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5.2. Creating a Basic Cluster Configuration File

Provided that cluster hardware, Red Hat Enterprise Linux, and High Availability Add-On software are installed, you can create a cluster configuration file (/etc/cluster/cluster.conf) and start running the High Availability Add-On. As a starting point only, this section describes how to create a skeleton cluster configuration file without fencing, failover domains, and HA services. Subsequent sections describe how to configure those parts of the configuration file.

Important

This is just an interim step to create a cluster configuration file; the resultant file does not have any fencing and is not considered to be a supported configuration.
The following steps describe how to create and configure a skeleton cluster configuration file. Ultimately, the configuration file for your cluster will vary according to the number of nodes, the type of fencing, the type and number of HA services, and other site-specific requirements.
  1. At any node in the cluster, create /etc/cluster/cluster.conf, using the template of the example in Example 5.1, “cluster.conf Sample: Basic Configuration”.
  2. (Optional) If you are configuring a two-node cluster, you can add the following line to the configuration file to allow a single node to maintain quorum (for example, if one node fails):
    <cman two_node="1" expected_votes="1"/>
    Refer to Example 5.2, “cluster.conf Sample: Basic Two-Node Configuration”.
  3. Specify the cluster name and the configuration version number using the cluster attributes: name and config_version (refer to Example 5.1, “cluster.conf Sample: Basic Configuration” or Example 5.2, “cluster.conf Sample: Basic Two-Node Configuration”).
  4. In the clusternodes section, specify the node name and the node ID of each node using the clusternode attributes: name and nodeid.
  5. Save /etc/cluster/cluster.conf.
  6. Validate the file with against the cluster schema (cluster.rng) by running the ccs_config_validate command. For example: 
    [root@example-01 ~]# ccs_config_validate 
Configuration validates
  7. Propagate the configuration file to /etc/cluster/ in each cluster node. For example, you could propagate the file to other cluster nodes using the scp command.

    Note

    Propagating the cluster configuration file this way is necessary the first time a cluster is created. Once a cluster is installed and running, the cluster configuration file can be propagated using the cman_tool version -r. It is possible to use the scp command to propagate an updated configuration file; however, the cluster software must be stopped on all nodes while using the scp command.In addition, you should run the ccs_config_validate if you propagate an updated configuration file via the scp.

    Note

    While there are other elements and attributes present in the sample configuration file (for example, fence and fencedevices, there is no need to populate them now. Subsequent procedures in this chapter provide information about specifying other elements and attributes.
  8. Start the cluster. At each cluster node run the following command:
    service cman start
    For example: 
    [root@example-01 ~]# 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  ]
  9. 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: 
    [root@example-01 ~]# cman_tool nodes
Node  Sts   Inc   Joined               Name
   1   M    548   2010-09-28 10:52:21  node-01.example.com
   2   M    548   2010-09-28 10:52:21  node-02.example.com
   3   M    544   2010-09-28 10:52:21  node-03.example.com
  10. If the cluster is running, proceed to Section 5.3, “Configuring Fencing”.

Basic Configuration Examples

Example 5.1, “cluster.conf Sample: Basic Configuration” and Example 5.2, “cluster.conf Sample: Basic Two-Node Configuration” (for a two-node cluster) each provide a very basic sample cluster configuration file as a starting point. Subsequent procedures in this chapter provide information about configuring fencing and HA services.
Example 5.1. cluster.conf Sample: Basic Configuration

<cluster name="mycluster" config_version="2">
   <clusternodes>
     <clusternode name="node-01.example.com" nodeid="1">
         <fence>
         </fence>
     </clusternode>
     <clusternode name="node-02.example.com" nodeid="2">
         <fence>
         </fence>
     </clusternode>
     <clusternode name="node-03.example.com" nodeid="3">
         <fence>
         </fence>
     </clusternode>
   </clusternodes>
   <fencedevices>
   </fencedevices>
   <rm>
   </rm>
</cluster>

Example 5.2. cluster.conf Sample: Basic Two-Node Configuration

<cluster name="mycluster" config_version="2">
   <cman two_node="1" expected_votes="1"/>
   <clusternodes>
     <clusternode name="node-01.example.com" nodeid="1">
         <fence>
         </fence>
     </clusternode>
     <clusternode name="node-02.example.com" nodeid="2">
         <fence>
         </fence>
     </clusternode>
   </clusternodes>
   <fencedevices>
   </fencedevices>
   <rm>
   </rm>
</cluster>