ceph-mds is the metadata server daemon for the Ceph distributed file system. One or more instances of ceph-mds collectively manage the file system namespace, coordinating access to the shared OSD cluster.
Each ceph-mds daemon instance should have a unique name. The name is used to identify daemon instances in the ceph.conf.
Once the daemon has started, the monitor cluster will normally assign it a logical rank, or put it in a standby pool to take over for another daemon that crashes. Some of the specified options can cause other behaviors.
If you specify hot-standby, you must either specify the rank on the command line, or specify one of the mds_standby_for_[rank|name] parameters in the config. The command line specification overrides the config, and specifying the rank overrides specifying the name.
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.
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.
Set gid after starting. If a group name is specified the group record is looked up to get a gid.
Use ceph.conf configuration file instead of the default /etc/ceph/ceph.conf to determine monitor addresses during startup.
Connect to specified monitor (instead of looking through ceph.conf).
Start as a hot standby for MDS <rank>.
ceph-mds 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.