Demote a Cloudmin master to a simple/regular host

Hi, people how do you suggest I go around this? I had lots of "fun" lately with servers going down (hardware) so trying to... harden my setup. That being said, I am not comfortable at all with my main server, the most powerful one, being the master, as it doesn't replicate it's own (very important ones) KVM guests.

So figured to build another dedicated master from parts around, and add another one later as a replica. So have to get rid of the old (now still a master) and set it as a regular KVM host. Legend:

host1 - the master at the time, an AMD EPYC, the one that needs to become only a host; remember this one runs a few KVM machines that just can't go down;

host4 - the "new" Xeon machine, built with with older parts, that needs to be the Cloudmin PRO master (will add a host5 replica for host4 if everything goes well);

host2, host3 - regular, simple KVM hosts controlled by the master.

My plan is (can it be THAT simple?):

  1. setup host4 as a replica of the current host1 master, as per documentation;

  2. set host4 as the primary master and host1 as a replica, so have to switch the roles between them; not sure in which order though, help?

  3. hoping that the VMs will run fine, I probably need to uninstall Cloudmin and dependencies from host1, using: yum remove webmin wbm-server-manager wbt-virtual-server-theme wbt-virtual-server-mobile wbm-security-updates

Will that be OK and leave the rest of the software stack in place? At what step do I need to set host4 as a standalone master?

  1. install only Webmin on host1, and register the system as a KVM host again in the new master host4

  2. find the running instances on host1, and boom! Done?

Interested mainly in responses from people that had some kind of experience doing this. Thank you very much!



That should be OK, although the only package you really need to remove is webmin wbm-server-manager (but make sure YUM doesn't also try to remove a bunch of dependencies).

fakemoth's picture
Submitted by fakemoth on Wed, 03/27/2019 - 00:24

Thanks, what about the timings at steps 2 & 3, do they matter? Should I switch first the old host1 Cloudmin master to a replica, and then host4 to standalone, at step 2?

For promoting a replica to master, you have to turn off the replication on the replica first and the remove it from the master system.