How do you manually call fencing agents from the commandline?

Environment

• Red Hat Enterprise Linux Server 5 (with the High Availability Add on)
• Red Hat Enterprise Linux Server 6 (with the High Availability Add on)

Issue

• How do you manually call fencing agents from the command line?

Resolution

There are three ways to execute a fence agent script. These 3 methods will attempt to reboot a particular machine with the fence device:

• Call the fence agent with command line args for the particular fence device script which is located in /sbin/fence_* or */usr/sbin/fence_**.

        $ fence_ipmilan -a 192.168.1.42 -l <username> -p <password> -o reboot
  

• Call the fence agent by piping stdin into the fence agents. Calling the fence agent and piping stdin into the agent can be accomplished a couple ways:

  • Redirection with file contents:

      $ cat /tmp/fence_ipmilan-args 
      ipaddr=192.168.1.42
      login=<username>
      password=<password>
      action=reboot 
      $ fence_ipmilan < /tmp/fence_ipmilan-args 
    

  • Echo a string via stdin into the fence agent:

      $ echo -e "ipaddr=192.168.1.42 \nlogin=<username> \npasswd=<password> \naction=reboot" | fence_ipmilan
    

• Call fence_node which will use the /etc/cluster/cluster.conf as arguments for the fence_agent.

  • The /etc/cluster/cluster.conf has the following arguments(some of the cluster.conf has been left out):

              <?xml version="1.0"?>
              <cluster config_version="1" name="cs-rh6cluster">
                ....
                <clusternodes>
                   <clusternode name="rhnode1.examplerh.com" nodeid="1">
                   <fence>
                     <method name="1">
                        <device name="rh5node1_ipmi"/>
                     </method>
                   </fence>
                    </clusternode>
                    ....
                 </clusternodes>
                 ....
                 <fencedevices>
                    <fencedevice agent="fence_ipmilan" ipaddr="192.168.1.42" login="username" name="rh5node1_ipmi" passwd="password"/>
                 </fencedevices>
                 ....
              </cluster>
    

  • The command that will be used to fence the node is:

      $ fence_node rh5node1.examplerh.com
    

For more information, see the tech brief at https://access.redhat.com/knowledge/techbriefs/fencing-red-hat-enterprise-linux-methods-use-cases-and-failover.

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