The Ceph admin socket allows you to query a daemon via a socket interface.

By default, Ceph sockets reside under /var/run/ceph. To access a daemon via the admin socket, you must login to the host running the daemon and use either of the following commands:

# ceph daemon {daemon-name} {command}
# ceph daemon {path-to-socket-file} {command}
# ceph --admin-daemon {path-to-socket-file} {command}

For example, the following are equivalent (on pulpos-admin, which runs a ceph-mon daemon):

[root@pulpo-admin ~]# ceph daemon mon.pulpo-admin help
[root@pulpo-admin ~]# ceph daemon /var/run/ceph/ceph-mon.pulpo-admin.asok help
[root@pulpo-admin ~]# ceph --admin-daemon /var/run/ceph/ceph-mon.pulpo-admin.asok help

You probably don’t want to restart Ceph daemon every time you make a change to your configuration. Fortunately, Ceph allows you to make changes to the configuration of a ceph-osd, ceph-mon, or ceph-mds daemon at runtime. The following reflects runtime configuration usage:

# ceph tell {daemon-type}.{id or *} injectargs --{name} {value} [--{name} {value}]