1MOUNT(8) System Administration MOUNT(8)
2
6 mount - mount a filesystem
7
9 mount [-l|-h|-V]
10 mount -a [-fFnrsvw] [-t fstype] [-O optlist]
12 mount [-fnrsvw] [-o options] device|dir
14 mount [-fnrsvw] [-t fstype] [-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. The filesystem is used to control how data is
23 stored on the device or provided in a virtual way by network or another
24 services.
25 The standard form of the mount command is:
27 mount -t type device dir
29 This tells the kernel to attach the filesystem found on device (which
31 is of type type) at the directory dir. The option -t type is optional.
32 The mount command is usually able to detect a filesystem. The root
33 permissions are necessary to mount a filesystem by default. See sec‐
34 tion "Non-superuser mounts" below for more details. The previous con‐
35 tents (if any) and owner and mode of dir become invisible, and as long
36 as this filesystem remains mounted, the pathname dir refers to the root
37 of the filesystem on device.
38 If only the directory or the device is given, for example:
40 mount /dir
42 then mount looks for a mountpoint (and if not found then for a device)
44 in the /etc/fstab file. It's possible to use the --target or --source
45 options to avoid ambivalent interpretation of the given argument. For
46 example:
47 mount --target /mountpoint
49 The same filesystem may be mounted more than once, and in some cases
52 (e.g. network filesystems) the same filesystem maybe be mounted on the
53 same mountpoint more times. The mount command does not implement any
54 policy to control this behavior. All behavior is controlled by kernel
55 and it is usually specific to filesystem driver. The exception is
56 --all, in this case already mounted filesystems are ignored (see --all
57 below for more details).
58 Listing the mounts
61 The listing mode is maintained for backward compatibility only.
62 For more robust and customizable output use findmnt(8), especially in
64 your scripts. Note that control characters in the mountpoint name are
65 replaced with '?'.
66 The following command lists all mounted filesystems (of type type):
68 mount [-l] [-t type]
70 The option -l adds labels to this listing. See below.
72 Indicating the device and filesystem
75 Most devices are indicated by a filename (of a block special device),
76 like /dev/sda1, but there are other possibilities. For example, in the
77 case of an NFS mount, device may look like knuth.cwi.nl:/dir. It is
78 also possible to indicate a block special device using its filesystem
79 label or UUID (see the -L and -U options below), or its partition label
80 or UUID. Partition identifiers are supported for example for GUID Par‐
81 tition Tables (GPT).
82 The device name of disk partitions are unstable; hardware reconfigura‐
84 tion, adding or removing a device can cause change in names. This is
85 reason why it's strongly recommended to use filesystem or partition
86 identificators like UUID or LABEL.
87 The command lsblk --fs provides overview of filesystems, LABELs and
89 UUIDs on available block devices. The command blkid -p <device> pro‐
90 vides details about a filesystem on the specified device.
91 Don't forget that there is no guarantee that UUIDs and labels are
93 really unique, especially if you move, share or copy the device. Use
94 lsblk -o +UUID,PARTUUID to verify that the UUIDs are really unique in
95 your system.
96 The recommended setup is to use tags (e.g. UUID=uuid) rather than
98 /dev/disk/by-{label,uuid,partuuid,partlabel} udev symlinks in the
99 /etc/fstab file. Tags are more readable, robust and portable. The
100 mount(8) command internally uses udev symlinks, so the use of symlinks
101 in /etc/fstab has no advantage over tags. For more details see lib‐
102 blkid(3).
103 Note that mount(8) uses UUIDs as strings. The UUIDs from the command
105 line or from fstab(5) are not converted to internal binary representa‐
106 tion. The string representation of the UUID should be based on lower
107 case characters.
108 The proc filesystem is not associated with a special device, and when
110 mounting it, an arbitrary keyword, such as proc can be used instead of
111 a device specification. (The customary choice none is less fortunate:
112 the error message `none already mounted' from mount can be confusing.)
113 The files /etc/fstab, /etc/mtab and /proc/mounts
116 The file /etc/fstab (see fstab(5)), may contain lines describing what
117 devices are usually mounted where, using which options. The default
118 location of the fstab(5) file can be overridden with the --fstab path
119 command-line option (see below for more details).
120 The command
122 mount -a [-t type] [-O optlist]
124 (usually given in a bootscript) causes all filesystems mentioned in
126 fstab (of the proper type and/or having or not having the proper
127 options) to be mounted as indicated, except for those whose line con‐
128 tains the noauto keyword. Adding the -F option will make mount fork,
129 so that the filesystems are mounted simultaneously.
130 When mounting a filesystem mentioned in fstab or mtab, it suffices to
132 specify on the command line only the device, or only the mount point.
133 The programs mount and umount traditionally maintained a list of cur‐
135 rently mounted filesystems in the file /etc/mtab. This real mtab file
136 is still supported, but on current Linux systems it is better to make
137 it a symlink to /proc/mounts instead, because a regular mtab file main‐
138 tained in userspace cannot reliably work with namespaces, containers
139 and other advanced Linux features.
140 If no arguments are given to mount, the list of mounted filesystems is
142 printed.
143 If you want to override mount options from /etc/fstab you have to use
145 the -o option:
146 mount device|dir -o options
148 and then the mount options from the command line will be appended to
150 the list of options from /etc/fstab. The usual behavior is that the
151 last option wins if there are conflicting ones.
152 The mount program does not read the /etc/fstab file if both device (or
154 LABEL, UUID, PARTUUID or PARTLABEL) and dir are specified. For exam‐
155 ple, to mount device foo at /dir:
156 mount /dev/foo /dir
158 Non-superuser mounts
162 Normally, only the superuser can mount filesystems. However, when
163 fstab contains the user option on a line, anybody can mount the corre‐
164 sponding filesystem.
165 Thus, given a line
167 /dev/cdrom /cd iso9660 ro,user,noauto,unhide
169 any user can mount the iso9660 filesystem found on an inserted CDROM
171 using the command:
172 mount /cd
173 Note that mount is very strict about non-root users and all paths spec‐
175 ified on command line are verified before fstab is parsed or a helper
176 program is executed. It's strongly recommended to use a valid mount‐
177 point to specify filesystem, otherwise mount may fail. For example it's
178 bad idea to use NFS or CIFS source on command line.
179 For more details, see fstab(5). Only the user that mounted a filesys‐
181 tem can unmount it again. If any user should be able to unmount it,
182 then use users instead of user in the fstab line. The owner option is
183 similar to the user option, with the restriction that the user must be
184 the owner of the special file. This may be useful e.g. for /dev/fd if
185 a login script makes the console user owner of this device. The group
186 option is similar, with the restriction that the user must be member of
187 the group of the special file.
188 Bind mount operation
191 Remount part of the file hierarchy somewhere else. The call is:
192 mount --bind olddir newdir
194 or by using this fstab entry:
196 /olddir /newdir none bind
198 After this call the same contents are accessible in two places.
200 It is important to understand that "bind" does not to create any sec‐
202 ond-class or special node in the kernel VFS. The "bind" is just another
203 operation to attach a filesystem. There is nowhere stored information
204 that the filesystem has been attached by "bind" operation. The olddir
205 and newdir are independent and the olddir maybe be umounted.
206 One can also remount a single file (on a single file). It's also pos‐
208 sible to use the bind mount to create a mountpoint from a regular
209 directory, for example:
210 mount --bind foo foo
212 The bind mount call attaches only (part of) a single filesystem, not
214 possible submounts. The entire file hierarchy including submounts is
215 attached a second place by using:
216 mount --rbind olddir newdir
218 Note that the filesystem mount options will remain the same as those on
220 the original mount point.
221 mount(8) since v2.27 allows to change the mount options by passing the
223 relevant options along with --bind. For example:
224 mount -o bind,ro foo foo
226 This feature is not supported by the Linux kernel; it is implemented in
228 userspace by an additional mount(2) remounting system call. This solu‐
229 tion is not atomic.
230 The alternative (classic) way to create a read-only bind mount is to
232 use the remount operation, for example:
233 mount --bind olddir newdir
235 mount -o remount,bind,ro olddir newdir
236 Note that a read-only bind will create a read-only mountpoint (VFS
238 entry), but the original filesystem superblock will still be writable,
239 meaning that the olddir will be writable, but the newdir will be read-
240 only.
241 It's also possible to change nosuid, nodev, noexec, noatime, nodiratime
243 and relatime VFS entry flags by "remount,bind" operation. It's impossi‐
244 ble to change mount options recursively (for example with -o rbind,ro).
245 mount(8) since v2.31 ignores the bind flag from /etc/fstab on remount
247 operation (if "-o remount" specified on command line). This is neces‐
248 sary to fully control mount options on remount by command line. In the
249 previous versions the bind flag has been always applied and it was
250 impossible to re-define mount options without interaction with the bind
251 semantic. This mount(8) behavior does not affect situations when
252 "remount,bind" is specified in the /etc/fstab file.
253 The move operation
256 Move a mounted tree to another place (atomically). The call is:
257 mount --move olddir newdir
259 This will cause the contents which previously appeared under olddir to
261 now be accessible under newdir. The physical location of the files is
262 not changed. Note that olddir has to be a mountpoint.
263 Note also that moving a mount residing under a shared mount is invalid
265 and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current
266 propagation flags.
267 Shared subtree operations
270 Since Linux 2.6.15 it is possible to mark a mount and its submounts as
271 shared, private, slave or unbindable. A shared mount provides the
272 ability to create mirrors of that mount such that mounts and unmounts
273 within any of the mirrors propagate to the other mirror. A slave mount
274 receives propagation from its master, but not vice versa. A private
275 mount carries no propagation abilities. An unbindable mount is a pri‐
276 vate mount which cannot be cloned through a bind operation. The
277 detailed semantics are documented in Documentation/filesystems/shared‐
278 subtree.txt file in the kernel source tree.
279 Supported operations are:
281 mount --make-shared mountpoint
283 mount --make-slave mountpoint
284 mount --make-private mountpoint
285 mount --make-unbindable mountpoint
286 The following commands allow one to recursively change the type of all
288 the mounts under a given mountpoint.
289 mount --make-rshared mountpoint
291 mount --make-rslave mountpoint
292 mount --make-rprivate mountpoint
293 mount --make-runbindable mountpoint
294 mount(8) does not read fstab(5) when a --make-* operation is requested.
296 All necessary information has to be specified on the command line.
297 Note that the Linux kernel does not allow to change multiple propaga‐
299 tion flags with a single mount(2) system call, and the flags cannot be
300 mixed with other mount options and operations.
301 Since util-linux 2.23 the mount command allows to do more propagation
303 (topology) changes by one mount(8) call and do it also together with
304 other mount operations. This feature is EXPERIMENTAL. The propagation
305 flags are applied by additional mount(2) system calls when the preced‐
306 ing mount operations were successful. Note that this use case is not
307 atomic. It is possible to specify the propagation flags in fstab(5) as
308 mount options (private, slave, shared, unbindable, rprivate, rslave,
309 rshared, runbindable).
310 For example:
312 mount --make-private --make-unbindable /dev/sda1 /foo
314 is the same as:
316 mount /dev/sda1 /foo
318 mount --make-private /foo
319 mount --make-unbindable /foo
320
323 The full set of mount options used by an invocation of mount is deter‐
324 mined by first extracting the mount options for the filesystem from the
325 fstab table, then applying any options specified by the -o argument,
326 and finally applying a -r or -w option, when present.
327 The command mount does not pass all command-line options to the
329 /sbin/mount.suffix mount helpers. The interface between mount and the
330 mount helpers is described below in the section EXTERNAL HELPERS.
331 Command-line options available for the mount command are:
333 -a, --all
335 Mount all filesystems (of the given types) mentioned in fstab
336 (except for those whose line contains the noauto keyword). The
337 filesystems are mounted following their order in fstab. The
338 mount command compares filesystem source, target (and fs root
339 for bind mount or btrfs) to detect already mounted filesystems.
340 The kernel table with already mounted filesystems is cached dur‐
341 ing mount --all. It means that all duplicated fstab entries will
342 be mounted.
343 Note that it is a bad practice to use mount -a for fstab check‐
345 ing. The recommended solution is findmnt --verify.
346 -B, --bind
348 Remount a subtree somewhere else (so that its contents are
349 available in both places). See above, under Bind mounts.
350 -c, --no-canonicalize
352 Don't canonicalize paths. The mount command canonicalizes all
353 paths (from command line or fstab) by default. This option can
354 be used together with the -f flag for already canonicalized
355 absolute paths. The option is designed for mount helpers which
356 call mount -i. It is strongly recommended to not use this com‐
357 mand-line option for normal mount operations.
358 Note that mount(8) does not pass this option to the
360 /sbin/mount.type helpers.
361 -F, --fork
363 (Used in conjunction with -a.) Fork off a new incarnation of
364 mount for each device. This will do the mounts on different
365 devices or different NFS servers in parallel. This has the
366 advantage that it is faster; also NFS timeouts go in parallel.
367 A disadvantage is that the mounts are done in undefined order.
368 Thus, you cannot use this option if you want to mount both /usr
369 and /usr/spool.
370 -f, --fake
372 Causes everything to be done except for the actual system call;
373 if it's not obvious, this ``fakes'' mounting the filesystem.
374 This option is useful in conjunction with the -v flag to deter‐
375 mine what the mount command is trying to do. It can also be
376 used to add entries for devices that were mounted earlier with
377 the -n option. The -f option checks for an existing record in
378 /etc/mtab and fails when the record already exists (with a regu‐
379 lar non-fake mount, this check is done by the kernel).
380 -i, --internal-only
382 Don't call the /sbin/mount.filesystem helper even if it exists.
383 -L, --label label
385 Mount the partition that has the specified label.
386 -l, --show-labels
388 Add the labels in the mount output. mount must have permission
389 to read the disk device (e.g. be set-user-ID root) for this to
390 work. One can set such a label for ext2, ext3 or ext4 using the
391 e2label(8) utility, or for XFS using xfs_admin(8), or for reis‐
392 erfs using reiserfstune(8).
393 -M, --move
395 Move a subtree to some other place. See above, the subsection
396 The move operation.
397 -n, --no-mtab
399 Mount without writing in /etc/mtab. This is necessary for exam‐
400 ple when /etc is on a read-only filesystem.
401 -O, --test-opts opts
403 Limit the set of filesystems to which the -a option applies. In
404 this regard it is like the -t option except that -O is useless
405 without -a. For example, the command:
406 mount -a -O no_netdev
408 mounts all filesystems except those which have the option _net‐
410 dev specified in the options field in the /etc/fstab file.
411 It is different from -t in that each option is matched exactly;
413 a leading no at the beginning of one option does not negate the
414 rest.
415 The -t and -O options are cumulative in effect; that is, the
417 command
418 mount -a -t ext2 -O _netdev
420 mounts all ext2 filesystems with the _netdev option, not all
422 filesystems that are either ext2 or have the _netdev option
423 specified.
424 -o, --options opts
426 Use the specified mount options. The opts argument is a comma-
427 separated list. For example:
428 mount LABEL=mydisk -o noatime,nodev,nosuid
430 For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS
433 and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.
434 -R, --rbind
437 Remount a subtree and all possible submounts somewhere else (so
438 that its contents are available in both places). See above, the
439 subsection Bind mounts.
440 -r, --read-only
442 Mount the filesystem read-only. A synonym is -o ro.
443 Note that, depending on the filesystem type, state and kernel
445 behavior, the system may still write to the device. For exam‐
446 ple, ext3 and ext4 will replay the journal if the filesystem is
447 dirty. To prevent this kind of write access, you may want to
448 mount an ext3 or ext4 filesystem with the ro,noload mount
449 options or set the block device itself to read-only mode, see
450 the blockdev(8) command.
451 -s Tolerate sloppy mount options rather than failing. This will
453 ignore mount options not supported by a filesystem type. Not
454 all filesystems support this option. Currently it's supported
455 by the mount.nfs mount helper only.
456 --source device
458 If only one argument for the mount command is given then the
459 argument might be interpreted as target (mountpoint) or source
460 (device). This option allows to explicitly define that the
461 argument is the mount source.
462 --target directory
464 If only one argument for the mount command is given then the
465 argument might be interpreted as target (mountpoint) or source
466 (device). This option allows to explicitly define that the
467 argument is the mount target.
468 -T, --fstab path
470 Specifies an alternative fstab file. If path is a directory
471 then the files in the directory are sorted by strverscmp(3);
472 files that start with "." or without an .fstab extension are
473 ignored. The option can be specified more than once. This
474 option is mostly designed for initramfs or chroot scripts where
475 additional configuration is specified beyond standard system
476 configuration.
477 Note that mount(8) does not pass the option --fstab to the
479 /sbin/mount.type helpers, meaning that the alternative fstab
480 files will be invisible for the helpers. This is no problem for
481 normal mounts, but user (non-root) mounts always require fstab
482 to verify the user's rights.
483 -t, --types fstype
485 The argument following the -t is used to indicate the filesystem
486 type. The filesystem types which are currently supported depend
487 on the running kernel. See /proc/filesystems and /lib/mod‐
488 ules/$(uname -r)/kernel/fs for a complete list of the filesys‐
489 tems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat,
490 sysfs, proc, nfs and cifs.
491 The programs mount and umount support filesystem subtypes. The
493 subtype is defined by a '.subtype' suffix. For example
494 'fuse.sshfs'. It's recommended to use subtype notation rather
495 than add any prefix to the mount source (for example
496 'sshfs#example.com' is deprecated).
497 If no -t option is given, or if the auto type is specified,
499 mount will try to guess the desired type. Mount uses the blkid
500 library for guessing the filesystem type; if that does not turn
501 up anything that looks familiar, mount will try to read the file
502 /etc/filesystems, or, if that does not exist, /proc/filesystems.
503 All of the filesystem types listed there will be tried, except
504 for those that are labeled "nodev" (e.g. devpts, proc and nfs).
505 If /etc/filesystems ends in a line with a single *, mount will
506 read /proc/filesystems afterwards. While trying, all filesystem
507 types will be mounted with the mount option silent.
508 The auto type may be useful for user-mounted floppies. Creating
510 a file /etc/filesystems can be useful to change the probe order
511 (e.g., to try vfat before msdos or ext3 before ext2) or if you
512 use a kernel module autoloader.
513 More than one type may be specified in a comma-separated list,
515 for option -t as well as in an /etc/fstab entry. The list of
516 filesystem types for option -t can be prefixed with no to spec‐
517 ify the filesystem types on which no action should be taken.
518 The prefix no has no effect when specified in an /etc/fstab
519 entry.
520 The prefix no can be meaningful with the -a option. For exam‐
522 ple, the command
523 mount -a -t nomsdos,smbfs
525 mounts all filesystems except those of type msdos and smbfs.
527 For most types all the mount program has to do is issue a simple
529 mount(2) system call, and no detailed knowledge of the filesys‐
530 tem type is required. For a few types however (like nfs, nfs4,
531 cifs, smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4,
532 cifs, smbfs, and ncpfs filesystems have a separate mount pro‐
533 gram. In order to make it possible to treat all types in a uni‐
534 form way, mount will execute the program /sbin/mount.type (if
535 that exists) when called with type type. Since different ver‐
536 sions of the smbmount program have different calling conven‐
537 tions, /sbin/mount.smbfs may have to be a shell script that sets
538 up the desired call.
539 -U, --uuid uuid
541 Mount the partition that has the specified uuid.
542 -v, --verbose
544 Verbose mode.
545 -w, --rw, --read-write
547 Mount the filesystem read/write. The read-write is kernel
548 default. A synonym is -o rw.
549 Note that specify -w on command line forces mount command to
551 never try read-only mount on write-protected devices. The
552 default is try read-only if the previous mount syscall with
553 read-write flags failed.
554 -V, --version
556 Display version information and exit.
557 -h, --help
559 Display help text and exit.
560
563 Some of these options are only useful when they appear in the
564 /etc/fstab file.
565 Some of these options could be enabled or disabled by default in the
567 system kernel. To check the current setting see the options in
568 /proc/mounts. Note that filesystems also have per-filesystem specific
569 default mount options (see for example tune2fs -l output for extN
570 filesystems).
571 The following options apply to any filesystem that is being mounted
573 (but not every filesystem actually honors them – e.g., the sync option
574 today has an effect only for ext2, ext3, ext4, fat, vfat and ufs):
575 async All I/O to the filesystem should be done asynchronously. (See
578 also the sync option.)
579 atime Do not use the noatime feature, so the inode access time is con‐
581 trolled by kernel defaults. See also the descriptions of the
582 relatime and strictatime mount options.
583 noatime
585 Do not update inode access times on this filesystem (e.g. for
586 faster access on the news spool to speed up news servers). This
587 works for all inode types (directories too), so it implies
588 nodiratime.
589 auto Can be mounted with the -a option.
591 noauto Can only be mounted explicitly (i.e., the -a option will not
593 cause the filesystem to be mounted).
594 context=context, fscontext=context, defcontext=context, and
596 rootcontext=context
597 The context= option is useful when mounting filesystems that do
598 not support extended attributes, such as a floppy or hard disk
599 formatted with VFAT, or systems that are not normally running
600 under SELinux, such as an ext3 or ext4 formatted
601 disk from a non-SELinux workstation. You can also use context=
603 on filesystems you do not trust, such as a floppy. It also
604 helps in compatibility with xattr-supporting filesystems on ear‐
605 lier 2.4.<x> kernel versions. Even where xattrs are supported,
606 you can save time not having to label every file by assigning
607 the entire disk one security context.
608 A commonly used option for removable media is
610 context="system_u:object_r:removable_t".
611 Two other options are fscontext= and defcontext=, both of which
613 are mutually exclusive of the context option. This means you
614 can use fscontext and defcontext with each other, but neither
615 can be used with context.
616 The fscontext= option works for all filesystems, regardless of
618 their xattr support. The fscontext option sets the overarching
619 filesystem label to a specific security context. This filesys‐
620 tem label is separate from the individual labels on the files.
621 It represents the entire filesystem for certain kinds of permis‐
622 sion checks, such as during mount or file creation. Individual
623 file labels are still obtained from the xattrs on the files
624 themselves. The context option actually sets the aggregate con‐
625 text that fscontext provides, in addition to supplying the same
626 label for individual files.
627 You can set the default security context for unlabeled files
629 using defcontext= option. This overrides the value set for
630 unlabeled files in the policy and requires a filesystem that
631 supports xattr labeling.
632 The rootcontext= option allows you to explicitly label the root
634 inode of a FS being mounted before that FS or inode becomes vis‐
635 ible to userspace. This was found to be useful for things like
636 stateless linux.
637 Note that the kernel rejects any remount request that includes
639 the context option, even when unchanged from the current con‐
640 text.
641 Warning: the context value might contain commas, in which case
643 the value has to be properly quoted, otherwise mount(8) will
644 interpret the comma as a separator between mount options. Don't
645 forget that the shell strips off quotes and thus double quoting
646 is required. For example:
647 mount -t tmpfs none /mnt -o \
649 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
650 For more details, see selinux(8).
652 defaults
655 Use the default options: rw, suid, dev, exec, auto, nouser, and
656 async.
657 Note that the real set of all default mount options depends on
659 kernel and filesystem type. See the beginning of this section
660 for more details.
661 dev Interpret character or block special devices on the filesystem.
663 nodev Do not interpret character or block special devices on the file
665 system.
666 diratime
668 Update directory inode access times on this filesystem. This is
669 the default. (This option is ignored when noatime is set.)
670 nodiratime
672 Do not update directory inode access times on this filesystem.
673 (This option is implied when noatime is set.)
674 dirsync
676 All directory updates within the filesystem should be done syn‐
677 chronously. This affects the following system calls: creat,
678 link, unlink, symlink, mkdir, rmdir, mknod and rename.
679 exec Permit execution of binaries.
681 noexec Do not permit direct execution of any binaries on the mounted
683 filesystem.
684 group Allow an ordinary user to mount the filesystem if one of that
686 user's groups matches the group of the device. This option
687 implies the options nosuid and nodev (unless overridden by sub‐
688 sequent options, as in the option line group,dev,suid).
689 iversion
691 Every time the inode is modified, the i_version field will be
692 incremented.
693 noiversion
695 Do not increment the i_version inode field.
696 mand Allow mandatory locks on this filesystem. See fcntl(2).
698 nomand Do not allow mandatory locks on this filesystem.
700 _netdev
702 The filesystem resides on a device that requires network access
703 (used to prevent the system from attempting to mount these
704 filesystems until the network has been enabled on the system).
705 nofail Do not report errors for this device if it does not exist.
707 relatime
709 Update inode access times relative to modify or change time.
710 Access time is only updated if the previous access time was ear‐
711 lier than the current modify or change time. (Similar to
712 noatime, but it doesn't break mutt or other applications that
713 need to know if a file has been read since the last time it was
714 modified.)
715 Since Linux 2.6.30, the kernel defaults to the behavior provided
717 by this option (unless noatime was specified), and the
718 strictatime option is required to obtain traditional semantics.
719 In addition, since Linux 2.6.30, the file's last access time is
720 always updated if it is more than 1 day old.
721 norelatime
723 Do not use the relatime feature. See also the strictatime mount
724 option.
725 strictatime
727 Allows to explicitly request full atime updates. This makes it
728 possible for the kernel to default to relatime or noatime but
729 still allow userspace to override it. For more details about
730 the default system mount options see /proc/mounts.
731 nostrictatime
733 Use the kernel's default behavior for inode access time updates.
734 lazytime
736 Only update times (atime, mtime, ctime) on the in-memory version
737 of the file inode.
738 This mount option significantly reduces writes to the inode ta‐
740 ble for workloads that perform frequent random writes to preal‐
741 located files.
742 The on-disk timestamps are updated only when:
744 - the inode needs to be updated for some change unrelated to
746 file timestamps
747 - the application employs fsync(2), syncfs(2), or sync(2)
749 - an undeleted inode is evicted from memory
751 - more than 24 hours have passed since the i-node was written to
753 disk.
754 nolazytime
757 Do not use the lazytime feature.
758 suid Allow set-user-ID or set-group-ID bits to take effect.
760 nosuid Do not allow set-user-ID or set-group-ID bits to take effect.
762 silent Turn on the silent flag.
764 loud Turn off the silent flag.
766 owner Allow an ordinary user to mount the filesystem if that user is
768 the owner of the device. This option implies the options nosuid
769 and nodev (unless overridden by subsequent options, as in the
770 option line owner,dev,suid).
771 remount
773 Attempt to remount an already-mounted filesystem. This is com‐
774 monly used to change the mount flags for a filesystem, espe‐
775 cially to make a readonly filesystem writable. It does not
776 change device or mount point.
777 The remount operation together with the bind flag has special
779 semantic. See above, the subsection Bind mounts.
780 The remount functionality follows the standard way the mount
782 command works with options from fstab. This means that mount
783 does not read fstab (or mtab) only when both device and dir are
784 specified.
785 mount -o remount,rw /dev/foo /dir
787 After this call all old mount options are replaced and arbitrary
789 stuff from fstab (or mtab) is ignored, except the loop= option
790 which is internally generated and maintained by the mount com‐
791 mand.
792 mount -o remount,rw /dir
794 After this call, mount reads fstab and merges these options with
796 the options from the command line (-o). If no mountpoint is
797 found in fstab, then a remount with unspecified source is
798 allowed.
799 ro Mount the filesystem read-only.
801 rw Mount the filesystem read-write.
803 sync All I/O to the filesystem should be done synchronously. In the
805 case of media with a limited number of write cycles (e.g. some
806 flash drives), sync may cause life-cycle shortening.
807 user Allow an ordinary user to mount the filesystem. The name of the
809 mounting user is written to the mtab file (or to the private
810 libmount file in /run/mount on systems without a regular mtab)
811 so that this same user can unmount the filesystem again. This
812 option implies the options noexec, nosuid, and nodev (unless
813 overridden by subsequent options, as in the option line
814 user,exec,dev,suid).
815 nouser Forbid an ordinary user to mount the filesystem. This is the
817 default; it does not imply any other options.
818 users Allow any user to mount and to unmount the filesystem, even when
820 some other ordinary user mounted it. This option implies the
821 options noexec, nosuid, and nodev (unless overridden by subse‐
822 quent options, as in the option line users,exec,dev,suid).
823 X-* All options prefixed with "X-" are interpreted as comments or as
825 userspace application-specific options. These options are not
826 stored in the user space (e.g. mtab file), nor sent to the
827 mount.type helpers nor to the mount(2) system call. The sug‐
828 gested format is X-appname.option.
829 x-* The same as X-* options, but stored permanently in the user
831 space. It means the options are also available for umount or
832 another operations. Note that maintain mount options in user
833 space is tricky, because it's necessary use libmount based tools
834 and there is no guarantee that the options will be always avail‐
835 able (for example after a move mount operation or in unshared
836 namespace).
837 Note that before util-linux v2.30 the x-* options have not been
839 maintained by libmount and stored in user space (functionality
840 was the same as have X-* now), but due to growing number of use-
841 cases (in initrd, systemd etc.) the functionality have been
842 extended to keep existing fstab configurations usable without a
843 change.
844 X-mount.mkdir[=mode]
846 Allow to make a target directory (mountpoint). The optional
847 argument mode specifies the filesystem access mode used for
848 mkdir(2) in octal notation. The default mode is 0755. This
849 functionality is supported only for root users. The option is
850 also supported as x-mount.mkdir, this notation is deprecated for
851 mount.mkdir since v2.30.
852
855 You should consult the respective man page for the filesystem first.
856 If you want to know what options the ext4 filesystem supports, then
857 check the ext4(5) man page. If that doesn't exist, you can also check
858 the corresponding mount page like mount.cifs(8). Note that you might
859 have to install the respective userland tools.
860 The following options apply only to certain filesystems. We sort them
862 by filesystem. They all follow the -o flag.
863 What options are supported depends a bit on the running kernel. More
865 info may be found in the kernel source subdirectory Documenta‐
866 tion/filesystems.
867 Mount options for adfs
870 uid=value and gid=value
871 Set the owner and group of the files in the filesystem (default:
872 uid=gid=0).
873 ownmask=value and othmask=value
875 Set the permission mask for ADFS 'owner' permissions and 'other'
876 permissions, respectively (default: 0700 and 0077, respec‐
877 tively). See also /usr/src/linux/Documentation/filesys‐
878 tems/adfs.txt.
879 Mount options for affs
882 uid=value and gid=value
883 Set the owner and group of the root of the filesystem (default:
884 uid=gid=0, but with option uid or gid without specified value,
885 the UID and GID of the current process are taken).
886 setuid=value and setgid=value
888 Set the owner and group of all files.
889 mode=value
891 Set the mode of all files to value & 0777 disregarding the orig‐
892 inal permissions. Add search permission to directories that
893 have read permission. The value is given in octal.
894 protect
896 Do not allow any changes to the protection bits on the filesys‐
897 tem.
898 usemp Set UID and GID of the root of the filesystem to the UID and GID
900 of the mount point upon the first sync or umount, and then clear
901 this option. Strange...
902 verbose
904 Print an informational message for each successful mount.
905 prefix=string
907 Prefix used before volume name, when following a link.
908 volume=string
910 Prefix (of length at most 30) used before '/' when following a
911 symbolic link.
912 reserved=value
914 (Default: 2.) Number of unused blocks at the start of the
915 device.
916 root=value
918 Give explicitly the location of the root block.
919 bs=value
921 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
922 grpquota|noquota|quota|usrquota
924 These options are accepted but ignored. (However, quota utili‐
925 ties may react to such strings in /etc/fstab.)
926 Mount options for debugfs
929 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
930 /sys/kernel/debug. As of kernel version 3.4, debugfs has the following
931 options:
932 uid=n, gid=n
934 Set the owner and group of the mountpoint.
935 mode=value
937 Sets the mode of the mountpoint.
938 Mount options for devpts
941 The devpts filesystem is a pseudo filesystem, traditionally mounted on
942 /dev/pts. In order to acquire a pseudo terminal, a process opens
943 /dev/ptmx; the number of the pseudo terminal is then made available to
944 the process and the pseudo terminal slave can be accessed as
945 /dev/pts/<number>.
946 uid=value and gid=value
948 This sets the owner or the group of newly created PTYs to the
949 specified values. When nothing is specified, they will be set
950 to the UID and GID of the creating process. For example, if
951 there is a tty group with GID 5, then gid=5 will cause newly
952 created PTYs to belong to the tty group.
953 mode=value
955 Set the mode of newly created PTYs to the specified value. The
956 default is 0600. A value of mode=620 and gid=5 makes "mesg y"
957 the default on newly created PTYs.
958 newinstance
960 Create a private instance of devpts filesystem, such that
961 indices of ptys allocated in this new instance are independent
962 of indices created in other instances of devpts.
963 All mounts of devpts without this newinstance option share the
965 same set of pty indices (i.e legacy mode). Each mount of devpts
966 with the newinstance option has a private set of pty indices.
967 This option is mainly used to support containers in the linux
969 kernel. It is implemented in linux kernel versions starting
970 with 2.6.29. Further, this mount option is valid only if CON‐
971 FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configu‐
972 ration.
973 To use this option effectively, /dev/ptmx must be a symbolic
975 link to pts/ptmx. See Documentation/filesystems/devpts.txt in
976 the linux kernel source tree for details.
977 ptmxmode=value
979 Set the mode for the new ptmx device node in the devpts filesys‐
981 tem.
982 With the support for multiple instances of devpts (see newin‐
984 stance option above), each instance has a private ptmx node in
985 the root of the devpts filesystem (typically /dev/pts/ptmx).
986 For compatibility with older versions of the kernel, the default
988 mode of the new ptmx node is 0000. ptmxmode=value specifies a
989 more useful mode for the ptmx node and is highly recommended
990 when the newinstance option is specified.
991 This option is only implemented in linux kernel versions start‐
993 ing with 2.6.29. Further, this option is valid only if CON‐
994 FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configu‐
995 ration.
996 Mount options for fat
999 (Note: fat is not a separate filesystem, but a common part of the
1000 msdos, umsdos and vfat filesystems.)
1001 blocksize={512|1024|2048}
1003 Set blocksize (default 512). This option is obsolete.
1004 uid=value and gid=value
1006 Set the owner and group of all files. (Default: the UID and GID
1007 of the current process.)
1008 umask=value
1010 Set the umask (the bitmask of the permissions that are not
1011 present). The default is the umask of the current process. The
1012 value is given in octal.
1013 dmask=value
1015 Set the umask applied to directories only. The default is the
1016 umask of the current process. The value is given in octal.
1017 fmask=value
1019 Set the umask applied to regular files only. The default is the
1020 umask of the current process. The value is given in octal.
1021 allow_utime=value
1023 This option controls the permission check of mtime/atime.
1024 20 If current process is in group of file's group ID, you
1026 can change timestamp.
1027 2 Other users can change timestamp.
1029 The default is set from `dmask' option. (If the directory is
1031 writable, utime(2) is also allowed. I.e. ~dmask & 022)
1032 Normally utime(2) checks current process is owner of the file,
1034 or it has CAP_FOWNER capability. But FAT filesystem doesn't
1035 have UID/GID on disk, so normal check is too inflexible. With
1036 this option you can relax it.
1037 check=value
1039 Three different levels of pickyness can be chosen:
1040 r[elaxed]
1042 Upper and lower case are accepted and equivalent, long
1043 name parts are truncated (e.g. verylongname.foobar
1044 becomes verylong.foo), leading and embedded spaces are
1045 accepted in each name part (name and extension).
1046 n[ormal]
1048 Like "relaxed", but many special characters (*, ?, <,
1049 spaces, etc.) are rejected. This is the default.
1050 s[trict]
1052 Like "normal", but names that contain long parts or spe‐
1053 cial characters that are sometimes used on Linux but are
1054 not accepted by MS-DOS (+, =, etc.) are rejected.
1055 codepage=value
1057 Sets the codepage for converting to shortname characters on FAT
1058 and VFAT filesystems. By default, codepage 437 is used.
1059 conv=mode
1061 This option is obsolete and may fail or being ignored.
1062 cvf_format=module
1064 Forces the driver to use the CVF (Compressed Volume File) module
1065 cvf_module instead of auto-detection. If the kernel supports
1066 kmod, the cvf_format=xxx option also controls on-demand CVF mod‐
1067 ule loading. This option is obsolete.
1068 cvf_option=option
1070 Option passed to the CVF module. This option is obsolete.
1071 debug Turn on the debug flag. A version string and a list of filesys‐
1073 tem parameters will be printed (these data are also printed if
1074 the parameters appear to be inconsistent).
1075 discard
1077 If set, causes discard/TRIM commands to be issued to the block
1078 device when blocks are freed. This is useful for SSD devices
1079 and sparse/thinly-provisioned LUNs.
1080 dos1xfloppy
1082 If set, use a fallback default BIOS Parameter Block configura‐
1083 tion, determined by backing device size. These static parame‐
1084 ters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320
1085 kiB, and 360 kiB floppies and floppy images.
1086 errors={panic|continue|remount-ro}
1088 Specify FAT behavior on critical errors: panic, continue without
1089 doing anything, or remount the partition in read-only mode
1090 (default behavior).
1091 fat={12|16|32}
1093 Specify a 12, 16 or 32 bit fat. This overrides the automatic
1094 FAT type detection routine. Use with caution!
1095 iocharset=value
1097 Character set to use for converting between 8 bit characters and
1098 16 bit Unicode characters. The default is iso8859-1. Long
1099 filenames are stored on disk in Unicode format.
1100 nfs={stale_rw|nostale_ro}
1102 Enable this only if you want to export the FAT filesystem over
1103 NFS.
1104 stale_rw: This option maintains an index (cache) of directory
1106 inodes which is used by the nfs-related code to improve look-
1107 ups. Full file operations (read/write) over NFS are supported
1108 but with cache eviction at NFS server, this could result in spu‐
1109 rious ESTALE errors.
1110 nostale_ro: This option bases the inode number and file handle
1112 on the on-disk location of a file in the FAT directory entry.
1113 This ensures that ESTALE will not be returned after a file is
1114 evicted from the inode cache. However, it means that operations
1115 such as rename, create and unlink could cause file handles that
1116 previously pointed at one file to point at a different file,
1117 potentially causing data corruption. For this reason, this
1118 option also mounts the filesystem readonly.
1119 To maintain backward compatibility, '-o nfs' is also accepted,
1121 defaulting to stale_rw.
1122 tz=UTC This option disables the conversion of timestamps between local
1124 time (as used by Windows on FAT) and UTC (which Linux uses
1125 internally). This is particularly useful when mounting devices
1126 (like digital cameras) that are set to UTC in order to avoid the
1127 pitfalls of local time.
1128 time_offset=minutes
1130 Set offset for conversion of timestamps from local time used by
1131 FAT to UTC. I.e., minutes will be subtracted from each time‐
1132 stamp to convert it to UTC used internally by Linux. This is
1133 useful when the time zone set in the kernel via settimeofday(2)
1134 is not the time zone used by the filesystem. Note that this
1135 option still does not provide correct time stamps in all cases
1136 in presence of DST - time stamps in a different DST setting will
1137 be off by one hour.
1138 quiet Turn on the quiet flag. Attempts to chown or chmod files do not
1140 return errors, although they fail. Use with caution!
1141 rodir FAT has the ATTR_RO (read-only) attribute. On Windows, the
1143 ATTR_RO of the directory will just be ignored, and is used only
1144 by applications as a flag (e.g. it's set for the customized
1145 folder).
1146 If you want to use ATTR_RO as read-only flag even for the direc‐
1148 tory, set this option.
1149 showexec
1151 If set, the execute permission bits of the file will be allowed
1152 only if the extension part of the name is .EXE, .COM, or .BAT.
1153 Not set by default.
1154 sys_immutable
1156 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag
1157 on Linux. Not set by default.
1158 flush If set, the filesystem will try to flush to disk more early than
1160 normal. Not set by default.
1161 usefree
1163 Use the "free clusters" value stored on FSINFO. It'll be used
1164 to determine number of free clusters without scanning disk. But
1165 it's not used by default, because recent Windows don't update it
1166 correctly in some case. If you are sure the "free clusters" on
1167 FSINFO is correct, by this option you can avoid scanning disk.
1168 dots, nodots, dotsOK=[yes|no]
1170 Various misguided attempts to force Unix or DOS conventions onto
1171 a FAT filesystem.
1172 Mount options for hfs
1175 creator=cccc, type=cccc
1176 Set the creator/type values as shown by the MacOS finder used
1177 for creating new files. Default values: '????'.
1178 uid=n, gid=n
1180 Set the owner and group of all files. (Default: the UID and GID
1181 of the current process.)
1182 dir_umask=n, file_umask=n, umask=n
1184 Set the umask used for all directories, all regular files, or
1185 all files and directories. Defaults to the umask of the current
1186 process.
1187 session=n
1189 Select the CDROM session to mount. Defaults to leaving that
1190 decision to the CDROM driver. This option will fail with any‐
1191 thing but a CDROM as underlying device.
1192 part=n Select partition number n from the device. Only makes sense for
1194 CDROMs. Defaults to not parsing the partition table at all.
1195 quiet Don't complain about invalid mount options.
1197 Mount options for hpfs
1200 uid=value and gid=value
1201 Set the owner and group of all files. (Default: the UID and GID
1202 of the current process.)
1203 umask=value
1205 Set the umask (the bitmask of the permissions that are not
1206 present). The default is the umask of the current process. The
1207 value is given in octal.
1208 case={lower|asis}
1210 Convert all files names to lower case, or leave them. (Default:
1211 case=lower.)
1212 conv=mode
1214 This option is obsolete and may fail or being ignored.
1215 nocheck
1217 Do not abort mounting when certain consistency checks fail.
1218 Mount options for iso9660
1221 ISO 9660 is a standard describing a filesystem structure to be used on
1222 CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1223 udf filesystem.)
1224 Normal iso9660 filenames appear in a 8.3 format (i.e., DOS-like
1226 restrictions on filename length), and in addition all characters are in
1227 upper case. Also there is no field for file ownership, protection,
1228 number of links, provision for block/character devices, etc.
1229 Rock Ridge is an extension to iso9660 that provides all of these UNIX-
1231 like features. Basically there are extensions to each directory record
1232 that supply all of the additional information, and when Rock Ridge is
1233 in use, the filesystem is indistinguishable from a normal UNIX filesys‐
1234 tem (except that it is read-only, of course).
1235 norock Disable the use of Rock Ridge extensions, even if available.
1237 Cf. map.
1238 nojoliet
1240 Disable the use of Microsoft Joliet extensions, even if avail‐
1241 able. Cf. map.
1242 check={r[elaxed]|s[trict]}
1244 With check=relaxed, a filename is first converted to lower case
1245 before doing the lookup. This is probably only meaningful
1246 together with norock and map=normal. (Default: check=strict.)
1247 uid=value and gid=value
1249 Give all files in the filesystem the indicated user or group id,
1250 possibly overriding the information found in the Rock Ridge
1251 extensions. (Default: uid=0,gid=0.)
1252 map={n[ormal]|o[ff]|a[corn]}
1254 For non-Rock Ridge volumes, normal name translation maps upper
1255 to lower case ASCII, drops a trailing `;1', and converts `;' to
1256 `.'. With map=off no name translation is done. See norock.
1257 (Default: map=normal.) map=acorn is like map=normal but also
1258 apply Acorn extensions if present.
1259 mode=value
1261 For non-Rock Ridge volumes, give all files the indicated mode.
1262 (Default: read and execute permission for everybody.) Octal
1263 mode values require a leading 0.
1264 unhide Also show hidden and associated files. (If the ordinary files
1266 and the associated or hidden files have the same filenames, this
1267 may make the ordinary files inaccessible.)
1268 block={512|1024|2048}
1270 Set the block size to the indicated value. (Default:
1271 block=1024.)
1272 conv=mode
1274 This option is obsolete and may fail or being ignored.
1275 cruft If the high byte of the file length contains other garbage, set
1277 this mount option to ignore the high order bits of the file
1278 length. This implies that a file cannot be larger than 16 MB.
1279 session=x
1281 Select number of session on multisession CD.
1282 sbsector=xxx
1284 Session begins from sector xxx.
1285 The following options are the same as for vfat and specifying them only
1287 makes sense when using discs encoded using Microsoft's Joliet exten‐
1288 sions.
1289 iocharset=value
1291 Character set to use for converting 16 bit Unicode characters on
1292 CD to 8 bit characters. The default is iso8859-1.
1293 utf8 Convert 16 bit Unicode characters on CD to UTF-8.
1295 Mount options for jfs
1298 iocharset=name
1299 Character set to use for converting from Unicode to ASCII. The
1300 default is to do no conversion. Use iocharset=utf8 for UTF8
1301 translations. This requires CONFIG_NLS_UTF8 to be set in the
1302 kernel .config file.
1303 resize=value
1305 Resize the volume to value blocks. JFS only supports growing a
1306 volume, not shrinking it. This option is only valid during a
1307 remount, when the volume is mounted read-write. The resize key‐
1308 word with no value will grow the volume to the full size of the
1309 partition.
1310 nointegrity
1312 Do not write to the journal. The primary use of this option is
1313 to allow for higher performance when restoring a volume from
1314 backup media. The integrity of the volume is not guaranteed if
1315 the system abnormally ends.
1316 integrity
1318 Default. Commit metadata changes to the journal. Use this
1319 option to remount a volume where the nointegrity option was pre‐
1320 viously specified in order to restore normal behavior.
1321 errors={continue|remount-ro|panic}
1323 Define the behavior when an error is encountered. (Either
1324 ignore errors and just mark the filesystem erroneous and con‐
1325 tinue, or remount the filesystem read-only, or panic and halt
1326 the system.)
1327 noquota|quota|usrquota|grpquota
1329 These options are accepted but ignored.
1330 Mount options for msdos
1333 See mount options for fat. If the msdos filesystem detects an incon‐
1334 sistency, it reports an error and sets the file system read-only. The
1335 filesystem can be made writable again by remounting it.
1336 Mount options for ncpfs
1339 Just like nfs, the ncpfs implementation expects a binary argument (a
1340 struct ncp_mount_data) to the mount system call. This argument is con‐
1341 structed by ncpmount(8) and the current version of mount (2.12) does
1342 not know anything about ncpfs.
1343 Mount options for ntfs
1346 iocharset=name
1347 Character set to use when returning file names. Unlike VFAT,
1348 NTFS suppresses names that contain nonconvertible characters.
1349 Deprecated.
1350 nls=name
1352 New name for the option earlier called iocharset.
1353 utf8 Use UTF-8 for converting file names.
1355 uni_xlate={0|1|2}
1357 For 0 (or `no' or `false'), do not use escape sequences for
1358 unknown Unicode characters. For 1 (or `yes' or `true') or 2,
1359 use vfat-style 4-byte escape sequences starting with ":". Here
1360 2 give a little-endian encoding and 1 a byteswapped bigendian
1361 encoding.
1362 posix=[0|1]
1364 If enabled (posix=1), the filesystem distinguishes between upper
1365 and lower case. The 8.3 alias names are presented as hard links
1366 instead of being suppressed. This option is obsolete.
1367 uid=value, gid=value and umask=value
1369 Set the file permission on the filesystem. The umask value is
1370 given in octal. By default, the files are owned by root and not
1371 readable by somebody else.
1372 Mount options for overlay
1375 Since Linux 3.18 the overlay pseudo filesystem implements a union mount
1376 for other filesystems.
1377 An overlay filesystem combines two filesystems - an upper filesystem
1379 and a lower filesystem. When a name exists in both filesystems, the
1380 object in the upper filesystem is visible while the object in the lower
1381 filesystem is either hidden or, in the case of directories, merged with
1382 the upper object.
1383 The lower filesystem can be any filesystem supported by Linux and does
1385 not need to be writable. The lower filesystem can even be another
1386 overlayfs. The upper filesystem will normally be writable and if it is
1387 it must support the creation of trusted.* extended attributes, and must
1388 provide a valid d_type in readdir responses, so NFS is not suitable.
1389 A read-only overlay of two read-only filesystems may use any filesystem
1391 type. The options lowerdir and upperdir are combined into a merged
1392 directory by using:
1393 mount -t overlay overlay \
1395 -olowerdir=/lower,upperdir=/upper,workdir=/work /merged
1396 lowerdir=directory
1399 Any filesystem, does not need to be on a writable filesystem.
1400 upperdir=directory
1402 The upperdir is normally on a writable filesystem.
1403 workdir=directory
1405 The workdir needs to be an empty directory on the same filesys‐
1406 tem as upperdir.
1407 Mount options for reiserfs
1410 Reiserfs is a journaling filesystem.
1411 conv Instructs version 3.6 reiserfs software to mount a version 3.5
1413 filesystem, using the 3.6 format for newly created objects.
1414 This filesystem will no longer be compatible with reiserfs 3.5
1415 tools.
1416 hash={rupasov|tea|r5|detect}
1418 Choose which hash function reiserfs will use to find files
1419 within directories.
1420 rupasov
1422 A hash invented by Yury Yu. Rupasov. It is fast and pre‐
1423 serves locality, mapping lexicographically close file
1424 names to close hash values. This option should not be
1425 used, as it causes a high probability of hash collisions.
1426 tea A Davis-Meyer function implemented by Jeremy
1428 Fitzhardinge. It uses hash permuting bits in the name.
1429 It gets high randomness and, therefore, low probability
1430 of hash collisions at some CPU cost. This may be used if
1431 EHASHCOLLISION errors are experienced with the r5 hash.
1432 r5 A modified version of the rupasov hash. It is used by
1434 default and is the best choice unless the filesystem has
1435 huge directories and unusual file-name patterns.
1436 detect Instructs mount to detect which hash function is in use
1438 by examining the filesystem being mounted, and to write
1439 this information into the reiserfs superblock. This is
1440 only useful on the first mount of an old format filesys‐
1441 tem.
1442 hashed_relocation
1444 Tunes the block allocator. This may provide performance
1445 improvements in some situations.
1446 no_unhashed_relocation
1448 Tunes the block allocator. This may provide performance
1449 improvements in some situations.
1450 noborder
1452 Disable the border allocator algorithm invented by Yury Yu.
1453 Rupasov. This may provide performance improvements in some sit‐
1454 uations.
1455 nolog Disable journaling. This will provide slight performance
1457 improvements in some situations at the cost of losing reiserfs's
1458 fast recovery from crashes. Even with this option turned on,
1459 reiserfs still performs all journaling operations, save for
1460 actual writes into its journaling area. Implementation of nolog
1461 is a work in progress.
1462 notail By default, reiserfs stores small files and `file tails'
1464 directly into its tree. This confuses some utilities such as
1465 LILO(8). This option is used to disable packing of files into
1466 the tree.
1467 replayonly
1469 Replay the transactions which are in the journal, but do not
1470 actually mount the filesystem. Mainly used by reiserfsck.
1471 resize=number
1473 A remount option which permits online expansion of reiserfs par‐
1474 titions. Instructs reiserfs to assume that the device has num‐
1475 ber blocks. This option is designed for use with devices which
1476 are under logical volume management (LVM). There is a special
1477 resizer utility which can be obtained from
1478 ftp://ftp.namesys.com/pub/reiserfsprogs.
1479 user_xattr
1481 Enable Extended User Attributes. See the attr(5) manual page.
1482 acl Enable POSIX Access Control Lists. See the acl(5) manual page.
1484 barrier=none / barrier=flush
1486 This disables / enables the use of write barriers in the jour‐
1487 naling code. barrier=none disables, barrier=flush enables
1488 (default). This also requires an IO stack which can support
1489 barriers, and if reiserfs gets an error on a barrier write, it
1490 will disable barriers again with a warning. Write barriers
1491 enforce proper on-disk ordering of journal commits, making
1492 volatile disk write caches safe to use, at some performance
1493 penalty. If your disks are battery-backed in one way or
1494 another, disabling barriers may safely improve performance.
1495 Mount options for ubifs
1498 UBIFS is a flash filesystem which works on top of UBI volumes. Note
1499 that atime is not supported and is always turned off.
1500 The device name may be specified as
1502 ubiX_Y UBI device number X, volume number Y
1503 ubiY UBI device number 0, volume number Y
1505 ubiX:NAME
1507 UBI device number X, volume with name NAME
1508 ubi:NAME
1510 UBI device number 0, volume with name NAME
1511 Alternative ! separator may be used instead of :.
1512 The following mount options are available:
1514 bulk_read
1516 Enable bulk-read. VFS read-ahead is disabled because it slows
1517 down the file system. Bulk-Read is an internal optimization.
1518 Some flashes may read faster if the data are read at one go,
1519 rather than at several read requests. For example, OneNAND can
1520 do "read-while-load" if it reads more than one NAND page.
1521 no_bulk_read
1523 Do not bulk-read. This is the default.
1524 chk_data_crc
1526 Check data CRC-32 checksums. This is the default.
1527 no_chk_data_crc.
1529 Do not check data CRC-32 checksums. With this option, the
1530 filesystem does not check CRC-32 checksum for data, but it does
1531 check it for the internal indexing information. This option
1532 only affects reading, not writing. CRC-32 is always calculated
1533 when writing the data.
1534 compr={none|lzo|zlib}
1536 Select the default compressor which is used when new files are
1537 written. It is still possible to read compressed files if
1538 mounted with the none option.
1539 Mount options for udf
1542 UDF is the "Universal Disk Format" filesystem defined by OSTA, the
1543 Optical Storage Technology Association, and is often used for DVD-ROM,
1544 frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, how‐
1545 ever, perfectly usable by itself on disk drives, flash drives and other
1546 block devices. See also iso9660.
1547 uid= Make all files in the filesystem belong to the given user.
1549 uid=forget can be specified independently of (or usually in
1550 addition to) uid=<user> and results in UDF not storing uids to
1551 the media. In fact the recorded uid is the 32-bit overflow uid
1552 -1 as defined by the UDF standard. The value is given as either
1553 <user> which is a valid user name or the corresponding decimal
1554 user id, or the special string "forget".
1555 gid= Make all files in the filesystem belong to the given group.
1557 gid=forget can be specified independently of (or usually in
1558 addition to) gid=<group> and results in UDF not storing gids to
1559 the media. In fact the recorded gid is the 32-bit overflow gid
1560 -1 as defined by the UDF standard. The value is given as either
1561 <group> which is a valid group name or the corresponding decimal
1562 group id, or the special string "forget".
1563 umask= Mask out the given permissions from all inodes read from the
1565 filesystem. The value is given in octal.
1566 mode= If mode= is set the permissions of all non-directory inodes read
1568 from the filesystem will be set to the given mode. The value is
1569 given in octal.
1570 dmode= If dmode= is set the permissions of all directory inodes read
1572 from the filesystem will be set to the given dmode. The value is
1573 given in octal.
1574 bs= Set the block size. Default value prior to kernel version 2.6.30
1576 was 2048. Since 2.6.30 and prior to 4.11 it was logical device
1577 block size with fallback to 2048. Since 4.11 it is logical block
1578 size with fallback to any valid block size between logical
1579 device block size and 4096.
1580 For other details see the mkudffs(8) 2.0+ manpage, sections COM‐
1582 PATIBILITY and BLOCK SIZE.
1583 unhide Show otherwise hidden files.
1585 undelete
1587 Show deleted files in lists.
1588 adinicb
1590 Embed data in the inode. (default)
1591 noadinicb
1593 Don't embed data in the inode.
1594 shortad
1596 Use short UDF address descriptors.
1597 longad Use long UDF address descriptors. (default)
1599 nostrict
1601 Unset strict conformance.
1602 iocharset=
1604 Set the NLS character set. This requires kernel compiled with
1605 CONFIG_UDF_NLS option.
1606 utf8 Set the UTF-8 character set.
1608 Mount options for debugging and disaster recovery
1610 novrs Ignore the Volume Recognition Sequence and attempt to mount any‐
1611 way.
1612 session=
1614 Select the session number for multi-session recorded optical
1615 media. (default= last session)
1616 anchor=
1618 Override standard anchor location. (default= 256)
1619 lastblock=
1621 Set the last block of the filesystem.
1622 Unused historical mount options that may be encountered and should be
1624 removed
1625 uid=ignore
1626 Ignored, use uid=<user> instead.
1627 gid=ignore
1629 Ignored, use gid=<group> instead.
1630 volume=
1632 Unimplemented and ignored.
1633 partition=
1635 Unimplemented and ignored.
1636 fileset=
1638 Unimplemented and ignored.
1639 rootdir=
1641 Unimplemented and ignored.
1642 Mount options for ufs
1645 ufstype=value
1646 UFS is a filesystem widely used in different operating systems.
1647 The problem are differences among implementations. Features of
1648 some implementations are undocumented, so its hard to recognize
1649 the type of ufs automatically. That's why the user must specify
1650 the type of ufs by mount option. Possible values are:
1651 old Old format of ufs, this is the default, read only.
1653 (Don't forget to give the -r option.)
1654 44bsd For filesystems created by a BSD-like system (NetBSD,
1656 FreeBSD, OpenBSD).
1657 ufs2 Used in FreeBSD 5.x supported as read-write.
1659 5xbsd Synonym for ufs2.
1661 sun For filesystems created by SunOS or Solaris on Sparc.
1663 sunx86 For filesystems created by Solaris on x86.
1665 hp For filesystems created by HP-UX, read-only.
1667 nextstep
1669 For filesystems created by NeXTStep (on NeXT station)
1670 (currently read only).
1671 nextstep-cd
1673 For NextStep CDROMs (block_size == 2048), read-only.
1674 openstep
1676 For filesystems created by OpenStep (currently read
1677 only). The same filesystem type is also used by Mac OS
1678 X.
1679 onerror=value
1682 Set behavior on error:
1683 panic If an error is encountered, cause a kernel panic.
1685 [lock|umount|repair]
1687 These mount options don't do anything at present; when an
1688 error is encountered only a console message is printed.
1689 Mount options for umsdos
1692 See mount options for msdos. The dotsOK option is explicitly killed by
1693 umsdos.
1694 Mount options for vfat
1697 First of all, the mount options for fat are recognized. The dotsOK
1698 option is explicitly killed by vfat. Furthermore, there are
1699 uni_xlate
1701 Translate unhandled Unicode characters to special escaped
1702 sequences. This lets you backup and restore filenames that are
1703 created with any Unicode characters. Without this option, a '?'
1704 is used when no translation is possible. The escape character
1705 is ':' because it is otherwise invalid on the vfat filesystem.
1706 The escape sequence that gets used, where u is the Unicode char‐
1707 acter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
1708 posix Allow two files with names that only differ in case. This
1710 option is obsolete.
1711 nonumtail
1713 First try to make a short name without sequence number, before
1714 trying name~num.ext.
1715 utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is
1717 used by the console. It can be enabled for the filesystem with
1718 this option or disabled with utf8=0, utf8=no or utf8=false. If
1719 `uni_xlate' gets set, UTF8 gets disabled.
1720 shortname=mode
1722 Defines the behavior for creation and display of filenames which
1723 fit into 8.3 characters. If a long name for a file exists, it
1724 will always be the preferred one for display. There are four
1725 modes:
1726 lower Force the short name to lower case upon display; store a
1728 long name when the short name is not all upper case.
1729 win95 Force the short name to upper case upon display; store a
1731 long name when the short name is not all upper case.
1732 winnt Display the short name as is; store a long name when the
1734 short name is not all lower case or all upper case.
1735 mixed Display the short name as is; store a long name when the
1737 short name is not all upper case. This mode is the
1738 default since Linux 2.6.32.
1739 Mount options for usbfs
1742 devuid=uid and devgid=gid and devmode=mode
1743 Set the owner and group and mode of the device files in the
1744 usbfs filesystem (default: uid=gid=0, mode=0644). The mode is
1745 given in octal.
1746 busuid=uid and busgid=gid and busmode=mode
1748 Set the owner and group and mode of the bus directories in the
1749 usbfs filesystem (default: uid=gid=0, mode=0555). The mode is
1750 given in octal.
1751 listuid=uid and listgid=gid and listmode=mode
1753 Set the owner and group and mode of the file devices (default:
1754 uid=gid=0, mode=0444). The mode is given in octal.
1755
1758 One further possible type is a mount via the loop device. For example,
1759 the command
1760 mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3
1762 will set up the loop device /dev/loop3 to correspond to the file
1764 /tmp/disk.img, and then mount this device on /mnt.
1765 If no explicit loop device is mentioned (but just an option `-o loop'
1767 is given), then mount will try to find some unused loop device and use
1768 that, for example
1769 mount /tmp/disk.img /mnt -o loop
1771 The mount command automatically creates a loop device from a regular
1773 file if a filesystem type is not specified or the filesystem is known
1774 for libblkid, for example:
1775 mount /tmp/disk.img /mnt
1777 mount -t ext4 /tmp/disk.img /mnt
1779 This type of mount knows about three options, namely loop, offset and
1781 sizelimit, that are really options to losetup(8). (These options can
1782 be used in addition to those specific to the filesystem type.)
1783 Since Linux 2.6.25 auto-destruction of loop devices is supported, mean‐
1785 ing that any loop device allocated by mount will be freed by umount
1786 independently of /etc/mtab.
1787 You can also free a loop device by hand, using losetup -d or umount -d.
1789 Since util-linux v2.29 mount command re-uses the loop device rather
1791 than initialize a new device if the same backing file is already used
1792 for some loop device with the same offset and sizelimit. This is neces‐
1793 sary to avoid a filesystem corruption.
1794
1797 mount has the following return codes (the bits can be ORed):
1798 0 success
1800 1 incorrect invocation or permissions
1802 2 system error (out of memory, cannot fork, no more loop devices)
1804 4 internal mount bug
1806 8 user interrupt
1808 16 problems writing or locking /etc/mtab
1810 32 mount failure
1812 64 some mount succeeded
1814 The command mount -a returns 0 (all succeeded), 32 (all failed), or 64
1816 (some failed, some succeeded).
1817
1820 The syntax of external mount helpers is:
1821 /sbin/mount.suffix spec dir [-sfnv] [-o options] [-t type.subtype]
1823 where the suffix is the filesystem type and the -sfnvo options have the
1825 same meaning as the normal mount options. The -t option is used for
1826 filesystems with subtypes support (for example /sbin/mount.fuse -t
1827 fuse.sshfs).
1828 The command mount does not pass the mount options unbindable, runbind‐
1830 able, private, rprivate, slave, rslave, shared, rshared, auto, noauto,
1831 comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers.
1832 All other options are used in a comma-separated list as argument to the
1833 -o option.
1834
1837 /etc/fstab filesystem table
1838 /etc/mtab table of mounted filesystems
1840 /etc/mtab~ lock file
1842 /etc/mtab.tmp temporary file
1844 /etc/filesystems a list of filesystem types to try
1846
1848 LIBMOUNT_FSTAB=<path>
1849 overrides the default location of the fstab file (ignored for
1850 suid)
1851 LIBMOUNT_MTAB=<path>
1853 overrides the default location of the mtab file (ignored for
1854 suid)
1855 LIBMOUNT_DEBUG=all
1857 enables libmount debug output
1858 LIBBLKID_DEBUG=all
1860 enables libblkid debug output
1861 LOOPDEV_DEBUG=all
1863 enables loop device setup debug output
1864
1866 mount(2), umount(2), umount(8), fstab(5), nfs(5), xfs(5), e2label(8),
1867 findmnt(8), losetup(8), mke2fs(8), mountd(8), nfsd(8), swapon(8),
1868 tune2fs(8), xfs_admin(8)
1869
1871 It is possible for a corrupted filesystem to cause a crash.
1872 Some Linux filesystems don't support -o sync nor -o dirsync (the ext2,
1874 ext3, ext4, fat and vfat filesystems do support synchronous updates (a
1875 la BSD) when mounted with the sync option).
1876 The -o remount may not be able to change mount parameters (all ext2fs-
1878 specific parameters, except sb, are changeable with a remount, for
1879 example, but you can't change gid or umask for the fatfs).
1880 It is possible that the files /etc/mtab and /proc/mounts don't match on
1882 systems with a regular mtab file. The first file is based only on the
1883 mount command options, but the content of the second file also depends
1884 on the kernel and others settings (e.g. on a remote NFS server -- in
1885 certain cases the mount command may report unreliable information about
1886 an NFS mount point and the /proc/mounts file usually contains more
1887 reliable information.) This is another reason to replace the mtab file
1888 with a symlink to the /proc/mounts file.
1889 Checking files on NFS filesystems referenced by file descriptors (i.e.
1891 the fcntl and ioctl families of functions) may lead to inconsistent
1892 results due to the lack of a consistency check in the kernel even if
1893 noac is used.
1894 The loop option with the offset or sizelimit options used may fail when
1896 using older kernels if the mount command can't confirm that the size of
1897 the block device has been configured as requested. This situation can
1898 be worked around by using the losetup command manually before calling
1899 mount with the configured loop device.
1900
1902 A mount command existed in Version 5 AT&T UNIX.
1903
1905 Karel Zak <kzak@redhat.com>
1906
1908 The mount command is part of the util-linux package and is available
1909 from https://www.kernel.org/pub/linux/utils/util-linux/.
1910util-linux August 2015 MOUNT(8)