Managing HP Serviceguard for Linux, Seventh Edition, July 2007

Cluster and Package Maintenance
Single-Node Operation
Chapter 7280
Single-Node Operation
In a multi-node cluster, you could have a situation in which all but one
node has failed, or you have shut down all but one node, leaving your
cluster in single-node operation. This remaining node will probably have
applications running on it. As long as the Serviceguard daemon cmcld is
active, other nodes can rejoin the cluster.
If the Serviceguard daemon fails when the cluster is in single-node
operation, it will leave the single node up and your applications running
NOTE This means that Serviceguard itself is no longer running.
It is not necessary to halt the single node in this scenario, since the
application is still running, and no other node is currently available for
package switching. (This is different from the loss of the Serviceguard
daemon in a multi-node cluster, which halts the node (system reset), and
causes packages to be switched to adoptive nodes.)
You should not try to restart Serviceguard, since data corruption might
occur if another node were to attempt to start up a new instance of the
application that is still running on the single node.
Instead of restarting the cluster, choose an appropriate time to shut
down the applications and reboot the node; this will allow Serviceguard
to restart the cluster after the reboot.