Managing HP Serviceguard for Linux, Sixth Edition, August 2006

Understanding Serviceguard Software Components
Serviceguard Architecture
Chapter 334
The cmcld daemon also detects the health of the networks on the system.
Finally, this daemon handles the management of Serviceguard packages,
determining where to run them and when to start them. The path for
this daemon is: $SGLBIN/cmcld.
NOTE The file /etc/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 122 for details.
NOTE The three central components of Serviceguard—Package Manager,
Cluster Manager, and Network Manager—run as parts of the cmcld
daemon. This daemon runs as a 94 priority process and is in the
SCHED_RR class. No other process is allowed to be a higher priority
real-time process.
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.
Lock LUN Daemon: cmlockdiskd
cmlockdiskd provides tie-breaking services when needed during cluster
re-formation. 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 in order to determine
which node will continue in a tie-breaking situation.
Each member of the cluster will initiate and maintain a connection to the
cmlocklistd daemon locally. If the cmlockdiskd daemon dies it will be
restarted by cmcld and the node will reconnect to it. If there is a cluster
reconfiguration while cmlockdiskd 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/cmlockdiskd.