OpenShift Host Preparation - Ansible Playbook

This repository is an Ansible Playbook that prepares hosts for an OpenShift installation.

It checks that the pre-requisites given in the OpenShift Documentation, sections Prerequisites and Host Preparation are met.

It uses the same inventory file as the openshift-ansible playbooks.

Usage

If not already done, craft your inventory file as described in the OpenShift documentation.

A very minimal inventory file would be:

[OSEv3]
machine1.mydomain.com
machine2.mydomain.com
 ...
machineX.mydomain.com

[OSEv3:vars]
ansible_user=john
openshift_master_default_subdomain=app.mydomain.com

The main parts of the inventory are:

• the OSEv3 group where you can declare all the machines of your cluster
• the ansible_user variable that hold the username used to connect to the machines using SSH
• the openshift_master_default_subdomain is your Wildcard DNS as explained here

Then, assuming you saved your inventory file in /etc/ansible/hosts, you can run the playbook with:

ansible-playbook -i /etc/ansible/hosts prepare.yml

What does this playbook

This playbook goes through the following steps:

• Make sure net.ipv4.ip_forward is set to 1
• Remove any locally installed DNS server that might interfere with OpenShift
• Make sure nothing is listening on port 53
• Ensures there is no residue of a previous installation of Kubernetes
• Activate SELinux if it has been disabled
• Install basic admin tools (for a complete list, check the playbook)
• Install and enable NetworkManager
• Check if the Wildcard DNS is working
• Make sure the DNS names of the machines are consistent
• Enable the OpenShift repositories
• Install Docker
• Configure Docker for OverlayFS
• Make sure the filesystem holding /var/lib/docker is formatted as XFS
• Install the openshift-ansible package

Note: several steps require a reboot to apply the new configuration or detect any misconfiguration, be prepared!