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, 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 formatted disk from a non-SELinux
601 workstation. You can also use context= on filesystems you do
602 not trust, such as a floppy. It also helps in compatibility
603 with xattr-supporting filesystems on earlier 2.4.<x> kernel ver‐
604 sions. Even where xattrs are supported, you can save time not
605 having to label every file by assigning the entire disk one
606 security context.
607 A commonly used option for removable media is
609 context="system_u:object_r:removable_t".
610 Two other options are fscontext= and defcontext=, both of which
612 are mutually exclusive of the context option. This means you
613 can use fscontext and defcontext with each other, but neither
614 can be used with context.
615 The fscontext= option works for all filesystems, regardless of
617 their xattr support. The fscontext option sets the overarching
618 filesystem label to a specific security context. This filesys‐
619 tem label is separate from the individual labels on the files.
620 It represents the entire filesystem for certain kinds of permis‐
621 sion checks, such as during mount or file creation. Individual
622 file labels are still obtained from the xattrs on the files
623 themselves. The context option actually sets the aggregate con‐
624 text that fscontext provides, in addition to supplying the same
625 label for individual files.
626 You can set the default security context for unlabeled files
628 using defcontext= option. This overrides the value set for
629 unlabeled files in the policy and requires a filesystem that
630 supports xattr labeling.
631 The rootcontext= option allows you to explicitly label the root
633 inode of a FS being mounted before that FS or inode becomes vis‐
634 ible to userspace. This was found to be useful for things like
635 stateless linux.
636 Note that the kernel rejects any remount request that includes
638 the context option, even when unchanged from the current con‐
639 text.
640 Warning: the context value might contain commas, in which case
642 the value has to be properly quoted, otherwise mount(8) will
643 interpret the comma as a separator between mount options. Don't
644 forget that the shell strips off quotes and thus double quoting
645 is required. For example:
646 mount -t tmpfs none /mnt -o \
648 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
649 For more details, see selinux(8).
651 defaults
654 Use the default options: rw, suid, dev, exec, auto, nouser, and
655 async.
656 Note that the real set of all default mount options depends on
658 kernel and filesystem type. See the beginning of this section
659 for more details.
660 dev Interpret character or block special devices on the filesystem.
662 nodev Do not interpret character or block special devices on the file
664 system.
665 diratime
667 Update directory inode access times on this filesystem. This is
668 the default. (This option is ignored when noatime is set.)
669 nodiratime
671 Do not update directory inode access times on this filesystem.
672 (This option is implied when noatime is set.)
673 dirsync
675 All directory updates within the filesystem should be done syn‐
676 chronously. This affects the following system calls: creat,
677 link, unlink, symlink, mkdir, rmdir, mknod and rename.
678 exec Permit execution of binaries.
680 noexec Do not permit direct execution of any binaries on the mounted
682 filesystem.
683 group Allow an ordinary user to mount the filesystem if one of that
685 user's groups matches the group of the device. This option
686 implies the options nosuid and nodev (unless overridden by sub‐
687 sequent options, as in the option line group,dev,suid).
688 iversion
690 Every time the inode is modified, the i_version field will be
691 incremented.
692 noiversion
694 Do not increment the i_version inode field.
695 mand Allow mandatory locks on this filesystem. See fcntl(2).
697 nomand Do not allow mandatory locks on this filesystem.
699 _netdev
701 The filesystem resides on a device that requires network access
702 (used to prevent the system from attempting to mount these
703 filesystems until the network has been enabled on the system).
704 nofail Do not report errors for this device if it does not exist.
706 relatime
708 Update inode access times relative to modify or change time.
709 Access time is only updated if the previous access time was ear‐
710 lier than the current modify or change time. (Similar to
711 noatime, but it doesn't break mutt or other applications that
712 need to know if a file has been read since the last time it was
713 modified.)
714 Since Linux 2.6.30, the kernel defaults to the behavior provided
716 by this option (unless noatime was specified), and the
717 strictatime option is required to obtain traditional semantics.
718 In addition, since Linux 2.6.30, the file's last access time is
719 always updated if it is more than 1 day old.
720 norelatime
722 Do not use the relatime feature. See also the strictatime mount
723 option.
724 strictatime
726 Allows to explicitly request full atime updates. This makes it
727 possible for the kernel to default to relatime or noatime but
728 still allow userspace to override it. For more details about
729 the default system mount options see /proc/mounts.
730 nostrictatime
732 Use the kernel's default behavior for inode access time updates.
733 lazytime
735 Only update times (atime, mtime, ctime) on the in-memory version
736 of the file inode.
737 This mount option significantly reduces writes to the inode ta‐
739 ble for workloads that perform frequent random writes to preal‐
740 located files.
741 The on-disk timestamps are updated only when:
743 - the inode needs to be updated for some change unrelated to
745 file timestamps
746 - the application employs fsync(2), syncfs(2), or sync(2)
748 - an undeleted inode is evicted from memory
750 - more than 24 hours have passed since the i-node was written to
752 disk.
753 nolazytime
756 Do not use the lazytime feature.
757 suid Allow set-user-ID or set-group-ID bits to take effect.
759 nosuid Do not allow set-user-ID or set-group-ID bits to take effect.
761 silent Turn on the silent flag.
763 loud Turn off the silent flag.
765 owner Allow an ordinary user to mount the filesystem if that user is
767 the owner of the device. This option implies the options nosuid
768 and nodev (unless overridden by subsequent options, as in the
769 option line owner,dev,suid).
770 remount
772 Attempt to remount an already-mounted filesystem. This is com‐
773 monly used to change the mount flags for a filesystem, espe‐
774 cially to make a readonly filesystem writable. It does not
775 change device or mount point.
776 The remount operation together with the bind flag has special
778 semantic. See above, the subsection Bind mounts.
779 The remount functionality follows the standard way the mount
781 command works with options from fstab. This means that mount
782 does not read fstab (or mtab) only when both device and dir are
783 specified.
784 mount -o remount,rw /dev/foo /dir
786 After this call all old mount options are replaced and arbitrary
788 stuff from fstab (or mtab) is ignored, except the loop= option
789 which is internally generated and maintained by the mount com‐
790 mand.
791 mount -o remount,rw /dir
793 After this call, mount reads fstab and merges these options with
795 the options from the command line (-o). If no mountpoint is
796 found in fstab, then a remount with unspecified source is
797 allowed.
798 ro Mount the filesystem read-only.
800 rw Mount the filesystem read-write.
802 sync All I/O to the filesystem should be done synchronously. In the
804 case of media with a limited number of write cycles (e.g. some
805 flash drives), sync may cause life-cycle shortening.
806 user Allow an ordinary user to mount the filesystem. The name of the
808 mounting user is written to the mtab file (or to the private
809 libmount file in /run/mount on systems without a regular mtab)
810 so that this same user can unmount the filesystem again. This
811 option implies the options noexec, nosuid, and nodev (unless
812 overridden by subsequent options, as in the option line
813 user,exec,dev,suid).
814 nouser Forbid an ordinary user to mount the filesystem. This is the
816 default; it does not imply any other options.
817 users Allow any user to mount and to unmount the filesystem, even when
819 some other ordinary user mounted it. This option implies the
820 options noexec, nosuid, and nodev (unless overridden by subse‐
821 quent options, as in the option line users,exec,dev,suid).
822 X-* All options prefixed with "X-" are interpreted as comments or as
824 userspace application-specific options. These options are not
825 stored in the user space (e.g. mtab file), nor sent to the
826 mount.type helpers nor to the mount(2) system call. The sug‐
827 gested format is X-appname.option.
828 x-* The same as X-* options, but stored permanently in the user
830 space. It means the options are also available for umount or
831 another operations. Note that maintain mount options in user
832 space is tricky, because it's necessary use libmount based tools
833 and there is no guarantee that the options will be always avail‐
834 able (for example after a move mount operation or in unshared
835 namespace).
836 Note that before util-linux v2.30 the x-* options have not been
838 maintained by libmount and stored in user space (functionality
839 was the same as have X-* now), but due to growing number of use-
840 cases (in initrd, systemd etc.) the functionality have been
841 extended to keep existing fstab configurations usable without a
842 change.
843 X-mount.mkdir[=mode]
845 Allow to make a target directory (mountpoint). The optional
846 argument mode specifies the filesystem access mode used for
847 mkdir(2) in octal notation. The default mode is 0755. This
848 functionality is supported only for root users. The option is
849 also supported as x-mount.mkdir, this notation is deprecated for
850 mount.mkdir since v2.30.
851
854 You should consult the respective man page for the filesystem first.
855 If you want to know what options the ext4 filesystem supports, then
856 check the ext4(5) man page. If that doesn't exist, you can also check
857 the corresponding mount page like mount.cifs(8). Note that you might
858 have to install the respective userland tools.
859 The following options apply only to certain filesystems. We sort them
861 by filesystem. They all follow the -o flag.
862 What options are supported depends a bit on the running kernel. More
864 info may be found in the kernel source subdirectory Documenta‐
865 tion/filesystems.
866 Mount options for adfs
869 uid=value and gid=value
870 Set the owner and group of the files in the filesystem (default:
871 uid=gid=0).
872 ownmask=value and othmask=value
874 Set the permission mask for ADFS 'owner' permissions and 'other'
875 permissions, respectively (default: 0700 and 0077, respec‐
876 tively). See also /usr/src/linux/Documentation/filesys‐
877 tems/adfs.txt.
878 Mount options for affs
881 uid=value and gid=value
882 Set the owner and group of the root of the filesystem (default:
883 uid=gid=0, but with option uid or gid without specified value,
884 the UID and GID of the current process are taken).
885 setuid=value and setgid=value
887 Set the owner and group of all files.
888 mode=value
890 Set the mode of all files to value & 0777 disregarding the orig‐
891 inal permissions. Add search permission to directories that
892 have read permission. The value is given in octal.
893 protect
895 Do not allow any changes to the protection bits on the filesys‐
896 tem.
897 usemp Set UID and GID of the root of the filesystem to the UID and GID
899 of the mount point upon the first sync or umount, and then clear
900 this option. Strange...
901 verbose
903 Print an informational message for each successful mount.
904 prefix=string
906 Prefix used before volume name, when following a link.
907 volume=string
909 Prefix (of length at most 30) used before '/' when following a
910 symbolic link.
911 reserved=value
913 (Default: 2.) Number of unused blocks at the start of the
914 device.
915 root=value
917 Give explicitly the location of the root block.
918 bs=value
920 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
921 grpquota|noquota|quota|usrquota
923 These options are accepted but ignored. (However, quota utili‐
924 ties may react to such strings in /etc/fstab.)
925 Mount options for debugfs
928 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
929 /sys/kernel/debug. As of kernel version 3.4, debugfs has the following
930 options:
931 uid=n, gid=n
933 Set the owner and group of the mountpoint.
934 mode=value
936 Sets the mode of the mountpoint.
937 Mount options for devpts
940 The devpts filesystem is a pseudo filesystem, traditionally mounted on
941 /dev/pts. In order to acquire a pseudo terminal, a process opens
942 /dev/ptmx; the number of the pseudo terminal is then made available to
943 the process and the pseudo terminal slave can be accessed as
944 /dev/pts/<number>.
945 uid=value and gid=value
947 This sets the owner or the group of newly created PTYs to the
948 specified values. When nothing is specified, they will be set
949 to the UID and GID of the creating process. For example, if
950 there is a tty group with GID 5, then gid=5 will cause newly
951 created PTYs to belong to the tty group.
952 mode=value
954 Set the mode of newly created PTYs to the specified value. The
955 default is 0600. A value of mode=620 and gid=5 makes "mesg y"
956 the default on newly created PTYs.
957 newinstance
959 Create a private instance of devpts filesystem, such that
960 indices of ptys allocated in this new instance are independent
961 of indices created in other instances of devpts.
962 All mounts of devpts without this newinstance option share the
964 same set of pty indices (i.e legacy mode). Each mount of devpts
965 with the newinstance option has a private set of pty indices.
966 This option is mainly used to support containers in the linux
968 kernel. It is implemented in linux kernel versions starting
969 with 2.6.29. Further, this mount option is valid only if CON‐
970 FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configu‐
971 ration.
972 To use this option effectively, /dev/ptmx must be a symbolic
974 link to pts/ptmx. See Documentation/filesystems/devpts.txt in
975 the linux kernel source tree for details.
976 ptmxmode=value
978 Set the mode for the new ptmx device node in the devpts filesys‐
980 tem.
981 With the support for multiple instances of devpts (see newin‐
983 stance option above), each instance has a private ptmx node in
984 the root of the devpts filesystem (typically /dev/pts/ptmx).
985 For compatibility with older versions of the kernel, the default
987 mode of the new ptmx node is 0000. ptmxmode=value specifies a
988 more useful mode for the ptmx node and is highly recommended
989 when the newinstance option is specified.
990 This option is only implemented in linux kernel versions start‐
992 ing with 2.6.29. Further, this option is valid only if CON‐
993 FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configu‐
994 ration.
995 Mount options for fat
998 (Note: fat is not a separate filesystem, but a common part of the
999 msdos, umsdos and vfat filesystems.)
1000 blocksize={512|1024|2048}
1002 Set blocksize (default 512). This option is obsolete.
1003 uid=value and gid=value
1005 Set the owner and group of all files. (Default: the UID and GID
1006 of the current process.)
1007 umask=value
1009 Set the umask (the bitmask of the permissions that are not
1010 present). The default is the umask of the current process. The
1011 value is given in octal.
1012 dmask=value
1014 Set the umask applied to directories only. The default is the
1015 umask of the current process. The value is given in octal.
1016 fmask=value
1018 Set the umask applied to regular files only. The default is the
1019 umask of the current process. The value is given in octal.
1020 allow_utime=value
1022 This option controls the permission check of mtime/atime.
1023 20 If current process is in group of file's group ID, you
1025 can change timestamp.
1026 2 Other users can change timestamp.
1028 The default is set from `dmask' option. (If the directory is
1030 writable, utime(2) is also allowed. I.e. ~dmask & 022)
1031 Normally utime(2) checks current process is owner of the file,
1033 or it has CAP_FOWNER capability. But FAT filesystem doesn't
1034 have UID/GID on disk, so normal check is too inflexible. With
1035 this option you can relax it.
1036 check=value
1038 Three different levels of pickyness can be chosen:
1039 r[elaxed]
1041 Upper and lower case are accepted and equivalent, long
1042 name parts are truncated (e.g. verylongname.foobar
1043 becomes verylong.foo), leading and embedded spaces are
1044 accepted in each name part (name and extension).
1045 n[ormal]
1047 Like "relaxed", but many special characters (*, ?, <,
1048 spaces, etc.) are rejected. This is the default.
1049 s[trict]
1051 Like "normal", but names that contain long parts or spe‐
1052 cial characters that are sometimes used on Linux but are
1053 not accepted by MS-DOS (+, =, etc.) are rejected.
1054 codepage=value
1056 Sets the codepage for converting to shortname characters on FAT
1057 and VFAT filesystems. By default, codepage 437 is used.
1058 conv=mode
1060 This option is obsolete and may fail or being ignored.
1061 cvf_format=module
1063 Forces the driver to use the CVF (Compressed Volume File) module
1064 cvf_module instead of auto-detection. If the kernel supports
1065 kmod, the cvf_format=xxx option also controls on-demand CVF mod‐
1066 ule loading. This option is obsolete.
1067 cvf_option=option
1069 Option passed to the CVF module. This option is obsolete.
1070 debug Turn on the debug flag. A version string and a list of filesys‐
1072 tem parameters will be printed (these data are also printed if
1073 the parameters appear to be inconsistent).
1074 discard
1076 If set, causes discard/TRIM commands to be issued to the block
1077 device when blocks are freed. This is useful for SSD devices
1078 and sparse/thinly-provisioned LUNs.
1079 dos1xfloppy
1081 If set, use a fallback default BIOS Parameter Block configura‐
1082 tion, determined by backing device size. These static parame‐
1083 ters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320
1084 kiB, and 360 kiB floppies and floppy images.
1085 errors={panic|continue|remount-ro}
1087 Specify FAT behavior on critical errors: panic, continue without
1088 doing anything, or remount the partition in read-only mode
1089 (default behavior).
1090 fat={12|16|32}
1092 Specify a 12, 16 or 32 bit fat. This overrides the automatic
1093 FAT type detection routine. Use with caution!
1094 iocharset=value
1096 Character set to use for converting between 8 bit characters and
1097 16 bit Unicode characters. The default is iso8859-1. Long
1098 filenames are stored on disk in Unicode format.
1099 nfs={stale_rw|nostale_ro}
1101 Enable this only if you want to export the FAT filesystem over
1102 NFS.
1103 stale_rw: This option maintains an index (cache) of directory
1105 inodes which is used by the nfs-related code to improve look-
1106 ups. Full file operations (read/write) over NFS are supported
1107 but with cache eviction at NFS server, this could result in spu‐
1108 rious ESTALE errors.
1109 nostale_ro: This option bases the inode number and file handle
1111 on the on-disk location of a file in the FAT directory entry.
1112 This ensures that ESTALE will not be returned after a file is
1113 evicted from the inode cache. However, it means that operations
1114 such as rename, create and unlink could cause file handles that
1115 previously pointed at one file to point at a different file,
1116 potentially causing data corruption. For this reason, this
1117 option also mounts the filesystem readonly.
1118 To maintain backward compatibility, '-o nfs' is also accepted,
1120 defaulting to stale_rw.
1121 tz=UTC This option disables the conversion of timestamps between local
1123 time (as used by Windows on FAT) and UTC (which Linux uses
1124 internally). This is particularly useful when mounting devices
1125 (like digital cameras) that are set to UTC in order to avoid the
1126 pitfalls of local time.
1127 time_offset=minutes
1129 Set offset for conversion of timestamps from local time used by
1130 FAT to UTC. I.e., minutes will be subtracted from each time‐
1131 stamp to convert it to UTC used internally by Linux. This is
1132 useful when the time zone set in the kernel via settimeofday(2)
1133 is not the time zone used by the filesystem. Note that this
1134 option still does not provide correct time stamps in all cases
1135 in presence of DST - time stamps in a different DST setting will
1136 be off by one hour.
1137 quiet Turn on the quiet flag. Attempts to chown or chmod files do not
1139 return errors, although they fail. Use with caution!
1140 rodir FAT has the ATTR_RO (read-only) attribute. On Windows, the
1142 ATTR_RO of the directory will just be ignored, and is used only
1143 by applications as a flag (e.g. it's set for the customized
1144 folder).
1145 If you want to use ATTR_RO as read-only flag even for the direc‐
1147 tory, set this option.
1148 showexec
1150 If set, the execute permission bits of the file will be allowed
1151 only if the extension part of the name is .EXE, .COM, or .BAT.
1152 Not set by default.
1153 sys_immutable
1155 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag
1156 on Linux. Not set by default.
1157 flush If set, the filesystem will try to flush to disk more early than
1159 normal. Not set by default.
1160 usefree
1162 Use the "free clusters" value stored on FSINFO. It'll be used
1163 to determine number of free clusters without scanning disk. But
1164 it's not used by default, because recent Windows don't update it
1165 correctly in some case. If you are sure the "free clusters" on
1166 FSINFO is correct, by this option you can avoid scanning disk.
1167 dots, nodots, dotsOK=[yes|no]
1169 Various misguided attempts to force Unix or DOS conventions onto
1170 a FAT filesystem.
1171 Mount options for hfs
1174 creator=cccc, type=cccc
1175 Set the creator/type values as shown by the MacOS finder used
1176 for creating new files. Default values: '????'.
1177 uid=n, gid=n
1179 Set the owner and group of all files. (Default: the UID and GID
1180 of the current process.)
1181 dir_umask=n, file_umask=n, umask=n
1183 Set the umask used for all directories, all regular files, or
1184 all files and directories. Defaults to the umask of the current
1185 process.
1186 session=n
1188 Select the CDROM session to mount. Defaults to leaving that
1189 decision to the CDROM driver. This option will fail with any‐
1190 thing but a CDROM as underlying device.
1191 part=n Select partition number n from the device. Only makes sense for
1193 CDROMs. Defaults to not parsing the partition table at all.
1194 quiet Don't complain about invalid mount options.
1196 Mount options for hpfs
1199 uid=value and gid=value
1200 Set the owner and group of all files. (Default: the UID and GID
1201 of the current process.)
1202 umask=value
1204 Set the umask (the bitmask of the permissions that are not
1205 present). The default is the umask of the current process. The
1206 value is given in octal.
1207 case={lower|asis}
1209 Convert all files names to lower case, or leave them. (Default:
1210 case=lower.)
1211 conv=mode
1213 This option is obsolete and may fail or being ignored.
1214 nocheck
1216 Do not abort mounting when certain consistency checks fail.
1217 Mount options for iso9660
1220 ISO 9660 is a standard describing a filesystem structure to be used on
1221 CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1222 udf filesystem.)
1223 Normal iso9660 filenames appear in a 8.3 format (i.e., DOS-like
1225 restrictions on filename length), and in addition all characters are in
1226 upper case. Also there is no field for file ownership, protection,
1227 number of links, provision for block/character devices, etc.
1228 Rock Ridge is an extension to iso9660 that provides all of these UNIX-
1230 like features. Basically there are extensions to each directory record
1231 that supply all of the additional information, and when Rock Ridge is
1232 in use, the filesystem is indistinguishable from a normal UNIX filesys‐
1233 tem (except that it is read-only, of course).
1234 norock Disable the use of Rock Ridge extensions, even if available.
1236 Cf. map.
1237 nojoliet
1239 Disable the use of Microsoft Joliet extensions, even if avail‐
1240 able. Cf. map.
1241 check={r[elaxed]|s[trict]}
1243 With check=relaxed, a filename is first converted to lower case
1244 before doing the lookup. This is probably only meaningful
1245 together with norock and map=normal. (Default: check=strict.)
1246 uid=value and gid=value
1248 Give all files in the filesystem the indicated user or group id,
1249 possibly overriding the information found in the Rock Ridge
1250 extensions. (Default: uid=0,gid=0.)
1251 map={n[ormal]|o[ff]|a[corn]}
1253 For non-Rock Ridge volumes, normal name translation maps upper
1254 to lower case ASCII, drops a trailing `;1', and converts `;' to
1255 `.'. With map=off no name translation is done. See norock.
1256 (Default: map=normal.) map=acorn is like map=normal but also
1257 apply Acorn extensions if present.
1258 mode=value
1260 For non-Rock Ridge volumes, give all files the indicated mode.
1261 (Default: read and execute permission for everybody.) Octal
1262 mode values require a leading 0.
1263 unhide Also show hidden and associated files. (If the ordinary files
1265 and the associated or hidden files have the same filenames, this
1266 may make the ordinary files inaccessible.)
1267 block={512|1024|2048}
1269 Set the block size to the indicated value. (Default:
1270 block=1024.)
1271 conv=mode
1273 This option is obsolete and may fail or being ignored.
1274 cruft If the high byte of the file length contains other garbage, set
1276 this mount option to ignore the high order bits of the file
1277 length. This implies that a file cannot be larger than 16 MB.
1278 session=x
1280 Select number of session on multisession CD.
1281 sbsector=xxx
1283 Session begins from sector xxx.
1284 The following options are the same as for vfat and specifying them only
1286 makes sense when using discs encoded using Microsoft's Joliet exten‐
1287 sions.
1288 iocharset=value
1290 Character set to use for converting 16 bit Unicode characters on
1291 CD to 8 bit characters. The default is iso8859-1.
1292 utf8 Convert 16 bit Unicode characters on CD to UTF-8.
1294 Mount options for jfs
1297 iocharset=name
1298 Character set to use for converting from Unicode to ASCII. The
1299 default is to do no conversion. Use iocharset=utf8 for UTF8
1300 translations. This requires CONFIG_NLS_UTF8 to be set in the
1301 kernel .config file.
1302 resize=value
1304 Resize the volume to value blocks. JFS only supports growing a
1305 volume, not shrinking it. This option is only valid during a
1306 remount, when the volume is mounted read-write. The resize key‐
1307 word with no value will grow the volume to the full size of the
1308 partition.
1309 nointegrity
1311 Do not write to the journal. The primary use of this option is
1312 to allow for higher performance when restoring a volume from
1313 backup media. The integrity of the volume is not guaranteed if
1314 the system abnormally ends.
1315 integrity
1317 Default. Commit metadata changes to the journal. Use this
1318 option to remount a volume where the nointegrity option was pre‐
1319 viously specified in order to restore normal behavior.
1320 errors={continue|remount-ro|panic}
1322 Define the behavior when an error is encountered. (Either
1323 ignore errors and just mark the filesystem erroneous and con‐
1324 tinue, or remount the filesystem read-only, or panic and halt
1325 the system.)
1326 noquota|quota|usrquota|grpquota
1328 These options are accepted but ignored.
1329 Mount options for msdos
1332 See mount options for fat. If the msdos filesystem detects an incon‐
1333 sistency, it reports an error and sets the file system read-only. The
1334 filesystem can be made writable again by remounting it.
1335 Mount options for ncpfs
1338 Just like nfs, the ncpfs implementation expects a binary argument (a
1339 struct ncp_mount_data) to the mount system call. This argument is con‐
1340 structed by ncpmount(8) and the current version of mount (2.12) does
1341 not know anything about ncpfs.
1342 Mount options for ntfs
1345 iocharset=name
1346 Character set to use when returning file names. Unlike VFAT,
1347 NTFS suppresses names that contain nonconvertible characters.
1348 Deprecated.
1349 nls=name
1351 New name for the option earlier called iocharset.
1352 utf8 Use UTF-8 for converting file names.
1354 uni_xlate={0|1|2}
1356 For 0 (or `no' or `false'), do not use escape sequences for
1357 unknown Unicode characters. For 1 (or `yes' or `true') or 2,
1358 use vfat-style 4-byte escape sequences starting with ":". Here
1359 2 give a little-endian encoding and 1 a byteswapped bigendian
1360 encoding.
1361 posix=[0|1]
1363 If enabled (posix=1), the filesystem distinguishes between upper
1364 and lower case. The 8.3 alias names are presented as hard links
1365 instead of being suppressed. This option is obsolete.
1366 uid=value, gid=value and umask=value
1368 Set the file permission on the filesystem. The umask value is
1369 given in octal. By default, the files are owned by root and not
1370 readable by somebody else.
1371 Mount options for overlay
1374 Since Linux 3.18 the overlay pseudo filesystem implements a union mount
1375 for other filesystems.
1376 An overlay filesystem combines two filesystems - an upper filesystem
1378 and a lower filesystem. When a name exists in both filesystems, the
1379 object in the upper filesystem is visible while the object in the lower
1380 filesystem is either hidden or, in the case of directories, merged with
1381 the upper object.
1382 The lower filesystem can be any filesystem supported by Linux and does
1384 not need to be writable. The lower filesystem can even be another
1385 overlayfs. The upper filesystem will normally be writable and if it is
1386 it must support the creation of trusted.* extended attributes, and must
1387 provide a valid d_type in readdir responses, so NFS is not suitable.
1388 A read-only overlay of two read-only filesystems may use any filesystem
1390 type. The options lowerdir and upperdir are combined into a merged
1391 directory by using:
1392 mount -t overlay overlay \
1394 -olowerdir=/lower,upperdir=/upper,workdir=/work /merged
1395 lowerdir=directory
1398 Any filesystem, does not need to be on a writable filesystem.
1399 upperdir=directory
1401 The upperdir is normally on a writable filesystem.
1402 workdir=directory
1404 The workdir needs to be an empty directory on the same filesys‐
1405 tem as upperdir.
1406 Mount options for reiserfs
1409 Reiserfs is a journaling filesystem.
1410 conv Instructs version 3.6 reiserfs software to mount a version 3.5
1412 filesystem, using the 3.6 format for newly created objects.
1413 This filesystem will no longer be compatible with reiserfs 3.5
1414 tools.
1415 hash={rupasov|tea|r5|detect}
1417 Choose which hash function reiserfs will use to find files
1418 within directories.
1419 rupasov
1421 A hash invented by Yury Yu. Rupasov. It is fast and pre‐
1422 serves locality, mapping lexicographically close file
1423 names to close hash values. This option should not be
1424 used, as it causes a high probability of hash collisions.
1425 tea A Davis-Meyer function implemented by Jeremy
1427 Fitzhardinge. It uses hash permuting bits in the name.
1428 It gets high randomness and, therefore, low probability
1429 of hash collisions at some CPU cost. This may be used if
1430 EHASHCOLLISION errors are experienced with the r5 hash.
1431 r5 A modified version of the rupasov hash. It is used by
1433 default and is the best choice unless the filesystem has
1434 huge directories and unusual file-name patterns.
1435 detect Instructs mount to detect which hash function is in use
1437 by examining the filesystem being mounted, and to write
1438 this information into the reiserfs superblock. This is
1439 only useful on the first mount of an old format filesys‐
1440 tem.
1441 hashed_relocation
1443 Tunes the block allocator. This may provide performance
1444 improvements in some situations.
1445 no_unhashed_relocation
1447 Tunes the block allocator. This may provide performance
1448 improvements in some situations.
1449 noborder
1451 Disable the border allocator algorithm invented by Yury Yu.
1452 Rupasov. This may provide performance improvements in some sit‐
1453 uations.
1454 nolog Disable journaling. This will provide slight performance
1456 improvements in some situations at the cost of losing reiserfs's
1457 fast recovery from crashes. Even with this option turned on,
1458 reiserfs still performs all journaling operations, save for
1459 actual writes into its journaling area. Implementation of nolog
1460 is a work in progress.
1461 notail By default, reiserfs stores small files and `file tails'
1463 directly into its tree. This confuses some utilities such as
1464 LILO(8). This option is used to disable packing of files into
1465 the tree.
1466 replayonly
1468 Replay the transactions which are in the journal, but do not
1469 actually mount the filesystem. Mainly used by reiserfsck.
1470 resize=number
1472 A remount option which permits online expansion of reiserfs par‐
1473 titions. Instructs reiserfs to assume that the device has num‐
1474 ber blocks. This option is designed for use with devices which
1475 are under logical volume management (LVM). There is a special
1476 resizer utility which can be obtained from
1477 ftp://ftp.namesys.com/pub/reiserfsprogs.
1478 user_xattr
1480 Enable Extended User Attributes. See the attr(5) manual page.
1481 acl Enable POSIX Access Control Lists. See the acl(5) manual page.
1483 barrier=none / barrier=flush
1485 This disables / enables the use of write barriers in the jour‐
1486 naling code. barrier=none disables, barrier=flush enables
1487 (default). This also requires an IO stack which can support
1488 barriers, and if reiserfs gets an error on a barrier write, it
1489 will disable barriers again with a warning. Write barriers
1490 enforce proper on-disk ordering of journal commits, making
1491 volatile disk write caches safe to use, at some performance
1492 penalty. If your disks are battery-backed in one way or
1493 another, disabling barriers may safely improve performance.
1494 Mount options for ubifs
1497 UBIFS is a flash filesystem which works on top of UBI volumes. Note
1498 that atime is not supported and is always turned off.
1499 The device name may be specified as
1501 ubiX_Y UBI device number X, volume number Y
1502 ubiY UBI device number 0, volume number Y
1504 ubiX:NAME
1506 UBI device number X, volume with name NAME
1507 ubi:NAME
1509 UBI device number 0, volume with name NAME
1510 Alternative ! separator may be used instead of :.
1511 The following mount options are available:
1513 bulk_read
1515 Enable bulk-read. VFS read-ahead is disabled because it slows
1516 down the file system. Bulk-Read is an internal optimization.
1517 Some flashes may read faster if the data are read at one go,
1518 rather than at several read requests. For example, OneNAND can
1519 do "read-while-load" if it reads more than one NAND page.
1520 no_bulk_read
1522 Do not bulk-read. This is the default.
1523 chk_data_crc
1525 Check data CRC-32 checksums. This is the default.
1526 no_chk_data_crc.
1528 Do not check data CRC-32 checksums. With this option, the
1529 filesystem does not check CRC-32 checksum for data, but it does
1530 check it for the internal indexing information. This option
1531 only affects reading, not writing. CRC-32 is always calculated
1532 when writing the data.
1533 compr={none|lzo|zlib}
1535 Select the default compressor which is used when new files are
1536 written. It is still possible to read compressed files if
1537 mounted with the none option.
1538 Mount options for udf
1541 UDF is the "Universal Disk Format" filesystem defined by OSTA, the
1542 Optical Storage Technology Association, and is often used for DVD-ROM,
1543 frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, how‐
1544 ever, perfectly usable by itself on disk drives, flash drives and other
1545 block devices. See also iso9660.
1546 uid= Make all files in the filesystem belong to the given user.
1548 uid=forget can be specified independently of (or usually in
1549 addition to) uid=<user> and results in UDF not storing uids to
1550 the media. In fact the recorded uid is the 32-bit overflow uid
1551 -1 as defined by the UDF standard. The value is given as either
1552 <user> which is a valid user name or the corresponding decimal
1553 user id, or the special string "forget".
1554 gid= Make all files in the filesystem belong to the given group.
1556 gid=forget can be specified independently of (or usually in
1557 addition to) gid=<group> and results in UDF not storing gids to
1558 the media. In fact the recorded gid is the 32-bit overflow gid
1559 -1 as defined by the UDF standard. The value is given as either
1560 <group> which is a valid group name or the corresponding decimal
1561 group id, or the special string "forget".
1562 umask= Mask out the given permissions from all inodes read from the
1564 filesystem. The value is given in octal.
1565 mode= If mode= is set the permissions of all non-directory inodes read
1567 from the filesystem will be set to the given mode. The value is
1568 given in octal.
1569 dmode= If dmode= is set the permissions of all directory inodes read
1571 from the filesystem will be set to the given dmode. The value is
1572 given in octal.
1573 bs= Set the block size. Default value prior to kernel version 2.6.30
1575 was 2048. Since 2.6.30 and prior to 4.11 it was logical device
1576 block size with fallback to 2048. Since 4.11 it is logical block
1577 size with fallback to any valid block size between logical
1578 device block size and 4096.
1579 For other details see the mkudffs(8) 2.0+ manpage, sections COM‐
1581 PATIBILITY and BLOCK SIZE.
1582 unhide Show otherwise hidden files.
1584 undelete
1586 Show deleted files in lists.
1587 adinicb
1589 Embed data in the inode. (default)
1590 noadinicb
1592 Don't embed data in the inode.
1593 shortad
1595 Use short UDF address descriptors.
1596 longad Use long UDF address descriptors. (default)
1598 nostrict
1600 Unset strict conformance.
1601 iocharset=
1603 Set the NLS character set. This requires kernel compiled with
1604 CONFIG_UDF_NLS option.
1605 utf8 Set the UTF-8 character set.
1607 Mount options for debugging and disaster recovery
1609 novrs Ignore the Volume Recognition Sequence and attempt to mount any‐
1610 way.
1611 session=
1613 Select the session number for multi-session recorded optical
1614 media. (default= last session)
1615 anchor=
1617 Override standard anchor location. (default= 256)
1618 lastblock=
1620 Set the last block of the filesystem.
1621 Unused historical mount options that may be encountered and should be
1623 removed
1624 uid=ignore
1625 Ignored, use uid=<user> instead.
1626 gid=ignore
1628 Ignored, use gid=<group> instead.
1629 volume=
1631 Unimplemented and ignored.
1632 partition=
1634 Unimplemented and ignored.
1635 fileset=
1637 Unimplemented and ignored.
1638 rootdir=
1640 Unimplemented and ignored.
1641 Mount options for ufs
1644 ufstype=value
1645 UFS is a filesystem widely used in different operating systems.
1646 The problem are differences among implementations. Features of
1647 some implementations are undocumented, so its hard to recognize
1648 the type of ufs automatically. That's why the user must specify
1649 the type of ufs by mount option. Possible values are:
1650 old Old format of ufs, this is the default, read only.
1652 (Don't forget to give the -r option.)
1653 44bsd For filesystems created by a BSD-like system (NetBSD,
1655 FreeBSD, OpenBSD).
1656 ufs2 Used in FreeBSD 5.x supported as read-write.
1658 5xbsd Synonym for ufs2.
1660 sun For filesystems created by SunOS or Solaris on Sparc.
1662 sunx86 For filesystems created by Solaris on x86.
1664 hp For filesystems created by HP-UX, read-only.
1666 nextstep
1668 For filesystems created by NeXTStep (on NeXT station)
1669 (currently read only).
1670 nextstep-cd
1672 For NextStep CDROMs (block_size == 2048), read-only.
1673 openstep
1675 For filesystems created by OpenStep (currently read
1676 only). The same filesystem type is also used by Mac OS
1677 X.
1678 onerror=value
1681 Set behavior on error:
1682 panic If an error is encountered, cause a kernel panic.
1684 [lock|umount|repair]
1686 These mount options don't do anything at present; when an
1687 error is encountered only a console message is printed.
1688 Mount options for umsdos
1691 See mount options for msdos. The dotsOK option is explicitly killed by
1692 umsdos.
1693 Mount options for vfat
1696 First of all, the mount options for fat are recognized. The dotsOK
1697 option is explicitly killed by vfat. Furthermore, there are
1698 uni_xlate
1700 Translate unhandled Unicode characters to special escaped
1701 sequences. This lets you backup and restore filenames that are
1702 created with any Unicode characters. Without this option, a '?'
1703 is used when no translation is possible. The escape character
1704 is ':' because it is otherwise invalid on the vfat filesystem.
1705 The escape sequence that gets used, where u is the Unicode char‐
1706 acter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
1707 posix Allow two files with names that only differ in case. This
1709 option is obsolete.
1710 nonumtail
1712 First try to make a short name without sequence number, before
1713 trying name~num.ext.
1714 utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is
1716 used by the console. It can be enabled for the filesystem with
1717 this option or disabled with utf8=0, utf8=no or utf8=false. If
1718 `uni_xlate' gets set, UTF8 gets disabled.
1719 shortname=mode
1721 Defines the behavior for creation and display of filenames which
1722 fit into 8.3 characters. If a long name for a file exists, it
1723 will always be the preferred one for display. There are four
1724 modes:
1725 lower Force the short name to lower case upon display; store a
1727 long name when the short name is not all upper case.
1728 win95 Force the short name to upper case upon display; store a
1730 long name when the short name is not all upper case.
1731 winnt Display the short name as is; store a long name when the
1733 short name is not all lower case or all upper case.
1734 mixed Display the short name as is; store a long name when the
1736 short name is not all upper case. This mode is the
1737 default since Linux 2.6.32.
1738 Mount options for usbfs
1741 devuid=uid and devgid=gid and devmode=mode
1742 Set the owner and group and mode of the device files in the
1743 usbfs filesystem (default: uid=gid=0, mode=0644). The mode is
1744 given in octal.
1745 busuid=uid and busgid=gid and busmode=mode
1747 Set the owner and group and mode of the bus directories in the
1748 usbfs filesystem (default: uid=gid=0, mode=0555). The mode is
1749 given in octal.
1750 listuid=uid and listgid=gid and listmode=mode
1752 Set the owner and group and mode of the file devices (default:
1753 uid=gid=0, mode=0444). The mode is given in octal.
1754
1757 One further possible type is a mount via the loop device. For example,
1758 the command
1759 mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3
1761 will set up the loop device /dev/loop3 to correspond to the file
1763 /tmp/disk.img, and then mount this device on /mnt.
1764 If no explicit loop device is mentioned (but just an option `-o loop'
1766 is given), then mount will try to find some unused loop device and use
1767 that, for example
1768 mount /tmp/disk.img /mnt -o loop
1770 The mount command automatically creates a loop device from a regular
1772 file if a filesystem type is not specified or the filesystem is known
1773 for libblkid, for example:
1774 mount /tmp/disk.img /mnt
1776 mount -t ext3 /tmp/disk.img /mnt
1778 This type of mount knows about three options, namely loop, offset and
1780 sizelimit, that are really options to losetup(8). (These options can
1781 be used in addition to those specific to the filesystem type.)
1782 Since Linux 2.6.25 auto-destruction of loop devices is supported, mean‐
1784 ing that any loop device allocated by mount will be freed by umount
1785 independently of /etc/mtab.
1786 You can also free a loop device by hand, using losetup -d or umount -d.
1788 Since util-linux v2.29 mount command re-uses the loop device rather
1790 than initialize a new device if the same backing file is already used
1791 for some loop device with the same offset and sizelimit. This is neces‐
1792 sary to avoid a filesystem corruption.
1793
1796 mount has the following return codes (the bits can be ORed):
1797 0 success
1799 1 incorrect invocation or permissions
1801 2 system error (out of memory, cannot fork, no more loop devices)
1803 4 internal mount bug
1805 8 user interrupt
1807 16 problems writing or locking /etc/mtab
1809 32 mount failure
1811 64 some mount succeeded
1813 The command mount -a returns 0 (all succeeded), 32 (all failed), or 64
1815 (some failed, some succeeded).
1816
1819 The syntax of external mount helpers is:
1820 /sbin/mount.suffix spec dir [-sfnv] [-o options] [-t type.subtype]
1822 where the suffix is the filesystem type and the -sfnvo options have the
1824 same meaning as the normal mount options. The -t option is used for
1825 filesystems with subtypes support (for example /sbin/mount.fuse -t
1826 fuse.sshfs).
1827 The command mount does not pass the mount options unbindable, runbind‐
1829 able, private, rprivate, slave, rslave, shared, rshared, auto, noauto,
1830 comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers.
1831 All other options are used in a comma-separated list as argument to the
1832 -o option.
1833
1836 /etc/fstab filesystem table
1837 /etc/mtab table of mounted filesystems
1839 /etc/mtab~ lock file
1841 /etc/mtab.tmp temporary file
1843 /etc/filesystems a list of filesystem types to try
1845
1847 LIBMOUNT_FSTAB=<path>
1848 overrides the default location of the fstab file (ignored for
1849 suid)
1850 LIBMOUNT_MTAB=<path>
1852 overrides the default location of the mtab file (ignored for
1853 suid)
1854 LIBMOUNT_DEBUG=all
1856 enables libmount debug output
1857 LIBBLKID_DEBUG=all
1859 enables libblkid debug output
1860 LOOPDEV_DEBUG=all
1862 enables loop device setup debug output
1863
1865 mount(2), umount(2), umount(8), fstab(5), nfs(5), xfs(5), e2label(8),
1866 findmnt(8), losetup(8), mke2fs(8), mountd(8), nfsd(8), swapon(8),
1867 tune2fs(8), xfs_admin(8)
1868
1870 It is possible for a corrupted filesystem to cause a crash.
1871 Some Linux filesystems don't support -o sync nor -o dirsync (the ext2,
1873 ext3, fat and vfat filesystems do support synchronous updates (a la
1874 BSD) when mounted with the sync option).
1875 The -o remount may not be able to change mount parameters (all ext2fs-
1877 specific parameters, except sb, are changeable with a remount, for
1878 example, but you can't change gid or umask for the fatfs).
1879 It is possible that the files /etc/mtab and /proc/mounts don't match on
1881 systems with a regular mtab file. The first file is based only on the
1882 mount command options, but the content of the second file also depends
1883 on the kernel and others settings (e.g. on a remote NFS server -- in
1884 certain cases the mount command may report unreliable information about
1885 an NFS mount point and the /proc/mounts file usually contains more
1886 reliable information.) This is another reason to replace the mtab file
1887 with a symlink to the /proc/mounts file.
1888 Checking files on NFS filesystems referenced by file descriptors (i.e.
1890 the fcntl and ioctl families of functions) may lead to inconsistent
1891 results due to the lack of a consistency check in the kernel even if
1892 noac is used.
1893 The loop option with the offset or sizelimit options used may fail when
1895 using older kernels if the mount command can't confirm that the size of
1896 the block device has been configured as requested. This situation can
1897 be worked around by using the losetup command manually before calling
1898 mount with the configured loop device.
1899
1901 A mount command existed in Version 5 AT&T UNIX.
1902
1904 Karel Zak <kzak@redhat.com>
1905
1907 The mount command is part of the util-linux package and is available
1908 from https://www.kernel.org/pub/linux/utils/util-linux/.
1909util-linux August 2015 MOUNT(8)