Managing Serviceguard Sixteenth Edition, March 2009

NOTE: The /sbin/init.d/cmcluster file may call files that Serviceguard stored
in the directories: /etc/cmcluster/rc (HP-UX) and ${SGCONF}/rc (Linux). The
directory is for Serviceguard use only! Do not move, delete, modify, or add files to this
directory.
Changing the System Message
You may find it useful to modify the system's login message to include a statement
such as the following:
This system is a node in a high availability cluster.
Halting this system may cause applications and services to
start up on another node in the cluster.
You might want to include a list of all cluster nodes in this message, together with
additional cluster-specific information.
The /etc/issue and /etc/motd files may be customized to include cluster-related
information.
Managing a Single-Node Cluster
The number of nodes you will need for your Serviceguard cluster depends on the
processing requirements of the applications you want to protect. You may want to
configure a single-node cluster to take advantage of Serviceguard’s network failure
protection.
In a single-node cluster, a cluster lock is not required, since there is no other node in
the cluster. The output from the cmquerycl command omits the cluster lock
information area if there is only one node.
You still need to have redundant networks, but you do not need to specify any heartbeat
LANs, since there is no other node to send heartbeats to. In the cluster configuration
file, specify all the LANs that you want Serviceguard to monitor. Use the
STATIONARY_IP parameter, rather than HEARTBEAT_IP, to specify LANs that already
have IP addresses. For standby LANs, all that is required is the NETWORK_INTERFACE
parameter with the LAN device name.
Single-Node Operation
Single-node operation occurs in a single-node cluster or in a multi-node cluster,
following a situation where all but one node has failed, or where you have shut down
all but one node, which will probably have applications running. As long as the
Serviceguard daemon cmcld is active, other nodes can rejoin the cluster at a later time.
If the Serviceguard daemon fails when in single-node operation, it will leave the single
node up and your applications running. This is different from the loss of the
Serviceguard daemon in a multi-node cluster, which halts the node with a system reset,
and causes packages to be switched to adoptive nodes.
Managing the Running Cluster 249