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mfsmaster - Man Page

start, restart or stop Lizard File System metadata server process


mfsmaster [-f] [-c CFGFILE] [-u] [-d] [-t LOCKTIMEOUT] [ACTION]
mfsmaster -s [-c CFGFILE]
mfsmaster -v
mfsmaster -h


mfsmaster is the metadata server program of Lizard File System. Depending on parameters it can start, restart or stop LizardFS metadata server process. Without any options it starts LizardFS metadata server, killing previously run process if lock file exists.

Metadata server can work in one of two modes (personalities):

  1. master
  2. shadow

If metadata server works with master personality it acts as main metadata server govering all file system metadata modifications. If metadata server works with shadow personality it acts as backup metadata server ready for immediate deployment as new master in case of current master failure. Shadow only accepts connections from lizardfs-admin, i.e. mfschunkserver, mfsmetalogger and mfsmount (the client) are not allowed to connect to shadow instance.

Current metadata server personality is defined in metadata server configuration file and can be changed on the fly from shadow to master by proper modification and reloading of its configuration file.

Master and shadow are designed to run simultaneously in sync forever. It is very unlikely but still (due to a memory corruption or a bug) possible that after some time their metadata will somehow differ. Since version 2.5.2 metadata checksum is maintained both by master and shadow, in order to detect and fix possible metadata corruptions. In case mismatch is detected shadow asks master to double check its metadata and dump its current snapshot. After the metadata is dumped and the checksum in master is recalculated shadow downloads the new metadata snapshot, which should ensure that master and all shadows have exactly the same metadata.

SIGHUP (or reload ACTION) forces mfsmaster to reload all configuration files.


print version information and exit


print usage information and exit


(deprecated, use start action instead) forcily run LizardFS master process, without trying to kill previous instance (this option allows to run LizardFS master if stale PID file exists)


(deprecated, use stop action instead) stop LizardFS master process


specify alternative path of configuration file (default is mfsmaster.cfg in system configuration directory)


log undefined configuration values (when default is assumed)


run in foreground, don’t daemonize


how long to wait for lockfile (default is 60 seconds)


is the one of start, stop, restart, reload, test, isalive or kill. Default action is restart.



configuration file for LizardFS master process (see mfsmaster.cfg(5) manual)


LizardFS access control file (used with mfsmounts 1.6.0 or later, see mfsexports.cfg(5) manual)


Network topology definitions (see mfstopology.cfg(5) manual)


PID file of running LizardFS master process


lock file of running LizardFS master process (created in data directory)

metadata.mfs,  metadata.mfs.back

LizardFS filesystem metadata image


LizardFS filesystem metadata change logs (merged into metadata.mfs once per hour)


LizardFS master charts state

Reporting Bugs

Report bugs to <contact@lizardfs.org>.

See Also

mfsmetarestore(8), mfschunkserver(8), mfsmount(1), mfsmaster.cfg(5), mfsexports.cfg(5), mfstopology.cfg(5), moosefs(7)

Referenced By

lizardfs(7), mfschunkserver(8), mfsexports.cfg(5), mfsmaster.cfg(5), mfsmetalogger(8), mfsmetarestore(8), mfsmount(1), mfstopology.cfg(5).