In Nautilus (Ubuntu Cloud Archive Train Version) the osd caps profile rbd-read-only seems broken. It is impossible to map a RBD if the user has the following caps: [client.yyy] key = AQBYL8NdHDpnERAAhk8XOKgFNwhUpCo3EMaW3g== caps mgr = "profile rbd" caps mon = "profile rbd" caps osd = "profile rbd-read-only" (also tried with 'caps osd = "profile rbd-read-only pool=rbd") This is what I do and what I get back: root@maas:~# sudo rbd map rbd/ltsp-01 --read-only --name client.yyy -m 10.101.0.24 --keyfile /etc/ceph/ceph.client.yyy.key rbd: sysfs write failed In some cases useful info is found in syslog - try "dmesg | tail". rbd: map failed: (1) Operation not permitted I can see no reason in dmesg: root@maas:~# dmesg | tail [ 4442.395179] rbd0: p1 [ 4442.396140] rbd: rbd0: capacity 21474836480 features 0x5 [ 4900.499466] libceph: mon0 (1)10.101.0.24:3300 socket closed (con state CONNECTING) [ 4900.884945] libceph: mon0 (1)10.101.0.24:3300 socket closed (con state CONNECTING) [ 4901.876882] libceph: mon0 (1)10.101.0.24:3300 socket closed (con state CONNECTING) [ 4903.892861] libceph: mon0 (1)10.101.0.24:3300 socket closed (con state CONNECTING) [ 4903.959079] libceph: mon1 (1)10.101.0.24:6789 session established [ 4903.959624] libceph: client15954 fsid afdda66a-000c-11ea-824b-00163e31d42c [ 4923.847328] libceph: mon1 (1)10.101.0.24:6789 session established [ 4923.847749] libceph: client15969 fsid afdda66a-000c-11ea-824b-00163e31d42c Using /sys/bus/rbd/add_single_major directly does not work as well: root@maas:~# echo "10.101.0.24 name=client.yyy,secret=AQBYL8NdHDpnERAAhk8XOKgFNwhUpCo3EMaW3g== rbd ltsp-01" | sudo tee /sys/bus/rbd/add_single_major 10.101.0.24 name=client.yyy,secret=AQBYL8NdHDpnERAAhk8XOKgFNwhUpCo3EMaW3g== rbd ltsp-01 tee: /sys/bus/rbd/add_single_major: Operation not permitted Using a client with 'caps osd = "profile rbd"' does work without any problems. System Information: Ubuntu 18.04.3 ceph version 14.2.2 (4f8fa0a0024755aae7d95567c63f11d6862d55be) nautilus (stable) Kernel: 5.3.0-19-generic (but also tested with 5.0.0-32-generic and 4.15.0-66-generic) The cluster was built with MAAS and JUJU from openstack-charmers stable charms: Ubuntu 18.04.3 ceph version 14.2.2 (4f8fa0a0024755aae7d95567c63f11d6862d55be) nautilus (stable) Kernel: 4.15.0-66-generic I wanted to file this as a bug report, but my account (trickkiste) has not been approved yet. Probably due to this bug according to jdillaman on IRC: https://tracker.ceph.com/issues/42667 Regards, Markus