NAME¶mfsmaster - start, restart or stop Lizard File System metadata server process
mfsmaster [-f] [-c CFGFILE] [-u] [-d] [-t LOCKTIMEOUT] [ACTION]
mfsmaster -s [-c CFGFILE]
DESCRIPTION¶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):
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.
REPORTING BUGS¶Report bugs to <email@example.com>.
COPYRIGHT¶Copyright 2008-2009 Gemius SA, 2013-2015 Skytechnology sp. z o.o.
LizardFS is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 3.
LizardFS is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with LizardFS. If not, see http://www.gnu.org/licenses/.
SEE ALSO¶mfsmetarestore(8), mfschunkserver(8), mfsmount(1), mfsmaster.cfg(5), mfsexports.cfg(5), mfstopology.cfg(5), moosefs(7)