Managing HP Serviceguard for Linux, Eighth Edition, March 2008

Understanding Serviceguard Software Components
Serviceguard Architecture
Chapter 340
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
If a lock LUN is being used, cmdisklockd runs on each node in the
cluster, providing tie-breaking services when needed during cluster
re-formation. It is started by cmcld when the node joins the cluster. The
path for this daemon is $SGLBIN/cmdisklockd.
Cluster Object Manager Daemon: cmomd
This daemon is responsible for providing information about the cluster to
clients—external products or tools that depend on knowledge of the state
of cluster objects. Clients send queries to cmomd and receive responses
from it.
Clients send queries to the object manager and receive responses from it
(this communication is done indirectly, through a Serviceguard API). The
queries are decomposed into categories (of classes) which are serviced by
various providers. The providers gather data from various sources,
including, commonly, the cmclconfd daemons on all connected nodes,
returning data to a central assimilation point where it is filtered to meet
the needs of a particular query.