2.4. Making Configuration Changes in a Sandbox

Often it is desirable to preview the effects of a series of changes before updating the configuration all at once. For this purpose, we have created crm_shadow which 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 the name of a configuration to create ^[7], and follow the simple on-screen instructions.

Warning

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

Example 2.7. 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 2.8. 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 cib_feature_revision="1" validate-with="pacemaker-1.0" admin_epoch="0" crm_feature_set="3.0" have-quorum="1" epoch="112"
      dc-uuid="c001n01" num_updates="1" cib-last-written="Fri Jun 27 12:17:10 2008">
    <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 cib_feature_revision="1" validate-with="pacemaker-1.0" admin_epoch="0" crm_feature_set="3.0" have-quorum="1" epoch="110"
       dc-uuid="c001n01" num_updates="551">
    <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"/>

^[7] Shadow copies are identified with a name, making it possible to have more than one.