5.4. Batch Configuration Changes with crm

⁠5.4. Batch Configuration Changes with crm_shadow

Often, it is desirable to preview the effects of a series of configuration changes before updating the live configuration all at once. For this purpose, crm_shadow creates a "shadow" copy of the configuration and arranges for all the command-line tools to use it.

To begin, simply invoke crm_shadow --create with a name of your choice, and follow the simple on-screen instructions. Shadow copies are identified with a name to make it possible to have more than one.

Warning

Read this section and the on-screen instructions carefully; failure to do so could result in destroying the cluster’s active configuration!

⁠

Example 5.6. Creating and displaying the active sandbox

# crm_shadow --create test
Setting up shadow instance
Type Ctrl-D to exit the crm_shadow shell
shadow[test]:
shadow[test] # crm_shadow --which
test

From this point on, all cluster commands will automatically use the shadow copy instead of talking to the cluster’s active configuration. Once you have finished experimenting, you can either make the changes active via the --commit option, or discard them using the --delete option. Again, be sure to follow the on-screen instructions carefully!

For a full list of crm_shadow options and commands, invoke it with the --help option.

⁠

Example 5.7. Use sandbox to make multiple changes all at once, discard them, and verify real configuration is untouched

 shadow[test] # crm_failcount -r rsc_c001n01 -G
 scope=status  name=fail-count-rsc_c001n01 value=0
 shadow[test] # crm_standby --node c001n02 -v on
 shadow[test] # crm_standby --node c001n02 -G
 scope=nodes  name=standby value=on

 shadow[test] # cibadmin --erase --force
 shadow[test] # cibadmin --query
 <cib crm_feature_set="3.0.14" validate-with="pacemaker-3.0" epoch="112" num_updates="2" admin_epoch="0" cib-last-written="Mon Jan  8 23:26:47 2018" update-origin="rhel7-1" update-client="crm_node" update-user="root" have-quorum="1" dc-uuid="1">
   <configuration>
     <crm_config/>
     <nodes/>
     <resources/>
     <constraints/>
   </configuration>
   <status/>
 </cib>
  shadow[test] # crm_shadow --delete test --force
  Now type Ctrl-D to exit the crm_shadow shell
  shadow[test] # exit
  # crm_shadow --which
  No active shadow configuration defined
  # cibadmin -Q
 <cib crm_feature_set="3.0.14" validate-with="pacemaker-3.0" epoch="110" num_updates="2" admin_epoch="0" cib-last-written="Mon Jan  8 23:26:47 2018" update-origin="rhel7-1" update-client="crm_node" update-user="root" have-quorum="1">
    <configuration>
       <crm_config>
          <cluster_property_set id="cib-bootstrap-options">
             <nvpair id="cib-bootstrap-1" name="stonith-enabled" value="1"/>
             <nvpair id="cib-bootstrap-2" name="pe-input-series-max" value="30000"/>

See the next section, Section 5.5, “Simulate Cluster Activity with crm_simulate”, for how to test your changes before committing them to the live cluster.