Managing HP Serviceguard for Linux Ninth Edition, April 2009

• On package startup and shutdown, as essentially the first and last functions the
package performs. These scripts are invoked by means of the parameter
external_pre_script (page 212); or
• During package execution, after volume-groups and file systems are activated,
and IP addresses are assigned, and before the service and resource functions are
executed; and again, in the reverse order, on package shutdown. These scripts are
invoked by means of the parameter external_script (page 212).
The scripts are also run when the package is validated by cmcheckconf and
cmapplyconf.
A package can make use of both kinds of script, and can launch more than one of each
kind; in that case the scripts will be executed in the order they are listed in the package
configuration file (and in the reverse order when the package shuts down).
Each external script must have three entry points: start, stop, and validate, and
should exit with one of the following values:
• 0 - indicating success.
• 1 - indicating the package will be halted, and should not be restarted, as a result
of failure in this script.
• 2 - indicating the package will be restarted on another node, or halted if no other
node is available.
NOTE: In the case of the validate entry point, exit values 1 and 2 are treated the
same; you can use either to indicate that validation failed.
The script can make use of a standard set of environment variables (including the
package name, SG_PACKAGE, and the name of the local node, SG_NODE) exported by
the package manager or the master control script that runs the package; and can also
call a function to source in a logging function and other utility functions. One of these
functions, sg_source_pkg_env(), provides access to all the parameters configured
for this package, including package-specific environment variables configured via the
pev_ parameter (page 211).
NOTE: Some variables, including SG_PACKAGE, and SG_NODE, are available only at
package run and halt time, not when the package is validated. You can use
SG_PACKAGE_NAME at validation time as a substitute for SG_PACKAGE.
For more information, see the template in $SGCONF/examples/
external_script.template.
A sample script follows. It assumes there is another script called monitor.sh, which
will be configured as a Serviceguard service to monitor some application. The
monitor.sh script (not included here) uses a parameter
PEV_MONITORING_INTERVAL, defined in the package configuration file, to
periodically poll the application it wants to monitor; for example:
138 Planning and Documenting an HA Cluster