Changing IP addresses and host names

GPFS™ assumes that IP addresses and host names remain constant. In the rare event that such a change becomes necessary or is inadvertently introduced by reinstalling a node with a disk image from a different node for example, follow the steps in this topic.

If all of the nodes in the cluster are affected:
  1. Issue the mmshutdown -a command to stop GPFS on all nodes.
  2. Using the documented procedures for the operating system, add the new host names or IP addresses but do not remove the old ones yet. This can be achieved, for example, by creating temporary alias entries in /etc/hosts. Do not restart the nodes until the mmchnode command in Step 3 is executed successfully. If any of these conditions cannot be met, use the alternate procedure described in this section.
  3. Update the nodes that the cluster uses as the administration interface node and the daemon interface node, if necessary. To update these values, issue the mmchnode command with the --admin-interface and the --daemon-interface options.
    Note: You cannot specify the --daemon-interface option for a quorum node if CCR is enabled. Temporarily change the node to a nonquorum node. Then issue the mmchnode command with the --daemon-interface option against the nonquorum node. Finally, change the node back into a quorum node.
  4. If the IP addresses over which the subnet attribute is defined are changed, you must update your configuration by issuing the mmchconfig command with the subnets attribute.
  5. Start GPFS on all nodes with mmstartup -a.
  6. Remove the unneeded old host names and IP addresses.
If only a subset of the nodes are affected, it may be easier to make the changes using these steps:
  1. Before any of the host names or IP addresses are changed:
    • Use the mmshutdown command to stop GPFS on all affected nodes.
    • If the host names or IP addresses of the primary or secondary GPFS cluster configuration server nodes must change, use the mmchcluster command to specify another node to serve as the primary or secondary GPFS cluster configuration server.
    • If the host names or IP addresses of an NSD server node must change, temporarily remove the node from being a server with the mmchnsd command. Then, after the node has been added back to the cluster, use the mmchnsd command to change the NSDs to their original configuration. Use the mmlsnsd command to obtain the NSD server node names.
    • Use the mmdelnode command to delete all affected nodes from the GPFS cluster.
  2. Change the node names and IP addresses using the documented procedures for the operating system.
  3. If the IP addresses over which the subnet attribute is defined are changed, you need to update your configuration by using the mmchconfig command with the subnets attribute.
  4. Issue the mmaddnode command to restore the nodes to the GPFS cluster.
  5. If necessary, use the mmchcluster and mmchnsd commands to restore the original configuration and the NSD servers.