ceph-mon – ceph monitor daemon


ceph-mon -i monid [ –mon-data mondatapath ]


ceph-mon is the cluster monitor daemon for the Ceph distributed file system. One or more instances of ceph-mon form a Paxos part-time parliament cluster that provides extremely reliable and durable storage of cluster membership, configuration, and state.

The mondatapath refers to a directory on a local file system storing monitor data. It is normally specified via the mon data option in the configuration file.


-f, --foreground

Foreground: do not daemonize after startup (run in foreground). Do not generate a pid file. Useful when run via ceph-run(8).


Debug mode: like -f, but also send all log output to stderr.

--setuser userorgid

Set uid after starting. If a username is specified, the user record is looked up to get a uid and a gid, and the gid is also set as well, unless –setgroup is also specified.

--setgroup grouporgid

Set gid after starting. If a group name is specified the group record is looked up to get a gid.

-c ceph.conf, --conf=ceph.conf

Use ceph.conf configuration file instead of the default /etc/ceph/ceph.conf to determine monitor addresses during startup.


Initialize the mon data directory with seed information to form and initial ceph file system or to join an existing monitor cluster. Three pieces of information must be provided:

  • The cluster fsid. This can come from a monmap (--monmap <path>) or explicitly via --fsid <uuid>.

  • A list of monitors and their addresses. This list of monitors can come from a monmap (--monmap <path>), the mon host configuration value (in ceph.conf or via -m host1,host2,...), or (for backward compatibility) the deprecated mon addr lines in ceph.conf. If this monitor is to be part of the initial monitor quorum for a new Ceph cluster, then it must be included in the initial list, matching either the name or address of a monitor in the list. When matching by address, either the public addr or public subnet options may be used.

  • The monitor secret key mon.. This must be included in the keyring provided via --keyring <path>.


Specify a keyring for use with --mkfs.


ceph-mon is part of Ceph, a massively scalable, open-source, distributed storage system. Please refer to the Ceph documentation at http://ceph.com/docs for more information.

See also

ceph(8), ceph-mds(8), ceph-osd(8)