The first thing to do after installation of cluster components such as Pacemaker, Corosync and pcs is to create a cluster. It then enables us to create and assign resources such as shared IP addresses or server services such as MySQL to our cluster.

A typical cluster consists of at least 3 nodes, though it is still possible to create a cluster from just 2 nodes. It is to avoid a condition called split-brain where each node in a cluster thinks that it is the only active node and causes unexpected behavior in a cluster system. The condition is a lot less likely the more nodes there are in a cluster.

A Pacemaker cluster could be created from the terminal using the pcs (Pacemaker/Corosync Configuration System) tool.

Steps to create a Pacemaker cluster using pcs:

  1. Launch terminal application on all nodes for the cluster.
  2. Install pacemaker, corosync and pcs on all of your cluster nodes.

    Related: How to install Pacemaker, Corosync and pcs on CentOS, Red Hat or Fedora
    Related: How to install Pacemaker, Corosync and pcs on Ubuntu or Debian

  3. Open hosts file using your favorite txt editor on all the cluster nodes. 

    $ sudo vi /etc/hosts [sudo] password for user:

  4. Add node's IP and host name information for all cluster nodes to setup a local DNS system. 

    192.168.111.11 node-01 192.168.111.12 node-02

    Cluster nodes are to communicate using assigned name, and it is crucial for each nodes to use static IP address to prevent communication error between the nodes.

  5. Test local DNS setup by pinging each nodes from each other using the configured host name. 

    $ ping -c3 node-01 && ping -c3 node-01 PING node-01 (192.168.111.11) 56(84) bytes of data. 64 bytes from node-01 (192.168.111.11): icmp_seq=1 ttl=64 time=0.061 ms 64 bytes from node-01 (192.168.111.11): icmp_seq=2 ttl=64 time=0.062 ms 64 bytes from node-01 (192.168.111.11): icmp_seq=3 ttl=64 time=0.133 ms  --- node-01 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2001ms rtt min/avg/max/mdev = 0.061/0.085/0.133/0.034 ms PING node-01 (192.168.111.11) 56(84) bytes of data. 64 bytes from node-01 (192.168.111.11): icmp_seq=1 ttl=64 time=0.050 ms 64 bytes from node-01 (192.168.111.11): icmp_seq=2 ttl=64 time=0.073 ms 64 bytes from node-01 (192.168.111.11): icmp_seq=3 ttl=64 time=0.070 ms  --- node-01 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2002ms rtt min/avg/max/mdev = 0.050/0.064/0.073/0.012 ms

  6. Authorise all nodes from one of the cluster nodes. 

    $ sudo pcs cluster auth node-01 node-02 Username: hacluster Password: node-02: Authorized node-01: Authorized

  7. Create a cluster specifying all the nodes as member from one of the cluster nodes. 

    $ sudo pcs cluster setup --name clustername node-01 node-02 Destroying cluster on nodes: node-01, node-02... node-02: Stopping Cluster (pacemaker)... node-01: Stopping Cluster (pacemaker)... node-01: Successfully destroyed cluster node-02: Successfully destroyed cluster  Sending 'pacemaker_remote authkey' to 'node-01', 'node-02' node-01: successful distribution of the file 'pacemaker_remote authkey' node-02: successful distribution of the file 'pacemaker_remote authkey' Sending cluster config files to the nodes... node-01: Succeeded node-02: Succeeded  Synchronizing pcsd certificates on nodes node-01, node-02... node-02: Success node-01: Success Restarting pcsd on the nodes in order to reload the certificates... node-02: Success node-01: Success

  8. Start cluster for all the cluster nodes from any of the cluster nodes. 

    $ sudo pcs cluster start --name clustername --all node-01: Starting Cluster (corosync)... node-02: Starting Cluster (corosync)... node-01: Starting Cluster (pacemaker)... node-02: Starting Cluster (pacemaker)...

  9. Configure cluster options from any of the cluster nodes. 

    $ sudo pcs property set stonith-enabled=false  $ sudo pcs property set no-quorum-policy=ignore

  10. Show cluster info to confirm a successful setup from any of the cluster nodes. 

    $ sudo pcs cluster status Cluster Status:  Stack: corosync  Current DC: node-02 (version 1.1.20-5.el7_7.1-3c4c782f70) - partition with quorum  Last updated: Mon Sep 30 04:40:20 2019  Last change: Mon Sep 30 04:39:46 2019 by root via cibadmin on node-01  2 nodes configured  0 resources configured  PCSD Status:   node-02: Online   node-01: Online