Solved: service cman start failed: Redhat cluster

During redhat cluster configuration, when adding the nodes into cluster, sometimes it is failed with below error on the screen.

service cman start failed

To resolve this issue, try to start the service from backend.

And we can see the actual error message.

[root@nglinux2 ~]# service cman start
Starting cluster: 
   Checking if cluster has been disabled at boot...        [  OK  ]
   Checking Network Manager... 
Network Manager is either running or configured to run. Please disable it in the cluster.
                                                           [FAILED]
Stopping cluster: 
   Leaving fence domain...                                 [  OK  ]
   Stopping gfs_controld...                                [  OK  ]
   Stopping dlm_controld...                                [  OK  ]
   Stopping fenced...                                      [  OK  ]
   Stopping cman...                                        [  OK  ]
   Unloading kernel modules...                             [  OK  ]
   Unmounting configfs...                                  [  OK  ]
[root@nglinux2 ~]# 

The actual issue is Network Manager service is running.

We need to turn network manager off and assign static IPs to the nodes for redhat cluster to work properly.

Lets turn it off:

[root@nglinux2 ~]# /etc/init.d/NetworkManager stop
Stopping NetworkManager daemon:                            [  OK  ]

### Make sure to switch if off on reboot otherwise cman will not start.
[root@nglinux2 ~]# chkconfig NetworkManager off

Now try to start the cman service.

[root@nglinux2 ~]# service cman start
Starting cluster: 
   Checking if cluster has been disabled at boot...        [  OK  ]
   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  ]
   Tuning DLM kernel config...                             [  OK  ]
   Starting gfs_controld...                                [  OK  ]
   Unfencing self...                                       [  OK  ]
   Joining fence domain...                                 [  OK  ]
[root@nglinux2 ~]# 

And it worked. Now we can start the cman service since Network manager service is off.

However make sure the IP addresses were made static and free from NM.

I hope it can help someone who is facing similar issue.

However do post your suggestions or comments so that we all can learn more.