mfsmaster(8)

NAME

mfsmaster - start, restart or stop Lizard File System metadata server process

SYNOPSIS

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

DESCRIPTION

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

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

  • master
  • shadow

If the metadata server works with master personality it acts as the main metadata server govering all file system metadata modifications. If the metadata server works with shadow personality it acts as backup metadata server ready for immediate deployment as new master in case of the current master failing.

Shadow only accepts connections from lizardfs-admin, i.e. mfschunkserver, mfsmetalogger and mfsmount (the client) are not allowed to connect to the shadow instance.

Current metadata server personality is defined in the 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 a 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 the master is recalculated, shadow downloads the new metadata snapshot, which should ensure that the master and all its shadows have exactly the same metadata.

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

-v print version information and exit
-h print usage information and exit
-f (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)
-s (deprecated, use stop action instead) stop LizardFS master process
-c CFGFILE specify alternative path of configuration file (default is mfsmaster.cfg in system configuration directory)
-u log undefined configuration values (when default is assumed)
-d run in foreground, don*t daemonize
-t LOCKTIMEOUT how long to wait for lockfile (default is 60 seconds)
ACTION
is one of start, stop, restart, reload, test, isalive or kill. The default action is restart.

FILES

mfsmaster.cfg
configuration file for the LizardFS master process (see mfsmaster.cfg(5))
mfsexports.cfg
LizardFS access control file (used with mfsmount`s 1.6.0 or later, see mfsexports.cfg(5))
mfstopology.cfg
Network topology definitions (see mfstopology.cfg(5))
mfsmaster.lock
PID file of running LizardFS master process
.mfsmaster.lock
lock file of the running LizardFS master process (created in data directory)
metadata.mfs, metadata.mfs.back
LizardFS filesystem metadata image
changelog.*.mfs
LizardFS filesystem metadata change logs (merged into metadata.mfs once per hour)
data.stats
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), lizardfs(7)