[ceph-users] Trouble removing MDS daemons | Luminous

John Spray jspray at redhat.com
Wed Nov 8 02:44:34 PST 2017

On Wed, Nov 8, 2017 at 10:39 AM, Geoffrey Rhodes <geoffrey at rhodes.org.za> wrote:
> Good day,
> Firstly I'd like to acknowledge that I consider myself a Ceph noob.
> OS: Ubuntu 16.04.3 LTS
> Ceph version: 12.2.1
> I'm running a small six node POC cluster with three MDS daemons. (One on
> each node,  node1, node2 and node3)
> I've also configured three ceph file systems fsys1, fsys2 and fsys3.
> I'd like to remove two of the file systems (fsys2 and fsys3) and at least
> one if not both of the MDS daemons.
> I was able to fail MDS on node3 using command "sudo ceph mds fail node3"
> followed by "sudo ceph mds rmfailed 0 --yes-i-really-mean-it".

When you want to remove a filesystem, you only need to do this:
ceph fs set <fs name> cluster_down true  # prevent any MDSs rejoining
the filesystem
ceph mds fail <daemon> # for each MDS that was in the filesystem
ceph fs rm <fs name> # should work because the MDSs are now no longer
involved in this filesystem.

> Then I removed the file system using command "sudo ceph fs rm fsys3
> --yes-i-really-mean-it".
> Running command "sudo ceph fs status" confirms that fsys3 is now failed and
> that the MDS daemon on node3 has become a standby MDS.
> I've combinations of "ceph mds (fail, deactivate, rm, rmfailed" but I can't
> seem to be able to remove the standby daemon.

You don't need to explicitly remove standby daemons using the ceph
CLI: you can just get rid of the daemon itself on the server where
it's running.  Ceph will just forget about the standby when it stops
receiving messages from that daemon.


> After rebooting node3 and running command "sudo ceph fs status" -  fsys3 is
> no longer a listed file system and node3 is still standby MDS.
> I've searched for details on this topic but what I have found has not helped
> me.
> Could anybody assist with the correct steps for removing MDS daemons and
> ceph file systems on nodes?
> It would be useful to be able to know how to completely remove all ceph file
> systems and MDS daemons should I have no further use for them in a cluster.
> Kind regards
> Geoffrey Rhodes
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> ceph-users at lists.ceph.com
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