1MOUNT(8) System Administration MOUNT(8)
2
3
4
6 mount - mount a filesystem
7
9 mount [-h|-V]
10
11 mount [-l] [-t fstype]
12
13 mount -a [-fFnrsvw] [-t fstype] [-O optlist]
14
15 mount [-fnrsvw] [-o options] device|mountpoint
16
17 mount [-fnrsvw] [-t fstype] [-o options] device mountpoint
18
19 mount --bind|--rbind|--move olddir newdir
20
21 mount --make-{shared|slave|private|unbindable|rshared|rslave|rpri‐
22 vate|runbindable} mountpoint
23
25 All files accessible in a Unix system are arranged in one big tree, the
26 file hierarchy, rooted at /. These files can be spread out over sev‐
27 eral devices. The mount command serves to attach the filesystem found
28 on some device to the big file tree. Conversely, the umount(8) command
29 will detach it again. The filesystem is used to control how data is
30 stored on the device or provided in a virtual way by network or other
31 services.
32
33 The standard form of the mount command is:
34
35 mount -t type device dir
36
37 This tells the kernel to attach the filesystem found on device (which
38 is of type type) at the directory dir. The option -t type is optional.
39 The mount command is usually able to detect a filesystem. The root
40 permissions are necessary to mount a filesystem by default. See sec‐
41 tion "Non-superuser mounts" below for more details. The previous con‐
42 tents (if any) and owner and mode of dir become invisible, and as long
43 as this filesystem remains mounted, the pathname dir refers to the root
44 of the filesystem on device.
45
46 If only the directory or the device is given, for example:
47
48 mount /dir
49
50 then mount looks for a mountpoint (and if not found then for a device)
51 in the /etc/fstab file. It's possible to use the --target or --source
52 options to avoid ambiguous interpretation of the given argument. For
53 example:
54
55 mount --target /mountpoint
56
57
58 The same filesystem may be mounted more than once, and in some cases
59 (e.g., network filesystems) the same filesystem may be mounted on the
60 same mountpoint multiple times. The mount command does not implement
61 any policy to control this behavior. All behavior is controlled by the
62 kernel and it is usually specific to the filesystem driver. The excep‐
63 tion is --all, in this case already mounted filesystems are ignored
64 (see --all below for more details).
65
66
67 Listing the mounts
68 The listing mode is maintained for backward compatibility only.
69
70 For more robust and customizable output use findmnt(8), especially in
71 your scripts. Note that control characters in the mountpoint name are
72 replaced with '?'.
73
74 The following command lists all mounted filesystems (of type type):
75
76 mount [-l] [-t type]
77
78 The option -l adds labels to this listing. See below.
79
80
81 Indicating the device and filesystem
82 Most devices are indicated by a filename (of a block special device),
83 like /dev/sda1, but there are other possibilities. For example, in the
84 case of an NFS mount, device may look like knuth.cwi.nl:/dir.
85
86 The device names of disk partitions are unstable; hardware reconfigura‐
87 tion, and adding or removing a device can cause changes in names. This
88 is the reason why it's strongly recommended to use filesystem or parti‐
89 tion identifiers like UUID or LABEL. Currently supported identifiers
90 (tags):
91
92 LABEL=label
93 Human readable filesystem identifier. See also -L.
94
95 UUID=uuid
96 Filesystem universally unique identifier. The format of
97 the UUID is usually a series of hex digits separated by
98 hyphens. See also -U.
99
100 Note that mount(8) uses UUIDs as strings. The UUIDs from
101 the command line or from fstab(5) are not converted to
102 internal binary representation. The string representa‐
103 tion of the UUID should be based on lower case charac‐
104 ters.
105
106 PARTLABEL=label
107 Human readable partition identifier. This identifier is
108 independent on filesystem and does not change by mkfs or
109 mkswap operations It's supported for example for GUID
110 Partition Tables (GPT).
111
112 PARTUUID=uuid
113 Partition universally unique identifier. This identifier
114 is independent on filesystem and does not change by mkfs
115 or mkswap operations It's supported for example for GUID
116 Partition Tables (GPT).
117
118 ID=id Hardware block device ID as generated by udevd. This
119 identifier is usually based on WWN (unique storage iden‐
120 tifier) and assigned by the hardware manufacturer. See
121 ls /dev/disk/by-id for more details, this directory and
122 running udevd is required. This identifier is not recom‐
123 mended for generic use as the identifier is not strictly
124 defined and it depends on udev, udev rules and hardware.
125
126 The command lsblk --fs provides an overview of filesystems, LABELs and
127 UUIDs on available block devices. The command blkid -p <device> pro‐
128 vides details about a filesystem on the specified device.
129
130 Don't forget that there is no guarantee that UUIDs and labels are
131 really unique, especially if you move, share or copy the device. Use
132 lsblk -o +UUID,PARTUUID to verify that the UUIDs are really unique in
133 your system.
134
135 The recommended setup is to use tags (e.g. UUID=uuid) rather than
136 /dev/disk/by-{label,uuid,id,partuuid,partlabel} udev symlinks in the
137 /etc/fstab file. Tags are more readable, robust and portable. The
138 mount(8) command internally uses udev symlinks, so the use of symlinks
139 in /etc/fstab has no advantage over tags. For more details see lib‐
140 blkid(3).
141
142 The proc filesystem is not associated with a special device, and when
143 mounting it, an arbitrary keyword—for example, proc—can be used instead
144 of a device specification. (The customary choice none is less fortu‐
145 nate: the error message `none already mounted' from mount can be con‐
146 fusing.)
147
148
149 The files /etc/fstab, /etc/mtab and /proc/mounts
150 The file /etc/fstab (see fstab(5)), may contain lines describing what
151 devices are usually mounted where, using which options. The default
152 location of the fstab(5) file can be overridden with the --fstab path
153 command-line option (see below for more details).
154
155 The command
156
157 mount -a [-t type] [-O optlist]
158
159 (usually given in a bootscript) causes all filesystems mentioned in
160 fstab (of the proper type and/or having or not having the proper
161 options) to be mounted as indicated, except for those whose line con‐
162 tains the noauto keyword. Adding the -F option will make mount fork,
163 so that the filesystems are mounted in parallel.
164
165 When mounting a filesystem mentioned in fstab or mtab, it suffices to
166 specify on the command line only the device, or only the mount point.
167
168 The programs mount and umount traditionally maintained a list of cur‐
169 rently mounted filesystems in the file /etc/mtab. The support for reg‐
170 ular classic /etc/mtab is completely disabled at compile time by
171 default, because on current Linux systems it is better to make
172 /etc/mtab a symlink to /proc/mounts instead. The regular mtab file
173 maintained in userspace cannot reliably work with namespaces, contain‐
174 ers and other advanced Linux features. If the regular mtab support is
175 enabled, then it's possible to use the file as well as the symlink.
176
177 If no arguments are given to mount, the list of mounted filesystems is
178 printed.
179
180 If you want to override mount options from /etc/fstab, you have to use
181 the -o option:
182
183 mount device|dir -o options
184
185 and then the mount options from the command line will be appended to
186 the list of options from /etc/fstab. This default behaviour can be
187 changed using the --options-mode command-line option. The usual behav‐
188 ior is that the last option wins if there are conflicting ones.
189
190 The mount program does not read the /etc/fstab file if both device (or
191 LABEL, UUID, ID, PARTUUID or PARTLABEL) and dir are specified. For
192 example, to mount device foo at /dir:
193
194 mount /dev/foo /dir
195
196 This default behaviour can be changed by using the
197 --options-source-force command-line option to always read configuration
198 from fstab. For non-root users mount always reads the fstab configura‐
199 tion.
200
201
202 Non-superuser mounts
203 Normally, only the superuser can mount filesystems. However, when
204 fstab contains the user option on a line, anybody can mount the corre‐
205 sponding filesystem.
206
207 Thus, given a line
208
209 /dev/cdrom /cd iso9660 ro,user,noauto,unhide
210
211 any user can mount the iso9660 filesystem found on an inserted CDROM
212 using the command:
213
214 mount /cd
215
216 Note that mount is very strict about non-root users and all paths spec‐
217 ified on command line are verified before fstab is parsed or a helper
218 program is executed. It's strongly recommended to use a valid mount‐
219 point to specify filesystem, otherwise mount may fail. For example it's
220 a bad idea to use NFS or CIFS source on command line.
221
222 Since util-linux 2.35, mount does not exit when user permissions are
223 inadequate according to libmount's internal security rules. Instead,
224 it drops suid permissions and continues as regular non-root user. This
225 behavior supports use-cases where root permissions are not necessary
226 (e.g., fuse filesystems, user namespaces, etc).
227
228 For more details, see fstab(5). Only the user that mounted a filesys‐
229 tem can unmount it again. If any user should be able to unmount it,
230 then use users instead of user in the fstab line. The owner option is
231 similar to the user option, with the restriction that the user must be
232 the owner of the special file. This may be useful e.g. for /dev/fd if
233 a login script makes the console user owner of this device. The group
234 option is similar, with the restriction that the user must be a member
235 of the group of the special file.
236
237
238 Bind mount operation
239 Remount part of the file hierarchy somewhere else. The call is:
240
241 mount --bind olddir newdir
242
243 or by using this fstab entry:
244
245 /olddir /newdir none bind
246
247 After this call the same contents are accessible in two places.
248
249 It is important to understand that "bind" does not create any second-
250 class or special node in the kernel VFS. The "bind" is just another
251 operation to attach a filesystem. There is nowhere stored information
252 that the filesystem has been attached by a "bind" operation. The olddir
253 and newdir are independent and the olddir may be unmounted.
254
255 One can also remount a single file (on a single file). It's also pos‐
256 sible to use a bind mount to create a mountpoint from a regular direc‐
257 tory, for example:
258
259 mount --bind foo foo
260
261 The bind mount call attaches only (part of) a single filesystem, not
262 possible submounts. The entire file hierarchy including submounts can
263 be attached a second place by using:
264
265 mount --rbind olddir newdir
266
267 Note that the filesystem mount options maintained by the kernel will
268 remain the same as those on the original mount point. The userspace
269 mount options (e.g., _netdev) will not be copied by mount and it's nec‐
270 essary to explicitly specify the options on the mount command line.
271
272 Since util-linux 2.27 mount(8) permits changing the mount options by
273 passing the relevant options along with --bind. For example:
274
275 mount -o bind,ro foo foo
276
277 This feature is not supported by the Linux kernel; it is implemented in
278 userspace by an additional mount(2) remounting system call. This solu‐
279 tion is not atomic.
280
281 The alternative (classic) way to create a read-only bind mount is to
282 use the remount operation, for example:
283
284 mount --bind olddir newdir
285 mount -o remount,bind,ro olddir newdir
286
287 Note that a read-only bind will create a read-only mountpoint (VFS
288 entry), but the original filesystem superblock will still be writable,
289 meaning that the olddir will be writable, but the newdir will be read-
290 only.
291
292 It's also possible to change nosuid, nodev, noexec, noatime, nodiratime
293 and relatime VFS entry flags via a "remount,bind" operation. The other
294 flags (for example filesystem-specific flags) are silently ignored.
295 It's impossible to change mount options recursively (for example with
296 -o rbind,ro).
297
298 Since util-linux 2.31, mount ignores the bind flag from /etc/fstab on a
299 remount operation (if "-o remount" is specified on command line). This
300 is necessary to fully control mount options on remount by command line.
301 In previous versions the bind flag has been always applied and it was
302 impossible to re-define mount options without interaction with the bind
303 semantic. This mount(8) behavior does not affect situations when
304 "remount,bind" is specified in the /etc/fstab file.
305
306
307 The move operation
308 Move a mounted tree to another place (atomically). The call is:
309
310 mount --move olddir newdir
311
312 This will cause the contents which previously appeared under olddir to
313 now be accessible under newdir. The physical location of the files is
314 not changed. Note that olddir has to be a mountpoint.
315
316 Note also that moving a mount residing under a shared mount is invalid
317 and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current
318 propagation flags.
319
320
321 Shared subtree operations
322 Since Linux 2.6.15 it is possible to mark a mount and its submounts as
323 shared, private, slave or unbindable. A shared mount provides the
324 ability to create mirrors of that mount such that mounts and unmounts
325 within any of the mirrors propagate to the other mirror. A slave mount
326 receives propagation from its master, but not vice versa. A private
327 mount carries no propagation abilities. An unbindable mount is a pri‐
328 vate mount which cannot be cloned through a bind operation. The
329 detailed semantics are documented in Documentation/filesystems/shared‐
330 subtree.txt file in the kernel source tree; see also mount_names‐
331 paces(7).
332
333 Supported operations are:
334
335 mount --make-shared mountpoint
336 mount --make-slave mountpoint
337 mount --make-private mountpoint
338 mount --make-unbindable mountpoint
339
340 The following commands allow one to recursively change the type of all
341 the mounts under a given mountpoint.
342
343 mount --make-rshared mountpoint
344 mount --make-rslave mountpoint
345 mount --make-rprivate mountpoint
346 mount --make-runbindable mountpoint
347
348 mount(8) does not read fstab(5) when a --make-* operation is requested.
349 All necessary information has to be specified on the command line.
350
351 Note that the Linux kernel does not allow changing multiple propagation
352 flags with a single mount(2) system call, and the flags cannot be mixed
353 with other mount options and operations.
354
355 Since util-linux 2.23 the mount command can be used to do more propaga‐
356 tion (topology) changes by one mount(8) call and do it also together
357 with other mount operations. This feature is EXPERIMENTAL. The propa‐
358 gation flags are applied by additional mount(2) system calls when the
359 preceding mount operations were successful. Note that this use case is
360 not atomic. It is possible to specify the propagation flags in
361 fstab(5) as mount options (private, slave, shared, unbindable, rpri‐
362 vate, rslave, rshared, runbindable).
363
364 For example:
365
366 mount --make-private --make-unbindable /dev/sda1 /foo
367
368 is the same as:
369
370 mount /dev/sda1 /foo
371 mount --make-private /foo
372 mount --make-unbindable /foo
373
374
376 The full set of mount options used by an invocation of mount is deter‐
377 mined by first extracting the mount options for the filesystem from the
378 fstab table, then applying any options specified by the -o argument,
379 and finally applying a -r or -w option, when present.
380
381 The mount command does not pass all command-line options to the
382 /sbin/mount.suffix mount helpers. The interface between mount and the
383 mount helpers is described below in the section EXTERNAL HELPERS.
384
385 Command-line options available for the mount command are:
386
387 -a, --all
388 Mount all filesystems (of the given types) mentioned in fstab
389 (except for those whose line contains the noauto keyword). The
390 filesystems are mounted following their order in fstab. The
391 mount command compares filesystem source, target (and fs root
392 for bind mount or btrfs) to detect already mounted filesystems.
393 The kernel table with already mounted filesystems is cached dur‐
394 ing mount --all. This means that all duplicated fstab entries
395 will be mounted.
396
397 The option --all is possible to use for remount operation too.
398 In this case all filters (-t and -O) are applied to the table of
399 already mounted filesystems.
400
401 Since version 2.35 is possible to use the command line option -o
402 to alter mount options from fstab (see also --options-mode).
403
404 Note that it is a bad practice to use mount -a for fstab check‐
405 ing. The recommended solution is findmnt --verify.
406
407 -B, --bind
408 Remount a subtree somewhere else (so that its contents are
409 available in both places). See above, under Bind mounts.
410
411 -c, --no-canonicalize
412 Don't canonicalize paths. The mount command canonicalizes all
413 paths (from the command line or fstab) by default. This option
414 can be used together with the -f flag for already canonicalized
415 absolute paths. The option is designed for mount helpers which
416 call mount -i. It is strongly recommended to not use this com‐
417 mand-line option for normal mount operations.
418
419 Note that mount(8) does not pass this option to the
420 /sbin/mount.type helpers.
421
422 -F, --fork
423 (Used in conjunction with -a.) Fork off a new incarnation of
424 mount for each device. This will do the mounts on different
425 devices or different NFS servers in parallel. This has the
426 advantage that it is faster; also NFS timeouts proceed in paral‐
427 lel. A disadvantage is that the order of the mount operations
428 is undefined. Thus, you cannot use this option if you want to
429 mount both /usr and /usr/spool.
430
431 -f, --fake
432 Causes everything to be done except for the actual system call;
433 if it's not obvious, this ``fakes'' mounting the filesystem.
434 This option is useful in conjunction with the -v flag to deter‐
435 mine what the mount command is trying to do. It can also be
436 used to add entries for devices that were mounted earlier with
437 the -n option. The -f option checks for an existing record in
438 /etc/mtab and fails when the record already exists (with a regu‐
439 lar non-fake mount, this check is done by the kernel).
440
441 -i, --internal-only
442 Don't call the /sbin/mount.filesystem helper even if it exists.
443
444 -L, --label label
445 Mount the partition that has the specified label.
446
447 -l, --show-labels
448 Add the labels in the mount output. mount must have permission
449 to read the disk device (e.g. be set-user-ID root) for this to
450 work. One can set such a label for ext2, ext3 or ext4 using the
451 e2label(8) utility, or for XFS using xfs_admin(8), or for reis‐
452 erfs using reiserfstune(8).
453
454 -M, --move
455 Move a subtree to some other place. See above, the subsection
456 The move operation.
457
458 -n, --no-mtab
459 Mount without writing in /etc/mtab. This is necessary for exam‐
460 ple when /etc is on a read-only filesystem.
461
462 -N, --namespace ns
463 Perform the mount operation in the mount namespace specified by
464 ns. ns is either PID of process running in that namespace or
465 special file representing that namespace.
466
467 mount(8) switches to the mount namespace when it reads
468 /etc/fstab, writes /etc/mtab (or writes to /run/mount) and calls
469 the mount(2) system call, otherwise it runs in the original
470 mount namespace. This means that the target namespace does not
471 have to contain any libraries or other requirements necessary to
472 execute the mount(2) call.
473
474 See mount_namespaces(7) for more information.
475
476 -O, --test-opts opts
477 Limit the set of filesystems to which the -a option applies. In
478 this regard it is like the -t option except that -O is useless
479 without -a. For example, the command:
480
481 mount -a -O no_netdev
482
483 mounts all filesystems except those which have the option _net‐
484 dev specified in the options field in the /etc/fstab file.
485
486 It is different from -t in that each option is matched exactly;
487 a leading no at the beginning of one option does not negate the
488 rest.
489
490 The -t and -O options are cumulative in effect; that is, the
491 command
492
493 mount -a -t ext2 -O _netdev
494
495 mounts all ext2 filesystems with the _netdev option, not all
496 filesystems that are either ext2 or have the _netdev option
497 specified.
498
499 -o, --options opts
500 Use the specified mount options. The opts argument is a comma-
501 separated list. For example:
502
503 mount LABEL=mydisk -o noatime,nodev,nosuid
504
505
506 For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS
507 and FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.
508
509
510 --options-mode mode
511 Controls how to combine options from fstab/mtab with options
512 from the command line. mode can be one of ignore, append,
513 prepend or replace. For example, append means that options from
514 fstab are appended to options from the command line. The
515 default value is prepend -- it means command line options are
516 evaluated after fstab options. Note that the last option wins
517 if there are conflicting ones.
518
519
520 --options-source source
521 Source of default options. source is a comma-separated list of
522 fstab, mtab and disable. disable disables fstab and mtab and
523 disables --options-source-force. The default value is
524 fstab,mtab.
525
526
527 --options-source-force
528 Use options from fstab/mtab even if both device and dir are
529 specified.
530
531
532 -R, --rbind
533 Remount a subtree and all possible submounts somewhere else (so
534 that its contents are available in both places). See above, the
535 subsection Bind mounts.
536
537 -r, --read-only
538 Mount the filesystem read-only. A synonym is -o ro.
539
540 Note that, depending on the filesystem type, state and kernel
541 behavior, the system may still write to the device. For exam‐
542 ple, ext3 and ext4 will replay the journal if the filesystem is
543 dirty. To prevent this kind of write access, you may want to
544 mount an ext3 or ext4 filesystem with the ro,noload mount
545 options or set the block device itself to read-only mode, see
546 the blockdev(8) command.
547
548 -s Tolerate sloppy mount options rather than failing. This will
549 ignore mount options not supported by a filesystem type. Not
550 all filesystems support this option. Currently it's supported
551 by the mount.nfs mount helper only.
552
553 --source device
554 If only one argument for the mount command is given, then the
555 argument might be interpreted as the target (mountpoint) or
556 source (device). This option allows you to explicitly define
557 that the argument is the mount source.
558
559 --target directory
560 If only one argument for the mount command is given, then the
561 argument might be interpreted as the target (mountpoint) or
562 source (device). This option allows you to explicitly define
563 that the argument is the mount target.
564
565 --target-prefix directory
566 Prepend the specified directory to all mount targets. This
567 option can be used to follow fstab, but mount operations are
568 done in another place, for example:
569
570 mount --all --target-prefix /chroot -o X-mount.mkdir
571
572 mounts all from system fstab to /chroot, all missing mountpoint
573 are created (due to X-mount.mkdir). See also --fstab to use an
574 alternative fstab.
575
576 -T, --fstab path
577 Specifies an alternative fstab file. If path is a directory,
578 then the files in the directory are sorted by strverscmp(3);
579 files that start with "." or without an .fstab extension are
580 ignored. The option can be specified more than once. This
581 option is mostly designed for initramfs or chroot scripts where
582 additional configuration is specified beyond standard system
583 configuration.
584
585 Note that mount(8) does not pass the option --fstab to the
586 /sbin/mount.type helpers, meaning that the alternative fstab
587 files will be invisible for the helpers. This is no problem for
588 normal mounts, but user (non-root) mounts always require fstab
589 to verify the user's rights.
590
591 -t, --types fstype
592 The argument following the -t is used to indicate the filesystem
593 type. The filesystem types which are currently supported depend
594 on the running kernel. See /proc/filesystems and /lib/mod‐
595 ules/$(uname -r)/kernel/fs for a complete list of the filesys‐
596 tems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat,
597 sysfs, proc, nfs and cifs.
598
599 The programs mount and umount support filesystem subtypes. The
600 subtype is defined by a '.subtype' suffix. For example
601 'fuse.sshfs'. It's recommended to use subtype notation rather
602 than add any prefix to the mount source (for example
603 'sshfs#example.com' is deprecated).
604
605 If no -t option is given, or if the auto type is specified,
606 mount will try to guess the desired type. Mount uses the blkid
607 library for guessing the filesystem type; if that does not turn
608 up anything that looks familiar, mount will try to read the file
609 /etc/filesystems, or, if that does not exist, /proc/filesystems.
610 All of the filesystem types listed there will be tried, except
611 for those that are labeled "nodev" (e.g. devpts, proc and nfs).
612 If /etc/filesystems ends in a line with a single *, mount will
613 read /proc/filesystems afterwards. While trying, all filesystem
614 types will be mounted with the mount option silent.
615
616 The auto type may be useful for user-mounted floppies. Creating
617 a file /etc/filesystems can be useful to change the probe order
618 (e.g., to try vfat before msdos or ext3 before ext2) or if you
619 use a kernel module autoloader.
620
621 More than one type may be specified in a comma-separated list,
622 for the -t option as well as in an /etc/fstab entry. The list
623 of filesystem types for the -t option can be prefixed with no to
624 specify the filesystem types on which no action should be taken.
625 The prefix no has no effect when specified in an /etc/fstab
626 entry.
627
628 The prefix no can be meaningful with the -a option. For exam‐
629 ple, the command
630
631 mount -a -t nomsdos,smbfs
632
633 mounts all filesystems except those of type msdos and smbfs.
634
635 For most types all the mount program has to do is issue a simple
636 mount(2) system call, and no detailed knowledge of the filesys‐
637 tem type is required. For a few types however (like nfs, nfs4,
638 cifs, smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4,
639 cifs, smbfs, and ncpfs filesystems have a separate mount pro‐
640 gram. In order to make it possible to treat all types in a uni‐
641 form way, mount will execute the program /sbin/mount.type (if
642 that exists) when called with type type. Since different ver‐
643 sions of the smbmount program have different calling conven‐
644 tions, /sbin/mount.smbfs may have to be a shell script that sets
645 up the desired call.
646
647 -U, --uuid uuid
648 Mount the partition that has the specified uuid.
649
650 -v, --verbose
651 Verbose mode.
652
653 -w, --rw, --read-write
654 Mount the filesystem read/write. Read-write is the kernel
655 default and the mount default is to try read-only if the previ‐
656 ous mount syscall with read-write flags on write-protected
657 devices of filesystems failed.
658
659 A synonym is -o rw.
660
661 Note that specifying -w on the command line forces mount to
662 never try read-only mount on write-protected devices or already
663 mounted read-only filesystems.
664
665 -V, --version
666 Display version information and exit.
667
668 -h, --help
669 Display help text and exit.
670
671
673 Some of these options are only useful when they appear in the
674 /etc/fstab file.
675
676 Some of these options could be enabled or disabled by default in the
677 system kernel. To check the current setting see the options in
678 /proc/mounts. Note that filesystems also have per-filesystem specific
679 default mount options (see for example tune2fs -l output for extN
680 filesystems).
681
682 The following options apply to any filesystem that is being mounted
683 (but not every filesystem actually honors them – e.g., the sync option
684 today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs):
685
686
687 async All I/O to the filesystem should be done asynchronously. (See
688 also the sync option.)
689
690 atime Do not use the noatime feature, so the inode access time is con‐
691 trolled by kernel defaults. See also the descriptions of the
692 relatime and strictatime mount options.
693
694 noatime
695 Do not update inode access times on this filesystem (e.g. for
696 faster access on the news spool to speed up news servers). This
697 works for all inode types (directories too), so it implies
698 nodiratime.
699
700 auto Can be mounted with the -a option.
701
702 noauto Can only be mounted explicitly (i.e., the -a option will not
703 cause the filesystem to be mounted).
704
705 context=context, fscontext=context, defcontext=context, and
706 rootcontext=context
707 The context= option is useful when mounting filesystems that do
708 not support extended attributes, such as a floppy or hard disk
709 formatted with VFAT, or systems that are not normally running
710 under SELinux, such as an ext3 or ext4 formatted disk from a
711 non-SELinux workstation. You can also use context= on filesys‐
712 tems you do not trust, such as a floppy. It also helps in com‐
713 patibility with xattr-supporting filesystems on earlier 2.4.<x>
714 kernel versions. Even where xattrs are supported, you can save
715 time not having to label every file by assigning the entire disk
716 one security context.
717
718 A commonly used option for removable media is
719 context="system_u:object_r:removable_t".
720
721 Two other options are fscontext= and defcontext=, both of which
722 are mutually exclusive of the context= option. This means you
723 can use fscontext and defcontext with each other, but neither
724 can be used with context.
725
726 The fscontext= option works for all filesystems, regardless of
727 their xattr support. The fscontext option sets the overarching
728 filesystem label to a specific security context. This filesys‐
729 tem label is separate from the individual labels on the files.
730 It represents the entire filesystem for certain kinds of permis‐
731 sion checks, such as during mount or file creation. Individual
732 file labels are still obtained from the xattrs on the files
733 themselves. The context option actually sets the aggregate con‐
734 text that fscontext provides, in addition to supplying the same
735 label for individual files.
736
737 You can set the default security context for unlabeled files
738 using defcontext= option. This overrides the value set for
739 unlabeled files in the policy and requires a filesystem that
740 supports xattr labeling.
741
742 The rootcontext= option allows you to explicitly label the root
743 inode of a FS being mounted before that FS or inode becomes vis‐
744 ible to userspace. This was found to be useful for things like
745 stateless Linux.
746
747 Note that the kernel rejects any remount request that includes
748 the context option, even when unchanged from the current con‐
749 text.
750
751 Warning: the context value might contain commas, in which case
752 the value has to be properly quoted, otherwise mount(8) will
753 interpret the comma as a separator between mount options. Don't
754 forget that the shell strips off quotes and thus double quoting
755 is required. For example:
756
757 mount -t tmpfs none /mnt -o \
758 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
759
760 For more details, see selinux(8).
761
762
763 defaults
764 Use the default options: rw, suid, dev, exec, auto, nouser, and
765 async.
766
767 Note that the real set of all default mount options depends on
768 the kernel and filesystem type. See the beginning of this sec‐
769 tion for more details.
770
771 dev Interpret character or block special devices on the filesystem.
772
773 nodev Do not interpret character or block special devices on the
774 filesystem.
775
776 diratime
777 Update directory inode access times on this filesystem. This is
778 the default. (This option is ignored when noatime is set.)
779
780 nodiratime
781 Do not update directory inode access times on this filesystem.
782 (This option is implied when noatime is set.)
783
784 dirsync
785 All directory updates within the filesystem should be done syn‐
786 chronously. This affects the following system calls: creat,
787 link, unlink, symlink, mkdir, rmdir, mknod and rename.
788
789 exec Permit execution of binaries.
790
791 noexec Do not permit direct execution of any binaries on the mounted
792 filesystem.
793
794 group Allow an ordinary user to mount the filesystem if one of that
795 user's groups matches the group of the device. This option
796 implies the options nosuid and nodev (unless overridden by sub‐
797 sequent options, as in the option line group,dev,suid).
798
799 iversion
800 Every time the inode is modified, the i_version field will be
801 incremented.
802
803 noiversion
804 Do not increment the i_version inode field.
805
806 mand Allow mandatory locks on this filesystem. See fcntl(2).
807
808 nomand Do not allow mandatory locks on this filesystem.
809
810 _netdev
811 The filesystem resides on a device that requires network access
812 (used to prevent the system from attempting to mount these
813 filesystems until the network has been enabled on the system).
814
815 nofail Do not report errors for this device if it does not exist.
816
817 relatime
818 Update inode access times relative to modify or change time.
819 Access time is only updated if the previous access time was ear‐
820 lier than the current modify or change time. (Similar to
821 noatime, but it doesn't break mutt or other applications that
822 need to know if a file has been read since the last time it was
823 modified.)
824
825 Since Linux 2.6.30, the kernel defaults to the behavior provided
826 by this option (unless noatime was specified), and the
827 strictatime option is required to obtain traditional semantics.
828 In addition, since Linux 2.6.30, the file's last access time is
829 always updated if it is more than 1 day old.
830
831 norelatime
832 Do not use the relatime feature. See also the strictatime mount
833 option.
834
835 strictatime
836 Allows to explicitly request full atime updates. This makes it
837 possible for the kernel to default to relatime or noatime but
838 still allow userspace to override it. For more details about
839 the default system mount options see /proc/mounts.
840
841 nostrictatime
842 Use the kernel's default behavior for inode access time updates.
843
844 lazytime
845 Only update times (atime, mtime, ctime) on the in-memory version
846 of the file inode.
847
848 This mount option significantly reduces writes to the inode ta‐
849 ble for workloads that perform frequent random writes to preal‐
850 located files.
851
852 The on-disk timestamps are updated only when:
853
854 - the inode needs to be updated for some change unrelated to
855 file timestamps
856
857 - the application employs fsync(2), syncfs(2), or sync(2)
858
859 - an undeleted inode is evicted from memory
860
861 - more than 24 hours have passed since the i-node was written to
862 disk.
863
864
865 nolazytime
866 Do not use the lazytime feature.
867
868 suid Honor set-user-ID and set-group-ID bits or file capabilities
869 when executing programs from this filesystem.
870
871 nosuid Do not honor set-user-ID and set-group-ID bits or file capabili‐
872 ties when executing programs from this filesystem.
873
874 silent Turn on the silent flag.
875
876 loud Turn off the silent flag.
877
878 owner Allow an ordinary user to mount the filesystem if that user is
879 the owner of the device. This option implies the options nosuid
880 and nodev (unless overridden by subsequent options, as in the
881 option line owner,dev,suid).
882
883 remount
884 Attempt to remount an already-mounted filesystem. This is com‐
885 monly used to change the mount flags for a filesystem, espe‐
886 cially to make a readonly filesystem writable. It does not
887 change device or mount point.
888
889 The remount operation together with the bind flag has special
890 semantics. See above, the subsection Bind mounts.
891
892 The remount functionality follows the standard way the mount
893 command works with options from fstab. This means that mount
894 does not read fstab (or mtab) only when both device and dir are
895 specified.
896
897 mount -o remount,rw /dev/foo /dir
898
899 After this call all old mount options are replaced and arbitrary
900 stuff from fstab (or mtab) is ignored, except the loop= option
901 which is internally generated and maintained by the mount com‐
902 mand.
903
904 mount -o remount,rw /dir
905
906 After this call, mount reads fstab and merges these options with
907 the options from the command line (-o). If no mountpoint is
908 found in fstab, then a remount with unspecified source is
909 allowed.
910
911 mount allows the use of --all to remount all already mounted
912 filesystems which match a specified filter (-O and -t). For
913 example:
914
915 mount --all -o remount,ro -t vfat
916
917 remounts all already mounted vfat filesystems in read-only mode.
918 Each of the filesystems is remounted by "mount -o remount,ro
919 /dir" semantic. This means the mount command reads fstab or
920 mtab and merges these options with the options from the command
921 line.
922
923 ro Mount the filesystem read-only.
924
925 rw Mount the filesystem read-write.
926
927 sync All I/O to the filesystem should be done synchronously. In the
928 case of media with a limited number of write cycles (e.g. some
929 flash drives), sync may cause life-cycle shortening.
930
931 user Allow an ordinary user to mount the filesystem. The name of the
932 mounting user is written to the mtab file (or to the private
933 libmount file in /run/mount on systems without a regular mtab)
934 so that this same user can unmount the filesystem again. This
935 option implies the options noexec, nosuid, and nodev (unless
936 overridden by subsequent options, as in the option line
937 user,exec,dev,suid).
938
939 nouser Forbid an ordinary user to mount the filesystem. This is the
940 default; it does not imply any other options.
941
942 users Allow any user to mount and to unmount the filesystem, even when
943 some other ordinary user mounted it. This option implies the
944 options noexec, nosuid, and nodev (unless overridden by subse‐
945 quent options, as in the option line users,exec,dev,suid).
946
947 X-* All options prefixed with "X-" are interpreted as comments or as
948 userspace application-specific options. These options are not
949 stored in user space (e.g., mtab file), nor sent to the
950 mount.type helpers nor to the mount(2) system call. The sug‐
951 gested format is X-appname.option.
952
953 x-* The same as X-* options, but stored permanently in user space.
954 This means the options are also available for umount or other
955 operations. Note that maintaining mount options in user space
956 is tricky, because it's necessary use libmount-based tools and
957 there is no guarantee that the options will be always available
958 (for example after a move mount operation or in unshared names‐
959 pace).
960
961 Note that before util-linux v2.30 the x-* options have not been
962 maintained by libmount and stored in user space (functionality
963 was the same as for X-* now), but due to the growing number of
964 use-cases (in initrd, systemd etc.) the functionality has been
965 extended to keep existing fstab configurations usable without a
966 change.
967
968 X-mount.mkdir[=mode]
969 Allow to make a target directory (mountpoint) if it does not
970 exit yet. The optional argument mode specifies the filesystem
971 access mode used for mkdir(2) in octal notation. The default
972 mode is 0755. This functionality is supported only for root
973 users or when mount executed without suid permissions. The
974 option is also supported as x-mount.mkdir, this notation is dep‐
975 recated since v2.30.
976
977 nosymfollow
978 Do not follow symlinks when resolving paths. Symlinks can still
979 be created, and readlink(1), readlink(2), realpath(1) and real‐
980 path(3) all still work properly.
981
982
984 This section lists options that are specific to particular filesystems.
985 Where possible, you should first consult filesystem-specific manual
986 pages for details. Some of those pages are listed in the following ta‐
987 ble.
988
989 Filesystem(s) Manual page
990 btrfs btrfs(5)
991 cifs mount.cifs(8)
992 ext2, ext3, ext4 ext4(5)
993 fuse fuse(8)
994 nfs nfs(5)
995 tmpfs tmpfs(5)
996 xfs xfs(5)
997
998 Note that some of the pages listed above might be available only after
999 you install the respective userland tools.
1000
1001 The following options apply only to certain filesystems. We sort them
1002 by filesystem. All options follow the -o flag.
1003
1004 What options are supported depends a bit on the running kernel. Fur‐
1005 ther information may be available in filesystem-specific files in the
1006 kernel source subdirectory Documentation/filesystems.
1007
1008 Mount options for adfs
1009 uid=value and gid=value
1010 Set the owner and group of the files in the filesystem (default:
1011 uid=gid=0).
1012
1013 ownmask=value and othmask=value
1014 Set the permission mask for ADFS 'owner' permissions and 'other'
1015 permissions, respectively (default: 0700 and 0077, respec‐
1016 tively). See also /usr/src/linux/Documentation/filesys‐
1017 tems/adfs.rst.
1018
1019
1020 Mount options for affs
1021 uid=value and gid=value
1022 Set the owner and group of the root of the filesystem (default:
1023 uid=gid=0, but with option uid or gid without specified value,
1024 the UID and GID of the current process are taken).
1025
1026 setuid=value and setgid=value
1027 Set the owner and group of all files.
1028
1029 mode=value
1030 Set the mode of all files to value & 0777 disregarding the orig‐
1031 inal permissions. Add search permission to directories that
1032 have read permission. The value is given in octal.
1033
1034 protect
1035 Do not allow any changes to the protection bits on the filesys‐
1036 tem.
1037
1038 usemp Set UID and GID of the root of the filesystem to the UID and GID
1039 of the mount point upon the first sync or umount, and then clear
1040 this option. Strange...
1041
1042 verbose
1043 Print an informational message for each successful mount.
1044
1045 prefix=string
1046 Prefix used before volume name, when following a link.
1047
1048 volume=string
1049 Prefix (of length at most 30) used before '/' when following a
1050 symbolic link.
1051
1052 reserved=value
1053 (Default: 2.) Number of unused blocks at the start of the
1054 device.
1055
1056 root=value
1057 Give explicitly the location of the root block.
1058
1059 bs=value
1060 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
1061
1062 grpquota|noquota|quota|usrquota
1063 These options are accepted but ignored. (However, quota utili‐
1064 ties may react to such strings in /etc/fstab.)
1065
1066
1067 Mount options for debugfs
1068 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1069 /sys/kernel/debug. As of kernel version 3.4, debugfs has the following
1070 options:
1071
1072 uid=n, gid=n
1073 Set the owner and group of the mountpoint.
1074
1075 mode=value
1076 Sets the mode of the mountpoint.
1077
1078
1079 Mount options for devpts
1080 The devpts filesystem is a pseudo filesystem, traditionally mounted on
1081 /dev/pts. In order to acquire a pseudo terminal, a process opens
1082 /dev/ptmx; the number of the pseudo terminal is then made available to
1083 the process and the pseudo terminal slave can be accessed as
1084 /dev/pts/<number>.
1085
1086 uid=value and gid=value
1087 This sets the owner or the group of newly created pseudo termi‐
1088 nals to the specified values. When nothing is specified, they
1089 will be set to the UID and GID of the creating process. For
1090 example, if there is a tty group with GID 5, then gid=5 will
1091 cause newly created pseudo terminals to belong to the tty group.
1092
1093 mode=value
1094 Set the mode of newly created pseudo terminals to the specified
1095 value. The default is 0600. A value of mode=620 and gid=5
1096 makes "mesg y" the default on newly created pseudo terminals.
1097
1098 newinstance
1099 Create a private instance of the devpts filesystem, such that
1100 indices of pseudo terminals allocated in this new instance are
1101 independent of indices created in other instances of devpts.
1102
1103 All mounts of devpts without this newinstance option share the
1104 same set of pseudo terminal indices (i.e., legacy mode). Each
1105 mount of devpts with the newinstance option has a private set of
1106 pseudo terminal indices.
1107
1108 This option is mainly used to support containers in the Linux
1109 kernel. It is implemented in Linux kernel versions starting
1110 with 2.6.29. Further, this mount option is valid only if CON‐
1111 FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configu‐
1112 ration.
1113
1114 To use this option effectively, /dev/ptmx must be a symbolic
1115 link to pts/ptmx. See Documentation/filesystems/devpts.txt in
1116 the Linux kernel source tree for details.
1117
1118 ptmxmode=value
1119
1120 Set the mode for the new ptmx device node in the devpts filesys‐
1121 tem.
1122
1123 With the support for multiple instances of devpts (see newin‐
1124 stance option above), each instance has a private ptmx node in
1125 the root of the devpts filesystem (typically /dev/pts/ptmx).
1126
1127 For compatibility with older versions of the kernel, the default
1128 mode of the new ptmx node is 0000. ptmxmode=value specifies a
1129 more useful mode for the ptmx node and is highly recommended
1130 when the newinstance option is specified.
1131
1132 This option is only implemented in Linux kernel versions start‐
1133 ing with 2.6.29. Further, this option is valid only if CON‐
1134 FIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel configu‐
1135 ration.
1136
1137
1138 Mount options for fat
1139 (Note: fat is not a separate filesystem, but a common part of the
1140 msdos, umsdos and vfat filesystems.)
1141
1142 blocksize={512|1024|2048}
1143 Set blocksize (default 512). This option is obsolete.
1144
1145 uid=value and gid=value
1146 Set the owner and group of all files. (Default: the UID and GID
1147 of the current process.)
1148
1149 umask=value
1150 Set the umask (the bitmask of the permissions that are not
1151 present). The default is the umask of the current process. The
1152 value is given in octal.
1153
1154 dmask=value
1155 Set the umask applied to directories only. The default is the
1156 umask of the current process. The value is given in octal.
1157
1158 fmask=value
1159 Set the umask applied to regular files only. The default is the
1160 umask of the current process. The value is given in octal.
1161
1162 allow_utime=value
1163 This option controls the permission check of mtime/atime.
1164
1165 20 If current process is in group of file's group ID, you
1166 can change timestamp.
1167
1168 2 Other users can change timestamp.
1169
1170 The default is set from `dmask' option. (If the directory is
1171 writable, utime(2) is also allowed. I.e. ~dmask & 022)
1172
1173 Normally utime(2) checks that the current process is owner of
1174 the file, or that it has the CAP_FOWNER capability. But FAT
1175 filesystems don't have UID/GID on disk, so the normal check is
1176 too inflexible. With this option you can relax it.
1177
1178 check=value
1179 Three different levels of pickiness can be chosen:
1180
1181 r[elaxed]
1182 Upper and lower case are accepted and equivalent, long
1183 name parts are truncated (e.g. verylongname.foobar
1184 becomes verylong.foo), leading and embedded spaces are
1185 accepted in each name part (name and extension).
1186
1187 n[ormal]
1188 Like "relaxed", but many special characters (*, ?, <,
1189 spaces, etc.) are rejected. This is the default.
1190
1191 s[trict]
1192 Like "normal", but names that contain long parts or spe‐
1193 cial characters that are sometimes used on Linux but are
1194 not accepted by MS-DOS (+, =, etc.) are rejected.
1195
1196 codepage=value
1197 Sets the codepage for converting to shortname characters on FAT
1198 and VFAT filesystems. By default, codepage 437 is used.
1199
1200 conv=mode
1201 This option is obsolete and may fail or be ignored.
1202
1203 cvf_format=module
1204 Forces the driver to use the CVF (Compressed Volume File) module
1205 cvf_module instead of auto-detection. If the kernel supports
1206 kmod, the cvf_format=xxx option also controls on-demand CVF mod‐
1207 ule loading. This option is obsolete.
1208
1209 cvf_option=option
1210 Option passed to the CVF module. This option is obsolete.
1211
1212 debug Turn on the debug flag. A version string and a list of filesys‐
1213 tem parameters will be printed (these data are also printed if
1214 the parameters appear to be inconsistent).
1215
1216 discard
1217 If set, causes discard/TRIM commands to be issued to the block
1218 device when blocks are freed. This is useful for SSD devices
1219 and sparse/thinly-provisioned LUNs.
1220
1221 dos1xfloppy
1222 If set, use a fallback default BIOS Parameter Block configura‐
1223 tion, determined by backing device size. These static parame‐
1224 ters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320
1225 kiB, and 360 kiB floppies and floppy images.
1226
1227 errors={panic|continue|remount-ro}
1228 Specify FAT behavior on critical errors: panic, continue without
1229 doing anything, or remount the partition in read-only mode
1230 (default behavior).
1231
1232 fat={12|16|32}
1233 Specify a 12, 16 or 32 bit fat. This overrides the automatic
1234 FAT type detection routine. Use with caution!
1235
1236 iocharset=value
1237 Character set to use for converting between 8 bit characters and
1238 16 bit Unicode characters. The default is iso8859-1. Long
1239 filenames are stored on disk in Unicode format.
1240
1241 nfs={stale_rw|nostale_ro}
1242 Enable this only if you want to export the FAT filesystem over
1243 NFS.
1244
1245 stale_rw: This option maintains an index (cache) of directory
1246 inodes which is used by the nfs-related code to improve look-
1247 ups. Full file operations (read/write) over NFS are supported
1248 but with cache eviction at NFS server, this could result in spu‐
1249 rious ESTALE errors.
1250
1251 nostale_ro: This option bases the inode number and file handle
1252 on the on-disk location of a file in the FAT directory entry.
1253 This ensures that ESTALE will not be returned after a file is
1254 evicted from the inode cache. However, it means that operations
1255 such as rename, create and unlink could cause file handles that
1256 previously pointed at one file to point at a different file,
1257 potentially causing data corruption. For this reason, this
1258 option also mounts the filesystem readonly.
1259
1260 To maintain backward compatibility, '-o nfs' is also accepted,
1261 defaulting to stale_rw.
1262
1263 tz=UTC This option disables the conversion of timestamps between local
1264 time (as used by Windows on FAT) and UTC (which Linux uses
1265 internally). This is particularly useful when mounting devices
1266 (like digital cameras) that are set to UTC in order to avoid the
1267 pitfalls of local time.
1268
1269 time_offset=minutes
1270 Set offset for conversion of timestamps from local time used by
1271 FAT to UTC. I.e., minutes will be subtracted from each time‐
1272 stamp to convert it to UTC used internally by Linux. This is
1273 useful when the time zone set in the kernel via settimeofday(2)
1274 is not the time zone used by the filesystem. Note that this
1275 option still does not provide correct time stamps in all cases
1276 in presence of DST - time stamps in a different DST setting will
1277 be off by one hour.
1278
1279 quiet Turn on the quiet flag. Attempts to chown or chmod files do not
1280 return errors, although they fail. Use with caution!
1281
1282 rodir FAT has the ATTR_RO (read-only) attribute. On Windows, the
1283 ATTR_RO of the directory will just be ignored, and is used only
1284 by applications as a flag (e.g. it's set for the customized
1285 folder).
1286
1287 If you want to use ATTR_RO as read-only flag even for the direc‐
1288 tory, set this option.
1289
1290 showexec
1291 If set, the execute permission bits of the file will be allowed
1292 only if the extension part of the name is .EXE, .COM, or .BAT.
1293 Not set by default.
1294
1295 sys_immutable
1296 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag
1297 on Linux. Not set by default.
1298
1299 flush If set, the filesystem will try to flush to disk more early than
1300 normal. Not set by default.
1301
1302 usefree
1303 Use the "free clusters" value stored on FSINFO. It'll be used
1304 to determine number of free clusters without scanning disk. But
1305 it's not used by default, because recent Windows don't update it
1306 correctly in some case. If you are sure the "free clusters" on
1307 FSINFO is correct, by this option you can avoid scanning disk.
1308
1309 dots, nodots, dotsOK=[yes|no]
1310 Various misguided attempts to force Unix or DOS conventions onto
1311 a FAT filesystem.
1312
1313
1314 Mount options for hfs
1315 creator=cccc, type=cccc
1316 Set the creator/type values as shown by the MacOS finder used
1317 for creating new files. Default values: '????'.
1318
1319 uid=n, gid=n
1320 Set the owner and group of all files. (Default: the UID and GID
1321 of the current process.)
1322
1323 dir_umask=n, file_umask=n, umask=n
1324 Set the umask used for all directories, all regular files, or
1325 all files and directories. Defaults to the umask of the current
1326 process.
1327
1328 session=n
1329 Select the CDROM session to mount. Defaults to leaving that
1330 decision to the CDROM driver. This option will fail with any‐
1331 thing but a CDROM as underlying device.
1332
1333 part=n Select partition number n from the device. Only makes sense for
1334 CDROMs. Defaults to not parsing the partition table at all.
1335
1336 quiet Don't complain about invalid mount options.
1337
1338
1339 Mount options for hpfs
1340 uid=value and gid=value
1341 Set the owner and group of all files. (Default: the UID and GID
1342 of the current process.)
1343
1344 umask=value
1345 Set the umask (the bitmask of the permissions that are not
1346 present). The default is the umask of the current process. The
1347 value is given in octal.
1348
1349 case={lower|asis}
1350 Convert all files names to lower case, or leave them. (Default:
1351 case=lower.)
1352
1353 conv=mode
1354 This option is obsolete and may fail or being ignored.
1355
1356 nocheck
1357 Do not abort mounting when certain consistency checks fail.
1358
1359
1360 Mount options for iso9660
1361 ISO 9660 is a standard describing a filesystem structure to be used on
1362 CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1363 udf filesystem.)
1364
1365 Normal iso9660 filenames appear in an 8.3 format (i.e., DOS-like
1366 restrictions on filename length), and in addition all characters are in
1367 upper case. Also there is no field for file ownership, protection,
1368 number of links, provision for block/character devices, etc.
1369
1370 Rock Ridge is an extension to iso9660 that provides all of these UNIX-
1371 like features. Basically there are extensions to each directory record
1372 that supply all of the additional information, and when Rock Ridge is
1373 in use, the filesystem is indistinguishable from a normal UNIX filesys‐
1374 tem (except that it is read-only, of course).
1375
1376 norock Disable the use of Rock Ridge extensions, even if available.
1377 Cf. map.
1378
1379 nojoliet
1380 Disable the use of Microsoft Joliet extensions, even if avail‐
1381 able. Cf. map.
1382
1383 check={r[elaxed]|s[trict]}
1384 With check=relaxed, a filename is first converted to lower case
1385 before doing the lookup. This is probably only meaningful
1386 together with norock and map=normal. (Default: check=strict.)
1387
1388 uid=value and gid=value
1389 Give all files in the filesystem the indicated user or group id,
1390 possibly overriding the information found in the Rock Ridge
1391 extensions. (Default: uid=0,gid=0.)
1392
1393 map={n[ormal]|o[ff]|a[corn]}
1394 For non-Rock Ridge volumes, normal name translation maps upper
1395 to lower case ASCII, drops a trailing `;1', and converts `;' to
1396 `.'. With map=off no name translation is done. See norock.
1397 (Default: map=normal.) map=acorn is like map=normal but also
1398 apply Acorn extensions if present.
1399
1400 mode=value
1401 For non-Rock Ridge volumes, give all files the indicated mode.
1402 (Default: read and execute permission for everybody.) Octal
1403 mode values require a leading 0.
1404
1405 unhide Also show hidden and associated files. (If the ordinary files
1406 and the associated or hidden files have the same filenames, this
1407 may make the ordinary files inaccessible.)
1408
1409 block={512|1024|2048}
1410 Set the block size to the indicated value. (Default:
1411 block=1024.)
1412
1413 conv=mode
1414 This option is obsolete and may fail or being ignored.
1415
1416 cruft If the high byte of the file length contains other garbage, set
1417 this mount option to ignore the high order bits of the file
1418 length. This implies that a file cannot be larger than 16 MB.
1419
1420 session=x
1421 Select number of session on multisession CD.
1422
1423 sbsector=xxx
1424 Session begins from sector xxx.
1425
1426 The following options are the same as for vfat and specifying them only
1427 makes sense when using discs encoded using Microsoft's Joliet exten‐
1428 sions.
1429
1430 iocharset=value
1431 Character set to use for converting 16 bit Unicode characters on
1432 CD to 8 bit characters. The default is iso8859-1.
1433
1434 utf8 Convert 16 bit Unicode characters on CD to UTF-8.
1435
1436
1437 Mount options for jfs
1438 iocharset=name
1439 Character set to use for converting from Unicode to ASCII. The
1440 default is to do no conversion. Use iocharset=utf8 for UTF8
1441 translations. This requires CONFIG_NLS_UTF8 to be set in the
1442 kernel .config file.
1443
1444 resize=value
1445 Resize the volume to value blocks. JFS only supports growing a
1446 volume, not shrinking it. This option is only valid during a
1447 remount, when the volume is mounted read-write. The resize key‐
1448 word with no value will grow the volume to the full size of the
1449 partition.
1450
1451 nointegrity
1452 Do not write to the journal. The primary use of this option is
1453 to allow for higher performance when restoring a volume from
1454 backup media. The integrity of the volume is not guaranteed if
1455 the system abnormally ends.
1456
1457 integrity
1458 Default. Commit metadata changes to the journal. Use this
1459 option to remount a volume where the nointegrity option was pre‐
1460 viously specified in order to restore normal behavior.
1461
1462 errors={continue|remount-ro|panic}
1463 Define the behavior when an error is encountered. (Either
1464 ignore errors and just mark the filesystem erroneous and con‐
1465 tinue, or remount the filesystem read-only, or panic and halt
1466 the system.)
1467
1468 noquota|quota|usrquota|grpquota
1469 These options are accepted but ignored.
1470
1471
1472 Mount options for msdos
1473 See mount options for fat. If the msdos filesystem detects an incon‐
1474 sistency, it reports an error and sets the file system read-only. The
1475 filesystem can be made writable again by remounting it.
1476
1477
1478 Mount options for ncpfs
1479 Just like nfs, the ncpfs implementation expects a binary argument (a
1480 struct ncp_mount_data) to the mount system call. This argument is con‐
1481 structed by ncpmount(8) and the current version of mount (2.12) does
1482 not know anything about ncpfs.
1483
1484
1485 Mount options for ntfs
1486 iocharset=name
1487 Character set to use when returning file names. Unlike VFAT,
1488 NTFS suppresses names that contain nonconvertible characters.
1489 Deprecated.
1490
1491 nls=name
1492 New name for the option earlier called iocharset.
1493
1494 utf8 Use UTF-8 for converting file names.
1495
1496 uni_xlate={0|1|2}
1497 For 0 (or `no' or `false'), do not use escape sequences for
1498 unknown Unicode characters. For 1 (or `yes' or `true') or 2,
1499 use vfat-style 4-byte escape sequences starting with ":". Here
1500 2 give a little-endian encoding and 1 a byteswapped bigendian
1501 encoding.
1502
1503 posix=[0|1]
1504 If enabled (posix=1), the filesystem distinguishes between upper
1505 and lower case. The 8.3 alias names are presented as hard links
1506 instead of being suppressed. This option is obsolete.
1507
1508 uid=value, gid=value and umask=value
1509 Set the file permission on the filesystem. The umask value is
1510 given in octal. By default, the files are owned by root and not
1511 readable by somebody else.
1512
1513
1514 Mount options for overlay
1515 Since Linux 3.18 the overlay pseudo filesystem implements a union mount
1516 for other filesystems.
1517
1518 An overlay filesystem combines two filesystems - an upper filesystem
1519 and a lower filesystem. When a name exists in both filesystems, the
1520 object in the upper filesystem is visible while the object in the lower
1521 filesystem is either hidden or, in the case of directories, merged with
1522 the upper object.
1523
1524 The lower filesystem can be any filesystem supported by Linux and does
1525 not need to be writable. The lower filesystem can even be another
1526 overlayfs. The upper filesystem will normally be writable and if it is
1527 it must support the creation of trusted.* extended attributes, and must
1528 provide a valid d_type in readdir responses, so NFS is not suitable.
1529
1530 A read-only overlay of two read-only filesystems may use any filesystem
1531 type. The options lowerdir and upperdir are combined into a merged
1532 directory by using:
1533
1534 mount -t overlay overlay \
1535 -olowerdir=/lower,upperdir=/upper,workdir=/work /merged
1536
1537
1538 lowerdir=directory
1539 Any filesystem, does not need to be on a writable filesystem.
1540
1541 upperdir=directory
1542 The upperdir is normally on a writable filesystem.
1543
1544 workdir=directory
1545 The workdir needs to be an empty directory on the same filesys‐
1546 tem as upperdir.
1547
1548
1549 Mount options for reiserfs
1550 Reiserfs is a journaling filesystem.
1551
1552 conv Instructs version 3.6 reiserfs software to mount a version 3.5
1553 filesystem, using the 3.6 format for newly created objects.
1554 This filesystem will no longer be compatible with reiserfs 3.5
1555 tools.
1556
1557 hash={rupasov|tea|r5|detect}
1558 Choose which hash function reiserfs will use to find files
1559 within directories.
1560
1561 rupasov
1562 A hash invented by Yury Yu. Rupasov. It is fast and pre‐
1563 serves locality, mapping lexicographically close file
1564 names to close hash values. This option should not be
1565 used, as it causes a high probability of hash collisions.
1566
1567 tea A Davis-Meyer function implemented by Jeremy
1568 Fitzhardinge. It uses hash permuting bits in the name.
1569 It gets high randomness and, therefore, low probability
1570 of hash collisions at some CPU cost. This may be used if
1571 EHASHCOLLISION errors are experienced with the r5 hash.
1572
1573 r5 A modified version of the rupasov hash. It is used by
1574 default and is the best choice unless the filesystem has
1575 huge directories and unusual file-name patterns.
1576
1577 detect Instructs mount to detect which hash function is in use
1578 by examining the filesystem being mounted, and to write
1579 this information into the reiserfs superblock. This is
1580 only useful on the first mount of an old format filesys‐
1581 tem.
1582
1583 hashed_relocation
1584 Tunes the block allocator. This may provide performance
1585 improvements in some situations.
1586
1587 no_unhashed_relocation
1588 Tunes the block allocator. This may provide performance
1589 improvements in some situations.
1590
1591 noborder
1592 Disable the border allocator algorithm invented by Yury Yu.
1593 Rupasov. This may provide performance improvements in some sit‐
1594 uations.
1595
1596 nolog Disable journaling. This will provide slight performance
1597 improvements in some situations at the cost of losing reiserfs's
1598 fast recovery from crashes. Even with this option turned on,
1599 reiserfs still performs all journaling operations, save for
1600 actual writes into its journaling area. Implementation of nolog
1601 is a work in progress.
1602
1603 notail By default, reiserfs stores small files and `file tails'
1604 directly into its tree. This confuses some utilities such as
1605 LILO(8). This option is used to disable packing of files into
1606 the tree.
1607
1608 replayonly
1609 Replay the transactions which are in the journal, but do not
1610 actually mount the filesystem. Mainly used by reiserfsck.
1611
1612 resize=number
1613 A remount option which permits online expansion of reiserfs par‐
1614 titions. Instructs reiserfs to assume that the device has num‐
1615 ber blocks. This option is designed for use with devices which
1616 are under logical volume management (LVM). There is a special
1617 resizer utility which can be obtained from
1618 ftp://ftp.namesys.com/pub/reiserfsprogs.
1619
1620 user_xattr
1621 Enable Extended User Attributes. See the attr(1) manual page.
1622
1623 acl Enable POSIX Access Control Lists. See the acl(5) manual page.
1624
1625 barrier=none / barrier=flush
1626 This disables / enables the use of write barriers in the jour‐
1627 naling code. barrier=none disables, barrier=flush enables
1628 (default). This also requires an IO stack which can support
1629 barriers, and if reiserfs gets an error on a barrier write, it
1630 will disable barriers again with a warning. Write barriers
1631 enforce proper on-disk ordering of journal commits, making
1632 volatile disk write caches safe to use, at some performance
1633 penalty. If your disks are battery-backed in one way or
1634 another, disabling barriers may safely improve performance.
1635
1636
1637 Mount options for ubifs
1638 UBIFS is a flash filesystem which works on top of UBI volumes. Note
1639 that atime is not supported and is always turned off.
1640
1641 The device name may be specified as
1642
1643 ubiX_Y UBI device number X, volume number Y
1644
1645 ubiY UBI device number 0, volume number Y
1646
1647 ubiX:NAME
1648 UBI device number X, volume with name NAME
1649
1650 ubi:NAME
1651 UBI device number 0, volume with name NAME
1652
1653 Alternative ! separator may be used instead of :.
1654
1655 The following mount options are available:
1656
1657 bulk_read
1658 Enable bulk-read. VFS read-ahead is disabled because it slows
1659 down the filesystem. Bulk-Read is an internal optimization.
1660 Some flashes may read faster if the data are read at one go,
1661 rather than at several read requests. For example, OneNAND can
1662 do "read-while-load" if it reads more than one NAND page.
1663
1664 no_bulk_read
1665 Do not bulk-read. This is the default.
1666
1667 chk_data_crc
1668 Check data CRC-32 checksums. This is the default.
1669
1670 no_chk_data_crc.
1671 Do not check data CRC-32 checksums. With this option, the
1672 filesystem does not check CRC-32 checksum for data, but it does
1673 check it for the internal indexing information. This option
1674 only affects reading, not writing. CRC-32 is always calculated
1675 when writing the data.
1676
1677 compr={none|lzo|zlib}
1678 Select the default compressor which is used when new files are
1679 written. It is still possible to read compressed files if
1680 mounted with the none option.
1681
1682
1683 Mount options for udf
1684 UDF is the "Universal Disk Format" filesystem defined by OSTA, the
1685 Optical Storage Technology Association, and is often used for DVD-ROM,
1686 frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, how‐
1687 ever, perfectly usable by itself on disk drives, flash drives and other
1688 block devices. See also iso9660.
1689
1690 uid= Make all files in the filesystem belong to the given user.
1691 uid=forget can be specified independently of (or usually in
1692 addition to) uid=<user> and results in UDF not storing uids to
1693 the media. In fact the recorded uid is the 32-bit overflow uid
1694 -1 as defined by the UDF standard. The value is given as either
1695 <user> which is a valid user name or the corresponding decimal
1696 user id, or the special string "forget".
1697
1698 gid= Make all files in the filesystem belong to the given group.
1699 gid=forget can be specified independently of (or usually in
1700 addition to) gid=<group> and results in UDF not storing gids to
1701 the media. In fact the recorded gid is the 32-bit overflow gid
1702 -1 as defined by the UDF standard. The value is given as either
1703 <group> which is a valid group name or the corresponding decimal
1704 group id, or the special string "forget".
1705
1706 umask= Mask out the given permissions from all inodes read from the
1707 filesystem. The value is given in octal.
1708
1709 mode= If mode= is set the permissions of all non-directory inodes read
1710 from the filesystem will be set to the given mode. The value is
1711 given in octal.
1712
1713 dmode= If dmode= is set the permissions of all directory inodes read
1714 from the filesystem will be set to the given dmode. The value is
1715 given in octal.
1716
1717 bs= Set the block size. Default value prior to kernel version 2.6.30
1718 was 2048. Since 2.6.30 and prior to 4.11 it was logical device
1719 block size with fallback to 2048. Since 4.11 it is logical block
1720 size with fallback to any valid block size between logical
1721 device block size and 4096.
1722
1723 For other details see the mkudffs(8) 2.0+ manpage, sections COM‐
1724 PATIBILITY and BLOCK SIZE.
1725
1726 unhide Show otherwise hidden files.
1727
1728 undelete
1729 Show deleted files in lists.
1730
1731 adinicb
1732 Embed data in the inode. (default)
1733
1734 noadinicb
1735 Don't embed data in the inode.
1736
1737 shortad
1738 Use short UDF address descriptors.
1739
1740 longad Use long UDF address descriptors. (default)
1741
1742 nostrict
1743 Unset strict conformance.
1744
1745 iocharset=
1746 Set the NLS character set. This requires kernel compiled with
1747 CONFIG_UDF_NLS option.
1748
1749 utf8 Set the UTF-8 character set.
1750
1751 Mount options for debugging and disaster recovery
1752 novrs Ignore the Volume Recognition Sequence and attempt to mount any‐
1753 way.
1754
1755 session=
1756 Select the session number for multi-session recorded optical
1757 media. (default= last session)
1758
1759 anchor=
1760 Override standard anchor location. (default= 256)
1761
1762 lastblock=
1763 Set the last block of the filesystem.
1764
1765 Unused historical mount options that may be encountered and should be
1766 removed
1767 uid=ignore
1768 Ignored, use uid=<user> instead.
1769
1770 gid=ignore
1771 Ignored, use gid=<group> instead.
1772
1773 volume=
1774 Unimplemented and ignored.
1775
1776 partition=
1777 Unimplemented and ignored.
1778
1779 fileset=
1780 Unimplemented and ignored.
1781
1782 rootdir=
1783 Unimplemented and ignored.
1784
1785
1786 Mount options for ufs
1787 ufstype=value
1788 UFS is a filesystem widely used in different operating systems.
1789 The problem are differences among implementations. Features of
1790 some implementations are undocumented, so its hard to recognize
1791 the type of ufs automatically. That's why the user must specify
1792 the type of ufs by mount option. Possible values are:
1793
1794 old Old format of ufs, this is the default, read only.
1795 (Don't forget to give the -r option.)
1796
1797 44bsd For filesystems created by a BSD-like system (NetBSD,
1798 FreeBSD, OpenBSD).
1799
1800 ufs2 Used in FreeBSD 5.x supported as read-write.
1801
1802 5xbsd Synonym for ufs2.
1803
1804 sun For filesystems created by SunOS or Solaris on Sparc.
1805
1806 sunx86 For filesystems created by Solaris on x86.
1807
1808 hp For filesystems created by HP-UX, read-only.
1809
1810 nextstep
1811 For filesystems created by NeXTStep (on NeXT station)
1812 (currently read only).
1813
1814 nextstep-cd
1815 For NextStep CDROMs (block_size == 2048), read-only.
1816
1817 openstep
1818 For filesystems created by OpenStep (currently read
1819 only). The same filesystem type is also used by Mac OS
1820 X.
1821
1822
1823 onerror=value
1824 Set behavior on error:
1825
1826 panic If an error is encountered, cause a kernel panic.
1827
1828 [lock|umount|repair]
1829 These mount options don't do anything at present; when an
1830 error is encountered only a console message is printed.
1831
1832
1833 Mount options for umsdos
1834 See mount options for msdos. The dotsOK option is explicitly killed by
1835 umsdos.
1836
1837
1838 Mount options for vfat
1839 First of all, the mount options for fat are recognized. The dotsOK
1840 option is explicitly killed by vfat. Furthermore, there are
1841
1842 uni_xlate
1843 Translate unhandled Unicode characters to special escaped
1844 sequences. This lets you backup and restore filenames that are
1845 created with any Unicode characters. Without this option, a '?'
1846 is used when no translation is possible. The escape character
1847 is ':' because it is otherwise invalid on the vfat filesystem.
1848 The escape sequence that gets used, where u is the Unicode char‐
1849 acter, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
1850
1851 posix Allow two files with names that only differ in case. This
1852 option is obsolete.
1853
1854 nonumtail
1855 First try to make a short name without sequence number, before
1856 trying name~num.ext.
1857
1858 utf8 UTF8 is the filesystem safe 8-bit encoding of Unicode that is
1859 used by the console. It can be enabled for the filesystem with
1860 this option or disabled with utf8=0, utf8=no or utf8=false. If
1861 `uni_xlate' gets set, UTF8 gets disabled.
1862
1863 shortname=mode
1864 Defines the behavior for creation and display of filenames which
1865 fit into 8.3 characters. If a long name for a file exists, it
1866 will always be the preferred one for display. There are four
1867 modes:
1868
1869 lower Force the short name to lower case upon display; store a
1870 long name when the short name is not all upper case.
1871
1872 win95 Force the short name to upper case upon display; store a
1873 long name when the short name is not all upper case.
1874
1875 winnt Display the short name as is; store a long name when the
1876 short name is not all lower case or all upper case.
1877
1878 mixed Display the short name as is; store a long name when the
1879 short name is not all upper case. This mode is the
1880 default since Linux 2.6.32.
1881
1882
1883 Mount options for usbfs
1884 devuid=uid and devgid=gid and devmode=mode
1885 Set the owner and group and mode of the device files in the
1886 usbfs filesystem (default: uid=gid=0, mode=0644). The mode is
1887 given in octal.
1888
1889 busuid=uid and busgid=gid and busmode=mode
1890 Set the owner and group and mode of the bus directories in the
1891 usbfs filesystem (default: uid=gid=0, mode=0555). The mode is
1892 given in octal.
1893
1894 listuid=uid and listgid=gid and listmode=mode
1895 Set the owner and group and mode of the file devices (default:
1896 uid=gid=0, mode=0444). The mode is given in octal.
1897
1898
1900 The device-mapper verity target provides read-only transparent
1901 integrity checking of block devices using kernel crypto API. The mount
1902 command can open the dm-verity device and do the integrity verification
1903 before on the device filesystem is mounted. Requires libcryptsetup
1904 with in libmount (optionally via dlopen). If libcryptsetup supports
1905 extracting the root hash of an already mounted device, existing devices
1906 will be automatically reused in case of a match. Mount options for dm-
1907 verity:
1908
1909 verity.hashdevice=path
1910 Path to the hash tree device associated with the source volume
1911 to pass to dm-verity.
1912
1913 verity.roothash=hex
1914 Hex-encoded hash of the root of verity.hashdevice Mutually
1915 exclusive with verity.roothashfile.
1916
1917 verity.roothashfile=path
1918 Path to file containing the hex-encoded hash of the root of ver‐
1919 ity.hashdevice. Mutually exclusive with verity.roothash.
1920
1921 verity.hashoffset=offset
1922 If the hash tree device is embedded in the source volume, offset
1923 (default: 0) is used by dm-verity to get to the tree.
1924
1925 verity.fecdevice=path
1926 Path to the Forward Error Correction (FEC) device associated
1927 with the source volume to pass to dm-verity. Optional. Requires
1928 kernel built with CONFIG_DM_VERITY_FEC.
1929
1930 verity.fecoffset=offset
1931 If the FEC device is embedded in the source volume, offset
1932 (default: 0) is used by dm-verity to get to the FEC area.
1933 Optional.
1934
1935 verity.fecroots=value
1936 Parity bytes for FEC (default: 2). Optional.
1937
1938 verity.roothashsig=path
1939 Path to pkcs7 signature of root hash hex string. Requires
1940 crypt_activate_by_signed_key() from cryptsetup and kernel built
1941 with CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG. For device reuse,
1942 signatures have to be either used by all mounts of a device or
1943 by none. Optional.
1944
1945 Supported since util-linux v2.35.
1946
1947 For example commands:
1948
1949 mksquashfs /etc /tmp/etc.squashfs
1950 dd if=/dev/zero of=/tmp/etc.hash bs=1M count=10
1951 veritysetup format /tmp/etc.squashfs /tmp/etc.hash
1952 openssl smime -sign -in <hash> -nocerts -inkey private.key \
1953 -signer private.crt -noattr -binary -outform der -out /tmp/etc.p7
1954 mount -o verity.hashdevice=/tmp/etc.hash,verity.roothash=<hash>,\
1955 verity.roothashsig=/tmp/etc.p7 /tmp/etc.squashfs /mnt
1956
1957 create squashfs image from /etc directory, verity hash device and mount
1958 verified filesystem image to /mnt. The kernel will verify that the
1959 root hash is signed by a key from the kernel keyring if roothashsig is
1960 used.
1961
1962
1964 One further possible type is a mount via the loop device. For example,
1965 the command
1966
1967 mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3
1968
1969 will set up the loop device /dev/loop3 to correspond to the file
1970 /tmp/disk.img, and then mount this device on /mnt.
1971
1972 If no explicit loop device is mentioned (but just an option `-o loop'
1973 is given), then mount will try to find some unused loop device and use
1974 that, for example
1975
1976 mount /tmp/disk.img /mnt -o loop
1977
1978 The mount command automatically creates a loop device from a regular
1979 file if a filesystem type is not specified or the filesystem is known
1980 for libblkid, for example:
1981
1982 mount /tmp/disk.img /mnt
1983
1984 mount -t ext4 /tmp/disk.img /mnt
1985
1986 This type of mount knows about three options, namely loop, offset and
1987 sizelimit, that are really options to losetup(8). (These options can
1988 be used in addition to those specific to the filesystem type.)
1989
1990 Since Linux 2.6.25 auto-destruction of loop devices is supported, mean‐
1991 ing that any loop device allocated by mount will be freed by umount
1992 independently of /etc/mtab.
1993
1994 You can also free a loop device by hand, using losetup -d or umount -d.
1995
1996 Since util-linux v2.29, mount re-uses the loop device rather than ini‐
1997 tializing a new device if the same backing file is already used for
1998 some loop device with the same offset and sizelimit. This is necessary
1999 to avoid a filesystem corruption.
2000
2001
2003 mount has the following exit status values (the bits can be ORed):
2004
2005 0 success
2006
2007 1 incorrect invocation or permissions
2008
2009 2 system error (out of memory, cannot fork, no more loop devices)
2010
2011 4 internal mount bug
2012
2013 8 user interrupt
2014
2015 16 problems writing or locking /etc/mtab
2016
2017 32 mount failure
2018
2019 64 some mount succeeded
2020
2021 The command mount -a returns 0 (all succeeded), 32 (all failed),
2022 or 64 (some failed, some succeeded).
2023
2024
2026 The syntax of external mount helpers is:
2027
2028 /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t
2029 type.subtype]
2030
2031 where the suffix is the filesystem type and the -sfnvoN options have
2032 the same meaning as the normal mount options. The -t option is used
2033 for filesystems with subtypes support (for example /sbin/mount.fuse -t
2034 fuse.sshfs).
2035
2036 The command mount does not pass the mount options unbindable, runbind‐
2037 able, private, rprivate, slave, rslave, shared, rshared, auto, noauto,
2038 comment, x-*, loop, offset and sizelimit to the mount.<suffix> helpers.
2039 All other options are used in a comma-separated list as an argument to
2040 the -o option.
2041
2042
2044 LIBMOUNT_FSTAB=<path>
2045 overrides the default location of the fstab file (ignored for
2046 suid)
2047
2048 LIBMOUNT_MTAB=<path>
2049 overrides the default location of the mtab file (ignored for
2050 suid)
2051
2052 LIBMOUNT_DEBUG=all
2053 enables libmount debug output
2054
2055 LIBBLKID_DEBUG=all
2056 enables libblkid debug output
2057
2058 LOOPDEV_DEBUG=all
2059 enables loop device setup debug output
2060
2062 See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section
2063 above.
2064
2065 /etc/fstab filesystem table
2066
2067 /run/mount libmount private runtime directory
2068
2069 /etc/mtab table of mounted filesystems or symlink to
2070 /proc/mounts
2071
2072 /etc/mtab~ lock file (unused on systems with mtab symlink)
2073
2074 /etc/mtab.tmp temporary file (unused on systems with mtab symlink)
2075
2076 /etc/filesystems a list of filesystem types to try
2077
2079 A mount command existed in Version 5 AT&T UNIX.
2080
2082 It is possible for a corrupted filesystem to cause a crash.
2083
2084 Some Linux filesystems don't support -o sync and -o dirsync (the ext2,
2085 ext3, ext4, fat and vfat filesystems do support synchronous updates (a
2086 la BSD) when mounted with the sync option).
2087
2088 The -o remount may not be able to change mount parameters (all ext2fs-
2089 specific parameters, except sb, are changeable with a remount, for
2090 example, but you can't change gid or umask for the fatfs).
2091
2092 It is possible that the files /etc/mtab and /proc/mounts don't match on
2093 systems with a regular mtab file. The first file is based only on the
2094 mount command options, but the content of the second file also depends
2095 on the kernel and others settings (e.g. on a remote NFS server -- in
2096 certain cases the mount command may report unreliable information about
2097 an NFS mount point and the /proc/mount file usually contains more reli‐
2098 able information.) This is another reason to replace the mtab file
2099 with a symlink to the /proc/mounts file.
2100
2101 Checking files on NFS filesystems referenced by file descriptors (i.e.
2102 the fcntl and ioctl families of functions) may lead to inconsistent
2103 results due to the lack of a consistency check in the kernel even if
2104 the noac mount option is used.
2105
2106 The loop option with the offset or sizelimit options used may fail when
2107 using older kernels if the mount command can't confirm that the size of
2108 the block device has been configured as requested. This situation can
2109 be worked around by using the losetup command manually before calling
2110 mount with the configured loop device.
2111
2113 Karel Zak <kzak@redhat.com>
2114
2116 lsblk(1), mount(2), umount(2), filesystems(5), fstab(5), nfs(5),
2117 xfs(5), mount_namespaces(7) xattr(7) e2label(8), findmnt(8), los‐
2118 etup(8), mke2fs(8), mountd(8), nfsd(8), swapon(8), tune2fs(8),
2119 umount(8), xfs_admin(8)
2120
2122 The mount command is part of the util-linux package and is available
2123 from https://www.kernel.org/pub/linux/utils/util-linux/.
2124
2125
2126
2127util-linux August 2015 MOUNT(8)