OpenShift 3.6 Generic Guest Template

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The generic template contains all an OpenShift master or regular node, as well as the support node, need to function. It is built in top of the basic template.

Clone the Basic Template

Use the basic template as a base image, and clone it, as described here:

Cloning a Guest

The process will produce a ocp36.generic-template.

Install OpenShift Binaries

Attach the Node to the OpenShift Subscription

More details about subscription management:

RedHat Subscription Manager

The node, being based on the basic template, should have been already registered with the subscription manager:

subscription-manager status
subscription-manager identity
subscription-manager list --available --matches '*OpenShift*'

Identify the OpenShift pool ID:

subscription-manager attach --pool=<pool-id>

Manage Repositories and Install Utilities

Once attached to the pool, all repositories must be first disabled, and then only select repositories are re-enabled:

subscription-manager repos --disable="*"
subscription-manager repos --list-enabled
yum repolist

If there are any enabled repositories, disable them with:

yum-config-manager --disable <repo_id>

Enable only the repositories required by OpenShift Container Platform 3.6:

subscription-manager repos --enable="rhel-7-server-rpms" --enable="rhel-7-server-extras-rpms" --enable="rhel-7-server-ose-3.6-rpms" --enable="rhel-7-fast-datapath-rpms"
subscription-manager repos --list-enabled
yum repolist
yum update -y

Install atomic-openshift-utils, which contains OpenShift installer utilities and other tools required by the installation process:

yum install atomic-openshift-utils

At this point, no OpenShift binaries, except installation utilities, are installed. The advanced installer knows how to override this and it will install the binaries as expected, without any further intervention.

Install Docker

Install Docker on the generic template. On the support host, it will simply not be activated. Docker is also required on masters too, but the image storage allocated to it can be made much smaller than on the nodes and infranodes. The binaries must be installed from the rhel-7-server-ose-3.*-rpms repository and have it running before installing OpenShift.

OpenShift 3.6 requires Docker 1.12.

yum install docker
docker version

Docker Storage Setup


Provision storage for the Docker server. The default loopback storage is not appropriate for production, it should be replaced by a thin-pool logical volume. Set up docker storage using Option A) described in the documentation: use an additional block device. In this case, the additional block device is provisioned as a 50GB dedicate volume group and exposed to the guest as the /dev/vdb block device.


# CONTAINER_ROOT_LV_MOUNT_PATH="/var/lib/containers/container-runtime"

Setting DATA_SIZE too small caused nodes not being able to start and OpenShift OutOfDisk events.

If this is template reconfiguration, remove previous Docker metadata:

 rm -r /var/lib/docker
 cat /dev/null > /etc/sysconfig/docker-storage


INFO: Volume group backing root filesystem could not be determined
INFO: Device node /dev/vdb1 exists.
 Physical volume "/dev/vdb1" successfully created.
 Volume group "docker_vg" successfully created
 Using default stripesize 64.00 KiB.
 Rounding up size to full physical extent 52.00 MiB
 Thin pool volume with chunk size 512.00 KiB can address at most 126.50 TiB of data.
 Logical volume "container-thinpool" created.
 Logical volume docker_vg/container-thinpool changed.
 LV                 VG        Attr       LSize  Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
 container-thinpool docker_vg twi-a-t--- 49.89g             0.00   0.11

After setup, disable docker-storage-setup at startup, is not needed, storage already setup.

 systemctl disable docker-storage-setup
 systemctl is-enabled docker-storage-setup

Docker and OpenShift Installation

The OpenShift advanced installation procedure is supposed to update /etc/sysconfig/docker on nodes with OpenShift-specific configuration. The documentation says that the advanced installation procedure will add an "--insecure-registry" option, but that does not seem to be the case, so based on previous installation experience, we learned to add it manually in /etc/sysconfig/docker:

OPTIONS=' --selinux-enabled  --log-driver=journald --insecure-registry'

The subnet value used to configure the insecure registry corresponds to the default value of the services subnet.

Test Start Docker

Enable docker to start at boot:

systemctl enable docker
systemctl start docker

Reboot the system and then check Docker Server Runtime.

Optimizing Docker Storage

Prevent Docker to Start at Boot

We do not want the template to start docker at boot, because in some cases we may want to modify the storage depending on the node's particularities.

Also we do not want to automatically start, because we may want to configure new storage manually.

 systemctl disable docker
 systemctl is-enabled docker
 systemctl disable docker-storage-setup
 systemctl is-enabled docker-storage-setup