Cannot place on myhost: Unknown hosts
Ran into this when attempting to use ceph orch to manage mgr’s.
It’s actually quite simple and has nothing (directly) to do with /etc/hosts or DNS. Only with the list of hosts that ceph knows internally.
And the problem — yet again — is that Ceph doesn’t manage multiple hostnames!!!
The hostname was registered as “myhost.mousetech.com”, but I had requested like this:
ceph orch apply mgr --placement="ceph01 myhost"
“ceph01” was OK, since that’s how Ceph had been set up. But when I added “myhost”, I did so with the fully-qualifed domain name. The bloody names must match what Ceph has on file exactly. Grrr!
So the proper command was:
ceph orch apply mgr --placement="ceph01 myhost.mousetech.com"