7.2.3. Detach and Reattach

⁠7.2.3. Detach and Reattach

The reattach method is a variant of a complete cluster shutdown, where the resources are left active and get re-detected when the cluster is restarted.

This method may not be used if the cluster contains any Pacemaker Remote nodes.

Tell the cluster to stop managing services. This is required to allow the services to remain active after the cluster shuts down.
```
# crm_attribute --name maintenance-mode --update true
```
On each node, shutdown the cluster software (pacemaker and the messaging layer), and upgrade the Pacemaker software. This may also include upgrading the messaging layer. While the underlying operating system may be upgraded at the same time, that will be more likely to cause outages in the detached services (certainly, if a reboot is required).
Check the configuration with the crm_verify tool.
On each node, start the cluster software. Currently, only Corosync version 2 and greater is supported as the cluster layer, but if another stack is supported in the future, the stack does not need to be the same one before the upgrade.
Verify that the cluster re-detected all resources correctly.
Allow the cluster to resume managing resources again:
```
# crm_attribute --name maintenance-mode --delete
```

Note

While the goal of the detach-and-reattach method is to avoid disturbing running services, resources may still move after the upgrade if any resource’s location is governed by a rule based on transient node attributes. Transient node attributes are erased when the node leaves the cluster. A common example is using the ocf:pacemaker:ping resource to set a node attribute used to locate other resources.