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6.4. Updating a Configuration

Updating the cluster configuration consists of editing the cluster configuration file (/etc/cluster/cluster.conf) and propagating it to each node in the cluster. You can update the configuration using either of the following procedures:

6.4.1. Updating a Configuration Using cman_tool version -r

To update the configuration using the cman_tool version -r command, perform the following steps:
  1. At any node in the cluster, edit the /etc/cluster/cluster.conf file.
  2. Update the config_version attribute by incrementing its value (for example, changing from config_version="2" to config_version="3">).
  3. Save /etc/cluster/cluster.conf.
  4. Run the cman_tool version -r command to propagate the configuration to the rest of the cluster nodes.
  5. Verify that the updated configuration file has been propagated.
  6. You may skip this step (restarting cluster software) if you have made only the following configuration changes:
    • Deleting a node from the cluster configuration—except where the node count changes from greater than two nodes to two nodes. For information about deleting a node from a cluster and transitioning from greater than two nodes to two nodes, refer to Section 6.2, “Deleting or Adding a Node”.
    • Adding a node to the cluster configuration—except where the node count changes from two nodes to greater than two nodes. For information about adding a node to a cluster and transitioning from two nodes tp greater than two nodes, refer to Section 6.2.2, “Adding a Node to a Cluster”.
    • Changes to how daemons log information.
    • HA service/VM maintenance (adding, editing, or deleting).
    • Resource maintenance (adding, editing, or deleting).
    • Failover domain maintenance (adding, editing, or deleting).
    Otherwise, you must restart the cluster software as follows:
    1. At each node, stop the cluster software according to Section 6.1.2, “Stopping Cluster Software”. For example:
      [[email protected] ~]# service rgmanager stop
      Stopping Cluster Service Manager:                          [  OK  ]
      [[email protected] ~]# service gfs2 stop
      Unmounting GFS2 filesystem (/mnt/gfsA):                    [  OK  ]
      Unmounting GFS2 filesystem (/mnt/gfsB):                    [  OK  ]
      [[email protected] ~]# service clvmd stop
      Signaling clvmd to exit                                    [  OK  ]
      clvmd terminated                                           [  OK  ]
      [[email protected] ~]# service cman stop
      Stopping cluster: 
         Leaving fence domain...                                 [  OK  ]
         Stopping gfs_controld...                                [  OK  ]
         Stopping dlm_controld...                                [  OK  ]
         Stopping fenced...                                      [  OK  ]
         Stopping cman...                                        [  OK  ]
         Waiting for corosync to shutdown:                       [  OK  ]
         Unloading kernel modules...                             [  OK  ]
         Unmounting configfs...                                  [  OK  ]
      [[email protected] ~]#
    2. At each node, start the cluster software according to Section 6.1.1, “Starting Cluster Software”. For example:
      [[email protected] ~]# service cman start
      Starting cluster: 
         Checking Network Manager...                             [  OK  ]
         Global setup...                                         [  OK  ]
         Loading kernel modules...                               [  OK  ]
         Mounting configfs...                                    [  OK  ]
         Starting cman...                                        [  OK  ]
         Waiting for quorum...                                   [  OK  ]
         Starting fenced...                                      [  OK  ]
         Starting dlm_controld...                                [  OK  ]
         Starting gfs_controld...                                [  OK  ]
         Unfencing self...                                       [  OK  ]
         Joining fence domain...                                 [  OK  ]
      [[email protected] ~]# service clvmd start
      Starting clvmd:                                            [  OK  ]
      Activating VG(s):   2 logical volume(s) in volume group "vg_example" now active
                                                                 [  OK  ]
      [[email protected] ~]# service gfs2 start
      Mounting GFS2 filesystem (/mnt/gfsA):                      [  OK  ]
      Mounting GFS2 filesystem (/mnt/gfsB):                      [  OK  ]
      [[email protected] ~]# service rgmanager start
      Starting Cluster Service Manager:                          [  OK  ]
      [[email protected] ~]#
      Stopping and starting the cluster software ensures that any configuration changes that are checked only at startup time are included in the running configuration.
  7. At any cluster node, run cman_tools nodes to verify that the nodes are functioning as members in the cluster (signified as "M" in the status column, "Sts"). For example:
    [[email protected] ~]# cman_tool nodes
    Node  Sts   Inc   Joined               Name
       1   M    548   2010-09-28 10:52:21
       2   M    548   2010-09-28 10:52:21
       3   M    544   2010-09-28 10:52:21
  8. At any node, using the clustat utility, verify that the HA services are running as expected. In addition, clustat displays status of the cluster nodes. For example:
    [[email protected] ~]#clustat
    Cluster Status for mycluster @ Wed Nov 17 05:40:00 2010
    Member Status: Quorate
     Member Name                             ID   Status
     ------ ----                             ---- ------                         3 Online, rgmanager                         2 Online, rgmanager                         1 Online, Local, rgmanager
     Service Name                   Owner (Last)                   State         
     ------- ----                   ----- ------                   -----           
     service:example_apache            started       
     service:example_apache2        (none)                         disabled
  9. If the cluster is running as expected, you are done updating the configuration.