mfsmount(8)

📦
version 4.59.2 · 5 versions
, in arch rolling, nixos 26.05, nixpkgs unstable, ubuntu stonking

💖 mfsmount(8) — like, the MooseFS mounter, bestie 💖

okay so this is mfsmount, part of MooseFS (the manual section 8 girlies know what's up), and she's the one who actually gets your MooseFS filesystem mounted. let's get into it 🫶

✨ NAME ✨

mfsmount — mount MooseFS. that's it. that's the whole job. and she ATE. 💅

🌈 SYNOPSIS 🌈

mfsmount [HOST[:PORT]:[PATH]] [options] mountpoint

mfsmount -h|--help

mfsmount -V|--version

and since version 3.0.75 (Linux only, sorry besties):

mount -t moosefs [options] [HOST[:PORT]:[PATH]] mountpoint

🦋 DESCRIPTION 🦋

Mount MooseFS. periodt. no cap, that's literally the whole description. iconic behavior honestly. ✨

🎀 OPTIONS 🎀

General options 🧚

  • -h, --help — shows you the help and then dips. bye! 👋
  • -V — tells you the version info and exits. slay.

FUSE options 🔥

  • -d, -o debug — turns on debug mode. heads up, this implies -f.
  • -f — foreground operation. she stays right there in your terminal, no running away.
  • -s — disables multi-threaded operation. single-threaded arc, lowkey.

MooseFS options 👑

  • -c CFGFILE, -o mfscfgfile=CFGFILE — loads a file with extra mount options. more options? yes please.
  • -m, --meta, -o mfsmeta — mounts the MFSMETA companion filesystem instead of the primary MooseFS. the side quest filesystem.
  • -n — omits the default mount options (-o allow_other). no defaults for you.
  • -p — prompts you for a password. it's the interactive version of -o mfspassword=PASS.
  • -H HOST, -o mfsmaster=HOST — connects to the MooseFS master on HOST (default is mfsmaster).
  • -P PORT, -o mfsport=PORT — connects to the MooseFS master on PORT (default is 9421).
  • -B IP, -o mfsbind=IP — the local address to use for connecting with the master, instead of the default one.
  • -L IP, -o mfsproxy=IP — defines the listen ip address of the local master proxy for communicating with tools (default: 127.0.0.1).
  • -S PATH, -o mfssubfolder=PATH — mounts the specified MooseFS directory (default is /, i.e. the whole entire filesystem, go big or go home).
  • -o mfspassword=PASSWORD — authenticates to the MooseFS master with PASSWORD.
  • -o mfspassfile=FILENAME — authenticates to the MooseFS master with the password stored in the first line of the file pointed to by FILENAME.
  • -o mfsmd5pass=MD5 — authenticates to the MooseFS master using the directly given MD5 (only if mfspassword option is not specified — she's backup).
  • -o mfsdonotrememberpassword — does not remember the password in memory. more secure, but when the session is lost then a new session is created without a password. the tradeoff is real 😭
  • -o mfsdebug — prints some MooseFS-specific debugging information.
  • -o mfsmemlock — tries to lock memory (all allocated memory will be mapped to physical RAM — which also means no swapping). she's committed, she's staying in RAM fr fr.
  • -o allowoomkiller — does not disable the out of memory killer (Linux only).
  • -o mfslimitarenas=N — if N>0 then limit glibc malloc arenas (Linux only — default: 4).
  • -o mfsflattrash — uses flat trash structure in meta. this option was added for compatibility reasons — since version 3.0.64 trash is split into 4096 subfolders which reduces problems with big trashes.
  • -o mfsdelayedinit — the connection with the master is done in background. with this option the mount can be run without network (good for being run from fstab / init scripts etc.).
  • -o mfsmkdircopysgid=N — sgid bit should be copied during mkdir operation (default depends on operating system).
  • -o mfssugidclearmode=SMODE — sets the sugid clear mode (see SUGID CLEAR MODES below; default depends on operating system).
  • -o mfscachemode=CMODE — sets the cache mode (see DATA CACHE MODES below; default is AUTO).
  • -o mfscachefiles — (deprecated!!) preserve file data in cache (equivalent to -o mfscachemode=YES). she's old, be nice to her.
  • -o mfsreaddirplusminto=SEC — sets the minimal entry/attributes cache timeout for readdirplus in seconds (default: 0.0001).
  • -o mfsattrcacheto=SEC — sets the attributes cache timeout in seconds (default: 1.0).
  • -o mfsxattrcacheto=SEC — sets the extended attributes (xattr) cache timeout in seconds (default: 30.0).
  • -o mfsentrycacheto=SEC — sets the file entry cache timeout in seconds (default: 0.0, i.e. no cache).
  • -o mfsdirentrycacheto=SEC — sets the directory entry cache timeout in seconds (default: 1.0).
  • -o mfsnegentrycacheto=SEC — sets the negative entry cache timeout in seconds (default: 0.0).
  • -o mfssymlinkcacheto=SEC — sets the symbolic link cache timeout in seconds (default: 300.0).
  • -o mfsgroupscacheto=SEC — sets the supplementary groups cache timeout in seconds (default: 300.0). setting this value to 0 disables supplementary groups support. bold move.
  • -o mfsrlimitnofile=N — tries to change the limit of simultaneously opened file descriptors on startup (default: 100000).
  • -o mfsnice=LEVEL — tries to change the nice level to the specified value on startup (default: -19). she's very nice.
  • -o mfswritecachesize=N — specifies write cache size in MiB (in range: 16..2048 — default: 256).
  • -o mfsreadaheadsize=N — defines the size of all read ahead buffers in MiB (in range: 16..2048 — default: 256).
  • -o mfsreadaheadleng=N — defines the amount of bytes to be additionally read (in range: 128KiB..2MiB — default: 1048576).
  • -o mfsreadaheadtrigger=N — defines the amount of bytes read sequentially that turns on read ahead (default: 10 * mfsreadaheadleng).
  • -o mfserroronlostchunk — when all known chunkservers are connected to the master and the required chunk is missing, then immediately finish I/O and return an error. no waiting around 💀
  • -o mfserroronnospace — when all known chunkservers are connected to the master and there is no free space, then immediately finish I/O and return an error.
  • -o mfsioretries=N — specifies the number of retries before an I/O error is returned (default: 30).
  • -o mfstimeout=N — defines the maximum timeout in seconds before an I/O error is returned (default: 0 — which means no timeout).
  • -o mfslogretry=N — defines the minimal retry counter on which the system will start logging I/O messages (default: 5).
  • -o mfsfsyncmintime=SEC — forces fsync before the last file close when the file was opened/created at least SEC seconds earlier (default: 0.0 — always do fsync before close).
  • -o mfspreflabels=LABELEXPR — specifies preferred labels for choosing chunkservers during I/O.
  • -o mfsnoxattrs — turns off xattr support.
  • -o mfsnoposixlocks — turns off support for global posix locks (lockf + ioctl) — locks will work locally.
  • -o mfsnobsdlocks — turns off support for global BSD locks (flock) — locks will work locally.

Mount options 🏔️

general mount options (see the mount(8) manual, bestie):

  • -o rw | -o ro — Mount file-system in read-write (default) or read-only mode respectively.
  • -o suid | -o nosuid — Enable or disable suid/sgid attributes to work.
  • -o dev | -o nodev — Enable or disable character or block special device files interpretation.
  • -o exec | -o noexec — Allow or disallow execution of binaries.

🌸 FILES 🌸

  • mfsmount.cfg — configuration file for the MooseFS mount daemon; refer to the mfsmount.cfg(5) manual for details. she has her own manual, respect her.

💜 NOTES 💜

Sugid clear mode 🎀

okay so during attribute change, file systems sometimes clear the flags suid and/or sgid. the behavior is different on different file systems. MFS tries to mimic the behavior of the most popular file system on the given operating system. she's a people pleaser, she adapts.

  • NEVER — MFS will not change the suid and sgid bit on chown.
  • ALWAYS — clear suid and sgid on every chown — safest operation.
  • OSX — standard behavior in OS X and Solaris (chown made by an unprivileged user clears suid and sgid).
  • BSD — standard behavior in *BSD systems (like in OSX, but only when something is really changed).
  • EXT — standard behavior in most file systems on Linux (directories not changed, others: suid cleared always, sgid only when the group exec bit is set).
  • XFS — standard behavior in XFS on Linux (like EXT but directories are changed by unprivileged users).

Data cache modes 🔥

there are four cache modes: DIRECT, NO, YES and AUTO. the default option is AUTO and you shuldn't change it unless you really know what you are doing (that typo is canon, bestie, i don't make the rules). in AUTO mode the data cache is managed automatically by mfsmaster.

  • DIRECT — forces direct io (bypasses cache). she goes straight through, no detours.
  • NO, NONE or NEVER — never allow file data to be kept in cache (safest but can reduce efficiency).
  • YES or ALWAYS — always allow file data to be kept in cache (dangerous 😭).
  • AUTO — file cache is managed by mfsmaster automatically (should be very safe and efficient).

Label expressions 🦋

the LABELEXPR grammar, verbatim, because she's precise:

LABELEXPR  -> S ; LABELEXPR | S

S          -> S + M | M

M          -> M L | L

L          -> a .. z | A .. Z | ( S ) | [ S ]

subexpressions should be placed in priority order. up to nine subexpressions (priorities) can be specified. nine is the limit, girlies.

Fstab 💅

on most Unix systems mfsmount can be invoked automatically from /etc/fstab. be aware that the rw or ro option has to be specified in options. also, on many systems there should be an option which informs the system that this mountpoint should be mounted after starting networking services (options such as _netdev or late).

Linux:

mfsmount mountpoint fuse options 0 0

BSD:

mfsmount_magic mountpoint moosefs options,mountprog=/usr/local/bin/mfsmount 0 0

since version 3.0.75 an alternative form can be used:

Linux:

HOST[:PORT]:[PATH] mountpoint moosefs options 0 0

BSD:

HOST[:PORT]:[PATH] mountpoint moosefs options,mountprog=/usr/local/bin/mfsmount 0 0

😭 REPORTING BUGS 😭

found a bug? report it to <bugs@moosefs.com>. be nice, they're doing their best 🫶

Copyright (C) 2026 Jakub Kruszona-Zawadzki, Saglabs SA

This file is part of MooseFS.

MooseFS 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 2 (only).

MooseFS 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 this program; if not, see <https://www.gnu.org/licenses/>.

🌈 SEE ALSO 🌈

mfsmaster(8), mfstools(1), mfsmount.cfg(5), mount(8) — go read those too, the lore is deep, iykyk 📚

and that's the whole page, bestie!! this is MooseFS 4.59.2-1, dated May 2026, and honestly? she's iconic. now go mount something 💖✨🦋

📦 where this page comes from