose-'
template_service_broker_prefix='registry.example.com/openshift3/ose-'

To allow users to push and pull images to the internal Docker registry from outside of the OpenShift Container Platform cluster, configure the registry route in the /etc/ansible/hosts file. By default, the registry route is docker-registry-default.router.default.svc.cluster.local.

For example:

openshift_hosted_registry_routehost=<path>
openshift_hosted_registry_routetermination=reencrypt
openshift_hosted_registry_routecertificates= "{'certfile': '<path>/org-cert.pem', 'keyfile': '<path>/org-privkey.pem', 'cafile': '<path>/org-chain.pem'}"

If you are using a Cockpit registry console image other than the default or require a specific version of the console, specify the desired registry within the /etc/ansible/hosts file:

openshift_cockpit_deployer_prefix=<registry_name>/<namespace>/
openshift_cockpit_deployer_version=<cockpit_image_tag>

For example: If your image is at registry.example.com/openshift3/registry-console and you require version 3.9.3, enter:

openshift_cockpit_deployer_prefix='registry.example.com/openshift3/'
openshift_cockpit_deployer_version='3.9.3'

Router sharding support is enabled by supplying the correct data to the inventory. The variable openshift_hosted_routers holds the data, which is in the form of a list. If no data is passed, then a default router is created. There are multiple combinations of router sharding. The following example supports routers on separate nodes:

openshift_hosted_routers=[{'name': 'router1', 'certificate': {'certfile': '/path/to/certificate/abc.crt',
'keyfile': '/path/to/certificate/abc.key', 'cafile':
'/path/to/certificate/ca.crt'}, 'replicas': 1, 'serviceaccount': 'router',
'namespace': 'default', 'stats_port': 1936, 'edits': [], 'images':
'openshift3/ose-${component}:${version}', 'selector': 'type=router1', 'ports':
['80:80', '443:443']},
{'name': 'router2', 'certificate': {'certfile': '/path/to/certificate/xyz.crt',
'keyfile': '/path/to/certificate/xyz.key', 'cafile':
'/path/to/certificate/ca.crt'}, 'replicas': 1, 'serviceaccount': 'router',
'namespace': 'default', 'stats_port': 1936, 'edits': [{'action': 'append',
'key': 'spec.template.spec.containers[0].env', 'value': {'name': 'ROUTE_LABELS',
'value': 'route=external'}}], 'images':
'openshift3/ose-${component}:${version}', 'selector': 'type=router2', 'ports':
['80:80', '443:443']}]

Red Hat Gluster Storage can be configured to provide persistent storage and dynamic provisioning for OpenShift Container Platform. It can be used both containerized within OpenShift Container Platform (Container-Native Storage) and non-containerized on its own nodes (Container-Ready Storage).

Additional information and examples, including the ones below, can be found at Persistent Storage Using Red Hat Gluster Storage.

An integrated OpenShift Container Registry can be deployed using the advanced installer.

[OSEv3:vars]

openshift_hosted_registry_storage_kind=nfs
openshift_hosted_registry_storage_access_modes=['ReadWriteMany']
openshift_hosted_registry_storage_nfs_directory=/exports
openshift_hosted_registry_storage_nfs_options='*(rw,root_squash)'
openshift_hosted_registry_storage_volume_name=registry
openshift_hosted_registry_storage_volume_size=10Gi

[OSEv3:vars]

openshift_hosted_registry_storage_kind=nfs
openshift_hosted_registry_storage_access_modes=['ReadWriteMany']
openshift_hosted_registry_storage_host=nfs.example.com
openshift_hosted_registry_storage_nfs_directory=/exports
openshift_hosted_registry_storage_volume_name=registry
openshift_hosted_registry_storage_volume_size=10Gi

[OSEv3:vars]

openshift_hosted_registry_storage_kind=openstack
openshift_hosted_registry_storage_access_modes=['ReadWriteOnce']
openshift_hosted_registry_storage_openstack_filesystem=ext4
openshift_hosted_registry_storage_openstack_volumeID=3a650b4f-c8c5-4e0a-8ca5-eaee11f16c57
openshift_hosted_registry_storage_volume_size=10Gi

[OSEv3:vars]

#openshift_hosted_registry_storage_kind=object
#openshift_hosted_registry_storage_provider=s3
#openshift_hosted_registry_storage_s3_accesskey=access_key_id
#openshift_hosted_registry_storage_s3_secretkey=secret_access_key
#openshift_hosted_registry_storage_s3_bucket=bucket_name
#openshift_hosted_registry_storage_s3_region=bucket_region
#openshift_hosted_registry_storage_s3_chunksize=26214400
#openshift_hosted_registry_storage_s3_rootdirectory=/registry
#openshift_hosted_registry_pullthrough=true
#openshift_hosted_registry_acceptschema2=true
#openshift_hosted_registry_enforcequota=true

openshift_hosted_registry_storage_s3_regionendpoint=https://myendpoint.example.com/

[OSEv3:vars]

openshift_hosted_registry_storage_provider=gcs
openshift_hosted_registry_storage_gcs_bucket=bucket01
openshift_hosted_registry_storage_gcs_keyfile=test.key
openshift_hosted_registry_storage_gcs_rootdirectory=/registry

If your hosts require use of a HTTP or HTTPS proxy in order to connect to external hosts, there are many components that must be configured to use the proxy, including masters, Docker, and builds. Node services only connect to the master API requiring no external access and therefore do not need to be configured to use a proxy.

In order to simplify this configuration, the following Ansible variables can be specified at a cluster or host level to apply these settings uniformly across your environment.

OpenShift Container Platform uses iptables as the default firewall, but you can configure your cluster to use firewalld during the install process.

Because iptables is the default firewall, OpenShift Container Platform is designed to have it configured automatically. However, iptables rules can break OpenShift Container Platform if not configured correctly. The advantages of firewalld include allowing multiple objects to safely share the firewall rules.

To use firewalld as the firewall for an OpenShift Container Platform installation, add the os_firewall_use_firewalld variable to the list of configuration variables in the Ansible host file at install:

[OSEv3:vars]
os_firewall_use_firewalld=True 1

Any hosts you designate as masters during the installation process should also be configured as nodes so that the masters are configured as part of the OpenShift SDN. You must do so by adding entries for these hosts to the [nodes] section:

[nodes]
master.example.com

In previous versions of OpenShift Container Platform, master hosts were marked as unschedulable nodes by default by the installer, meaning that new pods could not be placed on the hosts. Starting with OpenShift Container Platform 3.9, however, masters are marked schedulable automatically during installation. This change is mainly so that the web console, which used to run as part of the master itself, can instead be run as a pod deployed to the master.

If you want to change the schedulability of a host post-installation, see Marking Nodes as Unschedulable or Schedulable.

You can assign labels to node hosts during the Ansible install by configuring the /etc/ansible/hosts file. Labels are useful for determining the placement of pods onto nodes using the scheduler. Other than region=infra (referred to as dedicated infrastructure nodes and discussed further in Configuring Dedicated Infrastructure Nodes), the actual label names and values are arbitrary and can be assigned however you see fit per your cluster’s requirements.

To assign labels to a node host during an Ansible install, use the openshift_node_labels variable with the desired labels added to the desired node host entry in the [nodes] section. In the following example, labels are set for a region called primary and a zone called east:

[nodes]
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"

Starting in OpenShift Container Platform 3.9, masters are now marked as schedulable nodes by default. As a result, the default node selector (defined in the master configuration file’s projectConfig.defaultNodeSelector field to determine which node that projects will use by default when placing pods, and previously left blank by default) is now set by default during cluster installations. It is set to node-role.kubernetes.io/compute=true unless overridden using the osm_default_node_selector Ansible variable.

In addition, whether osm_default_node_selector is set or not, the following automatic labeling occurs for hosts defined in your inventory file during installation:

This ensures that the default node selector has available nodes to choose from when determining pod placement.

See Setting the Cluster-wide Default Node Selector for steps on adjusting this setting post-installation if needed.

# default selectors for router and registry services
# openshift_router_selector='region=infra'
# openshift_registry_selector='region=infra'

[nodes]
infra-node1.example.com openshift_node_labels="{'region': 'infra','zone': 'default'}"

openshift_hosted_manage_registry=false
openshift_hosted_manage_router=false

[nodes]
master.example.com openshift_node_labels="{'region': 'infra','zone': 'default'}" openshift_schedulable=true

Session options in the OAuth configuration are configurable in the inventory file. By default, Ansible populates a sessionSecretsFile with generated authentication and encryption secrets so that sessions generated by one master can be decoded by the others. The default location is /etc/origin/master/session-secrets.yaml, and this file will only be re-created if deleted on all masters.

You can set the session name and maximum number of seconds with openshift_master_session_name and openshift_master_session_max_seconds:

openshift_master_session_name=ssn
openshift_master_session_max_seconds=3600

If provided, openshift_master_session_auth_secrets and openshift_master_encryption_secrets must be equal length.

For openshift_master_session_auth_secrets, used to authenticate sessions using HMAC, it is recommended to use secrets with 32 or 64 bytes:

openshift_master_session_auth_secrets=['DONT+USE+THIS+SECRET+b4NV+pmZNSO']

For openshift_master_encryption_secrets, used to encrypt sessions, secrets must be 16, 24, or 32 characters long, to select AES-128, AES-192, or AES-256:

openshift_master_session_encryption_secrets=['DONT+USE+THIS+SECRET+b4NV+pmZNSO']

Custom serving certificates for the public host names of the OpenShift Container Platform API and web console can be deployed during an advanced installation and are configurable in the inventory file.

Certificate and key file paths can be configured using the openshift_master_named_certificates cluster variable:

openshift_master_named_certificates=[{"certfile": "/path/to/custom1.crt", "keyfile": "/path/to/custom1.key", "cafile": "/path/to/custom-ca1.crt"}]

File paths must be local to the system where Ansible will be run. Certificates are copied to master hosts and are deployed within the /etc/origin/master/named_certificates/ directory.

Ansible detects a certificate’s Common Name and Subject Alternative Names. Detected names can be overridden by providing the "names" key when setting openshift_master_named_certificates:

openshift_master_named_certificates=[{"certfile": "/path/to/custom1.crt", "keyfile": "/path/to/custom1.key", "names": ["public-master-host.com"], "cafile": "/path/to/custom-ca1.crt"}]

Certificates configured using openshift_master_named_certificates are cached on masters, meaning that each additional Ansible run with a different set of certificates results in all previously deployed certificates remaining in place on master hosts and within the master configuration file.

If you would like openshift_master_named_certificates to be overwritten with the provided value (or no value), specify the openshift_master_overwrite_named_certificates cluster variable:

openshift_master_overwrite_named_certificates=true

For a more complete example, consider the following cluster variables in an inventory file:

openshift_master_cluster_method=native
openshift_master_cluster_hostname=lb-internal.openshift.com
openshift_master_cluster_public_hostname=custom.openshift.com

To overwrite the certificates on a subsequent Ansible run, you could set the following:

openshift_master_named_certificates=[{"certfile": "/root/STAR.openshift.com.crt", "keyfile": "/root/STAR.openshift.com.key", "names": ["custom.openshift.com"]}]
openshift_master_overwrite_named_certificates=true

By default, the certificates used to govern the etcd, master, and kubelet expire after two to five years. The validity (length in days until they expire) for the auto-generated registry, CA, node, and master certificates can be configured during installation using the following variables (default values shown):

[OSEv3:vars]

openshift_hosted_registry_cert_expire_days=730
openshift_ca_cert_expire_days=1825
openshift_node_cert_expire_days=730
openshift_master_cert_expire_days=730
etcd_ca_default_days=1825

These values are also used when redeploying certificates via Ansible post-installation.

Cluster metrics are not set to automatically deploy. Set the following to enable cluster metrics when using the advanced installation method:

[OSEv3:vars]

openshift_metrics_install_metrics=true

The metrics public URL can be set during cluster installation using the openshift_metrics_hawkular_hostname Ansible variable, which defaults to:

https://hawkular-metrics.{{openshift_master_default_subdomain}}/hawkular/metrics

If you alter this variable, ensure the host name is accessible via your router.

openshift_metrics_hawkular_hostname=hawkular-metrics.{{openshift_master_default_subdomain}}

[OSEv3:vars]

openshift_metrics_cassandra_storage_type=dynamic

[OSEv3:vars]

openshift_metrics_storage_kind=nfs
openshift_metrics_storage_access_modes=['ReadWriteOnce']
openshift_metrics_storage_nfs_directory=/exports
openshift_metrics_storage_nfs_options='*(rw,root_squash)'
openshift_metrics_storage_volume_name=metrics
openshift_metrics_storage_volume_size=10Gi

[OSEv3:vars]

openshift_metrics_storage_kind=nfs
openshift_metrics_storage_access_modes=['ReadWriteOnce']
openshift_metrics_storage_host=nfs.example.com
openshift_metrics_storage_nfs_directory=/exports
openshift_metrics_storage_volume_name=metrics
openshift_metrics_storage_volume_size=10Gi

Cluster logging is not set to automatically deploy by default. Set the following to enable cluster logging when using the advanced installation method:

[OSEv3:vars]

openshift_logging_install_logging=true

[OSEv3:vars]

openshift_logging_es_pvc_dynamic=true

[OSEv3:vars]

openshift_logging_storage_kind=nfs
openshift_logging_storage_access_modes=['ReadWriteOnce']
openshift_logging_storage_nfs_directory=/exports
openshift_logging_storage_nfs_options='*(rw,root_squash)'
openshift_logging_storage_volume_name=logging
openshift_logging_storage_volume_size=10Gi

[OSEv3:vars]

openshift_logging_storage_kind=nfs
openshift_logging_storage_access_modes=['ReadWriteOnce']
openshift_logging_storage_host=nfs.example.com
openshift_logging_storage_nfs_directory=/exports
openshift_logging_storage_volume_name=logging
openshift_logging_storage_volume_size=10Gi

The service catalog is enabled by default during installation. Enabling the service broker allows you to register service brokers with the catalog. When the service catalog is enabled, the OpenShift Ansible broker and template service broker are both installed as well; see Configuring the OpenShift Ansible Broker and Configuring the Template Service Broker for more information. If you disable the service catalog, the OpenShift Ansible broker and template service broker are not installed.

To disable automatic deployment of the service catalog, set the following cluster variable in your inventory file:

openshift_enable_service_catalog=false

If you use your own registry, you must add:

For example:

openshift_service_catalog_image="docker-registry.default.example.com/openshift/ose-service-catalog:${version}"
openshift_service_catalog_image_prefix="docker-registry-default.example.com/openshift/ose-"
openshift_service_catalog_image_version="v3.9.30"
template_service_broker_selector={"role":"infra"}

When the service catalog is enabled, the OpenShift Ansible broker and template service broker are both enabled as well; see Configuring the OpenShift Ansible Broker and Configuring the Template Service Broker for more information.

ansible_service_broker_install=false

template_service_broker_install=false

openshift_template_service_broker_namespaces=['openshift','myproject']

template_service_broker_selector={"region": "infra"}

The following Ansible variables set master configuration options for customizing the web console. See Customizing the Web Console for more details on these customization options.

You can configure an environment with a single master and multiple nodes, and either a single or multiple number of external etcd hosts.

Single Master, Single etcd, and Multiple Nodes

The following table describes an example environment for a single master (with a single etcd on the same host), two nodes for hosting user applications, and two nodes with the region=infra label for hosting dedicated infrastructure:

You can see these example hosts present in the [masters], [etcd], and [nodes] sections of the following example inventory file:

# Create an OSEv3 group that contains the masters, nodes, and etcd groups
[OSEv3:children]
masters
nodes
etcd

# Set variables common for all OSEv3 hosts
[OSEv3:vars]
# SSH user, this user should allow ssh based auth without requiring a password
ansible_ssh_user=root

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

openshift_deployment_type=openshift-enterprise
oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true

# 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
[masters]
master.example.com

# host group for etcd
[etcd]
master.example.com

# host group for nodes, includes region info
[nodes]
master.example.com
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"
infra-node1.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
infra-node2.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"

To use this example, modify the file to match your environment and specifications, and save it as /etc/ansible/hosts.

Single Master, Multiple etcd, and Multiple Nodes

The following table describes an example environment for a single master, three etcd hosts, two nodes for hosting user applications, and two nodes with the region=infra label for hosting dedicated infrastructure:

You can see these example hosts present in the [masters], [nodes], and [etcd] sections of the following example inventory file:

# Create an OSEv3 group that contains the masters, nodes, and etcd groups
[OSEv3:children]
masters
nodes
etcd

# Set variables common for all OSEv3 hosts
[OSEv3:vars]
ansible_ssh_user=root
openshift_deployment_type=openshift-enterprise
oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true

# 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
[masters]
master.example.com

# host group for etcd
[etcd]
etcd1.example.com
etcd2.example.com
etcd3.example.com

# host group for nodes, includes region info
[nodes]
master.example.com
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"
infra-node1.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
infra-node2.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"

To use this example, modify the file to match your environment and specifications, and save it as /etc/ansible/hosts.

You can configure an environment with multiple masters, multiple etcd hosts, and multiple nodes. Configuring multiple masters for high availability (HA) ensures that the cluster has no single point of failure.

When configuring multiple masters, the advanced installation supports the native high availability (HA) method. This method leverages the native HA master capabilities built into OpenShift Container Platform and can be combined with any load balancing solution.

If a host is defined in the [lb] section of the inventory file, Ansible installs and configures HAProxy automatically as the load balancing solution. If no host is defined, it is assumed you have pre-configured an external load balancing solution of your choice to balance the master API (port 8443) on all master hosts.

For an external load balancing solution, you must have:

See the External Load Balancer Integrations example in Github for more information. For more on the high availability master architecture, see Kubernetes Infrastructure.

To configure multiple masters, refer to Multiple Masters with Multiple etcd

Multiple Masters Using Native HA with External Clustered etcd

The following describes an example environment for three masters using the native HA method:, one HAProxy load balancer, three etcd hosts, two nodes for hosting user applications, and two nodes with the region=infra label for hosting dedicated infrastructure:

You can see these example hosts present in the [masters], [etcd], [lb], and [nodes] sections of the following example 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.
[OSEv3:children]
masters
nodes
etcd
lb

# Set variables common for all OSEv3 hosts
[OSEv3:vars]
ansible_ssh_user=root
openshift_deployment_type=openshift-enterprise
oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true

# 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 availbility 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.
openshift_master_cluster_method=native
openshift_master_cluster_hostname=openshift-internal.example.com
openshift_master_cluster_public_hostname=openshift-cluster.example.com

# 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']}

# enable ntp on masters to ensure proper failover
openshift_clock_enabled=true

# host group for masters
[masters]
master1.example.com
master2.example.com
master3.example.com

# host group for etcd
[etcd]
etcd1.example.com
etcd2.example.com
etcd3.example.com

# Specify load balancer host
[lb]
lb.example.com

# host group for nodes, includes region info
[nodes]
master[1:3].example.com
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"
infra-node1.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
infra-node2.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"

To use this example, modify the file to match your environment and specifications, and save it as /etc/ansible/hosts.

Multiple Masters Using Native HA with Co-located Clustered etcd

The following describes an example environment for three masters using the native HA method (with etcd on each host), one HAProxy load balancer, two nodes for hosting user applications, and two nodes with the region=infra label for hosting dedicated infrastructure:

You can see these example hosts present in the [masters], [etcd], [lb], and [nodes] sections of the following example 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.
[OSEv3:children]
masters
nodes
etcd
lb

# Set variables common for all OSEv3 hosts
[OSEv3:vars]
ansible_ssh_user=root
openshift_deployment_type=openshift-enterprise
oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true

# 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.
openshift_master_cluster_method=native
openshift_master_cluster_hostname=openshift-internal.example.com
openshift_master_cluster_public_hostname=openshift-cluster.example.com

# host group for masters
[masters]
master1.example.com
master2.example.com
master3.example.com

# host group for etcd
[etcd]
master1.example.com
master2.example.com
master3.example.com

# Specify load balancer host
[lb]
lb.example.com

# host group for nodes, includes region info
[nodes]
master[1:3].example.com
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"
infra-node1.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
infra-node2.example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"

To use this example, modify the file to match your environment and specifications, and save it as /etc/ansible/hosts.

The RPM-based installer uses Ansible installed via RPM packages to run playbooks and configuration files available on the local host.

To run the RPM-based installer:

If for any reason the installation fails, before re-running the installer, see Known Issues to check for any specific instructions or workarounds.

The openshift3/ose-ansible image is a containerized version of the OpenShift Container Platform installer. This installer image provides the same functionality as the RPM-based installer, but it runs in a containerized environment that provides all of its dependencies rather than being installed directly on the host. The only requirement to use it is the ability to run a container.

# atomic install --system \
    --storage=ostree \
    --set INVENTORY_FILE=/path/to/inventory \
    --set PLAYBOOK_FILE=/usr/share/ansible/openshift-ansible/playbooks/openshift-checks/pre-install.yml \ 1
    --set OPTS="-v" \ 2
    registry.access.redhat.com/openshift3/ose-ansible:v3.9

$ ansible-playbook --user openshift \
  -i openshift-ansible/playbooks/openstack/inventory.py \
  -i inventory \
  openshift-ansible/playbooks/openstack/openshift-cluster/provision_install.yml

The main installation playbook /usr/share/ansible/openshift-ansible/playbooks/deploy_cluster.yml runs a set of individual component playbooks in a specific order, and the installer reports back at the end what phases you have gone through. If the installation fails, you are notified which phase failed along with the errors from the Ansible run.

After you resolve the errors, you can continue installation:

If you want to run only the remaining playbooks, start by running the playbook for the phase that failed and then run each of the remaining playbooks in order:

# ansible-playbook [-i /path/to/inventory] <playbook_file_location>

The following table lists the playbooks in the order that they must run:

You can also uninstall node components from specific hosts using the uninstall.yml playbook while leaving the remaining hosts and cluster alone:

When the playbook completes, all OpenShift Container Platform content should be removed from any specified hosts.

Before you sync with the required repositories, you may need to import the appropriate GPG key:

$ rpm --import /etc/pki/rpm-gpg/RPM-GPG-KEY-redhat-release

If the key is not imported, the indicated package is deleted after syncing the repository.

To sync the required repositories:

To sync the container images:

Container images can be exported from a system by first saving them to a tarball and then transporting them:

At this point you can perform the initial creation of the hosts that will be part of the OpenShift Container Platform environment. It is recommended to use the latest version of RHEL 7 and to perform a minimal installation. You will also want to pay attention to the other OpenShift Container Platform-specific prerequisites.

Once the hosts are initially built, the repositories can be set up.

On all of the relevant systems that will need OpenShift Container Platform software components, create the required repository definitions. Place the following text in the /etc/yum.repos.d/ose.repo file, replacing <server_IP> with the IP or host name of the Apache server hosting the software repositories:

[rhel-7-server-rpms]
name=rhel-7-server-rpms
baseurl=http://<server_IP>/repos/rhel-7-server-rpms
enabled=1
gpgcheck=0
[rhel-7-server-extras-rpms]
name=rhel-7-server-extras-rpms
baseurl=http://<server_IP>/repos/rhel-7-server-extras-rpms
enabled=1
gpgcheck=0
[rhel-7-fast-datapath-rpms]
name=rhel-7-fast-datapath-rpms
baseurl=http://<server_IP>/repos/rhel-7-fast-datapath-rpms
enabled=1
gpgcheck=0
[rhel-7-server-ansible-2.4-rpms]
name=rhel-7-server-ansible-2.4-rpms
baseurl=http://<server_IP>/repos/rhel-7-server-ansible-2.4-rpms
enabled=1
gpgcheck=0
[rhel-7-server-ose-3.9-rpms]
name=rhel-7-server-ose-3.9-rpms
baseurl=http://<server_IP>/repos/rhel-7-server-ose-3.9-rpms
enabled=1
gpgcheck=0

At this point, the systems are ready to continue to be prepared following the OpenShift Container Platform documentation.

Skip the section titled Host Registration and start with Installing Base Packages.

To import the relevant components, securely copy the images from the connected host to the individual OpenShift Container Platform hosts:

$ scp /var/www/html/repos/images/ose3-images.tar root@<openshift_host_name>:
$ ssh root@<openshift_host_name> "docker load -i ose3-images.tar"
$ scp /var/www/html/images/ose3-builder-images.tar root@<openshift_master_host_name>:
$ ssh root@<openshift_master_host_name> "docker load -i ose3-builder-images.tar"

Perform the same steps for the host components if your install will be containerized. Perform the same steps for the metrics and logging images, if your cluster will use them.

If you prefer, you could use wget on each OpenShift Container Platform host to fetch the tar file, and then perform the Docker import command locally.

You can now choose to follow the quick or advanced OpenShift Container Platform installation instructions in the documentation.

You now need to create the internal Docker registry.

If you want to install a stand-alone registry, you must pull the registry-console container image and set deployment_subtype=registry in the inventory file.

If you are using an image registry other than the default at registry.access.redhat.com, specify the desired registry within the /etc/ansible/hosts file.

oreg_url=example.com/openshift3/ose-${component}:${version}
openshift_examples_modify_imagestreams=true

Depending on your registry, you may need to configure:

openshift_docker_additional_registries=example.com
openshift_docker_insecure_registries=example.com

Pushing the container images into OpenShift Container Platform’s Docker registry requires a user with cluster-admin privileges. Because the default OpenShift Container Platform system administrator does not have a standard authorization token, they cannot be used to log in to the Docker registry.

To create an administrative user:

The openshift project is where all of the image streams for builder images are created by the installer. They are loaded by the installer from the /usr/share/openshift/examples directory. Change all of the definitions by deleting the image streams which had been loaded into OpenShift Container Platform’s database, then re-create them:

At this point the system is ready to load the container images.

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.

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

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:

# Create an OSEv3 group that contains the masters and nodes groups
[OSEv3:children]
masters
nodes
etcd

# Set variables common for all OSEv3 hosts
[OSEv3:vars]
# SSH user, this user should allow ssh based auth without requiring a password
ansible_ssh_user=root

openshift_master_default_subdomain=apps.test.example.com

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

openshift_deployment_type=openshift-enterprise
deployment_subtype=registry 1
openshift_hosted_infra_selector="" 2

# 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
[masters]
registry.example.com

# host group for etcd
[etcd]
registry.example.com

# host group for nodes
[nodes]
registry.example.com

# 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.
[OSEv3:children]
masters
nodes
etcd
lb

# Set variables common for all OSEv3 hosts
[OSEv3:vars]
ansible_ssh_user=root
openshift_deployment_type=openshift-enterprise
deployment_subtype=registry 1

openshift_master_default_subdomain=apps.test.example.com

# 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.
openshift_master_cluster_method=native
openshift_master_cluster_hostname=openshift-internal.example.com
openshift_master_cluster_public_hostname=openshift-cluster.example.com

# 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']}

# enable ntp on masters to ensure proper failover
openshift_clock_enabled=true

# host group for masters
[masters]
master1.example.com
master2.example.com
master3.example.com

# host group for etcd
[etcd]
etcd1.example.com
etcd2.example.com
etcd3.example.com

# Specify load balancer host
[lb]
lb.example.com

# host group for nodes, includes region info
[nodes]
master[1:3].example.com openshift_node_labels="{'region': 'infra', 'zone': 'default'}"
node1.example.com openshift_node_labels="{'region': 'primary', 'zone': 'east'}"
node2.example.com openshift_node_labels="{'region': 'primary', 'zone': 'west'}"

After you have configured Ansible by defining an inventory file in /etc/ansible/hosts: