Step-by-Step Guide to Installing an OpenShift 3.11 Cluster on CentOS VMs

The experiment uses three virtual machines, each acting as both a node and a master. The most frequent issue encountered was image download problems.

1. Pre‑installation Preparation

1.1 Host Allocation

Add the following host entries to /etc/hosts :

192.168.0.21 node01.example.com
192.168.0.32 node02.example.com
192.168.0.43 node03.example.com

1.2 SSH Password‑less Authentication

Configure node01 to SSH into the other machines without a password. Run the commands on each node if you need full password‑less access.

ssh-keygen  # generate key, press Enter for defaults
ssh-copy-id node01.example.com   # type yes, then password
ssh-copy-id node02.example.com   # type yes, then password
ssh-copy-id node03.example.com   # type yes, then password

1.3 Update OS Packages

Upgrade the CentOS 7.3 image to the latest 7.6 version:

yum update -y
yum install wget git net-tools bind-utils yum-utils iptables-services bridge-utils bash-completion kexec-tools sos psacct -y
reboot

1.4 Obtain Installation Scripts

Install Ansible 2.7 (the 2.4 version does not work) and clone the OpenShift playbooks:

yum -y install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
sed -i -e "s/^enabled=1/enabled=0/" /etc/yum.repos.d/epel.repo
yum -y --enablerepo=epel install ansible pyOpenSSL

git clone https://github.com/openshift/openshift-ansible
cd openshift-ansible
git checkout release-3.11

1.5 Import Required Docker Images

List of necessary images (example output of docker images ) is provided. Load the image tarballs:

docker load -i *.tar.gz

2. Start Cluster Installation

2.1 Prepare the Ansible hosts file

[OSEv3:children]
masters
nodes
etcd

[OSEv3:vars]
ansible_ssh_user=root
openshift_deployment_type=origin
openshift_disable_check=disk_availability,docker_storage,memory_availability,docker_image_availability
openshift_master_identity_providers=[{'name':'htpasswd_auth','login':'true','challenge':'true','kind':'HTPasswdPasswordIdentityProvider',}]
os_firewall_use_firewalld=true

[masters]
node01.example.com
node02.example.com
node03.example.com

[etcd]
node01.example.com
node02.example.com
node03.example.com

[nodes]
node01.example.com openshift_node_group_name='node-config-master'
node01.example.com openshift_node_group_name='node-config-compute'
node02.example.com openshift_node_group_name='node-config-master'
node02.example.com openshift_node_group_name='node-config-compute'
node03.example.com openshift_node_group_name='node-config-master'
node03.example.com openshift_node_group_name='node-config-compute'

2.2 Deploy the Cluster

ansible-playbook openshift-ansible/playbooks/prerequisites.yml   # pre‑install checks
ansible-playbook openshift-ansible/playbooks/deploy_cluster.yml   # actual deployment

2.3 Post‑Installation Tests

Create an admin account and log in:

htpasswd -b /etc/origin/master/htpasswd admin admin
oc login -u system:admin
oc adm policy add-cluster-role-to-user cluster-admin admin

After logging in, you can access the OpenShift web console (screenshots omitted).

FAQ

1. Monitoring installation fails

The monitoring pod shows an image pull error for prometheus-operator:v0.23.2 . Pull and retag the image manually:

docker pull tripleorocky/coreos-prometheus-operator:v0.23.2

docker tag tripleorocky/coreos-prometheus-operator:v0.23.2 quay.io/coreos/prometheus-operator:v0.23.2

Also ensure the required node label is set:

oc label node node01.example.com node-role.kubernetes.io/infra=true

2. Web‑console deployment error

This is also a label issue; apply the master label:

oc label node node01.example.com node-role.kubernetes.io/master=true

3. service‑catalog failure

Delete and recreate the failing pod to resolve liveness probe timeouts.

4. Export images

Save image names to images.txt and export them as tar.gz files:

docker images | awk '{print $1":"$2}' > images.txt

for image in `cat images.txt`; do
    zipname=`echo ${image} | awk -F / '{print $3}'`
    docker save ${image} > images/${zipname}.tar.gz
done

5. Metrics deployment error

The metrics role fails because the Python passlib library is missing. Install it and rerun the playbook:

pip install passlib
ansible-playbook openshift-ansible/playbooks/openshift-metrics/config.yml