Managing HP Serviceguard for Linux Ninth Edition, April 2009

NOTE: You cannot use the -t option with any command operating on a package in
maintenance mode; see “Maintaining a Package: Partial-Startup Maintenance Mode”
(page 237).
For more information about these commands, see their respective manpages. You can
also perform these preview functions in Serviceguard Manager: check the Preview
[...] box for the action in question.
When you use the -t option, the command, rather than executing as usual, predicts
the results that would occur, sending a summary to $stdout. For example, assume
that pkg1 is a high-priority package whose primary node is node1, and which depends
on pkg2 and pkg3 to run on the same node. These are lower-priority packages which
are currently running on node2. pkg1 is down and disabled, and you want to see the
effect of enabling it:
cmmodpkg -e -t pkg1
You will see output something like this:
package:pkg3|node:node2|action:failing
package:pkg2|node:node2|action:failing
package:pkg2|node:node1|action:starting
package:pkg3|node:node1|action:starting
package:pkg1|node:node1|action:starting
cmmodpkg: Command preview completed successfully
This shows that pkg1, when enabled, will “drag” pkg2 and pkg3 to its primary node,
node1. It can do this because of its higher priority; see “Dragging Rules for Simple
Dependencies” (page 123). Running the preview confirms that all three packages will
successfully start on node2 (assuming conditions do not change between now and
when you actually enable pkg1, and there are no failures in the run scripts).
NOTE: The preview cannot predict run and halt script failures.
For more information about package dependencies and priorities, see “About Package
Dependencies” (page 121).
Using cmeval
You can use cmeval to evaluate the effect of cluster changes on Serviceguard packages.
You can also use it simply to preview changes you are considering making to the cluster
as a whole.
You can use cmeval safely in a production environment; it does not affect the state of
the cluster or packages. Unlike command preview mode (the -t discussed above)
cmeval does not require you to be logged in to the cluster being evaluated, and in fact
that cluster does not have to be running, though it must use the same Serviceguard
release and patch version as the system on which you run cmeval.
Reconfiguring a Cluster 243