Replace a master node

ENTERPRISE

Replacing a master node in an existing DC/OS cluster

You can replace a master node in an existing DC/OS cluster. Only one master should be replaced at a time.

Remove the existing master

To begin, simply shut down the master node you want to replace.

Add the new master

The procedure for adding the new master node to replace the one taken offline in the previous step is quite simple.

master_discovery: static

If you have configured static master discovery in your config.yaml (i.e., master_discovery: static) then the new server must have the same internal IP address as the old.

Once you’ve double-checked that the new server has the same internal IP address as the old one and the old server is completely unreachable from the cluster you can proceed to install the new master as you would normally.

master_discovery: master_http_loadbalancer

If you have configured dynamic master discovery in your config.yaml (i.e., master_discovery: master_http_loadbalancer) then simply install the new master as you would normally.

Check that the new master is healthy

In order to confirm that the new master has joined the cluster successfully you must validate that the procedure was successful before proceeding.

The procedure is identical to the verification performed following a master node upgrade.

The exact steps are listed under ‘Validate the upgrade’ in the Upgrading a master section in the upgrade documentation.