Managing HP Serviceguard for Linux, Sixth Edition, August 2006

Understanding Serviceguard Software Components
Serviceguard Architecture
Chapter 3 35
Cluster Object Manager Daemon: cmomd
This daemon is responsible for providing information about the cluster to
clients—external products or tools such as Serviceguard Manager that
depend on knowledge of the state of cluster objects. Clients send queries
to cmomd and receive responses from it. This daemon may not be running
on your system; it is used only by clients of the object manager.
cmomd accepts connections from clients, and examines queries. 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 the exact client query. This daemon is started by xinetd.
Relevant parameters are found in the /etc/xinetd.d/hacl-probe file.
The path for this daemon is: $SGLBIN/cmomd.
Service Assistant Daemon: cmsrvassistd
This daemon forks and execs any script or processes as required by the
cluster daemon, cmcld. There are two type of forks that this daemon
carries out:
• Executing package run and halt scripts
• Launching services
For services, cmcld monitors the service process and, depending on the
number of service retries, cmcld either restarts the service through
cmsrvassistd or it causes the package to halt and moves the package to
an available alternate node. The path for this daemon is:
$SGLBIN/cmsrvassistd.
Resource Monitor Daemon: cmresmond
This daemon communicates with cmresserviced processes that are
launched by Serviceguard packages. The daemon reports on the status of
the resources (e.g., disks) for which a monitoring request is received. If a
device is found to be down, the cmresserviced process will exit, allowing
the package to fail over.
Resources are configured for monitoring by examining all the package
control scripts in the cluster and identifying the devices for which
monitoring is desired. These are included in a configuration file (by
default, this is named $SGCONF/cmresmond_config.xml), which the