1MOUNT(8) Linux Programmer's Manual MOUNT(8)
2
6 mount - mount a filesystem
7
9 mount [-lhV]
10 mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
12 mount [-fnrsvw] [-o option[,option]...] device|dir
14 mount [-fnrsvw] [-t vfstype] [-o options] device dir
16
18 All files accessible in a Unix system are arranged in one big tree, the
19 file hierarchy, rooted at /. These files can be spread out over sev‐
20 eral devices. The mount command serves to attach the filesystem found
21 on some device to the big file tree. Conversely, the umount(8) command
22 will detach it again.
23 The standard form of the mount command, is
25 mount -t type device dir
27 This tells the kernel to attach the filesystem found on device (which
29 is of type type) at the directory dir. The previous contents (if any)
30 and owner and mode of dir become invisible, and as long as this
31 filesystem remains mounted, the pathname dir refers to the root of the
32 filesystem on device.
33 The listing and help.
35 Three forms of invocation do not actually mount anything:
36 mount -h
38 prints a help message
39 mount -V
41 prints a version string
42 mount [-l] [-t type]
44 lists all mounted filesystems (of type type). The option
45 -l adds the labels in this listing. See below.
46 The device indication.
48 Most devices are indicated by a file name (of a block special
49 device), like /dev/sda1, but there are other possibilities. For
50 example, in the case of an NFS mount, device may look like
51 knuth.cwi.nl:/dir. It is possible to indicate a block special
52 device using its volume LABEL or UUID (see the -L and -U options
53 below).
54 The recommended setup is to use LABEL=<label> or UUID=<uuid>
56 tags rather than /dev/disk/by-{label,uuid} udev symlinks in the
57 /etc/fstab file. The tags are more readable, robust and porta‐
58 ble. The mount(8) command internally uses udev symlinks, so use
59 the symlinks in /etc/fstab is not advantage over LABEL=/UUID=.
60 For more details see libblkid(3).
61 The proc filesystem is not associated with a special device, and
63 when mounting it, an arbitrary keyword, such as proc can be used
64 instead of a device specification. (The customary choice none
65 is less fortunate: the error message `none busy' from umount can
66 be confusing.)
67 The /etc/fstab, /etc/mtab and /proc/mounts files.
69 The file /etc/fstab (see fstab(5)), may contain lines describing
70 what devices are usually mounted where, using which options.
71 The command
73 mount -a [-t type] [-O optlist]
75 (usually given in a bootscript) causes all filesystems mentioned
77 in fstab (of the proper type and/or having or not having the
78 proper options) to be mounted as indicated, except for those
79 whose line contains the noauto keyword. Adding the -F option
80 will make mount fork, so that the filesystems are mounted simul‐
81 taneously.
82 When mounting a filesystem mentioned in fstab or mtab, it suf‐
84 fices to give only the device, or only the mount point.
85 The programs mount and umount maintain a list of currently
88 mounted filesystems in the file /etc/mtab. If no arguments are
89 given to mount, this list is printed.
90 The mount program does not read the /etc/fstab file if device
92 (or LABEL/UUID) and dir are specified. For example:
93 mount /dev/foo /dir
95 If you want to override mount options from /etc/fstab you have
97 to use:
98 mount device|dir -o <options>
100 and then the mount options from command line will be appended to
102 the list of options from /etc/fstab. The usual behaviour is
103 that the last option wins if there is more duplicated options.
104 When the proc filesystem is mounted (say at /proc), the files
106 /etc/mtab and /proc/mounts have very similar contents. The for‐
107 mer has somewhat more information, such as the mount options
108 used, but is not necessarily up-to-date (cf. the -n option
109 below). It is possible to replace /etc/mtab by a symbolic link
110 to /proc/mounts, and especially when you have very large numbers
111 of mounts things will be much faster with that symlink, but some
112 information is lost that way, and in particular using the "user"
113 option will fail.
114 The non-superuser mounts.
116 Normally, only the superuser can mount filesystems. However,
117 when fstab contains the user option on a line, anybody can mount
118 the corresponding system.
119 Thus, given a line
121 /dev/cdrom /cd iso9660 ro,user,noauto,unhide
123 any user can mount the iso9660 filesystem found on his CDROM
125 using the command
126 mount /dev/cdrom
128 or
130 mount /cd
132 For more details, see fstab(5). Only the user that mounted a
134 filesystem can unmount it again. If any user should be able to
135 unmount, then use users instead of user in the fstab line. The
136 owner option is similar to the user option, with the restriction
137 that the user must be the owner of the special file. This may be
138 useful e.g. for /dev/fd if a login script makes the console user
139 owner of this device. The group option is similar, with the
140 restriction that the user must be member of the group of the
141 special file.
142 The bind mounts.
145 Since Linux 2.4.0 it is possible to remount part of the file
146 hierarchy somewhere else. The call is
147 mount --bind olddir newdir
148 or shortoption
149 mount -B olddir newdir
150 or fstab entry is:
151 /olddir /newdir none bind
152 After this call the same contents is accessible in two places.
154 One can also remount a single file (on a single file).
155 This call attaches only (part of) a single filesystem, not pos‐
157 sible submounts. The entire file hierarchy including submounts
158 is attached a second place using
159 mount --rbind olddir newdir
160 or shortoption
161 mount -R olddir newdir
162 Note that the filesystem mount options will remain the same as
164 those on the original mount point, and cannot be changed by
165 passing the -o option along with --bind/--rbind. The mount
166 options can be changed by a separate remount command, for exam‐
167 ple:
168 mount --bind olddir newdir
170 mount -o remount,ro newdir
171 The move operation.
174 Since Linux 2.5.1 it is possible to atomically move a mounted
175 tree to another place. The call is
176 mount --move olddir newdir
177 or shortoption
178 mount -M olddir newdir
179 This will cause the contents which previously appeared under
180 olddir to be accessed under newdir. The physical location of
181 the files is not changed.
182 Note also that moving a mount residing under a shared mount is
184 invalid and unsupported (in the other words the parent of the
185 olddir has to use private propagation flag). See
186 /proc/self/mountinfo for the current propagation flags.
187 The shared subtrees operations.
189 Since Linux 2.6.15 it is possible to mark a mount and its sub‐
190 mounts as shared, private, slave or unbindable. A shared mount
191 provides ability to create mirrors of that mount such that
192 mounts and umounts within any of the mirrors propagate to the
193 other mirror. A slave mount receives propagation from its mas‐
194 ter, but any not vice-versa. A private mount carries no propa‐
195 gation abilities. A unbindable mount is a private mount which
196 cannot cloned through a bind operation. Detailed semantics is
197 documented in Documentation/sharedsubtree.txt file in the kernel
198 source tree.
199 mount --make-shared mountpoint
201 mount --make-slave mountpoint
202 mount --make-private mountpoint
203 mount --make-unbindable mountpoint
204 The following commands allows one to recursively change the type
206 of all the mounts under a given mountpoint.
207 mount --make-rshared mountpoint
209 mount --make-rslave mountpoint
210 mount --make-rprivate mountpoint
211 mount --make-runbindable mountpoint
212
215 The full set of mount options used by an invocation of mount is deter‐
216 mined by first extracting the mount options for the filesystem from the
217 fstab table, then applying any options specified by the -o argument,
218 and finally applying a -r or -w option, when present.
219 Command line options available for the mount command:
221 -V, --version
223 Output version.
224 -h, --help
226 Print a help message.
227 -v, --verbose
229 Verbose mode.
230 -a, --all
232 Mount all filesystems (of the given types) mentioned in fstab.
233 -F, --fork
235 (Used in conjunction with -a.) Fork off a new incarnation of
236 mount for each device. This will do the mounts on different
237 devices or different NFS servers in parallel. This has the
238 advantage that it is faster; also NFS timeouts go in parallel. A
239 disadvantage is that the mounts are done in undefined order.
240 Thus, you cannot use this option if you want to mount both /usr
241 and /usr/spool.
242 -f, --fake
244 Causes everything to be done except for the actual system call;
245 if it's not obvious, this ``fakes'' mounting the filesystem.
246 This option is useful in conjunction with the -v flag to deter‐
247 mine what the mount command is trying to do. It can also be used
248 to add entries for devices that were mounted earlier with the -n
249 option. The -f option checks for existing record in /etc/mtab
250 and fails when the record already exists (with regular non-fake
251 mount, this check is done by kernel).
252 -i, --internal-only
254 Don't call the /sbin/mount.<filesystem> helper even if it
255 exists.
256 -l Add the labels in the mount output. Mount must have permission
258 to read the disk device (e.g. be suid root) for this to work.
259 One can set such a label for ext2, ext3 or ext4 using the
260 e2label(8) utility, or for XFS using xfs_admin(8), or for reis‐
261 erfs using reiserfstune(8).
262 -n, --no-mtab
264 Mount without writing in /etc/mtab. This is necessary for exam‐
265 ple when /etc is on a read-only filesystem.
266 --no-canonicalize
268 Don't canonicalize paths. The mount command canonicalizes all
269 paths (from command line or fstab) and stores canonicalized
270 paths to the /etc/mtab file. This option can be used together
271 with the -f flag for already canonicalized absolut paths.
272 -p, --pass-fd num
274 In case of a loop mount with encryption, read the passphrase
275 from file descriptor num instead of from the terminal.
276 -s Tolerate sloppy mount options rather than failing. This will
278 ignore mount options not supported by a filesystem type. Not all
279 filesystems support this option. This option exists for support
280 of the Linux autofs-based automounter.
281 -r, --read-only
283 Mount the filesystem read-only. A synonym is -o ro.
284 Note that, depending on the filesystem type, state and kernel
286 behavior, the system may still write to the device. For example,
287 Ext3 or ext4 will replay its journal if the filesystem is dirty.
288 To prevent this kind of write access, you may want to mount ext3
289 or ext4 filesystem with "ro,noload" mount options or set the
290 block device to read-only mode, see command blockdev(8).
291 -w, --rw
293 Mount the filesystem read/write. This is the default. A synonym
294 is -o rw.
295 -L label
297 Mount the partition that has the specified label.
298 -U uuid
300 Mount the partition that has the specified uuid. These two
301 options require the file /proc/partitions (present since Linux
302 2.1.116) to exist.
303 -t, --types vfstype
305 The argument following the -t is used to indicate the filesystem
306 type. The filesystem types which are currently supported
307 include: adfs, affs, autofs, cifs, coda, coherent, cramfs,
308 debugfs, devpts, efs, ext, ext2, ext3, ext4, hfs, hfsplus, hpfs,
309 iso9660, jfs, minix, msdos, ncpfs, nfs, nfs4, ntfs, proc, qnx4,
310 ramfs, reiserfs, romfs, squashfs, smbfs, sysv, tmpfs, ubifs,
311 udf, ufs, umsdos, usbfs, vfat, xenix, xfs, xiafs. Note that
312 coherent, sysv and xenix are equivalent and that xenix and
313 coherent will be removed at some point in the future — use sysv
314 instead. Since kernel version 2.1.21 the types ext and xiafs do
315 not exist anymore. Earlier, usbfs was known as usbdevfs. Note,
316 the real list of all supported filesystems depends on your ker‐
317 nel.
318 The programs mount and umount support filesystem subtypes. The
320 subtype is defined by '.subtype' suffix. For example
321 'fuse.sshfs'. It's recommended to use subtype notation rather
322 than add any prefix to the mount source (for example
323 'sshfs#example.com' is depreacated).
324 For most types all the mount program has to do is issue a simple
326 mount(2) system call, and no detailed knowledge of the filesys‐
327 tem type is required. For a few types however (like nfs, nfs4,
328 cifs, smbfs, ncpfs) ad hoc code is necessary. The nfs, nfs4,
329 cifs, smbfs, and ncpfs filesystems have a separate mount pro‐
330 gram. In order to make it possible to treat all types in a uni‐
331 form way, mount will execute the program /sbin/mount.TYPE (if
332 that exists) when called with type TYPE. Since various versions
333 of the smbmount program have different calling conventions,
334 /sbin/mount.smbfs may have to be a shell script that sets up the
335 desired call.
336 If no -t option is given, or if the auto type is specified,
338 mount will try to guess the desired type. Mount uses the blkid
339 or volume_id library for guessing the filesystem type; if that
340 does not turn up anything that looks familiar, mount will try to
341 read the file /etc/filesystems, or, if that does not exist,
342 /proc/filesystems. All of the filesystem types listed there
343 will be tried, except for those that are labeled "nodev" (e.g.,
344 devpts, proc and nfs). If /etc/filesystems ends in a line with
345 a single * only, mount will read /proc/filesystems afterwards.
346 The auto type may be useful for user-mounted floppies. Creating
348 a file /etc/filesystems can be useful to change the probe order
349 (e.g., to try vfat before msdos or ext3 before ext2) or if you
350 use a kernel module autoloader. Warning: the probing uses a
351 heuristic (the presence of appropriate `magic'), and could rec‐
352 ognize the wrong filesystem type, possibly with catastrophic
353 consequences. If your data is valuable, don't ask mount to
354 guess.
355 More than one type may be specified in a comma separated list.
357 The list of filesystem types can be prefixed with no to specify
358 the filesystem types on which no action should be taken. (This
359 can be meaningful with the -a option.) For example, the command:
360 mount -a -t nomsdos,ext
362 mounts all filesystems except those of type msdos and ext.
364 -O, --test-opts opts
366 Used in conjunction with -a, to limit the set of filesystems to
367 which the -a is applied. Like -t in this regard except that it
368 is useless except in the context of -a. For example, the com‐
369 mand:
370 mount -a -O no_netdev
372 mounts all filesystems except those which have the option _net‐
374 dev specified in the options field in the /etc/fstab file.
375 It is different from -t in that each option is matched exactly;
377 a leading no at the beginning of one option does not negate the
378 rest.
379 The -t and -O options are cumulative in effect; that is, the
381 command
382 mount -a -t ext2 -O _netdev
384 mounts all ext2 filesystems with the _netdev option, not all
386 filesystems that are either ext2 or have the _netdev option
387 specified.
388 -o, --options opts
390 Options are specified with a -o flag followed by a comma sepa‐
391 rated string of options. For example:
392 mount LABEL=mydisk -o noatime,nouser
394 For more details, see FILESYSTEM INDEPENDENT MOUNT OPTIONS and
397 FILESYSTEM SPECIFIC MOUNT OPTIONS sections.
398 -B, --bind
400 Remount a subtree somewhere else (so that its contents are
401 available in both places). See above.
402 -R, --rbind
404 Remount a subtree and all possible submounts somewhere else (so
405 that its contents are available in both places). See above.
406 -M, --move
408 Move a subtree to some other place. See above.
409
412 Some of these options are only useful when they appear in the
413 /etc/fstab file.
414 Some of these options could be enabled or disabled by default in the
416 system kernel. To check the current setting see the options in
417 /proc/mounts. Note that filesystems also have per-filesystem specific
418 default mount options (see for example tune2fs -l output for extN
419 filesystems).
420 The following options apply to any filesystem that is being mounted
422 (but not every filesystem actually honors them - e.g., the sync option
423 today has effect only for ext2, ext3, fat, vfat and ufs):
424 async All I/O to the filesystem should be done asynchronously. (See
427 also the sync option.)
428 atime Do not use noatime feature, then the inode access time is con‐
430 trolled by kernel defaults. See also the description for stric‐
431 tatime and relatime mount options.
432 noatime
434 Do not update inode access times on this filesystem (e.g, for
435 faster access on the news spool to speed up news servers).
436 auto Can be mounted with the -a option.
438 noauto Can only be mounted explicitly (i.e., the -a option will not
440 cause the filesystem to be mounted).
441 context=context, fscontext=context, defcontext=context and rootcon‐
443 text=context
444 The context= option is useful when mounting filesystems that do
445 not support extended attributes, such as a floppy or hard disk
446 formatted with VFAT, or systems that are not normally running
447 under SELinux, such as an ext3 formatted disk from a non-SELinux
448 workstation. You can also use context= on filesystems you do not
449 trust, such as a floppy. It also helps in compatibility with
450 xattr-supporting filesystems on earlier 2.4.<x> kernel versions.
451 Even where xattrs are supported, you can save time not having to
452 label every file by assigning the entire disk one security con‐
453 text.
454 A commonly used option for removable media is context=sys‐
456 tem_u:object_r:removable_t.
457 Two other options are fscontext= and defcontext=, both of which
459 are mutually exclusive of the context option. This means you can
460 use fscontext and defcontext with each other, but neither can be
461 used with context.
462 The fscontext= option works for all filesystems, regardless of
464 their xattr support. The fscontext option sets the overarching
465 filesystem label to a specific security context. This filesystem
466 label is separate from the individual labels on the files. It
467 represents the entire filesystem for certain kinds of permission
468 checks, such as during mount or file creation. Individual file
469 labels are still obtained from the xattrs on the files them‐
470 selves. The context option actually sets the aggregate context
471 that fscontext provides, in addition to supplying the same label
472 for individual files.
473 You can set the default security context for unlabeled files
475 using defcontext= option. This overrides the value set for unla‐
476 beled files in the policy and requires a filesystem that sup‐
477 ports xattr labeling.
478 The rootcontext= option allows you to explicitly label the root
480 inode of a FS being mounted before that FS or inode because vis‐
481 able to userspace. This was found to be useful for things like
482 stateless linux.
483 For more details, see selinux(8)
485 defaults
488 Use default options: rw, suid, dev, exec, auto, nouser, async,
489 and relatime.
490 Note that the real set of the all default mount options depends
492 on kernel and filesystem type. See the begin of this section for
493 more details.
494 dev Interpret character or block special devices on the filesystem.
496 nodev Do not interpret character or block special devices on the file
498 system.
499 diratime
501 Update directory inode access times on this filesystem. This is
502 the default.
503 nodiratime
505 Do not update directory inode access times on this filesystem.
506 dirsync
508 All directory updates within the filesystem should be done syn‐
509 chronously. This affects the following system calls: creat,
510 link, unlink, symlink, mkdir, rmdir, mknod and rename.
511 exec Permit execution of binaries.
513 noexec Do not allow direct execution of any binaries on the mounted
515 filesystem. (Until recently it was possible to run binaries
516 anyway using a command like /lib/ld*.so /mnt/binary. This trick
517 fails since Linux 2.4.25 / 2.6.0.)
518 group Allow an ordinary (i.e., non-root) user to mount the filesystem
520 if one of his groups matches the group of the device. This
521 option implies the options nosuid and nodev (unless overridden
522 by subsequent options, as in the option line group,dev,suid).
523 iversion
525 Every time the inode is modified, the i_version field will be
526 incremented.
527 noiversion
529 Do not increment the i_version inode field.
530 mand Allow mandatory locks on this filesystem. See fcntl(2).
532 nomand Do not allow mandatory locks on this filesystem.
534 _netdev
536 The filesystem resides on a device that requires network access
537 (used to prevent the system from attempting to mount these
538 filesystems until the network has been enabled on the system).
539 nofail Do not report errors for this device if it does not exist.
541 relatime
543 Update inode access times relative to modify or change time.
544 Access time is only updated if the previous access time was ear‐
545 lier than the current modify or change time. (Similar to noat‐
546 ime, but doesn't break mutt or other applications that need to
547 know if a file has been read since the last time it was modi‐
548 fied.)
549 Since Linux 2.6.30, the kernel defaults to the behavior provided
551 by this option (unless noatime was specified), and the stricta‐
552 time option is required to obtain traditional semantics. In
553 addition, since Linux 2.6.30, the file's last access time is
554 always updated if it is more than 1 day old.
555 norelatime
557 Do not use relatime feature. See also the strictatime mount
558 option.
559 strictatime
561 Allows to explicitly requesting full atime updates. This makes
562 it possible for kernel to defaults to relatime or noatime but
563 still allow userspace to override it. For more details about the
564 default system mount options see /proc/mounts.
565 nostrictatime
567 Use the kernel's default behaviour for inode access time
568 updates.
569 suid Allow set-user-identifier or set-group-identifier bits to take
571 effect.
572 nosuid Do not allow set-user-identifier or set-group-identifier bits to
574 take effect. (This seems safe, but is in fact rather unsafe if
575 you have suidperl(1) installed.)
576 owner Allow an ordinary (i.e., non-root) user to mount the filesystem
578 if he is the owner of the device. This option implies the
579 options nosuid and nodev (unless overridden by subsequent
580 options, as in the option line owner,dev,suid).
581 remount
583 Attempt to remount an already-mounted filesystem. This is com‐
584 monly used to change the mount flags for a filesystem, espe‐
585 cially to make a readonly filesystem writeable. It does not
586 change device or mount point.
587 The remount functionality follows the standard way how the mount
589 command works with options from fstab. It means the mount com‐
590 mand doesn't read fstab (or mtab) only when a device and dir are
591 fully specified.
592 mount -o remount,rw /dev/foo /dir
594 After this call all old mount options are replaced and arbitrary
596 stuff from fstab is ignored, except the loop= option which is
597 internally generated and maintained by the mount command.
598 mount -o remount,rw /dir
600 After this call mount reads fstab (or mtab) and merges these
602 options with options from command line ( -o ).
603 ro Mount the filesystem read-only.
605 _rnetdev
607 Like _netdev, except "fsck -a" checks this filesystem during
608 rc.sysinit.
609 rw Mount the filesystem read-write.
611 sync All I/O to the filesystem should be done synchronously. In case
613 of media with limited number of write cycles (e.g. some flash
614 drives) "sync" may cause life-cycle shortening.
615 user Allow an ordinary user to mount the filesystem. The name of the
617 mounting user is written to mtab so that he can unmount the
618 filesystem again. This option implies the options noexec,
619 nosuid, and nodev (unless overridden by subsequent options, as
620 in the option line user,exec,dev,suid).
621 nouser Forbid an ordinary (i.e., non-root) user to mount the filesys‐
623 tem. This is the default.
624 users Allow every user to mount and unmount the filesystem. This
626 option implies the options noexec, nosuid, and nodev (unless
627 overridden by subsequent options, as in the option line
628 users,exec,dev,suid).
629
632 The following options apply only to certain filesystems. We sort them
633 by filesystem. They all follow the -o flag.
634 What options are supported depends a bit on the running kernel. More
636 info may be found in the kernel source subdirectory Documenta‐
637 tion/filesystems.
638
641 uid=value and gid=value
642 Set the owner and group of the files in the filesystem (default:
643 uid=gid=0).
644 ownmask=value and othmask=value
646 Set the permission mask for ADFS 'owner' permissions and 'other'
647 permissions, respectively (default: 0700 and 0077, respec‐
648 tively). See also /usr/src/linux/Documentation/filesys‐
649 tems/adfs.txt.
650
652 uid=value and gid=value
653 Set the owner and group of the root of the filesystem (default:
654 uid=gid=0, but with option uid or gid without specified value,
655 the uid and gid of the current process are taken).
656 setuid=value and setgid=value
658 Set the owner and group of all files.
659 mode=value
661 Set the mode of all files to value & 0777 disregarding the orig‐
662 inal permissions. Add search permission to directories that
663 have read permission. The value is given in octal.
664 protect
666 Do not allow any changes to the protection bits on the filesys‐
667 tem.
668 usemp Set uid and gid of the root of the filesystem to the uid and gid
670 of the mount point upon the first sync or umount, and then clear
671 this option. Strange...
672 verbose
674 Print an informational message for each successful mount.
675 prefix=string
677 Prefix used before volume name, when following a link.
678 volume=string
680 Prefix (of length at most 30) used before '/' when following a
681 symbolic link.
682 reserved=value
684 (Default: 2.) Number of unused blocks at the start of the
685 device.
686 root=value
688 Give explicitly the location of the root block.
689 bs=value
691 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
692 grpquota|noquota|quota|usrquota
694 These options are accepted but ignored. (However, quota utili‐
695 ties may react to such strings in /etc/fstab.)
696
699 See the options section of the mount.cifs(8) man page (cifs-utils pack‐
700 age must be installed).
701
704 None.
705
708 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
709 /sys/kernel/debug. There are no mount options.
710
713 The devpts filesystem is a pseudo filesystem, traditionally mounted on
714 /dev/pts. In order to acquire a pseudo terminal, a process opens
715 /dev/ptmx; the number of the pseudo terminal is then made available to
716 the process and the pseudo terminal slave can be accessed as
717 /dev/pts/<number>.
718 uid=value and gid=value
720 This sets the owner or the group of newly created PTYs to the
721 specified values. When nothing is specified, they will be set to
722 the UID and GID of the creating process. For example, if there
723 is a tty group with GID 5, then gid=5 will cause newly created
724 PTYs to belong to the tty group.
725 mode=value
727 Set the mode of newly created PTYs to the specified value. The
728 default is 0600. A value of mode=620 and gid=5 makes "mesg y"
729 the default on newly created PTYs.
730 newinstance
732 Create a private instance of devpts filesystem, such that
733 indices of ptys allocated in this new instance are independent
734 of indices created in other instances of devpts.
735 All mounts of devpts without this newinstance option share the
737 same set of pty indices (i.e legacy mode). Each mount of devpts
738 with the newinstance option has a private set of pty indices.
739 This option is mainly used to support containers in the linux
741 kernel. It is implemented in linux kernel versions starting with
742 2.6.29. Further, this mount option is valid only if CON‐
743 FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configu‐
744 ration.
745 To use this option effectively, /dev/ptmx must be a symbolic
747 link to pts/ptmx. See Documentation/filesystems/devpts.txt in
748 the linux kernel source tree for details.
749 ptmxmode=value
751 Set the mode for the new ptmx device node in the devpts filesys‐
753 tem.
754 With the support for multiple instances of devpts (see newin‐
756 stance option above), each instance has a private ptmx node in
757 the root of the devpts filesystem (typically /dev/pts/ptmx).
758 For compatibility with older versions of the kernel, the default
760 mode of the new ptmx node is 0000. ptmxmode=value specifies a
761 more useful mode for the ptmx node and is highly recommended
762 when the newinstance option is specified.
763 This option is only implemented in linux kernel versions start‐
765 ing with 2.6.29. Further this option is valid only if CON‐
766 FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configu‐
767 ration.
768
771 None. Note that the `ext' filesystem is obsolete. Don't use it. Since
772 Linux version 2.1.21 extfs is no longer part of the kernel source.
773
776 The `ext2' filesystem is the standard Linux filesystem. Since Linux
777 2.5.46, for most mount options the default is determined by the
778 filesystem superblock. Set them with tune2fs(8).
779 acl|noacl
781 Support POSIX Access Control Lists (or not).
782 bsddf|minixdf
784 Set the behaviour for the statfs system call. The minixdf behav‐
785 iour is to return in the f_blocks field the total number of
786 blocks of the filesystem, while the bsddf behaviour (which is
787 the default) is to subtract the overhead blocks used by the ext2
788 filesystem and not available for file storage. Thus
789 % mount /k -o minixdf; df /k; umount /k
791 Filesystem 1024-blocks Used Available Capacity Mounted on
792 /dev/sda6 2630655 86954 2412169 3% /k
793 % mount /k -o bsddf; df /k; umount /k
794 Filesystem 1024-blocks Used Available Capacity Mounted on
795 /dev/sda6 2543714 13 2412169 0% /k
796 (Note that this example shows that one can add command line
798 options to the options given in /etc/fstab.)
799 check={none|nocheck}
802 No checking is done at mount time. This is the default. This is
803 fast. It is wise to invoke e2fsck(8) every now and then, e.g.
804 at boot time.
805 debug Print debugging info upon each (re)mount.
807 errors={continue|remount-ro|panic}
809 Define the behaviour when an error is encountered. (Either
810 ignore errors and just mark the filesystem erroneous and con‐
811 tinue, or remount the filesystem read-only, or panic and halt
812 the system.) The default is set in the filesystem superblock,
813 and can be changed using tune2fs(8).
814 grpid|bsdgroups and nogrpid|sysvgroups
816 These options define what group id a newly created file gets.
817 When grpid is set, it takes the group id of the directory in
818 which it is created; otherwise (the default) it takes the fsgid
819 of the current process, unless the directory has the setgid bit
820 set, in which case it takes the gid from the parent directory,
821 and also gets the setgid bit set if it is a directory itself.
822 grpquota|noquota|quota|usrquota
824 These options are accepted but ignored.
825 nobh Do not attach buffer_heads to file pagecache. (Since 2.5.49.)
827 nouid32
829 Disables 32-bit UIDs and GIDs. This is for interoperability
830 with older kernels which only store and expect 16-bit values.
831 oldalloc or orlov
833 Use old allocator or Orlov allocator for new inodes. Orlov is
834 default.
835 resgid=n and resuid=n
837 The ext2 filesystem reserves a certain percentage of the avail‐
838 able space (by default 5%, see mke2fs(8) and tune2fs(8)). These
839 options determine who can use the reserved blocks. (Roughly:
840 whoever has the specified uid, or belongs to the specified
841 group.)
842 sb=n Instead of block 1, use block n as superblock. This could be
844 useful when the filesystem has been damaged. (Earlier, copies
845 of the superblock would be made every 8192 blocks: in block 1,
846 8193, 16385, ... (and one got thousands of copies on a big
847 filesystem). Since version 1.08, mke2fs has a -s (sparse
848 superblock) option to reduce the number of backup superblocks,
849 and since version 1.15 this is the default. Note that this may
850 mean that ext2 filesystems created by a recent mke2fs cannot be
851 mounted r/w under Linux 2.0.*.) The block number here uses 1k
852 units. Thus, if you want to use logical block 32768 on a
853 filesystem with 4k blocks, use "sb=131072".
854 user_xattr|nouser_xattr
856 Support "user." extended attributes (or not).
857
861 The ext3 filesystem is a version of the ext2 filesystem which has been
862 enhanced with journalling. It supports the same options as ext2 as
863 well as the following additions:
864 journal=update
866 Update the ext3 filesystem's journal to the current format.
867 journal=inum
869 When a journal already exists, this option is ignored. Other‐
870 wise, it specifies the number of the inode which will represent
871 the ext3 filesystem's journal file; ext3 will create a new
872 journal, overwriting the old contents of the file whose inode
873 number is inum.
874 journal_dev=devnum
876 When the external journal device's major/minor numbers have
877 changed, this option allows the user to specify the new journal
878 location. The journal device is identified through its new
879 major/minor numbers encoded in devnum.
880 norecovery/noload
882 Don't load the journal on mounting. Note that if the filesystem
883 was not unmounted cleanly, skipping the journal replay will lead
884 to the filesystem containing inconsistencies that can lead to
885 any number of problems.
886 data={journal|ordered|writeback}
888 Specifies the journalling mode for file data. Metadata is
889 always journaled. To use modes other than ordered on the root
890 filesystem, pass the mode to the kernel as boot parameter, e.g.
891 rootflags=data=journal.
892 journal
894 All data is committed into the journal prior to being
895 written into the main filesystem.
896 ordered
898 This is the default mode. All data is forced directly
899 out to the main file system prior to its metadata being
900 committed to the journal.
901 writeback
903 Data ordering is not preserved - data may be written into
904 the main filesystem after its metadata has been committed
905 to the journal. This is rumoured to be the highest-
906 throughput option. It guarantees internal filesystem
907 integrity, however it can allow old data to appear in
908 files after a crash and journal recovery.
909 barrier=0 / barrier=1
911 This enables/disables barriers. barrier=0 disables it, bar‐
912 rier=1 enables it. Write barriers enforce proper on-disk order‐
913 ing of journal commits, making volatile disk write caches safe
914 to use, at some performance penalty. The ext3 filesystem
915 enables write barriers by default. Be sure to enable barriers
916 unless your disks are battery-backed one way or another. Other‐
917 wise you risk filesystem corruption in case of power failure.
918 commit=nrsec
920 Sync all data and metadata every nrsec seconds. The default
921 value is 5 seconds. Zero means default.
922 user_xattr
924 Enable Extended User Attributes. See the attr(5) manual page.
925 acl Enable POSIX Access Control Lists. See the acl(5) manual page.
927
930 The ext4 filesystem is an an advanced level of the ext3 filesystem
931 which incorporates scalability and reliability enhancements for sup‐
932 porting large filesystem.
933 The options journal_dev, noload, data, commit, orlov, oldalloc,
935 [no]user_xattr [no]acl, bsddf, minixdf, debug, errors, data_err, grpid,
936 bsdgroups, nogrpid sysvgroups, resgid, resuid, sb, quota, noquota,
937 grpquota, usrquota and [no]bh are backwardly compatible with ext3 or
938 ext2.
939 journal_checksum
941 Enable checksumming of the journal transactions. This will
942 allow the recovery code in e2fsck and the kernel to detect cor‐
943 ruption in the kernel. It is a compatible change and will be
944 ignored by older kernels.
945 journal_async_commit
947 Commit block can be written to disk without waiting for descrip‐
948 tor blocks. If enabled older kernels cannot mount the device.
949 This will enable
950 journal=update
952 Update the ext4 filesystem's journal to the current format.
953 barrier=0 / barrier=1 / barrier / nobarrier
955 This enables/disables the use of write barriers in the jbd code.
956 barrier=0 disables, barrier=1 enables. This also requires an IO
957 stack which can support barriers, and if jbd gets an error on a
958 barrier write, it will disable again with a warning. Write bar‐
959 riers enforce proper on-disk ordering of journal commits, making
960 volatile disk write caches safe to use, at some performance
961 penalty. If your disks are battery-backed in one way or
962 another, disabling barriers may safely improve performance. The
963 mount options "barrier" and "nobarrier" can also be used to
964 enable or disable barriers, for consistency with other ext4
965 mount options.
966 The ext4 filesystem enables write barriers by default.
968 inode_readahead_blks=n
970 This tuning parameter controls the maximum number of inode table
971 blocks that ext4's inode table readahead algorithm will pre-read
972 into the buffer cache. The value must be a power of 2. The
973 default value is 32 blocks.
974 stripe=n
976 Number of filesystem blocks that mballoc will try to use for
977 allocation size and alignment. For RAID5/6 systems this should
978 be the number of data disks * RAID chunk size in filesystem
979 blocks.
980 delalloc
982 Deferring block allocation until write-out time.
983 nodelalloc
985 Disable delayed allocation. Blocks are allocation when data is
986 copied from user to page cache.
987 max_batch_time=usec
989 Maximum amount of time ext4 should wait for additional filesys‐
990 tem operations to be batch together with a synchronous write
991 operation. Since a synchronous write operation is going to force
992 a commit and then a wait for the I/O complete, it doesn't cost
993 much, and can be a huge throughput win, we wait for a small
994 amount of time to see if any other transactions can piggyback on
995 the synchronous write. The algorithm used is designed to auto‐
996 matically tune for the speed of the disk, by measuring the
997 amount of time (on average) that it takes to finish committing a
998 transaction. Call this time the "commit time". If the time that
999 the transactoin has been running is less than the commit time,
1000 ext4 will try sleeping for the commit time to see if other oper‐
1001 ations will join the transaction. The commit time is capped by
1002 the max_batch_time, which defaults to 15000us (15ms). This opti‐
1003 mization can be turned off entirely by setting max_batch_time to
1004 0.
1005 min_batch_time=usec
1007 This parameter sets the commit time (as described above) to be
1008 at least min_batch_time. It defaults to zero microseconds.
1009 Increasing this parameter may improve the throughput of multi-
1010 threaded, synchronous workloads on very fast disks, at the cost
1011 of increasing latency.
1012 journal_ioprio=prio
1014 The I/O priority (from 0 to 7, where 0 is the highest priorty)
1015 which should be used for I/O operations submitted by kjournald2
1016 during a commit operation. This defaults to 3, which is a
1017 slightly higher priority than the default I/O priority.
1018 abort Simulate the effects of calling ext4_abort() for debugging pur‐
1020 poses. This is normally used while remounting a filesystem
1021 which is already mounted.
1022 auto_da_alloc|noauto_da_alloc
1024 Many broken applications don't use fsync() when noauto_da_alloc
1025 replacing existing files via patterns such as
1026 fd = open("foo.new")/write(fd,..)/close(fd)/ rename("foo.new",
1028 "foo")
1029 or worse yet
1031 fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).
1033 If auto_da_alloc is enabled, ext4 will detect the replace-via-
1035 rename and replace-via-truncate patterns and force that any
1036 delayed allocation blocks are allocated such that at the next
1037 journal commit, in the default data=ordered mode, the data
1038 blocks of the new file are forced to disk before the rename()
1039 operation is commited. This provides roughly the same level of
1040 guarantees as ext3, and avoids the "zero-length" problem that
1041 can happen when a system crashes before the delayed allocation
1042 blocks are forced to disk.
1043 discard/nodiscard
1045 Controls whether ext4 should issue discard/TRIM commands to the
1046 underlying block device when blocks are freed. This is useful
1047 for SSD devices and sparse/thinly-provisioned LUNs, but it is
1048 off by default until sufficient testing has been done.
1049 nouid32
1051 Disables 32-bit UIDs and GIDs. This is for interoperability
1052 with older kernels which only store and expect 16-bit values.
1053 resize Allows to resize filesystem to the end of the last existing
1055 block group, further resize has to be done with resize2fs either
1056 online, or offline. It can be used only with conjunction with
1057 remount.
1058 block_validity/noblock_validity
1060 This options allows to enables/disables the in-kernel facility
1061 for tracking filesystem metadata blocks within internal data
1062 structures. This allows multi- block allocator and other rou‐
1063 tines to quickly locate extents which might overlap with
1064 filesystem metadata blocks. This option is intended for debug‐
1065 ging purposes and since it negatively affects the performance,
1066 it is off by default.
1067 dioread_lock/dioread_nolock
1069 Controls whether or not ext4 should use the DIO read locking. If
1070 the dioread_nolock option is specified ext4 will allocate unini‐
1071 tialized extent before buffer write and convert the extent to
1072 initialized after IO completes. This approach allows ext4 code
1073 to avoid using inode mutex, which improves scalability on high
1074 speed storages. However this does not work with nobh option and
1075 the mount will fail. Nor does it work with data journaling and
1076 dioread_nolock option will be ignored with kernel warning. Note
1077 that dioread_nolock code path is only used for extent-based
1078 files. Because of the restrictions this options comprises it is
1079 off by default (e.g. dioread_lock).
1080 i_version
1082 Enable 64-bit inode version support. This option is off by
1083 default.
1084
1087 (Note: fat is not a separate filesystem, but a common part of the
1088 msdos, umsdos and vfat filesystems.)
1089 blocksize={512|1024|2048}
1091 Set blocksize (default 512). This option is obsolete.
1092 uid=value and gid=value
1094 Set the owner and group of all files. (Default: the uid and gid
1095 of the current process.)
1096 umask=value
1098 Set the umask (the bitmask of the permissions that are not
1099 present). The default is the umask of the current process. The
1100 value is given in octal.
1101 dmask=value
1103 Set the umask applied to directories only. The default is the
1104 umask of the current process. The value is given in octal.
1105 fmask=value
1107 Set the umask applied to regular files only. The default is the
1108 umask of the current process. The value is given in octal.
1109 allow_utime=value
1111 This option controls the permission check of mtime/atime.
1112 20 If current process is in group of file's group ID, you
1114 can change timestamp.
1115 2 Other users can change timestamp.
1117 The default is set from `dmask' option. (If the directory is
1119 writable, utime(2) is also allowed. I.e. ~dmask & 022)
1120 Normally utime(2) checks current process is owner of the file,
1122 or it has CAP_FOWNER capability. But FAT filesystem doesn't
1123 have uid/gid on disk, so normal check is too unflexible. With
1124 this option you can relax it.
1125 check=value
1127 Three different levels of pickyness can be chosen:
1128 r[elaxed]
1130 Upper and lower case are accepted and equivalent, long
1131 name parts are truncated (e.g. verylongname.foobar
1132 becomes verylong.foo), leading and embedded spaces are
1133 accepted in each name part (name and extension).
1134 n[ormal]
1136 Like "relaxed", but many special characters (*, ?, <,
1137 spaces, etc.) are rejected. This is the default.
1138 s[trict]
1140 Like "normal", but names may not contain long parts and
1141 special characters that are sometimes used on Linux, but
1142 are not accepted by MS-DOS are rejected. (+, =, spaces,
1143 etc.)
1144 codepage=value
1146 Sets the codepage for converting to shortname characters on FAT
1147 and VFAT filesystems. By default, codepage 437 is used.
1148 conv={b[inary]|t[ext]|a[uto]}
1150 The fat filesystem can perform CRLF<-->NL (MS-DOS text format to
1151 UNIX text format) conversion in the kernel. The following con‐
1152 version modes are available:
1153 binary no translation is performed. This is the default.
1155 text CRLF<-->NL translation is performed on all files.
1157 auto CRLF<-->NL translation is performed on all files that
1159 don't have a "well-known binary" extension. The list of
1160 known extensions can be found at the beginning of
1161 fs/fat/misc.c (as of 2.0, the list is: exe, com, bin,
1162 app, sys, drv, ovl, ovr, obj, lib, dll, pif, arc, zip,
1163 lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz, gz, tgz,
1164 deb, gif, bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl,
1165 dvi).
1166 Programs that do computed lseeks won't like in-kernel text con‐
1168 version. Several people have had their data ruined by this
1169 translation. Beware!
1170 For filesystems mounted in binary mode, a conversion tool (from‐
1172 dos/todos) is available. This option is obsolete.
1173 cvf_format=module
1175 Forces the driver to use the CVF (Compressed Volume File) module
1176 cvf_module instead of auto-detection. If the kernel supports
1177 kmod, the cvf_format=xxx option also controls on-demand CVF mod‐
1178 ule loading. This option is obsolete.
1179 cvf_option=option
1181 Option passed to the CVF module. This option is obsolete.
1182 debug Turn on the debug flag. A version string and a list of filesys‐
1184 tem parameters will be printed (these data are also printed if
1185 the parameters appear to be inconsistent).
1186 fat={12|16|32}
1188 Specify a 12, 16 or 32 bit fat. This overrides the automatic
1189 FAT type detection routine. Use with caution!
1190 iocharset=value
1192 Character set to use for converting between 8 bit characters and
1193 16 bit Unicode characters. The default is iso8859-1. Long file‐
1194 names are stored on disk in Unicode format.
1195 tz=UTC This option disables the conversion of timestamps between local
1197 time (as used by Windows on FAT) and UTC (which Linux uses
1198 internally). This is particularly useful when mounting devices
1199 (like digital cameras) that are set to UTC in order to avoid the
1200 pitfalls of local time.
1201 quiet Turn on the quiet flag. Attempts to chown or chmod files do not
1203 return errors, although they fail. Use with caution!
1204 showexec
1206 If set, the execute permission bits of the file will be allowed
1207 only if the extension part of the name is .EXE, .COM, or .BAT.
1208 Not set by default.
1209 sys_immutable
1211 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag
1212 on Linux. Not set by default.
1213 flush If set, the filesystem will try to flush to disk more early than
1215 normal. Not set by default.
1216 usefree
1218 Use the "free clusters" value stored on FSINFO. It'll be used to
1219 determine number of free clusters without scanning disk. But
1220 it's not used by default, because recent Windows don't update it
1221 correctly in some case. If you are sure the "free clusters" on
1222 FSINFO is correct, by this option you can avoid scanning disk.
1223 dots, nodots, dotsOK=[yes|no]
1225 Various misguided attempts to force Unix or DOS conventions onto
1226 a FAT filesystem.
1227
1230 creator=cccc, type=cccc
1231 Set the creator/type values as shown by the MacOS finder used
1232 for creating new files. Default values: '????'.
1233 uid=n, gid=n
1235 Set the owner and group of all files. (Default: the uid and gid
1236 of the current process.)
1237 dir_umask=n, file_umask=n, umask=n
1239 Set the umask used for all directories, all regular files, or
1240 all files and directories. Defaults to the umask of the current
1241 process.
1242 session=n
1244 Select the CDROM session to mount. Defaults to leaving that
1245 decision to the CDROM driver. This option will fail with any‐
1246 thing but a CDROM as underlying device.
1247 part=n Select partition number n from the device. Only makes sense for
1249 CDROMS. Defaults to not parsing the partition table at all.
1250 quiet Don't complain about invalid mount options.
1252
1255 uid=value and gid=value
1256 Set the owner and group of all files. (Default: the uid and gid
1257 of the current process.)
1258 umask=value
1260 Set the umask (the bitmask of the permissions that are not
1261 present). The default is the umask of the current process. The
1262 value is given in octal.
1263 case={lower|asis}
1265 Convert all files names to lower case, or leave them. (Default:
1266 case=lower.)
1267 conv={binary|text|auto}
1269 For conv=text, delete some random CRs (in particular, all fol‐
1270 lowed by NL) when reading a file. For conv=auto, choose more or
1271 less at random between conv=binary and conv=text. For
1272 conv=binary, just read what is in the file. This is the default.
1273 nocheck
1275 Do not abort mounting when certain consistency checks fail.
1276
1279 ISO 9660 is a standard describing a filesystem structure to be used on
1280 CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1281 udf filesystem.)
1282 Normal iso9660 filenames appear in a 8.3 format (i.e., DOS-like
1284 restrictions on filename length), and in addition all characters are in
1285 upper case. Also there is no field for file ownership, protection,
1286 number of links, provision for block/character devices, etc.
1287 Rock Ridge is an extension to iso9660 that provides all of these unix
1289 like features. Basically there are extensions to each directory record
1290 that supply all of the additional information, and when Rock Ridge is
1291 in use, the filesystem is indistinguishable from a normal UNIX filesys‐
1292 tem (except that it is read-only, of course).
1293 norock Disable the use of Rock Ridge extensions, even if available. Cf.
1295 map.
1296 nojoliet
1298 Disable the use of Microsoft Joliet extensions, even if avail‐
1299 able. Cf. map.
1300 check={r[elaxed]|s[trict]}
1302 With check=relaxed, a filename is first converted to lower case
1303 before doing the lookup. This is probably only meaningful
1304 together with norock and map=normal. (Default: check=strict.)
1305 uid=value and gid=value
1307 Give all files in the filesystem the indicated user or group id,
1308 possibly overriding the information found in the Rock Ridge
1309 extensions. (Default: uid=0,gid=0.)
1310 map={n[ormal]|o[ff]|a[corn]}
1312 For non-Rock Ridge volumes, normal name translation maps upper
1313 to lower case ASCII, drops a trailing `;1', and converts `;' to
1314 `.'. With map=off no name translation is done. See norock.
1315 (Default: map=normal.) map=acorn is like map=normal but also
1316 apply Acorn extensions if present.
1317 mode=value
1319 For non-Rock Ridge volumes, give all files the indicated mode.
1320 (Default: read permission for everybody.) Since Linux 2.1.37
1321 one no longer needs to specify the mode in decimal. (Octal is
1322 indicated by a leading 0.)
1323 unhide Also show hidden and associated files. (If the ordinary files
1325 and the associated or hidden files have the same filenames, this
1326 may make the ordinary files inaccessible.)
1327 block={512|1024|2048}
1329 Set the block size to the indicated value. (Default:
1330 block=1024.)
1331 conv={a[uto]|b[inary]|m[text]|t[ext]}
1333 (Default: conv=binary.) Since Linux 1.3.54 this option has no
1334 effect anymore. (And non-binary settings used to be very dan‐
1335 gerous, possibly leading to silent data corruption.)
1336 cruft If the high byte of the file length contains other garbage, set
1338 this mount option to ignore the high order bits of the file
1339 length. This implies that a file cannot be larger than 16MB.
1340 session=x
1342 Select number of session on multisession CD. (Since 2.3.4.)
1343 sbsector=xxx
1345 Session begins from sector xxx. (Since 2.3.4.)
1346 The following options are the same as for vfat and specifying them only
1348 makes sense when using discs encoded using Microsoft's Joliet exten‐
1349 sions.
1350 iocharset=value
1352 Character set to use for converting 16 bit Unicode characters on
1353 CD to 8 bit characters. The default is iso8859-1.
1354 utf8 Convert 16 bit Unicode characters on CD to UTF-8.
1356
1359 iocharset=name
1360 Character set to use for converting from Unicode to ASCII. The
1361 default is to do no conversion. Use iocharset=utf8 for UTF8
1362 translations. This requires CONFIG_NLS_UTF8 to be set in the
1363 kernel .config file.
1364 resize=value
1366 Resize the volume to value blocks. JFS only supports growing a
1367 volume, not shrinking it. This option is only valid during a
1368 remount, when the volume is mounted read-write. The resize key‐
1369 word with no value will grow the volume to the full size of the
1370 partition.
1371 nointegrity
1373 Do not write to the journal. The primary use of this option is
1374 to allow for higher performance when restoring a volume from
1375 backup media. The integrity of the volume is not guaranteed if
1376 the system abnormally abends.
1377 integrity
1379 Default. Commit metadata changes to the journal. Use this
1380 option to remount a volume where the nointegrity option was pre‐
1381 viously specified in order to restore normal behavior.
1382 errors={continue|remount-ro|panic}
1384 Define the behaviour when an error is encountered. (Either
1385 ignore errors and just mark the filesystem erroneous and con‐
1386 tinue, or remount the filesystem read-only, or panic and halt
1387 the system.)
1388 noquota|quota|usrquota|grpquota
1390 These options are accepted but ignored.
1391
1394 None.
1395
1398 See mount options for fat. If the msdos filesystem detects an incon‐
1399 sistency, it reports an error and sets the file system read-only. The
1400 filesystem can be made writeable again by remounting it.
1401
1404 Just like nfs, the ncpfs implementation expects a binary argument (a
1405 struct ncp_mount_data) to the mount system call. This argument is con‐
1406 structed by ncpmount(8) and the current version of mount (2.12) does
1407 not know anything about ncpfs.
1408
1411 See the options section of the nfs(5) man page (nfs-utils package must
1412 be installed).
1413 The nfs and nfs4 implementation expects a binary argument (a struct
1415 nfs_mount_data) to the mount system call. This argument is constructed
1416 by mount.nfs(8) and the current version of mount (2.13) does not know
1417 anything about nfs and nfs4.
1418
1421 iocharset=name
1422 Character set to use when returning file names. Unlike VFAT,
1423 NTFS suppresses names that contain unconvertible characters.
1424 Deprecated.
1425 nls=name
1427 New name for the option earlier called iocharset.
1428 utf8 Use UTF-8 for converting file names.
1430 uni_xlate={0|1|2}
1432 For 0 (or `no' or `false'), do not use escape sequences for
1433 unknown Unicode characters. For 1 (or `yes' or `true') or 2,
1434 use vfat-style 4-byte escape sequences starting with ":". Here 2
1435 give a little-endian encoding and 1 a byteswapped bigendian
1436 encoding.
1437 posix=[0|1]
1439 If enabled (posix=1), the filesystem distinguishes between upper
1440 and lower case. The 8.3 alias names are presented as hard links
1441 instead of being suppressed. This option is obsolete.
1442 uid=value, gid=value and umask=value
1444 Set the file permission on the filesystem. The umask value is
1445 given in octal. By default, the files are owned by root and not
1446 readable by somebody else.
1447
1450 uid=value and gid=value
1451 These options are recognized, but have no effect as far as I can
1452 see.
1453
1456 Ramfs is a memory based filesystem. Mount it and you have it. Unmount
1457 it and it is gone. Present since Linux 2.3.99pre4. There are no mount
1458 options.
1459
1462 Reiserfs is a journaling filesystem.
1463 conv Instructs version 3.6 reiserfs software to mount a version 3.5
1465 filesystem, using the 3.6 format for newly created objects. This
1466 filesystem will no longer be compatible with reiserfs 3.5 tools.
1467 hash={rupasov|tea|r5|detect}
1469 Choose which hash function reiserfs will use to find files
1470 within directories.
1471 rupasov
1473 A hash invented by Yury Yu. Rupasov. It is fast and pre‐
1474 serves locality, mapping lexicographically close file
1475 names to close hash values. This option should not be
1476 used, as it causes a high probability of hash collisions.
1477 tea A Davis-Meyer function implemented by Jeremy
1479 Fitzhardinge. It uses hash permuting bits in the name.
1480 It gets high randomness and, therefore, low probability
1481 of hash collisions at some CPU cost. This may be used if
1482 EHASHCOLLISION errors are experienced with the r5 hash.
1483 r5 A modified version of the rupasov hash. It is used by
1485 default and is the best choice unless the filesystem has
1486 huge directories and unusual file-name patterns.
1487 detect Instructs mount to detect which hash function is in use
1489 by examining the filesystem being mounted, and to write
1490 this information into the reiserfs superblock. This is
1491 only useful on the first mount of an old format filesys‐
1492 tem.
1493 hashed_relocation
1495 Tunes the block allocator. This may provide performance improve‐
1496 ments in some situations.
1497 no_unhashed_relocation
1499 Tunes the block allocator. This may provide performance improve‐
1500 ments in some situations.
1501 noborder
1503 Disable the border allocator algorithm invented by Yury Yu.
1504 Rupasov. This may provide performance improvements in some sit‐
1505 uations.
1506 nolog Disable journalling. This will provide slight performance
1508 improvements in some situations at the cost of losing reiserfs's
1509 fast recovery from crashes. Even with this option turned on,
1510 reiserfs still performs all journalling operations, save for
1511 actual writes into its journalling area. Implementation of
1512 nolog is a work in progress.
1513 notail By default, reiserfs stores small files and `file tails'
1515 directly into its tree. This confuses some utilities such as
1516 LILO(8). This option is used to disable packing of files into
1517 the tree.
1518 replayonly
1520 Replay the transactions which are in the journal, but do not
1521 actually mount the filesystem. Mainly used by reiserfsck.
1522 resize=number
1524 A remount option which permits online expansion of reiserfs par‐
1525 titions. Instructs reiserfs to assume that the device has num‐
1526 ber blocks. This option is designed for use with devices which
1527 are under logical volume management (LVM). There is a special
1528 resizer utility which can be obtained from
1529 ftp://ftp.namesys.com/pub/reiserfsprogs.
1530 user_xattr
1532 Enable Extended User Attributes. See the attr(5) manual page.
1533 acl Enable POSIX Access Control Lists. See the acl(5) manual page.
1535 barrier=none / barrier=flush
1537 This enables/disables the use of write barriers in the journal‐
1538 ing code. barrier=none disables it, barrier=flush enables it.
1539 Write barriers enforce proper on-disk ordering of journal com‐
1540 mits, making volatile disk write caches safe to use, at some
1541 performance penalty. The reiserfs filesystem does not enable
1542 write barriers by default. Be sure to enable barriers unless
1543 your disks are battery-backed one way or another. Otherwise you
1544 risk filesystem corruption in case of power failure.
1545
1548 None.
1549
1552 None.
1553
1556 Just like nfs, the smbfs implementation expects a binary argument (a
1557 struct smb_mount_data) to the mount system call. This argument is con‐
1558 structed by smbmount(8) and the current version of mount (2.12) does
1559 not know anything about smbfs.
1560
1563 None.
1564
1567 size=nbytes
1568 Override default maximum size of the filesystem. The size is
1569 given in bytes, and rounded up to entire pages. The default is
1570 half of the memory. The size parameter also accepts a suffix %
1571 to limit this tmpfs instance to that percentage of your physical
1572 RAM: the default, when neither size nor nr_blocks is specified,
1573 is size=50%
1574 nr_blocks=
1576 The same as size, but in blocks of PAGE_CACHE_SIZE
1577 nr_inodes=
1579 The maximum number of inodes for this instance. The default is
1580 half of the number of your physical RAM pages, or (on a machine
1581 with highmem) the number of lowmem RAM pages, whichever is the
1582 lower.
1583 The tmpfs mount options for sizing ( size, nr_blocks, and nr_inodes)
1585 accept a suffix k, m or g for Ki, Mi, Gi (binary kilo, mega and giga)
1586 and can be changed on remount.
1587 mode= Set initial permissions of the root directory.
1590 uid= The user id.
1592 gid= The group id.
1594 mpol=[default|prefer:Node|bind:NodeList|interleave|interleave:NodeList]
1596 Set the NUMA memory allocation policy for all files in that
1597 instance (if the kernel CONFIG_NUMA is enabled) - which can be
1598 adjusted on the fly via 'mount -o remount ...'
1599 default
1601 prefers to allocate memory from the local node
1602 prefer:Node
1604 prefers to allocate memory from the given Node
1605 bind:NodeList
1607 allocates memory only from nodes in NodeList
1608 interleave
1610 prefers to allocate from each node in turn
1611 interleave:NodeList
1613 allocates from each node of NodeList in turn.
1614 The NodeList format is a comma-separated list of decimal numbers
1616 and ranges, a range being two hyphen-separated decimal numbers,
1617 the smallest and largest node numbers in the range. For exam‐
1618 ple, mpol=bind:0-3,5,7,9-15
1619 Note that trying to mount a tmpfs with an mpol option will fail
1621 if the running kernel does not support NUMA; and will fail if
1622 its nodelist specifies a node which is not online. If your sys‐
1623 tem relies on that tmpfs being mounted, but from time to time
1624 runs a kernel built without NUMA capability (perhaps a safe
1625 recovery kernel), or with fewer nodes online, then it is advis‐
1626 able to omit the mpol option from automatic mount options. It
1627 can be added later, when the tmpfs is already mounted on Mount‐
1628 Point, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.
1629
1632 UBIFS is a flash file system which works on top of UBI volumes. Note
1633 that atime is not supported and is always turned off.
1634 The device name may be specified as
1636 ubiX_Y UBI device number X, volume number Y
1637 ubiY UBI device number 0, volume number Y
1639 ubiX:NAME
1641 UBI device number X, volume with name NAME
1642 ubi:NAME
1644 UBI device number 0, volume with name NAME
1645 Alternative ! separator may be used instead of :.
1646 The following mount options are available:
1648 bulk_read
1650 Enable bulk-read. VFS read-ahead is disabled because it slows
1651 down the file system. Bulk-Read is an internal optimization.
1652 Some flashes may read faster if the data are read at one go,
1653 rather than at several read requests. For example, OneNAND can
1654 do "read-while-load" if it reads more than one NAND page.
1655 no_bulk_read
1657 Do not bulk-read. This is the default.
1658 chk_data_crc
1660 Check data CRC-32 checksums. This is the default.
1661 no_chk_data_crc.
1663 Do not check data CRC-32 checksums. With this option, the
1664 filesystem does not check CRC-32 checksum for data, but it does
1665 check it for the internal indexing information. This option only
1666 affects reading, not writing. CRC-32 is always calculated when
1667 writing the data.
1668 compr={none|lzo|zlib}
1670 Select the default compressor which is used when new files are
1671 written. It is still possible to read compressed files if
1672 mounted with the none option.
1673
1676 udf is the "Universal Disk Format" filesystem defined by the Optical
1677 Storage Technology Association, and is often used for DVD-ROM. See
1678 also iso9660.
1679 gid= Set the default group.
1681 umask= Set the default umask. The value is given in octal.
1683 uid= Set the default user.
1685 unhide Show otherwise hidden files.
1687 undelete
1689 Show deleted files in lists.
1690 nostrict
1692 Unset strict conformance.
1693 iocharset
1695 Set the NLS character set.
1696 bs= Set the block size. (May not work unless 2048.)
1698 novrs Skip volume sequence recognition.
1700 session=
1702 Set the CDROM session counting from 0. Default: last session.
1703 anchor=
1705 Override standard anchor location. Default: 256.
1706 volume=
1708 Override the VolumeDesc location. (unused)
1709 partition=
1711 Override the PartitionDesc location. (unused)
1712 lastblock=
1714 Set the last block of the filesystem.
1715 fileset=
1717 Override the fileset block location. (unused)
1718 rootdir=
1720 Override the root directory location. (unused)
1721
1724 ufstype=value
1725 UFS is a filesystem widely used in different operating systems.
1726 The problem are differences among implementations. Features of
1727 some implementations are undocumented, so its hard to recognize
1728 the type of ufs automatically. That's why the user must specify
1729 the type of ufs by mount option. Possible values are:
1730 old Old format of ufs, this is the default, read only.
1732 (Don't forget to give the -r option.)
1733 44bsd For filesystems created by a BSD-like system (Net‐
1735 BSD,FreeBSD,OpenBSD).
1736 sun For filesystems created by SunOS or Solaris on Sparc.
1738 sunx86 For filesystems created by Solaris on x86.
1740 hp For filesystems created by HP-UX, read-only.
1742 nextstep
1744 For filesystems created by NeXTStep (on NeXT station)
1745 (currently read only).
1746 nextstep-cd
1748 For NextStep CDROMs (block_size == 2048), read-only.
1749 openstep
1751 For filesystems created by OpenStep (currently read
1752 only). The same filesystem type is also used by Mac OS
1753 X.
1754 onerror=value
1757 Set behaviour on error:
1758 panic If an error is encountered, cause a kernel panic.
1760 [lock|umount|repair]
1762 These mount options don't do anything at present; when an
1763 error is encountered only a console message is printed.
1764
1767 See mount options for msdos. The dotsOK option is explicitly killed by
1768 umsdos.
1769
1772 First of all, the mount options for fat are recognized. The dotsOK
1773 option is explicitly killed by vfat. Furthermore, there are
1774 uni_xlate
1776 Translate unhandled Unicode characters to special escaped
1777 sequences. This lets you backup and restore filenames that are
1778 created with any Unicode characters. Without this option, a '?'
1779 is used when no translation is possible. The escape character is
1780 ':' because it is otherwise illegal on the vfat filesystem. The
1781 escape sequence that gets used, where u is the unicode charac‐
1782 ter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
1783 posix Allow two files with names that only differ in case. This
1785 option is obsolete.
1786 nonumtail
1788 First try to make a short name without sequence number, before
1789 trying name~num.ext.
1790 utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is
1792 used by the console. It can be be enabled for the filesystem
1793 with this option or disabled with utf8=0, utf8=no or utf8=false.
1794 If `uni_xlate' gets set, UTF8 gets disabled.
1795 shortname={lower|win95|winnt|mixed}
1797 Defines the behaviour for creation and display of filenames
1799 which fit into 8.3 characters. If a long name for a file exists,
1800 it will always be preferred display. There are four modes: :
1801 lower Force the short name to lower case upon display; store a
1803 long name when the short name is not all upper case. This
1804 mode is the default.
1805 win95 Force the short name to upper case upon display; store a
1807 long name when the short name is not all upper case.
1808 winnt Display the shortname as is; store a long name when the
1810 short name is not all lower case or all upper case.
1811 mixed Display the short name as is; store a long name when the
1813 short name is not all upper case.
1814
1818 devuid=uid and devgid=gid and devmode=mode
1819 Set the owner and group and mode of the device files in the
1820 usbfs filesystem (default: uid=gid=0, mode=0644). The mode is
1821 given in octal.
1822 busuid=uid and busgid=gid and busmode=mode
1824 Set the owner and group and mode of the bus directories in the
1825 usbfs filesystem (default: uid=gid=0, mode=0555). The mode is
1826 given in octal.
1827 listuid=uid and listgid=gid and listmode=mode
1829 Set the owner and group and mode of the file devices (default:
1830 uid=gid=0, mode=0444). The mode is given in octal.
1831
1834 None.
1835
1838 allocsize=size
1839 Sets the buffered I/O end-of-file preallocation size when doing
1840 delayed allocation writeout. Valid values for this option are
1841 page size (typically 4KiB) through to 1GiB, inclusive, in power-
1842 of-2 increments.
1843 The default behavior is for dynamic end-of-file preallocation
1845 size, which uses a set of heuristics to optimise the prealloca‐
1846 tion size based on the current allocation patterns within the
1847 file and the access patterns to the file. Specifying a fixed
1848 allocsize value turns off the dynamic behavior.
1849 attr2|noattr2
1851 The options enable/disable an "opportunistic" improvement to be
1852 made in the way inline extended attributes are stored on-disk.
1853 When the new form is used for the first time when attr2 is
1854 selected (either when setting or removing extended attributes)
1855 the on-disk superblock feature bit field will be updated to
1856 reflect this format being in use.
1857 The default behavior is determined by the on-disk feature bit
1859 indicating that attr2 behavior is active. If either mount
1860 option it set, then that becomes the new default used by the
1861 filesystem.
1862 CRC enabled filesystems always use the attr2 format, and so will
1864 reject the noattr2 mount option if it is set.
1865 barrier|nobarrier
1867 Enables/disables the use of block layer write barriers for
1868 writes into the journal and for data integrity operations. This
1869 allows for drive level write caching to be enabled, for devices
1870 that support write barriers.
1871 discard|nodiscard
1873 Enable/disable the issuing of commands to let the block device
1874 reclaim space freed by the filesystem. This is useful for SSD
1875 devices, thinly provisioned LUNs and virtual machine images, but
1876 may have a performance impact.
1877 Note: It is currently recommended that you use the fstrim appli‐
1879 cation to discard unused blocks rather than the discard mount
1880 option because the performance impact of this option is quite
1881 severe.
1882 grpid|bsdgroups|nogrpid|sysvgroups
1884 These options define what group ID a newly created file gets.
1885 When grpid is set, it takes the group ID of the directory in
1886 which it is created; otherwise it takes the fsgid of the current
1887 process, unless the directory has the setgid bit set, in which
1888 case it takes the gid from the parent directory, and also gets
1889 the setgid bit set if it is a directory itself.
1890 filestreams
1892 Make the data allocator use the filestreams allocation mode
1893 across the entire filesystem rather than just on directories
1894 configured to use it.
1895 ikeep|noikeep
1897 When ikeep is specified, XFS does not delete empty inode clus‐
1898 ters and keeps them around on disk. When noikeep is specified,
1899 empty inode clusters are returned to the free space pool.
1900 inode32|inode64
1902 When inode32 is specified, it indicates that XFS limits inode
1903 creation to locations which will not result in inode numbers
1904 with more than 32 bits of significance.
1905 When inode64 is specified, it indicates that XFS is allowed to
1907 create inodes at any location in the filesystem, including those
1908 which will result in inode numbers occupying more than 32 bits
1909 of significance.
1910 inode32 is provided for backwards compatibility with older sys‐
1912 tems and applications, since 64 bits inode numbers might cause
1913 problems for some applications that cannot handle large inode
1914 numbers. If applications are in use which do not handle inode
1915 numbers bigger than 32 bits, the inode32 option should be speci‐
1916 fied.
1917 largeio|nolargeio
1919 If "nolargeio" is specified, the optimal I/O reported in st_blk‐
1920 size by stat(2) will be as small as possible to allow user
1921 applications to avoid inefficient read/modify/write I/O. This
1922 is typically the page size of the machine, as this is the granu‐
1923 larity of the page cache.
1924 If "largeio" specified, a filesystem that was created with a
1926 "swidth" specified will return the "swidth" value (in bytes) in
1927 st_blksize. If the filesystem does not have a "swidth" speci‐
1928 fied but does specify an "allocsize" then "allocsize" (in bytes)
1929 will be returned instead. Otherwise the behavior is the same as
1930 if "nolargeio" was specified.
1931 logbufs=value
1933 Set the number of in-memory log buffers. Valid numbers range
1934 from 2–8 inclusive.
1935 The default value is 8 buffers.
1937 If the memory cost of 8 log buffers is too high on small sys‐
1939 tems, then it may be reduced at some cost to performance on
1940 metadata intensive workloads. The logbsize option below con‐
1941 trols the size of each buffer and so is also relevant to this
1942 case.
1943 logbsize=value
1945 Set the size of each in-memory log buffer. The size may be
1946 specified in bytes, or in kibibytes (KiB) with a "k" suffix.
1947 Valid sizes for version 1 and version 2 logs are 16384
1948 (value=16k) and 32768 (value=32k). Valid sizes for version 2
1949 logs also include 65536 (value=64k), 131072 (value=128k) and
1950 262144 (value=256k). The logbsize must be an integer multiple
1951 of the log stripe unit configured at mkfs time.
1952 The default value for version 1 logs is 32768, while the default
1954 value for version 2 logs is MAX(32768, log_sunit).
1955 logdev=device and rtdev=device
1957 Use an external log (metadata journal) and/or real-time device.
1958 An XFS filesystem has up to three parts: a data section, a log
1959 section, and a real-time section. The real-time section is
1960 optional, and the log section can be separate from the data sec‐
1961 tion or contained within it.
1962 noalign
1964 Data allocations will not be aligned at stripe unit boundaries.
1965 This is only relevant to filesystems created with non-zero data
1966 alignment parameters (sunit, swidth) by mkfs.
1967 norecovery
1969 The filesystem will be mounted without running log recovery. If
1970 the filesystem was not cleanly unmounted, it is likely to be
1971 inconsistent when mounted in "norecovery" mode. Some files or
1972 directories may not be accessible because of this. Filesystems
1973 mounted "norecovery" must be mounted read-only or the mount will
1974 fail.
1975 nouuid Don't check for double mounted file systems using the file sys‐
1977 tem uuid. This is useful to mount LVM snapshot volumes, and
1978 often used in combination with "norecovery" for mounting read-
1979 only snapshots.
1980 noquota
1982 Forcibly turns off all quota accounting and enforcement within
1983 the filesystem.
1984 uquota/usrquota/uqnoenforce/quota
1986 User disk quota accounting enabled, and limits (optionally)
1987 enforced. Refer to xfs_quota(8) for further details.
1988 gquota/grpquota/gqnoenforce
1990 Group disk quota accounting enabled and limits (optionally)
1991 enforced. Refer to xfs_quota(8) for further details.
1992 pquota/prjquota/pqnoenforce
1994 Project disk quota accounting enabled and limits (optionally)
1995 enforced. Refer to xfs_quota(8) for further details.
1996 sunit=value and swidth=value
1998 Used to specify the stripe unit and width for a RAID device or a
1999 stripe volume. "value" must be specified in 512-byte block
2000 units. These options are only relevant to filesystems that were
2001 created with non-zero data alignment parameters.
2002 The sunit and swidth parameters specified must be compatible
2004 with the existing filesystem alignment characteristics. In gen‐
2005 eral, that means the only valid changes to sunit are increasing
2006 it by a power-of-2 multiple. Valid swidth values are any inte‐
2007 ger multiple of a valid sunit value.
2008 Typically the only time these mount options are necessary if
2010 after an underlying RAID device has had it's geometry modified,
2011 such as adding a new disk to a RAID5 lun and reshaping it.
2012 swalloc
2014 Data allocations will be rounded up to stripe width boundaries
2015 when the current end of file is being extended and the file size
2016 is larger than the stripe width size.
2017 wsync When specified, all filesystem namespace operations are executed
2019 synchronously. This ensures that when the namespace operation
2020 (create, unlink, etc) completes, the change to the namespace is
2021 on stable storage. This is useful in HA setups where failover
2022 must not result in clients seeing inconsistent namespace presen‐
2023 tation during or after a failover event.
2024
2027 None. Although nothing is wrong with xiafs, it is not used much, and is
2028 not maintained. Probably one shouldn't use it. Since Linux version
2029 2.1.21 xiafs is no longer part of the kernel source.
2030
2033 One further possible type is a mount via the loop device. For example,
2034 the command
2035 mount /tmp/fdimage /mnt -t vfat -o loop=/dev/loop3
2037 will set up the loop device /dev/loop3 to correspond to the file
2039 /tmp/fdimage, and then mount this device on /mnt.
2040 This type of mount knows about four options, namely loop, offset, size‐
2042 limit and encryption, that are really options to losetup(8). (These
2043 options can be used in addition to those specific to the filesystem
2044 type.)
2045 If no explicit loop device is mentioned (but just an option `-o loop'
2047 is given), then mount will try to find some unused loop device and use
2048 that.
2049 Since Linux 2.6.25 is supported auto-destruction of loop devices and
2051 then any loop device allocated by mount will be freed by umount inde‐
2052 pendently on /etc/mtab.
2053 You can also free a loop device by hand, using `losetup -d' or `umount
2055 -d`.
2056
2059 mount has the following return codes (the bits can be ORed):
2060 0 success
2062 1 incorrect invocation or permissions
2064 2 system error (out of memory, cannot fork, no more loop devices)
2066 4 internal mount bug
2068 8 user interrupt
2070 16 problems writing or locking /etc/mtab
2072 32 mount failure
2074 64 some mount succeeded
2076
2079 The syntax of external mount helpers is:
2080 /sbin/mount.<suffix> spec dir [-sfnv] [-o options] [-t type.sub‐
2082 type]
2083 where the <type> is filesystem type and -sfnvo options have same mean‐
2085 ing like standard mount options. The -t option is used for filesystems
2086 with subtypes support (for example /sbin/mount.fuse -t fuse.sshfs).
2087
2090 /etc/fstab filesystem table
2091 /etc/mtab table of mounted filesystems
2093 /etc/mtab~ lock file
2095 /etc/mtab.tmp temporary file
2097 /etc/filesystems a list of filesystem types to try
2099
2102 mount(2), umount(2), fstab(5), umount(8), swapon(8), nfs(5), xfs(5),
2103 e2label(8), xfs_admin(8), mountd(8), nfsd(8), mke2fs(8), tune2fs(8),
2104 losetup(8)
2105
2107 It is possible for a corrupted filesystem to cause a crash.
2108 Some Linux filesystems don't support -o sync and -o dirsync (the ext2,
2110 ext3, fat and vfat filesystems do support synchronous updates (a la
2111 BSD) when mounted with the sync option).
2112 The -o remount may not be able to change mount parameters (all ext2fs-
2114 specific parameters, except sb, are changeable with a remount, for
2115 example, but you can't change gid or umask for the fatfs).
2116 Mount by label or uuid will work only if your devices have the names
2118 listed in /proc/partitions. In particular, it may well fail if the
2119 kernel was compiled with devfs but devfs is not mounted.
2120 It is possible that files /etc/mtab and /proc/mounts don't match. The
2122 first file is based only on the mount command options, but the content
2123 of the second file also depends on the kernel and others settings (e.g.
2124 remote NFS server. In particular case the mount command may reports
2125 unreliable information about a NFS mount point and the /proc/mounts
2126 file usually contains more reliable information.)
2127 Checking files on NFS filesystem referenced by file descriptors (i.e.
2129 the fcntl and ioctl families of functions) may lead to inconsistent
2130 result due to the lack of consistency check in kernel even if noac is
2131 used.
2132
2134 A mount command existed in Version 5 AT&T UNIX.
2135
2137 The mount command is part of the util-linux-ng package and is available
2138 from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.
2139Linux 2.6 2004-12-16 MOUNT(8)