RHEL 6 Cluster Admin - 6.2.2. Adding a Node to a Cluster

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6.2.2. Adding a Node to a Cluster

Adding a node to a cluster consists of updating the cluster configuration, propagating the updated configuration to the node to be added, and starting the cluster software on that node. To add a node to a cluster, perform the following steps:

At any node in the cluster, edit the /etc/cluster/cluster.conf to add a clusternode section for the node that is to be added. For example, in Example 6.2, “Two-node Cluster Configuration”, if node-03.example.com is supposed to be added, then add a clusternode section for that node. If adding a node (or nodes) causes the cluster to transition from a two-node cluster to a cluster with three or more nodes, remove the following cman attributes from /etc/cluster/cluster.conf:
- cman two_node="1"
- expected_votes="1"
Refer to Section 6.2.3, “Examples of Three-Node and Two-Node Configurations” for comparison between a three-node and a two-node configuration.
Update the config_version attribute by incrementing its value (for example, changing from config_version="2" to config_version="3">).
Save /etc/cluster/cluster.conf.
(Optional) Validate the updated file against the cluster schema (cluster.rng) by running the ccs_config_validate command. For example:
```
[root@example-01 ~]# ccs_config_validate 
Configuration validates
```
Run the cman_tool version -r command to propagate the configuration to the rest of the cluster nodes.
Verify that the updated configuration file has been propagated.
Propagate the updated configuration file to /etc/cluster/ in each node to be added to the cluster. For example, use the scp command to send the updated configuration file to each node to be added to the cluster.

If the node count of the cluster has transitioned from two nodes to greater than two nodes, you must restart the cluster software in the existing cluster nodes as follows:

At each node, stop the cluster software according to Section 6.1.2, “Stopping Cluster Software”. For example:

[root@example-01 ~]# service rgmanager stop
Stopping Cluster Service Manager:                          [  OK  ]
[root@example-01 ~]# service gfs2 stop
Unmounting GFS2 filesystem (/mnt/gfsA):                    [  OK  ]
Unmounting GFS2 filesystem (/mnt/gfsB):                    [  OK  ]
[root@example-01 ~]# service clvmd stop
Signaling clvmd to exit                                    [  OK  ]
clvmd terminated                                           [  OK  ]
[root@example-01 ~]# 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  ]
[root@example-01 ~]#

At each node, start the cluster software according to Section 6.1.1, “Starting Cluster Software”. 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  ]
[root@example-01 ~]# service clvmd start
Starting clvmd:                                            [  OK  ]
Activating VG(s):   2 logical volume(s) in volume group "vg_example" now active
                                                           [  OK  ]
[root@example-01 ~]# service gfs2 start
Mounting GFS2 filesystem (/mnt/gfsA):                      [  OK  ]
Mounting GFS2 filesystem (/mnt/gfsB):                      [  OK  ]
[root@example-01 ~]# service rgmanager start
Starting Cluster Service Manager:                          [  OK  ]
[root@example-01 ~]#

At each node to be added to the cluster, start the cluster software according to Section 6.1.1, “Starting Cluster Software”. 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  ]
[root@example-01 ~]# service clvmd start
Starting clvmd:                                            [  OK  ]
Activating VG(s):   2 logical volume(s) in volume group "vg_example" now active
                                                           [  OK  ]
[root@example-01 ~]# service gfs2 start
Mounting GFS2 filesystem (/mnt/gfsA):                      [  OK  ]
Mounting GFS2 filesystem (/mnt/gfsB):                      [  OK  ]

[root@example-01 ~]# service rgmanager start
Starting Cluster Service Manager:                          [  OK  ]
[root@example-01 ~]#

At any node, using the clustat utility, verify that each added node is running and part of the cluster. For example:

[root@example-01 ~]#clustat
Cluster Status for mycluster @ Wed Nov 17 05:40:00 2010
Member Status: Quorate

 Member Name                             ID   Status
 ------ ----                             ---- ------
 node-03.example.com                         3 Online, rgmanager
 node-02.example.com                         2 Online, rgmanager
 node-01.example.com                         1 Online, Local, rgmanager

 Service Name                   Owner (Last)                   State         
 ------- ----                   ----- ------                   -----           
 service:example_apache         node-01.example.com            started       
 service:example_apache2        (none)                         disabled

For information about using clustat, refer to Section 6.3, “Managing High-Availability Services”.

In addition, you can use cman_tool status to verify node votes, node count, and quorum count. For example:

[root@example-01 ~]#cman_tool status
Version: 6.2.0
Config Version: 19
Cluster Name: mycluster 
Cluster Id: 3794
Cluster Member: Yes
Cluster Generation: 548
Membership state: Cluster-Member
Nodes: 3
Expected votes: 3
Total votes: 3
Node votes: 1
Quorum: 2  
Active subsystems: 9
Flags: 
Ports Bound: 0 11 177  
Node name: node-01.example.com
Node ID: 3
Multicast addresses: 239.192.14.224 
Node addresses: 10.15.90.58

At any node, you can use the clusvcadm utility to migrate or relocate a running service to the newly joined node. Also, you can enable any disabled services. For information about using clusvcadm, refer to Section 6.3, “Managing High-Availability Services”