How to change the hostname of a Pacemaker Cluster node

SUSE Linux Enterprise High Availability Extension 12
SUSE Linux Enterprise High Availability Extension 15
SUSE Linux Enterprise Server for SAP Applications 12
SUSE Linux Enterprise Server for SAP Applications 15

The hostname of a system that is a node of a Pacemaker Cluster must be changed.

IMPORTANT: this TID will only explain how to change the hostname of a system that is a node of a Pacemaker Cluster, based on the basic OS and Cluster configurations, and NOT how the change of the hostname will affect the applications, databases or any other software installed.

This example is based on a two node cluster, where the hostname of the nodes are: "green" and "blue". And the hostname of node "blue" will be changed to "yellow", as follows:

1. Open a root session on node "blue" and set it into standby mode, this will move all the cluster resources running on "blue" to node "green":

crm node standby


2. Once done, open a root session on node "green", and remove node "blue" from the cluster:

crm cluster remove blue


3. On node "blue", disable all the cluster related services, so it will not start after reboot:

systemctl disable --now pacemaker

systemctl disable --now corosync

systemctl disable --now sbd


4. Change the hostname of node "blue" to "yellow":

hostnamectl set-hostname yellow


5. Verify that the hostname was changed to "yellow" and then reboot the system:

hostnamectl status

systemctl reboot


6. Once node "yellow" is back online, verify again that the hostname was properly changed to "yellow":

hostnamectl status


7. Edit the /etc/hosts file on all the nodes in the cluster, and replace the old hostname "blue" for "yellow" in all the respective entries.


8. Join the node to the cluster, on node "yellow" run as root:

ha-cluster-join

And follow the instructions on screen.

NOTE: while the above example shows the procedure on a two node cluster, it is also valid for clusters with more than two nodes.

 

If using DRBD then do not forget to replace the old hostname for the new one in all the /etc/drbd.d/*.res files.