Managing HP Serviceguard for Linux, Seventh Edition, July 2007

Understanding Serviceguard Software Components
Serviceguard Architecture
Chapter 336
NOTE The file cmcluster.conf contains the mappings that resolve the
symbolic references to $SGCONF, $SGROOT, $SGLBIN etc., used in this
manual. See “Understanding the Location of Serviceguard Files” on
page 140 for details.
NOTE Two of the central components of Serviceguard—Package Manager, and
Cluster Manager—run as parts of the cmcld daemon. This daemon runs
at priority 94 and is in the SCHED_RR class. No other process is allowed a
higher real-time priority.
Log Daemon: cmlogd
cmlogd is used by cmcld to write messages to the system log file. Any
message written to the system log by cmcld it written through cmlogd.
This is to prevent any delays in writing to syslog from impacting the
timing of cmcld. The path for this daemon is $SGLBIN/cmlogd.
Network Manager Daemon: cmnetd
This daemon monitors the health of cluster networks. It also handles the
addition and deletion of relocatable package IP(s), for both IPv4 and IPv6
addresses.
Lock LUN Daemon: cmdisklockd
cmdisklockd provides tie-breaking services when needed during cluster
re-formation. If a lock LUN is being used, the lock LUN daemon runs on
each node in the cluster and is started by cmcld when the node joins the
cluster. The lock LUN daemon on each node uses the same physical LUN.
Each member of the cluster initiates and maintains a connection to the
cmdisklockd daemon locally. If the cmdisklockd daemon dies it will be
restarted by cmcld and the node will reconnect to it. If there is a cluster
reconfiguration while cmdisklockd is down and there is a partition in
the cluster that requires tie-breaking, the reconfiguration will fail. The
path for this daemon is $SGLBIN/cmdisklockd.