What you want to know is that pacemaker is not a "Node failover" solution where the backup node takes the configuration of the failed node, but a "resource failover" solution, where individual failed resources are moved to a backup node.
So you don't configure a host address, but a service address (also named floating address or dynamic address).
One resource agent (RA) to handle such addresses is IPaddr2
.
(In general you can get a description for any RA using a command like crm ra info
, i.e.: crm ra info IPaddr2
).
Then you have to configure your actual (network) resources to use that dynamic address.
Doing that you have to make sure that your resource runs on the same node as your IP address (called colocation).
Also your resource should be started after the IP address (called ordering).
A resource group can help to ensure colocation and ordering for simple configurations where no resources are shared (e.g.: when multiple services use the same IP address).
Now for the actions:
One node (domain controller or designated coordinator (DC)) runs the cluster resource manager (crm) which in turn uses the local resource manager on a node to execute actions.
Typically those are start
to start a resource, monitor
to check the status of a resource (sometimes also named probe
), and stop
to stop a resource (there are a few more, but these are the basics).
If a resource fails to stop, crm tries to fence (Shoot The Other Node In the Head (STONITH)) the node to make sure nothing continues to run on that node.
After STONITH was successful, then the resource (and actually all others that were affected by STONITH of the node) is started on another node.
There's more to say, but that should be enough for a quick introduction.
Maybe start with Clusters from Scratch.