Synnefo » snf-ganeti

Replication network changes

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The :command:`gnt-node modify -s` command can be used to change the

secondary IP of a node. This operation can only be performed if:

- No instance is active on the target node

- The new target IP is reachable from the master's secondary IP

Also this operation will not allow to change a node from single-homed

(same primary and secondary ip) to multi-homed (separate replication

network) or vice versa, unless:

- The target node is the master node and `--force` is passed.

- The target cluster is single-homed and the new primary ip is a change

  to single homed for a particular node.

- The target cluster is multi-homed and the new primary ip is a change

  to multi homed for a particular node.

For example to do a single-homed to multi-homed conversion::

  $ gnt-node modify --force -s %SECONDARY_IP% %MASTER_NAME%

  $ gnt-node modify -s %SECONDARY_IP% %NODE1_NAME%

  $ gnt-node modify -s %SECONDARY_IP% %NODE2_NAME%

  $ gnt-node modify -s %SECONDARY_IP% %NODE3_NAME%

  ...

The same commands can be used for multi-homed to single-homed except the

secondary IPs should be the same as the primaries for each node, for

that case.

    # When changing the secondary ip, verify if this is a single-homed to

    # multi-homed transition or vice versa, and apply the relevant

    # restrictions.

      if master_singlehomed and self.op.secondary_ip != node.primary_ip:

        if self.op.force and node.name == master.name:

          self.LogWarning("Transitioning from single-homed to multi-homed"

                          " cluster. All nodes will require a secondary ip.")

        else:

          raise errors.OpPrereqError("Changing the secondary ip on a"

                                     " single-homed cluster requires the"

                                     " --force option to be passed, and the"

                                     " target node to be the master",

                                     errors.ECODE_INVAL)

      elif not master_singlehomed and self.op.secondary_ip == node.primary_ip:

        if self.op.force and node.name == master.name:

          self.LogWarning("Transitioning from multi-homed to single-homed"

                          " cluster. Secondary IPs will have to be removed.")

        else:

          raise errors.OpPrereqError("Cannot set the secondary IP to be the"

                                     " same as the primary IP on a multi-homed"

                                     " cluster, unless the --force option is"

                                     " passed, and the target node is the"

                                     " master", errors.ECODE_INVAL)

operation is taking place. Remember that the secondary ip must be

reachable from the master secondary ip, when being changed, so be sure

that the node has the new IP already configured and active. In order to

convert a cluster from single homed to multi-homed or vice versa

``--force`` is needed as well, and the target node for the first change

must be the master.