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. The support for reg‐
136 ular classic /etc/mtab is completely disabled in compile time by
137 default, because on current Linux systems it is better to make it a
138 symlink to /proc/mounts instead. The regular mtab file maintained in
139 userspace cannot reliably work with namespaces, containers and other
140 advanced Linux features. If the regular mtab support is enabled than
141 it's possible to use the file as well as the symlink.
142 If no arguments are given to mount, the list of mounted filesystems is
144 printed.
145 If you want to override mount options from /etc/fstab you have to use
147 the -o option:
148 mount device|dir -o options
150 and then the mount options from the command line will be appended to
152 the list of options from /etc/fstab. This default behaviour is possi‐
153 ble to change by command line option --options-mode. The usual behav‐
154 ior is that the last option wins if there are conflicting ones.
155 The mount program does not read the /etc/fstab file if both device (or
157 LABEL, UUID, PARTUUID or PARTLABEL) and dir are specified. For exam‐
158 ple, to mount device foo at /dir:
159 mount /dev/foo /dir
161 This default behaviour is possible to change by command line option
163 --options-source-force to always read configuration from fstab. For
164 non-root users mount always read fstab configuration.
165 Non-superuser mounts
168 Normally, only the superuser can mount filesystems. However, when
169 fstab contains the user option on a line, anybody can mount the corre‐
170 sponding filesystem.
171 Thus, given a line
173 /dev/cdrom /cd iso9660 ro,user,noauto,unhide
175 any user can mount the iso9660 filesystem found on an inserted CDROM
177 using the command:
178 mount /cd
179 Note that mount is very strict about non-root users and all paths spec‐
181 ified on command line are verified before fstab is parsed or a helper
182 program is executed. It's strongly recommended to use a valid mount‐
183 point to specify filesystem, otherwise mount may fail. For example it's
184 bad idea to use NFS or CIFS source on command line.
185 For more details, see fstab(5). Only the user that mounted a filesys‐
187 tem can unmount it again. If any user should be able to unmount it,
188 then use users instead of user in the fstab line. The owner option is
189 similar to the user option, with the restriction that the user must be
190 the owner of the special file. This may be useful e.g. for /dev/fd if
191 a login script makes the console user owner of this device. The group
192 option is similar, with the restriction that the user must be member of
193 the group of the special file.
194 Bind mount operation
197 Remount part of the file hierarchy somewhere else. The call is:
198 mount --bind olddir newdir
200 or by using this fstab entry:
202 /olddir /newdir none bind
204 After this call the same contents are accessible in two places.
206 It is important to understand that "bind" does not to create any sec‐
208 ond-class or special node in the kernel VFS. The "bind" is just another
209 operation to attach a filesystem. There is nowhere stored information
210 that the filesystem has been attached by "bind" operation. The olddir
211 and newdir are independent and the olddir maybe be umounted.
212 One can also remount a single file (on a single file). It's also pos‐
214 sible to use the bind mount to create a mountpoint from a regular
215 directory, for example:
216 mount --bind foo foo
218 The bind mount call attaches only (part of) a single filesystem, not
220 possible submounts. The entire file hierarchy including submounts is
221 attached a second place by using:
222 mount --rbind olddir newdir
224 Note that the filesystem mount options maintained by kernel will remain
226 the same as those on the original mount point. The userspace mount
227 options (e.g. _netdev) will not be copied by mount(8) and it's neces‐
228 sary explicitly specify the options on mount command line.
229 mount(8) since v2.27 allows to change the mount options by passing the
231 relevant options along with --bind. For example:
232 mount -o bind,ro foo foo
234 This feature is not supported by the Linux kernel; it is implemented in
236 userspace by an additional mount(2) remounting system call. This solu‐
237 tion is not atomic.
238 The alternative (classic) way to create a read-only bind mount is to
240 use the remount operation, for example:
241 mount --bind olddir newdir
243 mount -o remount,bind,ro olddir newdir
244 Note that a read-only bind will create a read-only mountpoint (VFS
246 entry), but the original filesystem superblock will still be writable,
247 meaning that the olddir will be writable, but the newdir will be read-
248 only.
249 It's also possible to change nosuid, nodev, noexec, noatime, nodiratime
251 and relatime VFS entry flags by "remount,bind" operation. The another
252 (for example filesystem specific flags) are silently ignored. It's
253 impossible to change mount options recursively (for example with -o
254 rbind,ro).
255 mount(8) since v2.31 ignores the bind flag from /etc/fstab on remount
257 operation (if "-o remount" specified on command line). This is neces‐
258 sary to fully control mount options on remount by command line. In the
259 previous versions the bind flag has been always applied and it was
260 impossible to re-define mount options without interaction with the bind
261 semantic. This mount(8) behavior does not affect situations when
262 "remount,bind" is specified in the /etc/fstab file.
263 The move operation
266 Move a mounted tree to another place (atomically). The call is:
267 mount --move olddir newdir
269 This will cause the contents which previously appeared under olddir to
271 now be accessible under newdir. The physical location of the files is
272 not changed. Note that olddir has to be a mountpoint.
273 Note also that moving a mount residing under a shared mount is invalid
275 and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current
276 propagation flags.
277 Shared subtree operations
280 Since Linux 2.6.15 it is possible to mark a mount and its submounts as
281 shared, private, slave or unbindable. A shared mount provides the
282 ability to create mirrors of that mount such that mounts and unmounts
283 within any of the mirrors propagate to the other mirror. A slave mount
284 receives propagation from its master, but not vice versa. A private
285 mount carries no propagation abilities. An unbindable mount is a pri‐
286 vate mount which cannot be cloned through a bind operation. The
287 detailed semantics are documented in Documentation/filesystems/shared‐
288 subtree.txt file in the kernel source tree.
289 Supported operations are:
291 mount --make-shared mountpoint
293 mount --make-slave mountpoint
294 mount --make-private mountpoint
295 mount --make-unbindable mountpoint
296 The following commands allow one to recursively change the type of all
298 the mounts under a given mountpoint.
299 mount --make-rshared mountpoint
301 mount --make-rslave mountpoint
302 mount --make-rprivate mountpoint
303 mount --make-runbindable mountpoint
304 mount(8) does not read fstab(5) when a --make-* operation is requested.
306 All necessary information has to be specified on the command line.
307 Note that the Linux kernel does not allow to change multiple propaga‐
309 tion flags with a single mount(2) system call, and the flags cannot be
310 mixed with other mount options and operations.
311 Since util-linux 2.23 the mount command allows to do more propagation
313 (topology) changes by one mount(8) call and do it also together with
314 other mount operations. This feature is EXPERIMENTAL. The propagation
315 flags are applied by additional mount(2) system calls when the preced‐
316 ing mount operations were successful. Note that this use case is not
317 atomic. It is possible to specify the propagation flags in fstab(5) as
318 mount options (private, slave, shared, unbindable, rprivate, rslave,
319 rshared, runbindable).
320 For example:
322 mount --make-private --make-unbindable /dev/sda1 /foo
324 is the same as:
326 mount /dev/sda1 /foox
328 mount --make-private /foo
329 mount --make-unbindable /foo
330
333 The full set of mount options used by an invocation of mount is deter‐
334 mined by first extracting the mount options for the filesystem from the
335 fstab table, then applying any options specified by the -o argument,
336 and finally applying a -r or -w option, when present.
337 The command mount does not pass all command-line options to the
339 /sbin/mount.suffix mount helpers. The interface between mount and the
340 mount helpers is described below in the section EXTERNAL HELPERS.
341 Command-line options available for the mount command are:
343 -a, --all
345 Mount all filesystems (of the given types) mentioned in fstab
346 (except for those whose line contains the noauto keyword). The
347 filesystems are mounted following their order in fstab. The
348 mount command compares filesystem source, target (and fs root
349 for bind mount or btrfs) to detect already mounted filesystems.
350 The kernel table with already mounted filesystems is cached dur‐
351 ing mount --all. It means that all duplicated fstab entries will
352 be mounted.
353 Note that it is a bad practice to use mount -a for fstab check‐
355 ing. The recommended solution is findmnt --verify.
356 -B, --bind
358 Remount a subtree somewhere else (so that its contents are
359 available in both places). See above, under Bind mounts.
360 -c, --no-canonicalize
362 Don't canonicalize paths. The mount command canonicalizes all
363 paths (from command line or fstab) by default. This option can
364 be used together with the -f flag for already canonicalized
365 absolute paths. The option is designed for mount helpers which
366 call mount -i. It is strongly recommended to not use this com‐
367 mand-line option for normal mount operations.
368 Note that mount(8) does not pass this option to the
370 /sbin/mount.type helpers.
371 -F, --fork
373 (Used in conjunction with -a.) Fork off a new incarnation of
374 mount for each device. This will do the mounts on different
375 devices or different NFS servers in parallel. This has the
376 advantage that it is faster; also NFS timeouts go in parallel.
377 A disadvantage is that the mounts are done in undefined order.
378 Thus, you cannot use this option if you want to mount both /usr
379 and /usr/spool.
380 -f, --fake
382 Causes everything to be done except for the actual system call;
383 if it's not obvious, this ``fakes'' mounting the filesystem.
384 This option is useful in conjunction with the -v flag to deter‐
385 mine what the mount command is trying to do. It can also be
386 used to add entries for devices that were mounted earlier with
387 the -n option. The -f option checks for an existing record in
388 /etc/mtab and fails when the record already exists (with a regu‐
389 lar non-fake mount, this check is done by the kernel).
390 -i, --internal-only
392 Don't call the /sbin/mount.filesystem helper even if it exists.
393 -L, --label label
395 Mount the partition that has the specified label.
396 -l, --show-labels
398 Add the labels in the mount output. mount must have permission
399 to read the disk device (e.g. be set-user-ID root) for this to
400 work. One can set such a label for ext2, ext3 or ext4 using the
401 e2label(8) utility, or for XFS using xfs_admin(8), or for reis‐
402 erfs using reiserfstune(8).
403 -M, --move
405 Move a subtree to some other place. See above, the subsection
406 The move operation.
407 -n, --no-mtab
409 Mount without writing in /etc/mtab. This is necessary for exam‐
410 ple when /etc is on a read-only filesystem.
411 -N, --namespace ns
413 Perform mount in namespace specified by ns. ns is either PID of
414 process running in that namespace or special file representing
415 that namespace.
416 mount(8) switches to the namespace when it reads /etc/fstab,
418 writes /etc/mtab (or writes to /run/mount) and calls mount(2)
419 system call, otherwise it runs in the original namespace. It
420 means that the target namespace does not have to contain any
421 libraries or another requirements necessary to execute mount(2)
422 command.
423 See namespaces(7) for more information.
425 -O, --test-opts opts
427 Limit the set of filesystems to which the -a option applies. In
428 this regard it is like the -t option except that -O is useless
429 without -a. For example, the command:
430 mount -a -O no_netdev
432 mounts all filesystems except those which have the option _net‐
434 dev specified in the options field in the /etc/fstab file.
435 It is different from -t in that each option is matched exactly;
437 a leading no at the beginning of one option does not negate the
438 rest.
439 The -t and -O options are cumulative in effect; that is, the
441 command
442 mount -a -t ext2 -O _netdev
444 mounts all ext2 filesystems with the _netdev option, not all
446 filesystems that are either ext2 or have the _netdev option
447 specified.
448 -o, --options opts
450 Use the specified mount options. The opts argument is a comma-
451 separated list. For example:
452 mount LABEL=mydisk -o noatime,nodev,nosuid
454 For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS
457 and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.
458 --options-mode mode
461 Controls how to combine options from fstab/mtab with options
462 from command line. mode can be one of ignore, append, prepend
463 or replace. For example append means that options from fstab
464 are appended to options from command line. Default value is
465 prepend -- it means command line options are evaluated after
466 fstab options. Note that the last option wins if there are con‐
467 flicting ones.
468 --options-source source
471 Source of default options. source is comma separated list of
472 fstab, mtab and disable. disable disables fstab and mtab and
473 disables --options-source-force. Default value is fstab,mtab.
474 --options-source-force
477 Use options from fstab/mtab even if both device and dir are
478 specified.
479 -R, --rbind
482 Remount a subtree and all possible submounts somewhere else (so
483 that its contents are available in both places). See above, the
484 subsection Bind mounts.
485 -r, --read-only
487 Mount the filesystem read-only. A synonym is -o ro.
488 Note that, depending on the filesystem type, state and kernel
490 behavior, the system may still write to the device. For exam‐
491 ple, ext3 and ext4 will replay the journal if the filesystem is
492 dirty. To prevent this kind of write access, you may want to
493 mount an ext3 or ext4 filesystem with the ro,noload mount
494 options or set the block device itself to read-only mode, see
495 the blockdev(8) command.
496 -s Tolerate sloppy mount options rather than failing. This will
498 ignore mount options not supported by a filesystem type. Not
499 all filesystems support this option. Currently it's supported
500 by the mount.nfs mount helper only.
501 --source device
503 If only one argument for the mount command is given then the
504 argument might be interpreted as target (mountpoint) or source
505 (device). This option allows to explicitly define that the
506 argument is the mount source.
507 --target directory
509 If only one argument for the mount command is given then the
510 argument might be interpreted as target (mountpoint) or source
511 (device). This option allows to explicitly define that the
512 argument is the mount target.
513 -T, --fstab path
515 Specifies an alternative fstab file. If path is a directory
516 then the files in the directory are sorted by strverscmp(3);
517 files that start with "." or without an .fstab extension are
518 ignored. The option can be specified more than once. This
519 option is mostly designed for initramfs or chroot scripts where
520 additional configuration is specified beyond standard system
521 configuration.
522 Note that mount(8) does not pass the option --fstab to the
524 /sbin/mount.type helpers, meaning that the alternative fstab
525 files will be invisible for the helpers. This is no problem for
526 normal mounts, but user (non-root) mounts always require fstab
527 to verify the user's rights.
528 -t, --types fstype
530 The argument following the -t is used to indicate the filesystem
531 type. The filesystem types which are currently supported depend
532 on the running kernel. See /proc/filesystems and /lib/mod‐
533 ules/$(uname -r)/kernel/fs for a complete list of the filesys‐
534 tems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat,
535 sysfs, proc, nfs and cifs.
536 The programs mount and umount support filesystem subtypes. The
538 subtype is defined by a '.subtype' suffix. For example
539 'fuse.sshfs'. It's recommended to use subtype notation rather
540 than add any prefix to the mount source (for example
541 'sshfs#example.com' is deprecated).
542 If no -t option is given, or if the auto type is specified,
544 mount will try to guess the desired type. Mount uses the blkid
545 library for guessing the filesystem type; if that does not turn
546 up anything that looks familiar, mount will try to read the file
547 /etc/filesystems, or, if that does not exist, /proc/filesystems.
548 All of the filesystem types listed there will be tried, except
549 for those that are labeled "nodev" (e.g. devpts, proc and nfs).
550 If /etc/filesystems ends in a line with a single *, mount will
551 read /proc/filesystems afterwards. While trying, all filesystem
552 types will be mounted with the mount option silent.
553 The auto type may be useful for user-mounted floppies. Creating
555 a file /etc/filesystems can be useful to change the probe order
556 (e.g., to try vfat before msdos or ext3 before ext2) or if you
557 use a kernel module autoloader.
558 More than one type may be specified in a comma-separated list,
560 for option -t as well as in an /etc/fstab entry. The list of
561 filesystem types for option -t can be prefixed with no to spec‐
562 ify the filesystem types on which no action should be taken.
563 The prefix no has no effect when specified in an /etc/fstab
564 entry.
565 The prefix no can be meaningful with the -a option. For exam‐
567 ple, the command
568 mount -a -t nomsdos,smbfs
570 mounts all filesystems except those of type msdos and smbfs.
572 For most types all the mount program has to do is issue a simple
574 mount(2) system call, and no detailed knowledge of the filesys‐
575 tem type is required. For a few types however (like nfs, nfs4,
576 cifs, smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4,
577 cifs, smbfs, and ncpfs filesystems have a separate mount pro‐
578 gram. In order to make it possible to treat all types in a uni‐
579 form way, mount will execute the program /sbin/mount.type (if
580 that exists) when called with type type. Since different ver‐
581 sions of the smbmount program have different calling conven‐
582 tions, /sbin/mount.smbfs may have to be a shell script that sets
583 up the desired call.
584 -U, --uuid uuid
586 Mount the partition that has the specified uuid.
587 -v, --verbose
589 Verbose mode.
590 -w, --rw, --read-write
592 Mount the filesystem read/write. The read-write is kernel
593 default. A synonym is -o rw.
594 Note that specify -w on command line forces mount command to
596 never try read-only mount on write-protected devices. The
597 default is try read-only if the previous mount syscall with
598 read-write flags failed.
599 -V, --version
601 Display version information and exit.
602 -h, --help
604 Display help text and exit.
605
608 Some of these options are only useful when they appear in the
609 /etc/fstab file.
610 Some of these options could be enabled or disabled by default in the
612 system kernel. To check the current setting see the options in
613 /proc/mounts. Note that filesystems also have per-filesystem specific
614 default mount options (see for example tune2fs -l output for extN
615 filesystems).
616 The following options apply to any filesystem that is being mounted
618 (but not every filesystem actually honors them – e.g., the sync option
619 today has an effect only for ext2, ext3, ext4, fat, vfat and ufs):
620 async All I/O to the filesystem should be done asynchronously. (See
623 also the sync option.)
624 atime Do not use the noatime feature, so the inode access time is con‐
626 trolled by kernel defaults. See also the descriptions of the
627 relatime and strictatime mount options.
628 noatime
630 Do not update inode access times on this filesystem (e.g. for
631 faster access on the news spool to speed up news servers). This
632 works for all inode types (directories too), so it implies
633 nodiratime.
634 auto Can be mounted with the -a option.
636 noauto Can only be mounted explicitly (i.e., the -a option will not
638 cause the filesystem to be mounted).
639 context=context, fscontext=context, defcontext=context, and
641 rootcontext=context
642 The context= option is useful when mounting filesystems that do
643 not support extended attributes, such as a floppy or hard disk
644 formatted with VFAT, or systems that are not normally running
645 under SELinux, such as an ext3 or ext4 formatted
646 disk from a non-SELinux workstation. You can also use context=
648 on filesystems you do not trust, such as a floppy. It also
649 helps in compatibility with xattr-supporting filesystems on ear‐
650 lier 2.4.<x> kernel versions. Even where xattrs are supported,
651 you can save time not having to label every file by assigning
652 the entire disk one security context.
653 A commonly used option for removable media is
655 context="system_u:object_r:removable_t".
656 Two other options are fscontext= and defcontext=, both of which
658 are mutually exclusive of the context option. This means you
659 can use fscontext and defcontext with each other, but neither
660 can be used with context.
661 The fscontext= option works for all filesystems, regardless of
663 their xattr support. The fscontext option sets the overarching
664 filesystem label to a specific security context. This filesys‐
665 tem label is separate from the individual labels on the files.
666 It represents the entire filesystem for certain kinds of permis‐
667 sion checks, such as during mount or file creation. Individual
668 file labels are still obtained from the xattrs on the files
669 themselves. The context option actually sets the aggregate con‐
670 text that fscontext provides, in addition to supplying the same
671 label for individual files.
672 You can set the default security context for unlabeled files
674 using defcontext= option. This overrides the value set for
675 unlabeled files in the policy and requires a filesystem that
676 supports xattr labeling.
677 The rootcontext= option allows you to explicitly label the root
679 inode of a FS being mounted before that FS or inode becomes vis‐
680 ible to userspace. This was found to be useful for things like
681 stateless linux.
682 Note that the kernel rejects any remount request that includes
684 the context option, even when unchanged from the current con‐
685 text.
686 Warning: the context value might contain commas, in which case
688 the value has to be properly quoted, otherwise mount(8) will
689 interpret the comma as a separator between mount options. Don't
690 forget that the shell strips off quotes and thus double quoting
691 is required. For example:
692 mount -t tmpfs none /mnt -o \
694 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
695 For more details, see selinux(8).
697 defaults
700 Use the default options: rw, suid, dev, exec, auto, nouser, and
701 async.
702 Note that the real set of all default mount options depends on
704 kernel and filesystem type. See the beginning of this section
705 for more details.
706 dev Interpret character or block special devices on the filesystem.
708 nodev Do not interpret character or block special devices on the file
710 system.
711 diratime
713 Update directory inode access times on this filesystem. This is
714 the default. (This option is ignored when noatime is set.)
715 nodiratime
717 Do not update directory inode access times on this filesystem.
718 (This option is implied when noatime is set.)
719 dirsync
721 All directory updates within the filesystem should be done syn‐
722 chronously. This affects the following system calls: creat,
723 link, unlink, symlink, mkdir, rmdir, mknod and rename.
724 exec Permit execution of binaries.
726 noexec Do not permit direct execution of any binaries on the mounted
728 filesystem.
729 group Allow an ordinary user to mount the filesystem if one of that
731 user's groups matches the group of the device. This option
732 implies the options nosuid and nodev (unless overridden by sub‐
733 sequent options, as in the option line group,dev,suid).
734 iversion
736 Every time the inode is modified, the i_version field will be
737 incremented.
738 noiversion
740 Do not increment the i_version inode field.
741 mand Allow mandatory locks on this filesystem. See fcntl(2).
743 nomand Do not allow mandatory locks on this filesystem.
745 _netdev
747 The filesystem resides on a device that requires network access
748 (used to prevent the system from attempting to mount these
749 filesystems until the network has been enabled on the system).
750 nofail Do not report errors for this device if it does not exist.
752 relatime
754 Update inode access times relative to modify or change time.
755 Access time is only updated if the previous access time was ear‐
756 lier than the current modify or change time. (Similar to
757 noatime, but it doesn't break mutt or other applications that
758 need to know if a file has been read since the last time it was
759 modified.)
760 Since Linux 2.6.30, the kernel defaults to the behavior provided
762 by this option (unless noatime was specified), and the
763 strictatime option is required to obtain traditional semantics.
764 In addition, since Linux 2.6.30, the file's last access time is
765 always updated if it is more than 1 day old.
766 norelatime
768 Do not use the relatime feature. See also the strictatime mount
769 option.
770 strictatime
772 Allows to explicitly request full atime updates. This makes it
773 possible for the kernel to default to relatime or noatime but
774 still allow userspace to override it. For more details about
775 the default system mount options see /proc/mounts.
776 nostrictatime
778 Use the kernel's default behavior for inode access time updates.
779 lazytime
781 Only update times (atime, mtime, ctime) on the in-memory version
782 of the file inode.
783 This mount option significantly reduces writes to the inode ta‐
785 ble for workloads that perform frequent random writes to preal‐
786 located files.
787 The on-disk timestamps are updated only when:
789 - the inode needs to be updated for some change unrelated to
791 file timestamps
792 - the application employs fsync(2), syncfs(2), or sync(2)
794 - an undeleted inode is evicted from memory
796 - more than 24 hours have passed since the i-node was written to
798 disk.
799 nolazytime
802 Do not use the lazytime feature.
803 suid Honor set-user-ID and set-group-ID bits or file capabilities
805 when executing programs from this filesystem.
806 nosuid Do not honor set-user-ID and set-group-ID bits or file capabili‐
808 ties when executing programs from this filesystem.
809 silent Turn on the silent flag.
811 loud Turn off the silent flag.
813 owner Allow an ordinary user to mount the filesystem if that user is
815 the owner of the device. This option implies the options nosuid
816 and nodev (unless overridden by subsequent options, as in the
817 option line owner,dev,suid).
818 remount
820 Attempt to remount an already-mounted filesystem. This is com‐
821 monly used to change the mount flags for a filesystem, espe‐
822 cially to make a readonly filesystem writable. It does not
823 change device or mount point.
824 The remount operation together with the bind flag has special
826 semantic. See above, the subsection Bind mounts.
827 The remount functionality follows the standard way the mount
829 command works with options from fstab. This means that mount
830 does not read fstab (or mtab) only when both device and dir are
831 specified.
832 mount -o remount,rw /dev/foo /dir
834 After this call all old mount options are replaced and arbitrary
836 stuff from fstab (or mtab) is ignored, except the loop= option
837 which is internally generated and maintained by the mount com‐
838 mand.
839 mount -o remount,rw /dir
841 After this call, mount reads fstab and merges these options with
843 the options from the command line (-o). If no mountpoint is
844 found in fstab, then a remount with unspecified source is
845 allowed.
846 ro Mount the filesystem read-only.
848 rw Mount the filesystem read-write.
850 sync All I/O to the filesystem should be done synchronously. In the
852 case of media with a limited number of write cycles (e.g. some
853 flash drives), sync may cause life-cycle shortening.
854 user Allow an ordinary user to mount the filesystem. The name of the
856 mounting user is written to the mtab file (or to the private
857 libmount file in /run/mount on systems without a regular mtab)
858 so that this same user can unmount the filesystem again. This
859 option implies the options noexec, nosuid, and nodev (unless
860 overridden by subsequent options, as in the option line
861 user,exec,dev,suid).
862 nouser Forbid an ordinary user to mount the filesystem. This is the
864 default; it does not imply any other options.
865 users Allow any user to mount and to unmount the filesystem, even when
867 some other ordinary user mounted it. This option implies the
868 options noexec, nosuid, and nodev (unless overridden by subse‐
869 quent options, as in the option line users,exec,dev,suid).
870 X-* All options prefixed with "X-" are interpreted as comments or as
872 userspace application-specific options. These options are not
873 stored in the user space (e.g. mtab file), nor sent to the
874 mount.type helpers nor to the mount(2) system call. The sug‐
875 gested format is X-appname.option.
876 x-* The same as X-* options, but stored permanently in the user
878 space. It means the options are also available for umount or
879 another operations. Note that maintain mount options in user
880 space is tricky, because it's necessary use libmount based tools
881 and there is no guarantee that the options will be always avail‐
882 able (for example after a move mount operation or in unshared
883 namespace).
884 Note that before util-linux v2.30 the x-* options have not been
886 maintained by libmount and stored in user space (functionality
887 was the same as have X-* now), but due to growing number of use-
888 cases (in initrd, systemd etc.) the functionality have been
889 extended to keep existing fstab configurations usable without a
890 change.
891 X-mount.mkdir[=mode]
893 Allow to make a target directory (mountpoint). The optional
894 argument mode specifies the filesystem access mode used for
895 mkdir(2) in octal notation. The default mode is 0755. This
896 functionality is supported only for root users. The option is
897 also supported as x-mount.mkdir, this notation is deprecated for
898 mount.mkdir since v2.30.
899
902 You should consult the respective man page for the filesystem first.
903 If you want to know what options the ext4 filesystem supports, then
904 check the ext4(5) man page. If that doesn't exist, you can also check
905 the corresponding mount page like mount.cifs(8). Note that you might
906 have to install the respective userland tools.
907 The following options apply only to certain filesystems. We sort them
909 by filesystem. They all follow the -o flag.
910 What options are supported depends a bit on the running kernel. More
912 info may be found in the kernel source subdirectory Documenta‐
913 tion/filesystems.
914 Mount options for adfs
917 uid=value and gid=value
918 Set the owner and group of the files in the filesystem (default:
919 uid=gid=0).
920 ownmask=value and othmask=value
922 Set the permission mask for ADFS 'owner' permissions and 'other'
923 permissions, respectively (default: 0700 and 0077, respec‐
924 tively). See also /usr/src/linux/Documentation/filesys‐
925 tems/adfs.txt.
926 Mount options for affs
929 uid=value and gid=value
930 Set the owner and group of the root of the filesystem (default:
931 uid=gid=0, but with option uid or gid without specified value,
932 the UID and GID of the current process are taken).
933 setuid=value and setgid=value
935 Set the owner and group of all files.
936 mode=value
938 Set the mode of all files to value & 0777 disregarding the orig‐
939 inal permissions. Add search permission to directories that
940 have read permission. The value is given in octal.
941 protect
943 Do not allow any changes to the protection bits on the filesys‐
944 tem.
945 usemp Set UID and GID of the root of the filesystem to the UID and GID
947 of the mount point upon the first sync or umount, and then clear
948 this option. Strange...
949 verbose
951 Print an informational message for each successful mount.
952 prefix=string
954 Prefix used before volume name, when following a link.
955 volume=string
957 Prefix (of length at most 30) used before '/' when following a
958 symbolic link.
959 reserved=value
961 (Default: 2.) Number of unused blocks at the start of the
962 device.
963 root=value
965 Give explicitly the location of the root block.
966 bs=value
968 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
969 grpquota|noquota|quota|usrquota
971 These options are accepted but ignored. (However, quota utili‐
972 ties may react to such strings in /etc/fstab.)
973 Mount options for debugfs
976 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
977 /sys/kernel/debug. As of kernel version 3.4, debugfs has the following
978 options:
979 uid=n, gid=n
981 Set the owner and group of the mountpoint.
982 mode=value
984 Sets the mode of the mountpoint.
985 Mount options for devpts
988 The devpts filesystem is a pseudo filesystem, traditionally mounted on
989 /dev/pts. In order to acquire a pseudo terminal, a process opens
990 /dev/ptmx; the number of the pseudo terminal is then made available to
991 the process and the pseudo terminal slave can be accessed as
992 /dev/pts/<number>.
993 uid=value and gid=value
995 This sets the owner or the group of newly created PTYs to the
996 specified values. When nothing is specified, they will be set
997 to the UID and GID of the creating process. For example, if
998 there is a tty group with GID 5, then gid=5 will cause newly
999 created PTYs to belong to the tty group.
1000 mode=value
1002 Set the mode of newly created PTYs to the specified value. The
1003 default is 0600. A value of mode=620 and gid=5 makes "mesg y"
1004 the default on newly created PTYs.
1005 newinstance
1007 Create a private instance of devpts filesystem, such that
1008 indices of ptys allocated in this new instance are independent
1009 of indices created in other instances of devpts.
1010 All mounts of devpts without this newinstance option share the
1012 same set of pty indices (i.e. legacy mode). Each mount of
1013 devpts with the newinstance option has a private set of pty
1014 indices.
1015 This option is mainly used to support containers in the linux
1017 kernel. It is implemented in linux kernel versions starting
1018 with 2.6.29. Further, this mount option is valid only if CON‐
1019 FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configu‐
1020 ration.
1021 To use this option effectively, /dev/ptmx must be a symbolic
1023 link to pts/ptmx. See Documentation/filesystems/devpts.txt in
1024 the linux kernel source tree for details.
1025 ptmxmode=value
1027 Set the mode for the new ptmx device node in the devpts filesys‐
1029 tem.
1030 With the support for multiple instances of devpts (see newin‐
1032 stance option above), each instance has a private ptmx node in
1033 the root of the devpts filesystem (typically /dev/pts/ptmx).
1034 For compatibility with older versions of the kernel, the default
1036 mode of the new ptmx node is 0000. ptmxmode=value specifies a
1037 more useful mode for the ptmx node and is highly recommended
1038 when the newinstance option is specified.
1039 This option is only implemented in linux kernel versions start‐
1041 ing with 2.6.29. Further, this option is valid only if CON‐
1042 FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configu‐
1043 ration.
1044 Mount options for fat
1047 (Note: fat is not a separate filesystem, but a common part of the
1048 msdos, umsdos and vfat filesystems.)
1049 blocksize={512|1024|2048}
1051 Set blocksize (default 512). This option is obsolete.
1052 uid=value and gid=value
1054 Set the owner and group of all files. (Default: the UID and GID
1055 of the current process.)
1056 umask=value
1058 Set the umask (the bitmask of the permissions that are not
1059 present). The default is the umask of the current process. The
1060 value is given in octal.
1061 dmask=value
1063 Set the umask applied to directories only. The default is the
1064 umask of the current process. The value is given in octal.
1065 fmask=value
1067 Set the umask applied to regular files only. The default is the
1068 umask of the current process. The value is given in octal.
1069 allow_utime=value
1071 This option controls the permission check of mtime/atime.
1072 20 If current process is in group of file's group ID, you
1074 can change timestamp.
1075 2 Other users can change timestamp.
1077 The default is set from `dmask' option. (If the directory is
1079 writable, utime(2) is also allowed. I.e. ~dmask & 022)
1080 Normally utime(2) checks current process is owner of the file,
1082 or it has CAP_FOWNER capability. But FAT filesystem doesn't
1083 have UID/GID on disk, so normal check is too inflexible. With
1084 this option you can relax it.
1085 check=value
1087 Three different levels of pickiness can be chosen:
1088 r[elaxed]
1090 Upper and lower case are accepted and equivalent, long
1091 name parts are truncated (e.g. verylongname.foobar
1092 becomes verylong.foo), leading and embedded spaces are
1093 accepted in each name part (name and extension).
1094 n[ormal]
1096 Like "relaxed", but many special characters (*, ?, <,
1097 spaces, etc.) are rejected. This is the default.
1098 s[trict]
1100 Like "normal", but names that contain long parts or spe‐
1101 cial characters that are sometimes used on Linux but are
1102 not accepted by MS-DOS (+, =, etc.) are rejected.
1103 codepage=value
1105 Sets the codepage for converting to shortname characters on FAT
1106 and VFAT filesystems. By default, codepage 437 is used.
1107 conv=mode
1109 This option is obsolete and may fail or being ignored.
1110 cvf_format=module
1112 Forces the driver to use the CVF (Compressed Volume File) module
1113 cvf_module instead of auto-detection. If the kernel supports
1114 kmod, the cvf_format=xxx option also controls on-demand CVF mod‐
1115 ule loading. This option is obsolete.
1116 cvf_option=option
1118 Option passed to the CVF module. This option is obsolete.
1119 debug Turn on the debug flag. A version string and a list of filesys‐
1121 tem parameters will be printed (these data are also printed if
1122 the parameters appear to be inconsistent).
1123 discard
1125 If set, causes discard/TRIM commands to be issued to the block
1126 device when blocks are freed. This is useful for SSD devices
1127 and sparse/thinly-provisioned LUNs.
1128 dos1xfloppy
1130 If set, use a fallback default BIOS Parameter Block configura‐
1131 tion, determined by backing device size. These static parame‐
1132 ters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320
1133 kiB, and 360 kiB floppies and floppy images.
1134 errors={panic|continue|remount-ro}
1136 Specify FAT behavior on critical errors: panic, continue without
1137 doing anything, or remount the partition in read-only mode
1138 (default behavior).
1139 fat={12|16|32}
1141 Specify a 12, 16 or 32 bit fat. This overrides the automatic
1142 FAT type detection routine. Use with caution!
1143 iocharset=value
1145 Character set to use for converting between 8 bit characters and
1146 16 bit Unicode characters. The default is iso8859-1. Long
1147 filenames are stored on disk in Unicode format.
1148 nfs={stale_rw|nostale_ro}
1150 Enable this only if you want to export the FAT filesystem over
1151 NFS.
1152 stale_rw: This option maintains an index (cache) of directory
1154 inodes which is used by the nfs-related code to improve look-
1155 ups. Full file operations (read/write) over NFS are supported
1156 but with cache eviction at NFS server, this could result in spu‐
1157 rious ESTALE errors.
1158 nostale_ro: This option bases the inode number and file handle
1160 on the on-disk location of a file in the FAT directory entry.
1161 This ensures that ESTALE will not be returned after a file is
1162 evicted from the inode cache. However, it means that operations
1163 such as rename, create and unlink could cause file handles that
1164 previously pointed at one file to point at a different file,
1165 potentially causing data corruption. For this reason, this
1166 option also mounts the filesystem readonly.
1167 To maintain backward compatibility, '-o nfs' is also accepted,
1169 defaulting to stale_rw.
1170 tz=UTC This option disables the conversion of timestamps between local
1172 time (as used by Windows on FAT) and UTC (which Linux uses
1173 internally). This is particularly useful when mounting devices
1174 (like digital cameras) that are set to UTC in order to avoid the
1175 pitfalls of local time.
1176 time_offset=minutes
1178 Set offset for conversion of timestamps from local time used by
1179 FAT to UTC. I.e., minutes will be subtracted from each time‐
1180 stamp to convert it to UTC used internally by Linux. This is
1181 useful when the time zone set in the kernel via settimeofday(2)
1182 is not the time zone used by the filesystem. Note that this
1183 option still does not provide correct time stamps in all cases
1184 in presence of DST - time stamps in a different DST setting will
1185 be off by one hour.
1186 quiet Turn on the quiet flag. Attempts to chown or chmod files do not
1188 return errors, although they fail. Use with caution!
1189 rodir FAT has the ATTR_RO (read-only) attribute. On Windows, the
1191 ATTR_RO of the directory will just be ignored, and is used only
1192 by applications as a flag (e.g. it's set for the customized
1193 folder).
1194 If you want to use ATTR_RO as read-only flag even for the direc‐
1196 tory, set this option.
1197 showexec
1199 If set, the execute permission bits of the file will be allowed
1200 only if the extension part of the name is .EXE, .COM, or .BAT.
1201 Not set by default.
1202 sys_immutable
1204 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag
1205 on Linux. Not set by default.
1206 flush If set, the filesystem will try to flush to disk more early than
1208 normal. Not set by default.
1209 usefree
1211 Use the "free clusters" value stored on FSINFO. It'll be used
1212 to determine number of free clusters without scanning disk. But
1213 it's not used by default, because recent Windows don't update it
1214 correctly in some case. If you are sure the "free clusters" on
1215 FSINFO is correct, by this option you can avoid scanning disk.
1216 dots, nodots, dotsOK=[yes|no]
1218 Various misguided attempts to force Unix or DOS conventions onto
1219 a FAT filesystem.
1220 Mount options for hfs
1223 creator=cccc, type=cccc
1224 Set the creator/type values as shown by the MacOS finder used
1225 for creating new files. Default values: '????'.
1226 uid=n, gid=n
1228 Set the owner and group of all files. (Default: the UID and GID
1229 of the current process.)
1230 dir_umask=n, file_umask=n, umask=n
1232 Set the umask used for all directories, all regular files, or
1233 all files and directories. Defaults to the umask of the current
1234 process.
1235 session=n
1237 Select the CDROM session to mount. Defaults to leaving that
1238 decision to the CDROM driver. This option will fail with any‐
1239 thing but a CDROM as underlying device.
1240 part=n Select partition number n from the device. Only makes sense for
1242 CDROMs. Defaults to not parsing the partition table at all.
1243 quiet Don't complain about invalid mount options.
1245 Mount options for hpfs
1248 uid=value and gid=value
1249 Set the owner and group of all files. (Default: the UID and GID
1250 of the current process.)
1251 umask=value
1253 Set the umask (the bitmask of the permissions that are not
1254 present). The default is the umask of the current process. The
1255 value is given in octal.
1256 case={lower|asis}
1258 Convert all files names to lower case, or leave them. (Default:
1259 case=lower.)
1260 conv=mode
1262 This option is obsolete and may fail or being ignored.
1263 nocheck
1265 Do not abort mounting when certain consistency checks fail.
1266 Mount options for iso9660
1269 ISO 9660 is a standard describing a filesystem structure to be used on
1270 CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1271 udf filesystem.)
1272 Normal iso9660 filenames appear in an 8.3 format (i.e., DOS-like
1274 restrictions on filename length), and in addition all characters are in
1275 upper case. Also there is no field for file ownership, protection,
1276 number of links, provision for block/character devices, etc.
1277 Rock Ridge is an extension to iso9660 that provides all of these UNIX-
1279 like features. Basically there are extensions to each directory record
1280 that supply all of the additional information, and when Rock Ridge is
1281 in use, the filesystem is indistinguishable from a normal UNIX filesys‐
1282 tem (except that it is read-only, of course).
1283 norock Disable the use of Rock Ridge extensions, even if available.
1285 Cf. map.
1286 nojoliet
1288 Disable the use of Microsoft Joliet extensions, even if avail‐
1289 able. Cf. map.
1290 check={r[elaxed]|s[trict]}
1292 With check=relaxed, a filename is first converted to lower case
1293 before doing the lookup. This is probably only meaningful
1294 together with norock and map=normal. (Default: check=strict.)
1295 uid=value and gid=value
1297 Give all files in the filesystem the indicated user or group id,
1298 possibly overriding the information found in the Rock Ridge
1299 extensions. (Default: uid=0,gid=0.)
1300 map={n[ormal]|o[ff]|a[corn]}
1302 For non-Rock Ridge volumes, normal name translation maps upper
1303 to lower case ASCII, drops a trailing `;1', and converts `;' to
1304 `.'. With map=off no name translation is done. See norock.
1305 (Default: map=normal.) map=acorn is like map=normal but also
1306 apply Acorn extensions if present.
1307 mode=value
1309 For non-Rock Ridge volumes, give all files the indicated mode.
1310 (Default: read and execute permission for everybody.) Octal
1311 mode values require a leading 0.
1312 unhide Also show hidden and associated files. (If the ordinary files
1314 and the associated or hidden files have the same filenames, this
1315 may make the ordinary files inaccessible.)
1316 block={512|1024|2048}
1318 Set the block size to the indicated value. (Default:
1319 block=1024.)
1320 conv=mode
1322 This option is obsolete and may fail or being ignored.
1323 cruft If the high byte of the file length contains other garbage, set
1325 this mount option to ignore the high order bits of the file
1326 length. This implies that a file cannot be larger than 16 MB.
1327 session=x
1329 Select number of session on multisession CD.
1330 sbsector=xxx
1332 Session begins from sector xxx.
1333 The following options are the same as for vfat and specifying them only
1335 makes sense when using discs encoded using Microsoft's Joliet exten‐
1336 sions.
1337 iocharset=value
1339 Character set to use for converting 16 bit Unicode characters on
1340 CD to 8 bit characters. The default is iso8859-1.
1341 utf8 Convert 16 bit Unicode characters on CD to UTF-8.
1343 Mount options for jfs
1346 iocharset=name
1347 Character set to use for converting from Unicode to ASCII. The
1348 default is to do no conversion. Use iocharset=utf8 for UTF8
1349 translations. This requires CONFIG_NLS_UTF8 to be set in the
1350 kernel .config file.
1351 resize=value
1353 Resize the volume to value blocks. JFS only supports growing a
1354 volume, not shrinking it. This option is only valid during a
1355 remount, when the volume is mounted read-write. The resize key‐
1356 word with no value will grow the volume to the full size of the
1357 partition.
1358 nointegrity
1360 Do not write to the journal. The primary use of this option is
1361 to allow for higher performance when restoring a volume from
1362 backup media. The integrity of the volume is not guaranteed if
1363 the system abnormally ends.
1364 integrity
1366 Default. Commit metadata changes to the journal. Use this
1367 option to remount a volume where the nointegrity option was pre‐
1368 viously specified in order to restore normal behavior.
1369 errors={continue|remount-ro|panic}
1371 Define the behavior when an error is encountered. (Either
1372 ignore errors and just mark the filesystem erroneous and con‐
1373 tinue, or remount the filesystem read-only, or panic and halt
1374 the system.)
1375 noquota|quota|usrquota|grpquota
1377 These options are accepted but ignored.
1378 Mount options for msdos
1381 See mount options for fat. If the msdos filesystem detects an incon‐
1382 sistency, it reports an error and sets the file system read-only. The
1383 filesystem can be made writable again by remounting it.
1384 Mount options for ncpfs
1387 Just like nfs, the ncpfs implementation expects a binary argument (a
1388 struct ncp_mount_data) to the mount system call. This argument is con‐
1389 structed by ncpmount(8) and the current version of mount (2.12) does
1390 not know anything about ncpfs.
1391 Mount options for ntfs
1394 iocharset=name
1395 Character set to use when returning file names. Unlike VFAT,
1396 NTFS suppresses names that contain nonconvertible characters.
1397 Deprecated.
1398 nls=name
1400 New name for the option earlier called iocharset.
1401 utf8 Use UTF-8 for converting file names.
1403 uni_xlate={0|1|2}
1405 For 0 (or `no' or `false'), do not use escape sequences for
1406 unknown Unicode characters. For 1 (or `yes' or `true') or 2,
1407 use vfat-style 4-byte escape sequences starting with ":". Here
1408 2 give a little-endian encoding and 1 a byteswapped bigendian
1409 encoding.
1410 posix=[0|1]
1412 If enabled (posix=1), the filesystem distinguishes between upper
1413 and lower case. The 8.3 alias names are presented as hard links
1414 instead of being suppressed. This option is obsolete.
1415 uid=value, gid=value and umask=value
1417 Set the file permission on the filesystem. The umask value is
1418 given in octal. By default, the files are owned by root and not
1419 readable by somebody else.
1420 Mount options for overlay
1423 Since Linux 3.18 the overlay pseudo filesystem implements a union mount
1424 for other filesystems.
1425 An overlay filesystem combines two filesystems - an upper filesystem
1427 and a lower filesystem. When a name exists in both filesystems, the
1428 object in the upper filesystem is visible while the object in the lower
1429 filesystem is either hidden or, in the case of directories, merged with
1430 the upper object.
1431 The lower filesystem can be any filesystem supported by Linux and does
1433 not need to be writable. The lower filesystem can even be another
1434 overlayfs. The upper filesystem will normally be writable and if it is
1435 it must support the creation of trusted.* extended attributes, and must
1436 provide a valid d_type in readdir responses, so NFS is not suitable.
1437 A read-only overlay of two read-only filesystems may use any filesystem
1439 type. The options lowerdir and upperdir are combined into a merged
1440 directory by using:
1441 mount -t overlay overlay \
1443 -olowerdir=/lower,upperdir=/upper,workdir=/work /merged
1444 lowerdir=directory
1447 Any filesystem, does not need to be on a writable filesystem.
1448 upperdir=directory
1450 The upperdir is normally on a writable filesystem.
1451 workdir=directory
1453 The workdir needs to be an empty directory on the same filesys‐
1454 tem as upperdir.
1455 Mount options for reiserfs
1458 Reiserfs is a journaling filesystem.
1459 conv Instructs version 3.6 reiserfs software to mount a version 3.5
1461 filesystem, using the 3.6 format for newly created objects.
1462 This filesystem will no longer be compatible with reiserfs 3.5
1463 tools.
1464 hash={rupasov|tea|r5|detect}
1466 Choose which hash function reiserfs will use to find files
1467 within directories.
1468 rupasov
1470 A hash invented by Yury Yu. Rupasov. It is fast and pre‐
1471 serves locality, mapping lexicographically close file
1472 names to close hash values. This option should not be
1473 used, as it causes a high probability of hash collisions.
1474 tea A Davis-Meyer function implemented by Jeremy
1476 Fitzhardinge. It uses hash permuting bits in the name.
1477 It gets high randomness and, therefore, low probability
1478 of hash collisions at some CPU cost. This may be used if
1479 EHASHCOLLISION errors are experienced with the r5 hash.
1480 r5 A modified version of the rupasov hash. It is used by
1482 default and is the best choice unless the filesystem has
1483 huge directories and unusual file-name patterns.
1484 detect Instructs mount to detect which hash function is in use
1486 by examining the filesystem being mounted, and to write
1487 this information into the reiserfs superblock. This is
1488 only useful on the first mount of an old format filesys‐
1489 tem.
1490 hashed_relocation
1492 Tunes the block allocator. This may provide performance
1493 improvements in some situations.
1494 no_unhashed_relocation
1496 Tunes the block allocator. This may provide performance
1497 improvements in some situations.
1498 noborder
1500 Disable the border allocator algorithm invented by Yury Yu.
1501 Rupasov. This may provide performance improvements in some sit‐
1502 uations.
1503 nolog Disable journaling. This will provide slight performance
1505 improvements in some situations at the cost of losing reiserfs's
1506 fast recovery from crashes. Even with this option turned on,
1507 reiserfs still performs all journaling operations, save for
1508 actual writes into its journaling area. Implementation of nolog
1509 is a work in progress.
1510 notail By default, reiserfs stores small files and `file tails'
1512 directly into its tree. This confuses some utilities such as
1513 LILO(8). This option is used to disable packing of files into
1514 the tree.
1515 replayonly
1517 Replay the transactions which are in the journal, but do not
1518 actually mount the filesystem. Mainly used by reiserfsck.
1519 resize=number
1521 A remount option which permits online expansion of reiserfs par‐
1522 titions. Instructs reiserfs to assume that the device has num‐
1523 ber blocks. This option is designed for use with devices which
1524 are under logical volume management (LVM). There is a special
1525 resizer utility which can be obtained from
1526 ftp://ftp.namesys.com/pub/reiserfsprogs.
1527 user_xattr
1529 Enable Extended User Attributes. See the attr(5) manual page.
1530 acl Enable POSIX Access Control Lists. See the acl(5) manual page.
1532 barrier=none / barrier=flush
1534 This disables / enables the use of write barriers in the jour‐
1535 naling code. barrier=none disables, barrier=flush enables
1536 (default). This also requires an IO stack which can support
1537 barriers, and if reiserfs gets an error on a barrier write, it
1538 will disable barriers again with a warning. Write barriers
1539 enforce proper on-disk ordering of journal commits, making
1540 volatile disk write caches safe to use, at some performance
1541 penalty. If your disks are battery-backed in one way or
1542 another, disabling barriers may safely improve performance.
1543 Mount options for ubifs
1546 UBIFS is a flash filesystem which works on top of UBI volumes. Note
1547 that atime is not supported and is always turned off.
1548 The device name may be specified as
1550 ubiX_Y UBI device number X, volume number Y
1551 ubiY UBI device number 0, volume number Y
1553 ubiX:NAME
1555 UBI device number X, volume with name NAME
1556 ubi:NAME
1558 UBI device number 0, volume with name NAME
1559 Alternative ! separator may be used instead of :.
1560 The following mount options are available:
1562 bulk_read
1564 Enable bulk-read. VFS read-ahead is disabled because it slows
1565 down the file system. Bulk-Read is an internal optimization.
1566 Some flashes may read faster if the data are read at one go,
1567 rather than at several read requests. For example, OneNAND can
1568 do "read-while-load" if it reads more than one NAND page.
1569 no_bulk_read
1571 Do not bulk-read. This is the default.
1572 chk_data_crc
1574 Check data CRC-32 checksums. This is the default.
1575 no_chk_data_crc.
1577 Do not check data CRC-32 checksums. With this option, the
1578 filesystem does not check CRC-32 checksum for data, but it does
1579 check it for the internal indexing information. This option
1580 only affects reading, not writing. CRC-32 is always calculated
1581 when writing the data.
1582 compr={none|lzo|zlib}
1584 Select the default compressor which is used when new files are
1585 written. It is still possible to read compressed files if
1586 mounted with the none option.
1587 Mount options for udf
1590 UDF is the "Universal Disk Format" filesystem defined by OSTA, the
1591 Optical Storage Technology Association, and is often used for DVD-ROM,
1592 frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, how‐
1593 ever, perfectly usable by itself on disk drives, flash drives and other
1594 block devices. See also iso9660.
1595 uid= Make all files in the filesystem belong to the given user.
1597 uid=forget can be specified independently of (or usually in
1598 addition to) uid=<user> and results in UDF not storing uids to
1599 the media. In fact the recorded uid is the 32-bit overflow uid
1600 -1 as defined by the UDF standard. The value is given as either
1601 <user> which is a valid user name or the corresponding decimal
1602 user id, or the special string "forget".
1603 gid= Make all files in the filesystem belong to the given group.
1605 gid=forget can be specified independently of (or usually in
1606 addition to) gid=<group> and results in UDF not storing gids to
1607 the media. In fact the recorded gid is the 32-bit overflow gid
1608 -1 as defined by the UDF standard. The value is given as either
1609 <group> which is a valid group name or the corresponding decimal
1610 group id, or the special string "forget".
1611 umask= Mask out the given permissions from all inodes read from the
1613 filesystem. The value is given in octal.
1614 mode= If mode= is set the permissions of all non-directory inodes read
1616 from the filesystem will be set to the given mode. The value is
1617 given in octal.
1618 dmode= If dmode= is set the permissions of all directory inodes read
1620 from the filesystem will be set to the given dmode. The value is
1621 given in octal.
1622 bs= Set the block size. Default value prior to kernel version 2.6.30
1624 was 2048. Since 2.6.30 and prior to 4.11 it was logical device
1625 block size with fallback to 2048. Since 4.11 it is logical block
1626 size with fallback to any valid block size between logical
1627 device block size and 4096.
1628 For other details see the mkudffs(8) 2.0+ manpage, sections COM‐
1630 PATIBILITY and BLOCK SIZE.
1631 unhide Show otherwise hidden files.
1633 undelete
1635 Show deleted files in lists.
1636 adinicb
1638 Embed data in the inode. (default)
1639 noadinicb
1641 Don't embed data in the inode.
1642 shortad
1644 Use short UDF address descriptors.
1645 longad Use long UDF address descriptors. (default)
1647 nostrict
1649 Unset strict conformance.
1650 iocharset=
1652 Set the NLS character set. This requires kernel compiled with
1653 CONFIG_UDF_NLS option.
1654 utf8 Set the UTF-8 character set.
1656 Mount options for debugging and disaster recovery
1658 novrs Ignore the Volume Recognition Sequence and attempt to mount any‐
1659 way.
1660 session=
1662 Select the session number for multi-session recorded optical
1663 media. (default= last session)
1664 anchor=
1666 Override standard anchor location. (default= 256)
1667 lastblock=
1669 Set the last block of the filesystem.
1670 Unused historical mount options that may be encountered and should be
1672 removed
1673 uid=ignore
1674 Ignored, use uid=<user> instead.
1675 gid=ignore
1677 Ignored, use gid=<group> instead.
1678 volume=
1680 Unimplemented and ignored.
1681 partition=
1683 Unimplemented and ignored.
1684 fileset=
1686 Unimplemented and ignored.
1687 rootdir=
1689 Unimplemented and ignored.
1690 Mount options for ufs
1693 ufstype=value
1694 UFS is a filesystem widely used in different operating systems.
1695 The problem are differences among implementations. Features of
1696 some implementations are undocumented, so its hard to recognize
1697 the type of ufs automatically. That's why the user must specify
1698 the type of ufs by mount option. Possible values are:
1699 old Old format of ufs, this is the default, read only.
1701 (Don't forget to give the -r option.)
1702 44bsd For filesystems created by a BSD-like system (NetBSD,
1704 FreeBSD, OpenBSD).
1705 ufs2 Used in FreeBSD 5.x supported as read-write.
1707 5xbsd Synonym for ufs2.
1709 sun For filesystems created by SunOS or Solaris on Sparc.
1711 sunx86 For filesystems created by Solaris on x86.
1713 hp For filesystems created by HP-UX, read-only.
1715 nextstep
1717 For filesystems created by NeXTStep (on NeXT station)
1718 (currently read only).
1719 nextstep-cd
1721 For NextStep CDROMs (block_size == 2048), read-only.
1722 openstep
1724 For filesystems created by OpenStep (currently read
1725 only). The same filesystem type is also used by Mac OS
1726 X.
1727 onerror=value
1730 Set behavior on error:
1731 panic If an error is encountered, cause a kernel panic.
1733 [lock|umount|repair]
1735 These mount options don't do anything at present; when an
1736 error is encountered only a console message is printed.
1737 Mount options for umsdos
1740 See mount options for msdos. The dotsOK option is explicitly killed by
1741 umsdos.
1742 Mount options for vfat
1745 First of all, the mount options for fat are recognized. The dotsOK
1746 option is explicitly killed by vfat. Furthermore, there are
1747 uni_xlate
1749 Translate unhandled Unicode characters to special escaped
1750 sequences. This lets you backup and restore filenames that are
1751 created with any Unicode characters. Without this option, a '?'
1752 is used when no translation is possible. The escape character
1753 is ':' because it is otherwise invalid on the vfat filesystem.
1754 The escape sequence that gets used, where u is the Unicode char‐
1755 acter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
1756 posix Allow two files with names that only differ in case. This
1758 option is obsolete.
1759 nonumtail
1761 First try to make a short name without sequence number, before
1762 trying name~num.ext.
1763 utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is
1765 used by the console. It can be enabled for the filesystem with
1766 this option or disabled with utf8=0, utf8=no or utf8=false. If
1767 `uni_xlate' gets set, UTF8 gets disabled.
1768 shortname=mode
1770 Defines the behavior for creation and display of filenames which
1771 fit into 8.3 characters. If a long name for a file exists, it
1772 will always be the preferred one for display. There are four
1773 modes:
1774 lower Force the short name to lower case upon display; store a
1776 long name when the short name is not all upper case.
1777 win95 Force the short name to upper case upon display; store a
1779 long name when the short name is not all upper case.
1780 winnt Display the short name as is; store a long name when the
1782 short name is not all lower case or all upper case.
1783 mixed Display the short name as is; store a long name when the
1785 short name is not all upper case. This mode is the
1786 default since Linux 2.6.32.
1787 Mount options for usbfs
1790 devuid=uid and devgid=gid and devmode=mode
1791 Set the owner and group and mode of the device files in the
1792 usbfs filesystem (default: uid=gid=0, mode=0644). The mode is
1793 given in octal.
1794 busuid=uid and busgid=gid and busmode=mode
1796 Set the owner and group and mode of the bus directories in the
1797 usbfs filesystem (default: uid=gid=0, mode=0555). The mode is
1798 given in octal.
1799 listuid=uid and listgid=gid and listmode=mode
1801 Set the owner and group and mode of the file devices (default:
1802 uid=gid=0, mode=0444). The mode is given in octal.
1803
1806 One further possible type is a mount via the loop device. For example,
1807 the command
1808 mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3
1810 will set up the loop device /dev/loop3 to correspond to the file
1812 /tmp/disk.img, and then mount this device on /mnt.
1813 If no explicit loop device is mentioned (but just an option `-o loop'
1815 is given), then mount will try to find some unused loop device and use
1816 that, for example
1817 mount /tmp/disk.img /mnt -o loop
1819 The mount command automatically creates a loop device from a regular
1821 file if a filesystem type is not specified or the filesystem is known
1822 for libblkid, for example:
1823 mount /tmp/disk.img /mnt
1825 mount -t ext4 /tmp/disk.img /mnt
1827 This type of mount knows about three options, namely loop, offset and
1829 sizelimit, that are really options to losetup(8). (These options can
1830 be used in addition to those specific to the filesystem type.)
1831 Since Linux 2.6.25 auto-destruction of loop devices is supported, mean‐
1833 ing that any loop device allocated by mount will be freed by umount
1834 independently of /etc/mtab.
1835 You can also free a loop device by hand, using losetup -d or umount -d.
1837 Since util-linux v2.29 mount command re-uses the loop device rather
1839 than initialize a new device if the same backing file is already used
1840 for some loop device with the same offset and sizelimit. This is neces‐
1841 sary to avoid a filesystem corruption.
1842
1845 mount has the following return codes (the bits can be ORed):
1846 0 success
1848 1 incorrect invocation or permissions
1850 2 system error (out of memory, cannot fork, no more loop devices)
1852 4 internal mount bug
1854 8 user interrupt
1856 16 problems writing or locking /etc/mtab
1858 32 mount failure
1860 64 some mount succeeded
1862 The command mount -a returns 0 (all succeeded), 32 (all failed), or 64
1864 (some failed, some succeeded).
1865
1868 The syntax of external mount helpers is:
1869 /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t
1871 type.subtype]
1872 where the suffix is the filesystem type and the -sfnvoN options have
1874 the same meaning as the normal mount options. The -t option is used
1875 for filesystems with subtypes support (for example /sbin/mount.fuse -t
1876 fuse.sshfs).
1877 The command mount does not pass the mount options unbindable, runbind‐
1879 able, private, rprivate, slave, rslave, shared, rshared, auto, noauto,
1880 comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers.
1881 All other options are used in a comma-separated list as argument to the
1882 -o option.
1883
1886 See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section
1887 above.
1888 /etc/fstab filesystem table
1890 /run/mount libmount private runtime directory
1892 /etc/mtab table of mounted filesystems or symlink to
1894 /proc/mounts
1895 /etc/mtab~ lock file (unused on systems with mtab symlink)
1897 /etc/mtab.tmp temporary file (unused on systems with mtab symlink)
1899 /etc/filesystems a list of filesystem types to try
1901
1903 LIBMOUNT_FSTAB=<path>
1904 overrides the default location of the fstab file (ignored for
1905 suid)
1906 LIBMOUNT_MTAB=<path>
1908 overrides the default location of the mtab file (ignored for
1909 suid)
1910 LIBMOUNT_DEBUG=all
1912 enables libmount debug output
1913 LIBBLKID_DEBUG=all
1915 enables libblkid debug output
1916 LOOPDEV_DEBUG=all
1918 enables loop device setup debug output
1919
1921 mount(2), umount(2), umount(8), fstab(5), nfs(5), xfs(5), e2label(8),
1922 findmnt(8), losetup(8), mke2fs(8), mountd(8), nfsd(8), swapon(8),
1923 tune2fs(8), xfs_admin(8)
1924
1926 It is possible for a corrupted filesystem to cause a crash.
1927 Some Linux filesystems don't support -o sync nor -o dirsync (the ext2,
1929 ext3, ext4, fat and vfat filesystems do support synchronous updates (a
1930 la BSD) when mounted with the sync option).
1931 The -o remount may not be able to change mount parameters (all ext2fs-
1933 specific parameters, except sb, are changeable with a remount, for
1934 example, but you can't change gid or umask for the fatfs).
1935 It is possible that the files /etc/mtab and /proc/mounts don't match on
1937 systems with a regular mtab file. The first file is based only on the
1938 mount command options, but the content of the second file also depends
1939 on the kernel and others settings (e.g. on a remote NFS server -- in
1940 certain cases the mount command may report unreliable information about
1941 an NFS mount point and the /proc/mounts file usually contains more
1942 reliable information.) This is another reason to replace the mtab file
1943 with a symlink to the /proc/mounts file.
1944 Checking files on NFS filesystems referenced by file descriptors (i.e.
1946 the fcntl and ioctl families of functions) may lead to inconsistent
1947 results due to the lack of a consistency check in the kernel even if
1948 noac is used.
1949 The loop option with the offset or sizelimit options used may fail when
1951 using older kernels if the mount command can't confirm that the size of
1952 the block device has been configured as requested. This situation can
1953 be worked around by using the losetup command manually before calling
1954 mount with the configured loop device.
1955
1957 A mount command existed in Version 5 AT&T UNIX.
1958
1960 Karel Zak <kzak@redhat.com>
1961
1963 The mount command is part of the util-linux package and is available
1964 from https://www.kernel.org/pub/linux/utils/util-linux/.
1965util-linux August 2015 MOUNT(8)