Managing HP Serviceguard A.11.20.10 for Linux, December 2012

• cmhaltnode [–t] [–f] <node_name>
• cmrunnode [–t] <node_name>
• cmhaltpkg [–t] <package_name>
• cmrunpkg [–t] [-n node_name] <package_name>
• cmmodpkg { -e [-t] | -d } [-n node_name] <package_name>
• cmruncl –v [–t]
NOTE: You cannot use the -t option with any command operating on a package in maintenance
mode; see “Maintaining a Package: Maintenance Mode” (page 212).
For more information about these commands, see their respective manpages. You can also perform
these preview functions in Serviceguard Manager: Select the Preview [] check box for the
action on the respective pages.
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 109).
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 107).
7.6.1.3 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.
Use cmeval rather than command preview mode when you want to see more than the effect of
a single command, and especially when you want to see the results of large-scale changes, or
changes that may interact in complex ways, such as changes to package priorities, node order,
dependencies and so on.
Using cmeval involves three major steps:
218 Cluster and Package Maintenance