Managing HP Serviceguard A.11.20.20 for Linux, March 2014

7.6.1 Previewing the Effect of Cluster Changes
Many variables affect package placement, including the availability of cluster nodes; the availability
of networks and other resources on those nodes; failover and failback policies; and package
weights, dependencies, and priorities, if you have configured them. You can preview the effect
on packages of certain actions or events before they actually occur.
For example, you might want to check to see if the packages are placed as you expect when the
cluster first comes up; or preview what happens to the packages running on a given node if the
node halts, or if the node is then restarted; or you might want to see the effect on other packages
if another, currently disabled, package is enabled, or if a package halts and cannot restart because
none of the nodes on its node_list is available.
Serviceguard provides two ways to do this: you can use the preview mode of Serviceguard
commands, or you can use the cmeval (1m) command to simulate different cluster states.
Alternatively, you might want to model changes to the cluster as a whole; cmeval allows you to
do this; see “Using cmeval” (page 227).
7.6.1.1 What You Can Preview
You can preview any of the following, or all of them simultaneously:
• Cluster bring-up (cmruncl)
• Cluster node state changes (cmrunnode, cmhaltnode)
• Package state changes (cmrunpkg, cmhaltpkg)
• Package movement from one node to another
• Package switching changes (cmmodpkg -e)
• Availability of package subnets, resources, and storage
• Changes in package priority, node order, dependency, failover and failback policy, node
capacity and package weight
7.6.1.2 Using Preview mode for Commands in Serviceguard Manager
The following commands support the -t option, which allows you to run the command in preview
mode:
• 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 220).
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:
226 Cluster and Package Maintenance