1MOUNT(8)                     System Administration                    MOUNT(8)
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3
4

NAME

6       mount - mount a filesystem
7

SYNOPSIS

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
22       --make-[shared|slave|private|unbindable|rshared|rslave|rprivate|runbindable]
23       mountpoint
24

DESCRIPTION

26       All files accessible in a Unix system are arranged in one big tree, the
27       file hierarchy, rooted at /. These files can be spread out over several
28       devices. The mount command serves to attach the filesystem found on
29       some device to the big file tree. Conversely, the umount(8) command
30       will detach it again. The filesystem is used to control how data is
31       stored on the device or provided in a virtual way by network or other
32       services.
33
34       The standard form of the mount command is:
35
36          mount -t type device dir
37
38       This tells the kernel to attach the filesystem found on device (which
39       is of type type) at the directory dir. The option -t type is optional.
40       The mount command is usually able to detect a filesystem. The root
41       permissions are necessary to mount a filesystem by default. See section
42       "Non-superuser mounts" below for more details. The previous contents
43       (if any) and owner and mode of dir become invisible, and as long as
44       this filesystem remains mounted, the pathname dir refers to the root of
45       the filesystem on device.
46
47       If only the directory or the device is given, for example:
48
49          mount /dir
50
51       then mount looks for a mountpoint (and if not found then for a device)
52       in the /etc/fstab file. It’s possible to use the --target or --source
53       options to avoid ambiguous interpretation of the given argument. For
54       example:
55
56          mount --target /mountpoint
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
63       exception is --all, in this case already mounted filesystems are
64       ignored (see --all below for more details).
65
66   Listing the mounts
67       The listing mode is maintained for backward compatibility only.
68
69       For more robust and customizable output use findmnt(8), especially in
70       your scripts. Note that control characters in the mountpoint name are
71       replaced with '?'.
72
73       The following command lists all mounted filesystems (of type type):
74
75          mount [-l] [-t type]
76
77       The option -l adds labels to this listing. See below.
78
79   Indicating the device and filesystem
80       Most devices are indicated by a filename (of a block special device),
81       like /dev/sda1, but there are other possibilities. For example, in the
82       case of an NFS mount, device may look like knuth.cwi.nl:/dir.
83
84       The device names of disk partitions are unstable; hardware
85       reconfiguration, and adding or removing a device can cause changes in
86       names. This is the reason why it’s strongly recommended to use
87       filesystem or partition identifiers like UUID or LABEL. Currently
88       supported identifiers (tags):
89
90       LABEL=label
91           Human readable filesystem identifier. See also -L.
92
93       UUID=uuid
94           Filesystem universally unique identifier. The format of the UUID is
95           usually a series of hex digits separated by hyphens. See also -U.
96
97           Note that mount uses UUIDs as strings. The UUIDs from the command
98           line or from fstab(5) are not converted to internal binary
99           representation. The string representation of the UUID should be
100           based on lower case characters.
101
102       PARTLABEL=label
103           Human readable partition identifier. This identifier is independent
104           on filesystem and does not change by mkfs or mkswap operations It’s
105           supported for example for GUID Partition Tables (GPT).
106
107       PARTUUID=uuid
108           Partition universally unique identifier. This identifier is
109           independent on filesystem and does not change by mkfs or mkswap
110           operations It’s supported for example for GUID Partition Tables
111           (GPT).
112
113       ID=id
114           Hardware block device ID as generated by udevd. This identifier is
115           usually based on WWN (unique storage identifier) and assigned by
116           the hardware manufacturer. See ls /dev/disk/by-id for more details,
117           this directory and running udevd is required. This identifier is
118           not recommended for generic use as the identifier is not strictly
119           defined and it depends on udev, udev rules and hardware.
120
121       The command lsblk --fs provides an overview of filesystems, LABELs and
122       UUIDs on available block devices. The command blkid -p <device>
123       provides details about a filesystem on the specified device.
124
125       Don’t forget that there is no guarantee that UUIDs and labels are
126       really unique, especially if you move, share or copy the device. Use
127       lsblk -o +UUID,PARTUUID to verify that the UUIDs are really unique in
128       your system.
129
130       The recommended setup is to use tags (e.g. UUID=uuid) rather than
131       /dev/disk/by-{label,uuid,id,partuuid,partlabel} udev symlinks in the
132       /etc/fstab file. Tags are more readable, robust and portable. The
133       mount(8) command internally uses udev symlinks, so the use of symlinks
134       in /etc/fstab has no advantage over tags. For more details see
135       libblkid(3).
136
137       The proc filesystem is not associated with a special device, and when
138       mounting it, an arbitrary keyword - for example, proc - can be used
139       instead of a device specification. (The customary choice none is less
140       fortunate: the error message 'none already mounted' from mount can be
141       confusing.)
142
143   The files /etc/fstab, /etc/mtab and /proc/mounts
144       The file /etc/fstab (see fstab(5)), may contain lines describing what
145       devices are usually mounted where, using which options. The default
146       location of the fstab(5) file can be overridden with the --fstab path
147       command-line option (see below for more details).
148
149       The command
150
151          mount -a [-t type] [-O optlist]
152
153       (usually given in a bootscript) causes all filesystems mentioned in
154       fstab (of the proper type and/or having or not having the proper
155       options) to be mounted as indicated, except for those whose line
156       contains the noauto keyword. Adding the -F option will make mount fork,
157       so that the filesystems are mounted in parallel.
158
159       When mounting a filesystem mentioned in fstab or mtab, it suffices to
160       specify on the command line only the device, or only the mount point.
161
162       The programs mount and umount(8) traditionally maintained a list of
163       currently mounted filesystems in the file /etc/mtab. The support for
164       regular classic /etc/mtab is completely disabled at compile time by
165       default, because on current Linux systems it is better to make
166       /etc/mtab a symlink to /proc/mounts instead. The regular mtab file
167       maintained in userspace cannot reliably work with namespaces,
168       containers and other advanced Linux features. If the regular mtab
169       support is enabled, then it’s possible to use the file as well as the
170       symlink.
171
172       If no arguments are given to mount, the list of mounted filesystems is
173       printed.
174
175       If you want to override mount options from /etc/fstab, you have to use
176       the -o option:
177
178          mount device**|dir -o options
179
180       and then the mount options from the command line will be appended to
181       the list of options from /etc/fstab. This default behaviour can be
182       changed using the --options-mode command-line option. The usual
183       behavior is that the last option wins if there are conflicting ones.
184
185       The mount program does not read the /etc/fstab file if both device (or
186       LABEL, UUID, ID, PARTUUID or PARTLABEL) and dir are specified. For
187       example, to mount device foo at /dir:
188
189          mount /dev/foo /dir
190
191       This default behaviour can be changed by using the
192       --options-source-force command-line option to always read configuration
193       from fstab. For non-root users mount always reads the fstab
194       configuration.
195
196   Non-superuser mounts
197       Normally, only the superuser can mount filesystems. However, when fstab
198       contains the user option on a line, anybody can mount the corresponding
199       filesystem.
200
201       Thus, given a line
202
203          /dev/cdrom /cd iso9660 ro,user,noauto,unhide
204
205       any user can mount the iso9660 filesystem found on an inserted CDROM
206       using the command:
207
208          mount /cd
209
210       Note that mount is very strict about non-root users and all paths
211       specified on command line are verified before fstab is parsed or a
212       helper program is executed. It’s strongly recommended to use a valid
213       mountpoint to specify filesystem, otherwise mount may fail. For example
214       it’s a bad idea to use NFS or CIFS source on command line.
215
216       Since util-linux 2.35, mount does not exit when user permissions are
217       inadequate according to libmount’s internal security rules. Instead, it
218       drops suid permissions and continues as regular non-root user. This
219       behavior supports use-cases where root permissions are not necessary
220       (e.g., fuse filesystems, user namespaces, etc).
221
222       For more details, see fstab(5). Only the user that mounted a filesystem
223       can unmount it again. If any user should be able to unmount it, then
224       use users instead of user in the fstab line. The owner option is
225       similar to the user option, with the restriction that the user must be
226       the owner of the special file. This may be useful e.g. for /dev/fd if a
227       login script makes the console user owner of this device. The group
228       option is similar, with the restriction that the user must be a member
229       of the group of the special file.
230
231   Bind mount operation
232       Remount part of the file hierarchy somewhere else. The call is:
233
234          mount --bind olddir newdir
235
236       or by using this fstab entry:
237
238          /olddir /newdir none bind
239
240       After this call the same contents are accessible in two places.
241
242       It is important to understand that "bind" does not create any
243       second-class or special node in the kernel VFS. The "bind" is just
244       another operation to attach a filesystem. There is nowhere stored
245       information that the filesystem has been attached by a "bind"
246       operation. The olddir and newdir are independent and the olddir may be
247       unmounted.
248
249       One can also remount a single file (on a single file). It’s also
250       possible to use a bind mount to create a mountpoint from a regular
251       directory, for example:
252
253          mount --bind foo foo
254
255       The bind mount call attaches only (part of) a single filesystem, not
256       possible submounts. The entire file hierarchy including submounts can
257       be attached a second place by using:
258
259          mount --rbind olddir newdir
260
261       Note that the filesystem mount options maintained by the kernel will
262       remain the same as those on the original mount point. The userspace
263       mount options (e.g., _netdev) will not be copied by mount and it’s
264       necessary to explicitly specify the options on the mount command line.
265
266       Since util-linux 2.27 mount permits changing the mount options by
267       passing the relevant options along with --bind. For example:
268
269          mount -o bind,ro foo foo
270
271       This feature is not supported by the Linux kernel; it is implemented in
272       userspace by an additional mount(2) remounting system call. This
273       solution is not atomic.
274
275       The alternative (classic) way to create a read-only bind mount is to
276       use the remount operation, for example:
277
278          mount --bind olddir newdir mount -o remount,bind,ro olddir
279          newdir
280
281       Note that a read-only bind will create a read-only mountpoint (VFS
282       entry), but the original filesystem superblock will still be writable,
283       meaning that the olddir will be writable, but the newdir will be
284       read-only.
285
286       It’s also possible to change nosuid, nodev, noexec, noatime, nodiratime
287       and relatime VFS entry flags via a "remount,bind" operation. The other
288       flags (for example filesystem-specific flags) are silently ignored.
289       It’s impossible to change mount options recursively (for example with
290       -o rbind,ro).
291
292       Since util-linux 2.31, mount ignores the bind flag from /etc/fstab on a
293       remount operation (if "-o remount" is specified on command line). This
294       is necessary to fully control mount options on remount by command line.
295       In previous versions the bind flag has been always applied and it was
296       impossible to re-define mount options without interaction with the bind
297       semantic. This mount behavior does not affect situations when
298       "remount,bind" is specified in the /etc/fstab file.
299
300   The move operation
301       Move a mounted tree to another place (atomically). The call is:
302
303          mount --move olddir newdir
304
305       This will cause the contents which previously appeared under olddir to
306       now be accessible under newdir. The physical location of the files is
307       not changed. Note that olddir has to be a mountpoint.
308
309       Note also that moving a mount residing under a shared mount is invalid
310       and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current
311       propagation flags.
312
313   Shared subtree operations
314       Since Linux 2.6.15 it is possible to mark a mount and its submounts as
315       shared, private, slave or unbindable. A shared mount provides the
316       ability to create mirrors of that mount such that mounts and unmounts
317       within any of the mirrors propagate to the other mirror. A slave mount
318       receives propagation from its master, but not vice versa. A private
319       mount carries no propagation abilities. An unbindable mount is a
320       private mount which cannot be cloned through a bind operation. The
321       detailed semantics are documented in
322       Documentation/filesystems/sharedsubtree.txt file in the kernel source
323       tree; see also mount_namespaces(7).
324
325       Supported operations are:
326
327           mount --make-shared mountpoint
328           mount --make-slave mountpoint
329           mount --make-private mountpoint
330           mount --make-unbindable mountpoint
331
332       The following commands allow one to recursively change the type of all
333       the mounts under a given mountpoint.
334
335           mount --make-rshared mountpoint
336           mount --make-rslave mountpoint
337           mount --make-rprivate mountpoint
338           mount --make-runbindable mountpoint
339
340       mount(8) does not read fstab(5) when a --make-* operation is requested.
341       All necessary information has to be specified on the command line.
342
343       Note that the Linux kernel does not allow changing multiple propagation
344       flags with a single mount(2) system call, and the flags cannot be mixed
345       with other mount options and operations.
346
347       Since util-linux 2.23 the mount command can be used to do more
348       propagation (topology) changes by one mount(8) call and do it also
349       together with other mount operations. The propagation flags are applied
350       by additional mount(2) system calls when the preceding mount operations
351       were successful. Note that this use case is not atomic. It is possible
352       to specify the propagation flags in fstab(5) as mount options (private,
353       slave, shared, unbindable, rprivate, rslave, rshared, runbindable).
354
355       For example:
356
357           mount --make-private --make-unbindable /dev/sda1 /foo
358
359       is the same as:
360
361           mount /dev/sda1 /foo
362           mount --make-private /foo
363           mount --make-unbindable /foo
364

COMMAND-LINE OPTIONS

366       The full set of mount options used by an invocation of mount is
367       determined by first extracting the mount options for the filesystem
368       from the fstab table, then applying any options specified by the -o
369       argument, and finally applying a -r or -w option, when present.
370
371       The mount command does not pass all command-line options to the
372       /sbin/mount.suffix mount helpers. The interface between mount and the
373       mount helpers is described below in the section EXTERNAL HELPERS.
374
375       Command-line options available for the mount command are:
376
377       -a, --all
378           Mount all filesystems (of the given types) mentioned in fstab
379           (except for those whose line contains the noauto keyword). The
380           filesystems are mounted following their order in fstab. The mount
381           command compares filesystem source, target (and fs root for bind
382           mount or btrfs) to detect already mounted filesystems. The kernel
383           table with already mounted filesystems is cached during mount
384           --all. This means that all duplicated fstab entries will be
385           mounted.
386
387           The option --all is possible to use for remount operation too. In
388           this case all filters (-t and -O) are applied to the table of
389           already mounted filesystems.
390
391           Since version 2.35 is possible to use the command line option -o to
392           alter mount options from fstab (see also --options-mode).
393
394           Note that it is a bad practice to use mount -a for fstab checking.
395           The recommended solution is findmnt --verify.
396
397       -B, --bind
398           Remount a subtree somewhere else (so that its contents are
399           available in both places). See above, under Bind mounts.
400
401       -c, --no-canonicalize
402           Don’t canonicalize paths. The mount command canonicalizes all paths
403           (from the command line or fstab) by default. This option can be
404           used together with the -f flag for already canonicalized absolute
405           paths. The option is designed for mount helpers which call mount
406           -i. It is strongly recommended to not use this command-line option
407           for normal mount operations.
408
409           Note that mount does not pass this option to the /sbin/mount.type
410           helpers.
411
412       -F, --fork
413           (Used in conjunction with -a.) Fork off a new incarnation of mount
414           for each device. This will do the mounts on different devices or
415           different NFS servers in parallel. This has the advantage that it
416           is faster; also NFS timeouts proceed in parallel. A disadvantage is
417           that the order of the mount operations is undefined. Thus, you
418           cannot use this option if you want to mount both /usr and
419           /usr/spool.
420
421       -f, --fake
422           Causes everything to be done except for the actual system call; if
423           it’s not obvious, this "fakes" mounting the filesystem. This option
424           is useful in conjunction with the -v flag to determine what the
425           mount command is trying to do. It can also be used to add entries
426           for devices that were mounted earlier with the -n option. The -f
427           option checks for an existing record in /etc/mtab and fails when
428           the record already exists (with a regular non-fake mount, this
429           check is done by the kernel).
430
431       -i, --internal-only
432           Don’t call the /sbin/mount.filesystem helper even if it exists.
433
434       -L, --label label
435           Mount the partition that has the specified label.
436
437       -l, --show-labels
438           Add the labels in the mount output. mount must have permission to
439           read the disk device (e.g. be set-user-ID root) for this to work.
440           One can set such a label for ext2, ext3 or ext4 using the
441           e2label(8) utility, or for XFS using xfs_admin(8), or for reiserfs
442           using reiserfstune(8).
443
444       -M, --move
445           Move a subtree to some other place. See above, the subsection The
446           move operation.
447
448       -n, --no-mtab
449           Mount without writing in /etc/mtab. This is necessary for example
450           when /etc is on a read-only filesystem.
451
452       -N, --namespace ns
453           Perform the mount operation in the mount namespace specified by ns.
454           ns is either PID of process running in that namespace or special
455           file representing that namespace.
456
457           mount switches to the mount namespace when it reads /etc/fstab,
458           writes /etc/mtab: (or writes to _/run/mount) and calls the mount(2)
459           system call, otherwise it runs in the original mount namespace.
460           This means that the target namespace does not have to contain any
461           libraries or other requirements necessary to execute the mount(2)
462           call.
463
464           See mount_namespaces(7) for more information.
465
466       -O, --test-opts opts
467           Limit the set of filesystems to which the -a option applies. In
468           this regard it is like the -t option except that -O is useless
469           without -a. For example, the command
470
471           mount -a -O no_netdev
472
473           mounts all filesystems except those which have the option netdev
474           specified in the options field in the /etc/fstab file.
475
476           It is different from -t in that each option is matched exactly; a
477           leading no at the beginning of one option does not negate the rest.
478
479           The -t and -O options are cumulative in effect; that is, the
480           command
481
482           mount -a -t ext2 -O  _netdev
483
484           mounts all ext2 filesystems with the _netdev option, not all
485           filesystems that are either ext2 or have the _netdev option
486           specified.
487
488       -o, --options opts
489           Use the specified mount options. The opts argument is a
490           comma-separated list. For example:
491
492           mount LABEL=mydisk -o noatime,nodev,nosuid
493
494           For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and
495           FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.
496
497       --options-mode mode
498           Controls how to combine options from fstab/mtab with options from
499           the command line. mode can be one of ignore, append, prepend or
500           replace. For example, append means that options from fstab are
501           appended to options from the command line. The default value is
502           prepend — it means command line options are evaluated after fstab
503           options. Note that the last option wins if there are conflicting
504           ones.
505
506       --options-source source
507           Source of default options. source is a comma-separated list of
508           fstab, mtab and disable. disable disables fstab and mtab and
509           disables --options-source-force. The default value is fstab,mtab.
510
511       --options-source-force
512           Use options from fstab/mtab even if both device and dir are
513           specified.
514
515       -R, --rbind
516           Remount a subtree and all possible submounts somewhere else (so
517           that its contents are available in both places). See above, the
518           subsection Bind mounts.
519
520       -r, --read-only
521           Mount the filesystem read-only. A synonym is -o ro.
522
523           Note that, depending on the filesystem type, state and kernel
524           behavior, the system may still write to the device. For example,
525           ext3 and ext4 will replay the journal if the filesystem is dirty.
526           To prevent this kind of write access, you may want to mount an ext3
527           or ext4 filesystem with the ro,noload mount options or set the
528           block device itself to read-only mode, see the blockdev(8) command.
529
530       -s
531           Tolerate sloppy mount options rather than failing. This will ignore
532           mount options not supported by a filesystem type. Not all
533           filesystems support this option. Currently it’s supported by the
534           mount.nfs mount helper only.
535
536       --source device
537           If only one argument for the mount command is given, then the
538           argument might be interpreted as the target (mountpoint) or source
539           (device). This option allows you to explicitly define that the
540           argument is the mount source.
541
542       --target directory
543           If only one argument for the mount command is given, then the
544           argument might be interpreted as the target (mountpoint) or source
545           (device). This option allows you to explicitly define that the
546           argument is the mount target.
547
548       --target-prefix directory
549           Prepend the specified directory to all mount targets. This option
550           can be used to follow fstab, but mount operations are done in
551           another place, for example:
552
553           mount --all --target-prefix /chroot -o X-mount.mkdir
554
555           mounts all from system fstab to /chroot, all missing mountpoint are
556           created (due to X-mount.mkdir). See also --fstab to use an
557           alternative fstab.
558
559       -T, --fstab path
560           Specifies an alternative fstab file. If path is a directory, then
561           the files in the directory are sorted by strverscmp(3); files that
562           start with "." or without an .fstab extension are ignored. The
563           option can be specified more than once. This option is mostly
564           designed for initramfs or chroot scripts where additional
565           configuration is specified beyond standard system configuration.
566
567           Note that mount does not pass the option --fstab to the
568           /sbin/mount.type helpers, meaning that the alternative fstab files
569           will be invisible for the helpers. This is no problem for normal
570           mounts, but user (non-root) mounts always require fstab to verify
571           the user’s rights.
572
573       -t, --types fstype
574           The argument following the -t is used to indicate the filesystem
575           type. The filesystem types which are currently supported depend on
576           the running kernel. See /proc/filesystems and /lib/modules/$(uname
577           -r)/kernel/fs for a complete list of the filesystems. The most
578           common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and
579           cifs.
580
581           The programs mount and umount(8) support filesystem subtypes. The
582           subtype is defined by a '.subtype' suffix. For example
583           'fuse.sshfs'. It’s recommended to use subtype notation rather than
584           add any prefix to the mount source (for example 'sshfs#example.com'
585           is deprecated).
586
587           If no -t option is given, or if the auto type is specified, mount
588           will try to guess the desired type. mount uses the libblkid(3)
589           library for guessing the filesystem type; if that does not turn up
590           anything that looks familiar, mount will try to read the file
591           /etc/filesystems, or, if that does not exist, /proc/filesystems.
592           All of the filesystem types listed there will be tried, except for
593           those that are labeled "nodev" (e.g. devpts, proc and nfs). If
594           /etc/filesystems ends in a line with a single *, mount will read
595           /proc/filesystems afterwards. While trying, all filesystem types
596           will be mounted with the mount option silent.
597
598           The auto type may be useful for user-mounted floppies. Creating a
599           file /etc/filesystems can be useful to change the probe order
600           (e.g., to try vfat before msdos or ext3 before ext2) or if you use
601           a kernel module autoloader.
602
603           More than one type may be specified in a comma-separated list, for
604           the -t option as well as in an /etc/fstab entry. The list of
605           filesystem types for the -t option can be prefixed with no to
606           specify the filesystem types on which no action should be taken.
607           The prefix no has no effect when specified in an /etc/fstab entry.
608
609           The prefix no can be meaningful with the -a option. For example,
610           the command
611
612           mount -a -t nomsdos,smbfs
613
614           mounts all filesystems except those of type msdos and smbfs.
615
616           For most types all the mount program has to do is issue a simple
617           mount(2) system call, and no detailed knowledge of the filesystem
618           type is required. For a few types however (like nfs, nfs4, cifs,
619           smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4, cifs,
620           smbfs, and ncpfs filesystems have a separate mount program. In
621           order to make it possible to treat all types in a uniform way,
622           mount will execute the program /sbin/mount.type (if that exists)
623           when called with type type. Since different versions of the
624           smbmount program have different calling conventions,
625           /sbin/mount.smbfs may have to be a shell script that sets up the
626           desired call.
627
628       -U, --uuid uuid
629           Mount the partition that has the specified uuid.
630
631       -v, --verbose
632           Verbose mode.
633
634       -w, --rw, --read-write
635           Mount the filesystem read/write. Read-write is the kernel default
636           and the mount default is to try read-only if the previous mount
637           syscall with read-write flags on write-protected devices of
638           filesystems failed.
639
640           A synonym is -o rw.
641
642           Note that specifying -w on the command line forces mount to never
643           try read-only mount on write-protected devices or already mounted
644           read-only filesystems.
645
646       -V, --version
647           Display version information and exit.
648
649       -h, --help
650           Display help text and exit.
651

FILESYSTEM-INDEPENDENT MOUNT OPTIONS

653       Some of these options are only useful when they appear in the
654       /etc/fstab file.
655
656       Some of these options could be enabled or disabled by default in the
657       system kernel. To check the current setting see the options in
658       /proc/mounts. Note that filesystems also have per-filesystem specific
659       default mount options (see for example tune2fs -l output for ext_N_
660       filesystems).
661
662       The following options apply to any filesystem that is being mounted
663       (but not every filesystem actually honors them - e.g., the sync option
664       today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs):
665
666       async
667           All I/O to the filesystem should be done asynchronously. (See also
668           the sync option.)
669
670       atime
671           Do not use the noatime feature, so the inode access time is
672           controlled by kernel defaults. See also the descriptions of the
673           relatime and strictatime mount options.
674
675       noatime
676           Do not update inode access times on this filesystem (e.g. for
677           faster access on the news spool to speed up news servers). This
678           works for all inode types (directories too), so it implies
679           nodiratime.
680
681       auto
682           Can be mounted with the -a option.
683
684       noauto
685           Can only be mounted explicitly (i.e., the -a option will not cause
686           the filesystem to be mounted).
687
688       context=context, fscontext=context, defcontext=context, and
689       rootcontext=context
690           The context= option is useful when mounting filesystems that do not
691           support extended attributes, such as a floppy or hard disk
692           formatted with VFAT, or systems that are not normally running under
693           SELinux, such as an ext3 or ext4 formatted disk from a non-SELinux
694           workstation. You can also use context= on filesystems you do not
695           trust, such as a floppy. It also helps in compatibility with
696           xattr-supporting filesystems on earlier 2.4.<x> kernel versions.
697           Even where xattrs are supported, you can save time not having to
698           label every file by assigning the entire disk one security context.
699
700           A commonly used option for removable media is
701           context="system_u:object_r:removable_t.
702
703           The fscontext= option works for all filesystems, regardless of
704           their xattr support. The fscontext option sets the overarching
705           filesystem label to a specific security context. This filesystem
706           label is separate from the individual labels on the files. It
707           represents the entire filesystem for certain kinds of permission
708           checks, such as during mount or file creation. Individual file
709           labels are still obtained from the xattrs on the files themselves.
710           The context option actually sets the aggregate context that
711           fscontext provides, in addition to supplying the same label for
712           individual files.
713
714           You can set the default security context for unlabeled files using
715           defcontext= option. This overrides the value set for unlabeled
716           files in the policy and requires a filesystem that supports xattr
717           labeling.
718
719           The rootcontext= option allows you to explicitly label the root
720           inode of a FS being mounted before that FS or inode becomes visible
721           to userspace. This was found to be useful for things like stateless
722           Linux.
723
724           Note that the kernel rejects any remount request that includes the
725           context option, even when unchanged from the current context.
726
727           Warning: the context value might contain commas, in which case the
728           value has to be properly quoted, otherwise mount will interpret the
729           comma as a separator between mount options. Don’t forget that the
730           shell strips off quotes and thus double quoting is required. For
731           example:
732
733          mount -t tmpfs none /mnt -o \
734          'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
735
736       For more details, see selinux(8).
737
738       defaults
739           Use the default options: rw, suid, dev, exec, auto, nouser, and
740           async.
741
742           Note that the real set of all default mount options depends on the
743           kernel and filesystem type. See the beginning of this section for
744           more details.
745
746       dev
747           Interpret character or block special devices on the filesystem.
748
749       nodev
750           Do not interpret character or block special devices on the
751           filesystem.
752
753       diratime
754           Update directory inode access times on this filesystem. This is the
755           default. (This option is ignored when noatime is set.)
756
757       nodiratime
758           Do not update directory inode access times on this filesystem.
759           (This option is implied when noatime is set.)
760
761       dirsync
762           All directory updates within the filesystem should be done
763           synchronously. This affects the following system calls: creat(2),
764           link(2), unlink(2), symlink(2), mkdir(2), rmdir(2), mknod(2) and
765           rename(2).
766
767       exec
768           Permit execution of binaries.
769
770       noexec
771           Do not permit direct execution of any binaries on the mounted
772           filesystem.
773
774       group
775           Allow an ordinary user to mount the filesystem if one of that
776           user’s groups matches the group of the device. This option implies
777           the options nosuid and nodev (unless overridden by subsequent
778           options, as in the option line group,dev,suid).
779
780       iversion
781           Every time the inode is modified, the i_version field will be
782           incremented.
783
784       noiversion
785           Do not increment the i_version inode field.
786
787       mand
788           Allow mandatory locks on this filesystem. See fcntl(2).
789
790       nomand
791           Do not allow mandatory locks on this filesystem.
792
793       _netdev
794           The filesystem resides on a device that requires network access
795           (used to prevent the system from attempting to mount these
796           filesystems until the network has been enabled on the system).
797
798       nofail
799           Do not report errors for this device if it does not exist.
800
801       relatime
802           Update inode access times relative to modify or change time. Access
803           time is only updated if the previous access time was earlier than
804           the current modify or change time. (Similar to noatime, but it
805           doesn’t break mutt(1) or other applications that need to know if a
806           file has been read since the last time it was modified.)
807
808           Since Linux 2.6.30, the kernel defaults to the behavior provided by
809           this option (unless noatime was specified), and the strictatime
810           option is required to obtain traditional semantics. In addition,
811           since Linux 2.6.30, the file’s last access time is always updated
812           if it is more than 1 day old.
813
814       norelatime
815           Do not use the relatime feature. See also the strictatime mount
816           option.
817
818       strictatime
819           Allows to explicitly request full atime updates. This makes it
820           possible for the kernel to default to relatime or noatime but still
821           allow userspace to override it. For more details about the default
822           system mount options see /proc/mounts.
823
824       nostrictatime
825           Use the kernel’s default behavior for inode access time updates.
826
827       lazytime
828           Only update times (atime, mtime, ctime) on the in-memory version of
829           the file inode.
830
831           This mount option significantly reduces writes to the inode table
832           for workloads that perform frequent random writes to preallocated
833           files.
834
835           The on-disk timestamps are updated only when:
836
837           •   the inode needs to be updated for some change unrelated to file
838               timestamps
839
840           •   the application employs fsync(2), syncfs(2), or sync(2)
841
842           •   an undeleted inode is evicted from memory
843
844           •   more than 24 hours have passed since the inode was written to
845               disk.
846
847       nolazytime
848           Do not use the lazytime feature.
849
850       suid
851           Honor set-user-ID and set-group-ID bits or file capabilities when
852           executing programs from this filesystem.
853
854       nosuid
855           Do not honor set-user-ID and set-group-ID bits or file capabilities
856           when executing programs from this filesystem. In addition, SELinux
857           domain transitions require permission nosuid_transition, which in
858           turn needs also policy capability nnp_nosuid_transition.
859
860       silent
861           Turn on the silent flag.
862
863       loud
864           Turn off the silent flag.
865
866       owner
867           Allow an ordinary user to mount the filesystem if that user is the
868           owner of the device. This option implies the options nosuid and
869           nodev (unless overridden by subsequent options, as in the option
870           line owner,dev,suid).
871
872       remount
873           Attempt to remount an already-mounted filesystem. This is commonly
874           used to change the mount flags for a filesystem, especially to make
875           a readonly filesystem writable. It does not change device or mount
876           point.
877
878           The remount operation together with the bind flag has special
879           semantics. See above, the subsection Bind mounts.
880
881           The remount functionality follows the standard way the mount
882           command works with options from fstab. This means that mount does
883           not read fstab (or mtab) only when both device and dir are
884           specified.
885
886           mount -o remount,rw /dev/foo /dir
887
888           After this call all old mount options are replaced and arbitrary
889           stuff from fstab (or mtab) is ignored, except the loop= option
890           which is internally generated and maintained by the mount command.
891
892           mount -o remount,rw /dir
893
894           After this call, mount reads fstab and merges these options with
895           the options from the command line (-o). If no mountpoint is found
896           in fstab, then a remount with unspecified source is allowed.
897
898           mount allows the use of --all to remount all already mounted
899           filesystems which match a specified filter (-O and -t). For
900           example:
901
902           mount --all -o remount,ro -t vfat
903
904           remounts all already mounted vfat filesystems in read-only mode.
905           Each of the filesystems is remounted by mount -o remount,ro /dir
906           semantic. This means the mount command reads fstab or mtab and
907           merges these options with the options from the command line.
908
909       ro
910           Mount the filesystem read-only.
911
912       rw
913           Mount the filesystem read-write.
914
915       sync
916           All I/O to the filesystem should be done synchronously. In the case
917           of media with a limited number of write cycles (e.g. some flash
918           drives), sync may cause life-cycle shortening.
919
920       user
921           Allow an ordinary user to mount the filesystem. The name of the
922           mounting user is written to the mtab file (or to the private
923           libmount file in /run/mount on systems without a regular mtab) so
924           that this same user can unmount the filesystem again. This option
925           implies the options noexec, nosuid, and nodev (unless overridden by
926           subsequent options, as in the option line user,exec,dev,suid).
927
928       nouser
929           Forbid an ordinary user to mount the filesystem. This is the
930           default; it does not imply any other options.
931
932       users
933           Allow any user to mount and to unmount the filesystem, even when
934           some other ordinary user mounted it. This option implies the
935           options noexec, nosuid, and nodev (unless overridden by subsequent
936           options, as in the option line users,exec,dev,suid).
937
938       X-*
939           All options prefixed with "X-" are interpreted as comments or as
940           userspace application-specific options. These options are not
941           stored in user space (e.g., mtab file), nor sent to the mount.type
942           helpers nor to the mount(2) system call. The suggested format is
943           X-appname.option.
944
945       x-*
946           The same as X-* options, but stored permanently in user space. This
947           means the options are also available for umount(8) or other
948           operations. Note that maintaining mount options in user space is
949           tricky, because it’s necessary use libmount-based tools and there
950           is no guarantee that the options will be always available (for
951           example after a move mount operation or in unshared namespace).
952
953           Note that before util-linux v2.30 the x-* options have not been
954           maintained by libmount and stored in user space (functionality was
955           the same as for X-* now), but due to the growing number of
956           use-cases (in initrd, systemd etc.) the functionality has been
957           extended to keep existing fstab configurations usable without a
958           change.
959
960       X-mount.mkdir[=mode]
961           Allow to make a target directory (mountpoint) if it does not exit
962           yet. The optional argument mode specifies the filesystem access
963           mode used for mkdir(2) in octal notation. The default mode is 0755.
964           This functionality is supported only for root users or when mount
965           executed without suid permissions. The option is also supported as
966           x-mount.mkdir, this notation is deprecated since v2.30.
967
968       nosymfollow
969           Do not follow symlinks when resolving paths. Symlinks can still be
970           created, and readlink(1), readlink(2), realpath(1), and realpath(3)
971           all still work properly.
972

FILESYSTEM-SPECIFIC MOUNT OPTIONS

974       This section lists options that are specific to particular filesystems.
975       Where possible, you should first consult filesystem-specific manual
976       pages for details. Some of those pages are listed in the following
977       table.
978
979       ┌─────────────────┬───────────────┐
980       │                 │               │
981Filesystem(s)    Manual page   
982       ├─────────────────┼───────────────┤
983       │                 │               │
984       │btrfs            │ btrfs(5)
985       ├─────────────────┼───────────────┤
986       │                 │               │
987       │cifs             │ mount.cifs(8)
988       ├─────────────────┼───────────────┤
989       │                 │               │
990       │ext2, ext3, ext4 │ ext4(5)
991       ├─────────────────┼───────────────┤
992       │                 │               │
993       │fuse             │ fuse(8)       │
994       ├─────────────────┼───────────────┤
995       │                 │               │
996       │nfs              │ nfs(5)
997       ├─────────────────┼───────────────┤
998       │                 │               │
999       │tmpfs            │ tmpfs(5)
1000       ├─────────────────┼───────────────┤
1001       │                 │               │
1002       │xfs              │ xfs(5)
1003       └─────────────────┴───────────────┘
1004
1005       Note that some of the pages listed above might be available only after
1006       you install the respective userland tools.
1007
1008       The following options apply only to certain filesystems. We sort them
1009       by filesystem. All options follow the -o flag.
1010
1011       What options are supported depends a bit on the running kernel. Further
1012       information may be available in filesystem-specific files in the kernel
1013       source subdirectory Documentation/filesystems.
1014
1015   Mount options for adfs
1016       uid=value and gid=value
1017           Set the owner and group of the files in the filesystem (default:
1018           uid=gid=0).
1019
1020       ownmask=value and othmask=value
1021           Set the permission mask for ADFS 'owner' permissions and 'other'
1022           permissions, respectively (default: 0700 and 0077, respectively).
1023           See also /usr/src/linux/Documentation/filesystems/adfs.rst.
1024
1025   Mount options for affs
1026       uid=value and gid=value
1027           Set the owner and group of the root of the filesystem (default:
1028           uid=gid=0, but with option uid or gid without specified value, the
1029           UID and GID of the current process are taken).
1030
1031       setuid=value and setgid=value
1032           Set the owner and group of all files.
1033
1034       mode=value
1035           Set the mode of all files to value & 0777 disregarding the original
1036           permissions. Add search permission to directories that have read
1037           permission. The value is given in octal.
1038
1039       protect
1040           Do not allow any changes to the protection bits on the filesystem.
1041
1042       usemp
1043           Set UID and GID of the root of the filesystem to the UID and GID of
1044           the mount point upon the first sync or umount, and then clear this
1045           option. Strange...
1046
1047       verbose
1048           Print an informational message for each successful mount.
1049
1050       prefix=string
1051           Prefix used before volume name, when following a link.
1052
1053       volume=string
1054           Prefix (of length at most 30) used before '/' when following a
1055           symbolic link.
1056
1057       reserved=value
1058           (Default: 2.) Number of unused blocks at the start of the device.
1059
1060       root=value
1061           Give explicitly the location of the root block.
1062
1063       bs=value
1064           Give blocksize. Allowed values are 512, 1024, 2048, 4096.
1065
1066       grpquota|noquota|quota|usrquota
1067           These options are accepted but ignored. (However, quota utilities
1068           may react to such strings in /etc/fstab.)
1069
1070   Mount options for debugfs
1071       The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1072       /sys/kernel/debug. As of kernel version 3.4, debugfs has the following
1073       options:
1074
1075       uid=n, gid=n
1076           Set the owner and group of the mountpoint.
1077
1078       mode=value
1079           Sets the mode of the mountpoint.
1080
1081   Mount options for devpts
1082       The devpts filesystem is a pseudo filesystem, traditionally mounted on
1083       /dev/pts. In order to acquire a pseudo terminal, a process opens
1084       /dev/ptmx; the number of the pseudo terminal is then made available to
1085       the process and the pseudo terminal slave can be accessed as
1086       /dev/pts/<number>.
1087
1088       uid=value and gid=value
1089           This sets the owner or the group of newly created pseudo terminals
1090           to the specified values. When nothing is specified, they will be
1091           set to the UID and GID of the creating process. For example, if
1092           there is a tty group with GID 5, then gid=5 will cause newly
1093           created pseudo terminals to belong to the tty group.
1094
1095       mode=value
1096           Set the mode of newly created pseudo terminals to the specified
1097           value. The default is 0600. A value of mode=620 and gid=5 makes
1098           "mesg y" the default on newly created pseudo terminals.
1099
1100       newinstance
1101           Create a private instance of the devpts filesystem, such that
1102           indices of pseudo terminals allocated in this new instance are
1103           independent of indices created in other instances of devpts.
1104
1105           All mounts of devpts without this newinstance option share the same
1106           set of pseudo terminal indices (i.e., legacy mode). Each mount of
1107           devpts with the newinstance option has a private set of pseudo
1108           terminal indices.
1109
1110           This option is mainly used to support containers in the Linux
1111           kernel. It is implemented in Linux kernel versions starting with
1112           2.6.29. Further, this mount option is valid only if
1113           CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1114           configuration.
1115
1116           To use this option effectively, /dev/ptmx must be a symbolic link
1117           to pts/ptmx. See Documentation/filesystems/devpts.txt in the Linux
1118           kernel source tree for details.
1119
1120       ptmxmode=value
1121           Set the mode for the new ptmx device node in the devpts filesystem.
1122
1123           With the support for multiple instances of devpts (see newinstance
1124           option above), each instance has a private ptmx node in the root of
1125           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 more
1129           useful mode for the ptmx node and is highly recommended when the
1130           newinstance option is specified.
1131
1132           This option is only implemented in Linux kernel versions starting
1133           with 2.6.29. Further, this option is valid only if
1134           CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1135           configuration.
1136
1137   Mount options for fat
1138       (Note: fat is not a separate filesystem, but a common part of the
1139       msdos, umsdos and vfat filesystems.)
1140
1141       blocksize={512|1024|2048}
1142           Set blocksize (default 512). This option is obsolete.
1143
1144       uid=value and gid=value
1145           Set the owner and group of all files. (Default: the UID and GID of
1146           the current process.)
1147
1148       umask=value
1149           Set the umask (the bitmask of the permissions that are not
1150           present). The default is the umask of the current process. The
1151           value is given in octal.
1152
1153       dmask=value
1154           Set the umask applied to directories only. The default is the umask
1155           of the current process. The value is given in octal.
1156
1157       fmask=value
1158           Set the umask applied to regular files only. The default is the
1159           umask of the current process. The value is given in octal.
1160
1161       allow_utime=value
1162           This option controls the permission check of mtime/atime.
1163
1164           20
1165               If current process is in group of file’s group ID, you can
1166               change timestamp.
1167
1168           2
1169               Other users can change timestamp.
1170
1171       The default is set from 'dmask' option. (If the directory is writable,
1172       utime(2) is also allowed. I.e. ~dmask & 022)
1173
1174       Normally utime(2) checks that the current process is owner of the file,
1175       or that it has the CAP_FOWNER capability. But FAT filesystems don’t
1176       have UID/GID on disk, so the normal check is too inflexible. With this
1177       option you can relax it.
1178
1179       check=value
1180           Three different levels of pickiness can be chosen:
1181
1182           r[elaxed]
1183               Upper and lower case are accepted and equivalent, long name
1184               parts are truncated (e.g. verylongname.foobar becomes
1185               verylong.foo), leading and embedded spaces are accepted in each
1186               name part (name and extension).
1187
1188           n[ormal]
1189               Like "relaxed", but many special characters (*, ?, <, spaces,
1190               etc.) are rejected. This is the default.
1191
1192           s[trict]
1193               Like "normal", but names that contain long parts or special
1194               characters that are sometimes used on Linux but are not
1195               accepted by MS-DOS (+, =, etc.) are rejected.
1196
1197       codepage=value
1198           Sets the codepage for converting to shortname characters on FAT and
1199           VFAT filesystems. By default, codepage 437 is used.
1200
1201       conv=mode
1202           This option is obsolete and may fail or be ignored.
1203
1204       cvf_format=module
1205           Forces the driver to use the CVF (Compressed Volume File) module
1206           cvf__module_ instead of auto-detection. If the kernel supports
1207           kmod, the cvf_format=xxx option also controls on-demand CVF module
1208           loading. This option is obsolete.
1209
1210       cvf_option=option
1211           Option passed to the CVF module. This option is obsolete.
1212
1213       debug
1214           Turn on the debug flag. A version string and a list of filesystem
1215           parameters will be printed (these data are also printed if the
1216           parameters appear to be inconsistent).
1217
1218       discard
1219           If set, causes discard/TRIM commands to be issued to the block
1220           device when blocks are freed. This is useful for SSD devices and
1221           sparse/thinly-provisioned LUNs.
1222
1223       dos1xfloppy
1224           If set, use a fallback default BIOS Parameter Block configuration,
1225           determined by backing device size. These static parameters match
1226           defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360
1227           kiB floppies and floppy images.
1228
1229       errors={panic|continue|remount-ro}
1230           Specify FAT behavior on critical errors: panic, continue without
1231           doing anything, or remount the partition in read-only mode (default
1232           behavior).
1233
1234       fat={12|16|32}
1235           Specify a 12, 16 or 32 bit fat. This overrides the automatic FAT
1236           type detection routine. Use with caution!
1237
1238       iocharset=value
1239           Character set to use for converting between 8 bit characters and 16
1240           bit Unicode characters. The default is iso8859-1. Long filenames
1241           are stored on disk in Unicode format.
1242
1243       nfs={stale_rw|nostale_ro}
1244           Enable this only if you want to export the FAT filesystem over NFS.
1245
1246           stale_rw: This option maintains an index (cache) of directory
1247           inodes which is used by the nfs-related code to improve look-ups.
1248           Full file operations (read/write) over NFS are supported but with
1249           cache eviction at NFS server, this could result in spurious ESTALE
1250           errors.
1251
1252           nostale_ro: This option bases the inode number and file handle on
1253           the on-disk location of a file in the FAT directory entry. This
1254           ensures that ESTALE will not be returned after a file is evicted
1255           from the inode cache. However, it means that operations such as
1256           rename, create and unlink could cause file handles that previously
1257           pointed at one file to point at a different file, potentially
1258           causing data corruption. For this reason, this option also mounts
1259           the filesystem readonly.
1260
1261           To maintain backward compatibility, -o nfs is also accepted,
1262           defaulting to stale_rw.
1263
1264       tz=UTC
1265           This option disables the conversion of timestamps between local
1266           time (as used by Windows on FAT) and UTC (which Linux uses
1267           internally). This is particularly useful when mounting devices
1268           (like digital cameras) that are set to UTC in order to avoid the
1269           pitfalls of local time.
1270
1271       time_offset=minutes
1272           Set offset for conversion of timestamps from local time used by FAT
1273           to UTC. I.e., minutes will be subtracted from each timestamp to
1274           convert it to UTC used internally by Linux. This is useful when the
1275           time zone set in the kernel via settimeofday(2) is not the time
1276           zone used by the filesystem. Note that this option still does not
1277           provide correct time stamps in all cases in presence of DST - time
1278           stamps in a different DST setting will be off by one hour.
1279
1280       quiet
1281           Turn on the quiet flag. Attempts to chown or chmod files do not
1282           return errors, although they fail. Use with caution!
1283
1284       rodir
1285           FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO
1286           of the directory will just be ignored, and is used only by
1287           applications as a flag (e.g. it’s set for the customized folder).
1288
1289           If you want to use ATTR_RO as read-only flag even for the
1290           directory, set this option.
1291
1292       showexec
1293           If set, the execute permission bits of the file will be allowed
1294           only if the extension part of the name is .EXE, .COM, or .BAT. Not
1295           set by default.
1296
1297       sys_immutable
1298           If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on
1299           Linux. Not set by default.
1300
1301       flush
1302           If set, the filesystem will try to flush to disk more early than
1303           normal. Not set by default.
1304
1305       usefree
1306           Use the "free clusters" value stored on FSINFO. It’ll be used to
1307           determine number of free clusters without scanning disk. But it’s
1308           not used by default, because recent Windows don’t update it
1309           correctly in some case. If you are sure the "free clusters" on
1310           FSINFO is correct, by this option you can avoid scanning disk.
1311
1312       dots, nodots, dotsOK=[yes|no]
1313           Various misguided attempts to force Unix or DOS conventions onto a
1314           FAT filesystem.
1315
1316   Mount options for hfs
1317       creator=cccc, type=cccc
1318           Set the creator/type values as shown by the MacOS finder used for
1319           creating new files. Default values: '????'.
1320
1321       uid=n, gid=n
1322           Set the owner and group of all files. (Default: the UID and GID of
1323           the current process.)
1324
1325       dir_umask=n, file_umask=n, umask=n
1326           Set the umask used for all directories, all regular files, or all
1327           files and directories. Defaults to the umask of the current
1328           process.
1329
1330       session=n
1331           Select the CDROM session to mount. Defaults to leaving that
1332           decision to the CDROM driver. This option will fail with anything
1333           but a CDROM as underlying device.
1334
1335       part=n
1336           Select partition number n from the device. Only makes sense for
1337           CDROMs. Defaults to not parsing the partition table at all.
1338
1339       quiet
1340           Don’t complain about invalid mount options.
1341
1342   Mount options for hpfs
1343       uid=value and gid=value
1344           Set the owner and group of all files. (Default: the UID and GID of
1345           the current process.)
1346
1347       umask=value
1348           Set the umask (the bitmask of the permissions that are not
1349           present). The default is the umask of the current process. The
1350           value is given in octal.
1351
1352       case={lower|asis}
1353           Convert all files names to lower case, or leave them. (Default:
1354           case=lower.)
1355
1356       conv=mode
1357           This option is obsolete and may fail or being ignored.
1358
1359       nocheck
1360           Do not abort mounting when certain consistency checks fail.
1361
1362   Mount options for iso9660
1363       ISO 9660 is a standard describing a filesystem structure to be used on
1364       CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1365       udf filesystem.)
1366
1367       Normal iso9660 filenames appear in an 8.3 format (i.e., DOS-like
1368       restrictions on filename length), and in addition all characters are in
1369       upper case. Also there is no field for file ownership, protection,
1370       number of links, provision for block/character devices, etc.
1371
1372       Rock Ridge is an extension to iso9660 that provides all of these
1373       UNIX-like features. Basically there are extensions to each directory
1374       record that supply all of the additional information, and when Rock
1375       Ridge is in use, the filesystem is indistinguishable from a normal UNIX
1376       filesystem (except that it is read-only, of course).
1377
1378       norock
1379           Disable the use of Rock Ridge extensions, even if available. Cf.
1380           map.
1381
1382       nojoliet
1383           Disable the use of Microsoft Joliet extensions, even if available.
1384           Cf. map.
1385
1386       check={r[elaxed]|s[trict]}
1387           With check=relaxed, a filename is first converted to lower case
1388           before doing the lookup. This is probably only meaningful together
1389           with norock and map=normal. (Default: check=strict.)
1390
1391       uid=value and gid=value
1392           Give all files in the filesystem the indicated user or group id,
1393           possibly overriding the information found in the Rock Ridge
1394           extensions. (Default: uid=0,gid=0.)
1395
1396       map={n[ormal]|o[ff]|a[corn]}
1397           For non-Rock Ridge volumes, normal name translation maps upper to
1398           lower case ASCII, drops a trailing ';1', and converts ';' to '.'.
1399           With map=off no name translation is done. See norock. (Default:
1400           map=normal.) map=acorn is like map=normal but also apply Acorn
1401           extensions if present.
1402
1403       mode=value
1404           For non-Rock Ridge volumes, give all files the indicated mode.
1405           (Default: read and execute permission for everybody.) Octal mode
1406           values require a leading 0.
1407
1408       unhide
1409           Also show hidden and associated files. (If the ordinary files and
1410           the associated or hidden files have the same filenames, this may
1411           make the ordinary files inaccessible.)
1412
1413       block={512|1024|2048}
1414           Set the block size to the indicated value. (Default: block=1024.)
1415
1416       conv=mode
1417           This option is obsolete and may fail or being ignored.
1418
1419       cruft
1420           If the high byte of the file length contains other garbage, set
1421           this mount option to ignore the high order bits of the file length.
1422           This implies that a file cannot be larger than 16 MB.
1423
1424       session=x
1425           Select number of session on a multisession CD.
1426
1427       sbsector=xxx
1428           Session begins from sector xxx.
1429
1430       The following options are the same as for vfat and specifying them only
1431       makes sense when using discs encoded using Microsoft’s Joliet
1432       extensions.
1433
1434       iocharset=value
1435           Character set to use for converting 16 bit Unicode characters on CD
1436           to 8 bit characters. The default is iso8859-1.
1437
1438       utf8
1439           Convert 16 bit Unicode characters on CD to UTF-8.
1440
1441   Mount options for jfs
1442       iocharset=name
1443           Character set to use for converting from Unicode to ASCII. The
1444           default is to do no conversion. Use iocharset=utf8 for UTF8
1445           translations. This requires CONFIG_NLS_UTF8 to be set in the kernel
1446           .config file.
1447
1448       resize=value
1449           Resize the volume to value blocks. JFS only supports growing a
1450           volume, not shrinking it. This option is only valid during a
1451           remount, when the volume is mounted read-write. The resize keyword
1452           with no value will grow the volume to the full size of the
1453           partition.
1454
1455       nointegrity
1456           Do not write to the journal. The primary use of this option is to
1457           allow for higher performance when restoring a volume from backup
1458           media. The integrity of the volume is not guaranteed if the system
1459           abnormally ends.
1460
1461       integrity
1462           Default. Commit metadata changes to the journal. Use this option to
1463           remount a volume where the nointegrity option was previously
1464           specified in order to restore normal behavior.
1465
1466       errors={continue|remount-ro|panic}
1467           Define the behavior when an error is encountered. (Either ignore
1468           errors and just mark the filesystem erroneous and continue, or
1469           remount the filesystem read-only, or panic and halt the system.)
1470
1471       noquota|quota|usrquota|grpquota
1472           These options are accepted but ignored.
1473
1474   Mount options for msdos
1475       See mount options for fat. If the msdos filesystem detects an
1476       inconsistency, it reports an error and sets the file system read-only.
1477       The filesystem can be made writable again by remounting it.
1478
1479   Mount options for ncpfs
1480       Just like nfs, the ncpfs implementation expects a binary argument (a
1481       struct ncp_mount_data) to the mount system call. This argument is
1482       constructed by ncpmount(8) and the current version of mount (2.12) does
1483       not know anything about ncpfs.
1484
1485   Mount options for ntfs
1486       iocharset=name
1487           Character set to use when returning file names. Unlike VFAT, NTFS
1488           suppresses names that contain nonconvertible characters.
1489           Deprecated.
1490
1491       nls=name
1492           New name for the option earlier called iocharset.
1493
1494       utf8
1495           Use UTF-8 for converting file names.
1496
1497       uni_xlate={0|1|2}
1498           For 0 (or 'no' or 'false'), do not use escape sequences for unknown
1499           Unicode characters. For 1 (or 'yes' or 'true') or 2, use vfat-style
1500           4-byte escape sequences starting with ":". Here 2 gives a
1501           little-endian encoding and 1 a byteswapped bigendian 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 given
1510           in octal. By default, the files are owned by root and not readable
1511           by somebody else.
1512
1513   Mount options for overlay
1514       Since Linux 3.18 the overlay pseudo filesystem implements a union mount
1515       for other filesystems.
1516
1517       An overlay filesystem combines two filesystems - an upper filesystem
1518       and a lower filesystem. When a name exists in both filesystems, the
1519       object in the upper filesystem is visible while the object in the lower
1520       filesystem is either hidden or, in the case of directories, merged with
1521       the upper object.
1522
1523       The lower filesystem can be any filesystem supported by Linux and does
1524       not need to be writable. The lower filesystem can even be another
1525       overlayfs. The upper filesystem will normally be writable and if it is
1526       it must support the creation of trusted.* extended attributes, and must
1527       provide a valid d_type in readdir responses, so NFS is not suitable.
1528
1529       A read-only overlay of two read-only filesystems may use any filesystem
1530       type. The options lowerdir and upperdir are combined into a merged
1531       directory by using:
1532
1533              mount -t overlay  overlay  \
1534                -olowerdir=/lower,upperdir=/upper,workdir=/work  /merged
1535
1536       lowerdir=directory
1537           Any filesystem, does not need to be on a writable filesystem.
1538
1539       upperdir=directory
1540           The upperdir is normally on a writable filesystem.
1541
1542       workdir=directory
1543           The workdir needs to be an empty directory on the same filesystem
1544           as upperdir.
1545
1546       userxattr
1547           Use the "user.overlay." xattr namespace instead of
1548           "trusted.overlay.". This is useful for unprivileged mounting of
1549           overlayfs.
1550
1551       redirect_dir={on|off|follow|nofollow}
1552           If the redirect_dir feature is enabled, then the directory will be
1553           copied up (but not the contents). Then the
1554           "{trusted|user}.overlay.redirect" extended attribute is set to the
1555           path of the original location from the root of the overlay. Finally
1556           the directory is moved to the new location.
1557
1558           on
1559               Redirects are enabled.
1560
1561           off
1562               Redirects are not created and only followed if
1563               "redirect_always_follow" feature is enabled in the
1564               kernel/module config.
1565
1566           follow
1567               Redirects are not created, but followed.
1568
1569           nofollow
1570               Redirects are not created and not followed (equivalent to
1571               "redirect_dir=off" if "redirect_always_follow" feature is not
1572               enabled).
1573
1574       index={on|off}
1575           Inode index. If this feature is disabled and a file with multiple
1576           hard links is copied up, then this will "break" the link. Changes
1577           will not be propagated to other names referring to the same inode.
1578
1579       uuid={on|off}
1580           Can be used to replace UUID of the underlying filesystem in file
1581           handles with null, and effectively disable UUID checks. This can be
1582           useful in case the underlying disk is copied and the UUID of this
1583           copy is changed. This is only applicable if all lower/upper/work
1584           directories are on the same filesystem, otherwise it will fallback
1585           to normal behaviour.
1586
1587       nfs_export={on|off}
1588           When the underlying filesystems supports NFS export and the
1589           "nfs_export" feature is enabled, an overlay filesystem may be
1590           exported to NFS.
1591
1592           With the “nfs_export” feature, on copy_up of any lower object, an
1593           index entry is created under the index directory. The index entry
1594           name is the hexadecimal representation of the copy up origin file
1595           handle. For a non-directory object, the index entry is a hard link
1596           to the upper inode. For a directory object, the index entry has an
1597           extended attribute "{trusted|user}.overlay.upper" with an encoded
1598           file handle of the upper directory inode.
1599
1600           When encoding a file handle from an overlay filesystem object, the
1601           following rules apply
1602
1603               •   For a non-upper object, encode a lower file handle from
1604                   lower inode
1605
1606               •   For an indexed object, encode a lower file handle from
1607                   copy_up origin
1608
1609               •   For a pure-upper object and for an existing non-indexed
1610                   upper object, encode an upper file handle from upper inode
1611
1612           The encoded overlay file handle includes
1613
1614               •   Header including path type information (e.g. lower/upper)
1615
1616               •   UUID of the underlying filesystem
1617
1618               •   Underlying filesystem encoding of underlying inode
1619
1620           This encoding format is identical to the encoding format file
1621           handles that are stored in extended attribute
1622           "{trusted|user}.overlay.origin". When decoding an overlay file
1623           handle, the following steps are followed
1624
1625               •   Find underlying layer by UUID and path type information.
1626
1627               •   Decode the underlying filesystem file handle to underlying
1628                   dentry.
1629
1630               •   For a lower file handle, lookup the handle in index
1631                   directory by name.
1632
1633               •   If a whiteout is found in index, return ESTALE. This
1634                   represents an overlay object that was deleted after its
1635                   file handle was encoded.
1636
1637               •   For a non-directory, instantiate a disconnected overlay
1638                   dentry from the decoded underlying dentry, the path type
1639                   and index inode, if found.
1640
1641               •   For a directory, use the connected underlying decoded
1642                   dentry, path type and index, to lookup a connected overlay
1643                   dentry.
1644
1645           Decoding a non-directory file handle may return a disconnected
1646           dentry. copy_up of that disconnected dentry will create an upper
1647           index entry with no upper alias.
1648
1649           When overlay filesystem has multiple lower layers, a middle layer
1650           directory may have a "redirect" to lower directory. Because middle
1651           layer "redirects" are not indexed, a lower file handle that was
1652           encoded from the "redirect" origin directory, cannot be used to
1653           find the middle or upper layer directory. Similarly, a lower file
1654           handle that was encoded from a descendant of the "redirect" origin
1655           directory, cannot be used to reconstruct a connected overlay path.
1656           To mitigate the cases of directories that cannot be decoded from a
1657           lower file handle, these directories are copied up on encode and
1658           encoded as an upper file handle. On an overlay filesystem with no
1659           upper layer this mitigation cannot be used NFS export in this setup
1660           requires turning off redirect follow (e.g.
1661           "redirect_dir=nofollow").
1662
1663           The overlay filesystem does not support non-directory connectable
1664           file handles, so exporting with the subtree_check exportfs
1665           configuration will cause failures to lookup files over NFS.
1666
1667           When the NFS export feature is enabled, all directory index entries
1668           are verified on mount time to check that upper file handles are not
1669           stale. This verification may cause significant overhead in some
1670           cases.
1671
1672           Note: the mount options index=off,nfs_export=on are conflicting for
1673           a read-write mount and will result in an error.
1674
1675       xinfo={on|off|auto}
1676           The "xino" feature composes a unique object identifier from the
1677           real object st_ino and an underlying fsid index. The "xino" feature
1678           uses the high inode number bits for fsid, because the underlying
1679           filesystems rarely use the high inode number bits. In case the
1680           underlying inode number does overflow into the high xino bits,
1681           overlay filesystem will fall back to the non xino behavior for that
1682           inode.
1683
1684           For a detailed description of the effect of this option please
1685           refer to
1686           https://www.kernel.org/doc/html/latest/filesystems/overlayfs.html?highlight=overlayfs
1687
1688       metacopy={on|off}
1689           When metadata only copy up feature is enabled, overlayfs will only
1690           copy up metadata (as opposed to whole file), when a metadata
1691           specific operation like chown/chmod is performed. Full file will be
1692           copied up later when file is opened for WRITE operation.
1693
1694           In other words, this is delayed data copy up operation and data is
1695           copied up when there is a need to actually modify data.
1696
1697       volatile
1698           Volatile mounts are not guaranteed to survive a crash. It is
1699           strongly recommended that volatile mounts are only used if data
1700           written to the overlay can be recreated without significant effort.
1701
1702           The advantage of mounting with the "volatile" option is that all
1703           forms of sync calls to the upper filesystem are omitted.
1704
1705           In order to avoid a giving a false sense of safety, the syncfs (and
1706           fsync) semantics of volatile mounts are slightly different than
1707           that of the rest of VFS. If any writeback error occurs on the
1708           upperdir’s filesystem after a volatile mount takes place, all sync
1709           functions will return an error. Once this condition is reached, the
1710           filesystem will not recover, and every subsequent sync call will
1711           return an error, even if the upperdir has not experience a new
1712           error since the last sync call.
1713
1714           When overlay is mounted with "volatile" option, the directory
1715           "$workdir/work/incompat/volatile" is created. During next mount,
1716           overlay checks for this directory and refuses to mount if present.
1717           This is a strong indicator that user should throw away upper and
1718           work directories and create fresh one. In very limited cases where
1719           the user knows that the system has not crashed and contents of
1720           upperdir are intact, The "volatile" directory can be removed.
1721
1722   Mount options for reiserfs
1723       Reiserfs is a journaling filesystem.
1724
1725       conv
1726           Instructs version 3.6 reiserfs software to mount a version 3.5
1727           filesystem, using the 3.6 format for newly created objects. This
1728           filesystem will no longer be compatible with reiserfs 3.5 tools.
1729
1730       hash={rupasov|tea|r5|detect}
1731           Choose which hash function reiserfs will use to find files within
1732           directories.
1733
1734           rupasov
1735               A hash invented by Yury Yu. Rupasov. It is fast and preserves
1736               locality, mapping lexicographically close file names to close
1737               hash values. This option should not be used, as it causes a
1738               high probability of hash collisions.
1739
1740           tea
1741               A Davis-Meyer function implemented by Jeremy Fitzhardinge. It
1742               uses hash permuting bits in the name. It gets high randomness
1743               and, therefore, low probability of hash collisions at some CPU
1744               cost. This may be used if EHASHCOLLISION errors are experienced
1745               with the r5 hash.
1746
1747           r5
1748               A modified version of the rupasov hash. It is used by default
1749               and is the best choice unless the filesystem has huge
1750               directories and unusual file-name patterns.
1751
1752           detect
1753               Instructs mount to detect which hash function is in use by
1754               examining the filesystem being mounted, and to write this
1755               information into the reiserfs superblock. This is only useful
1756               on the first mount of an old format filesystem.
1757
1758       hashed_relocation
1759           Tunes the block allocator. This may provide performance
1760           improvements in some situations.
1761
1762       no_unhashed_relocation
1763           Tunes the block allocator. This may provide performance
1764           improvements in some situations.
1765
1766       noborder
1767           Disable the border allocator algorithm invented by Yury Yu.
1768           Rupasov. This may provide performance improvements in some
1769           situations.
1770
1771       nolog
1772           Disable journaling. This will provide slight performance
1773           improvements in some situations at the cost of losing reiserfs’s
1774           fast recovery from crashes. Even with this option turned on,
1775           reiserfs still performs all journaling operations, save for actual
1776           writes into its journaling area. Implementation of nolog is a work
1777           in progress.
1778
1779       notail
1780           By default, reiserfs stores small files and 'file tails' directly
1781           into its tree. This confuses some utilities such as lilo(8). This
1782           option is used to disable packing of files into the tree.
1783
1784       replayonly
1785           Replay the transactions which are in the journal, but do not
1786           actually mount the filesystem. Mainly used by reiserfsck.
1787
1788       resize=number
1789           A remount option which permits online expansion of reiserfs
1790           partitions. Instructs reiserfs to assume that the device has number
1791           blocks. This option is designed for use with devices which are
1792           under logical volume management (LVM). There is a special resizer
1793           utility which can be obtained from
1794           ftp://ftp.namesys.com/pub/reiserfsprogs.
1795
1796       user_xattr
1797           Enable Extended User Attributes. See the attr(1) manual page.
1798
1799       acl
1800           Enable POSIX Access Control Lists. See the acl(5) manual page.
1801
1802       barrier=none / barrier=flush
1803           This disables / enables the use of write barriers in the journaling
1804           code. barrier=none disables, barrier=flush enables (default). This
1805           also requires an IO stack which can support barriers, and if
1806           reiserfs gets an error on a barrier write, it will disable barriers
1807           again with a warning. Write barriers enforce proper on-disk
1808           ordering of journal commits, making volatile disk write caches safe
1809           to use, at some performance penalty. If your disks are
1810           battery-backed in one way or another, disabling barriers may safely
1811           improve performance.
1812
1813   Mount options for ubifs
1814       UBIFS is a flash filesystem which works on top of UBI volumes. Note
1815       that atime is not supported and is always turned off.
1816
1817       The device name may be specified as
1818
1819          ubiX_Y
1820              UBI device number X, volume number Y
1821
1822          ubiY
1823              UBI device number 0, volume number Y
1824
1825          ubiX:NAME
1826              UBI device number X, volume with name NAME
1827
1828          ubi:NAME
1829              UBI device number 0, volume with name NAME
1830
1831       Alternative ! separator may be used instead of :.
1832
1833       The following mount options are available:
1834
1835       bulk_read
1836           Enable bulk-read. VFS read-ahead is disabled because it slows down
1837           the filesystem. Bulk-Read is an internal optimization. Some flashes
1838           may read faster if the data are read at one go, rather than at
1839           several read requests. For example, OneNAND can do
1840           "read-while-load" if it reads more than one NAND page.
1841
1842       no_bulk_read
1843           Do not bulk-read. This is the default.
1844
1845       chk_data_crc
1846           Check data CRC-32 checksums. This is the default.
1847
1848       no_chk_data_crc
1849           Do not check data CRC-32 checksums. With this option, the
1850           filesystem does not check CRC-32 checksum for data, but it does
1851           check it for the internal indexing information. This option only
1852           affects reading, not writing. CRC-32 is always calculated when
1853           writing the data.
1854
1855       compr={none|lzo|zlib}
1856           Select the default compressor which is used when new files are
1857           written. It is still possible to read compressed files if mounted
1858           with the none option.
1859
1860   Mount options for udf
1861       UDF is the "Universal Disk Format" filesystem defined by OSTA, the
1862       Optical Storage Technology Association, and is often used for DVD-ROM,
1863       frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is,
1864       however, perfectly usable by itself on disk drives, flash drives and
1865       other block devices. See also iso9660.
1866
1867       uid=
1868           Make all files in the filesystem belong to the given user.
1869           uid=forget can be specified independently of (or usually in
1870           addition to) uid=<user> and results in UDF not storing uids to the
1871           media. In fact the recorded uid is the 32-bit overflow uid -1 as
1872           defined by the UDF standard. The value is given as either <user>
1873           which is a valid user name or the corresponding decimal user id, or
1874           the special string "forget".
1875
1876       gid=
1877           Make all files in the filesystem belong to the given group.
1878           gid=forget can be specified independently of (or usually in
1879           addition to) gid=<group> and results in UDF not storing gids to the
1880           media. In fact the recorded gid is the 32-bit overflow gid -1 as
1881           defined by the UDF standard. The value is given as either <group>
1882           which is a valid group name or the corresponding decimal group id,
1883           or the special string "forget".
1884
1885       umask=
1886           Mask out the given permissions from all inodes read from the
1887           filesystem. The value is given in octal.
1888
1889       mode=
1890           If mode= is set the permissions of all non-directory inodes read
1891           from the filesystem will be set to the given mode. The value is
1892           given in octal.
1893
1894       dmode=
1895           If dmode= is set the permissions of all directory inodes read from
1896           the filesystem will be set to the given dmode. The value is given
1897           in octal.
1898
1899       bs=
1900           Set the block size. Default value prior to kernel version 2.6.30
1901           was 2048. Since 2.6.30 and prior to 4.11 it was logical device
1902           block size with fallback to 2048. Since 4.11 it is logical block
1903           size with fallback to any valid block size between logical device
1904           block size and 4096.
1905
1906           For other details see the mkudffs(8) 2.0+ manpage, sections
1907           COMPATIBILITY and BLOCK SIZE.
1908
1909       unhide
1910           Show otherwise hidden files.
1911
1912       undelete
1913           Show deleted files in lists.
1914
1915       adinicb
1916           Embed data in the inode. (default)
1917
1918       noadinicb
1919           Don’t embed data in the inode.
1920
1921       shortad
1922           Use short UDF address descriptors.
1923
1924       longad
1925           Use long UDF address descriptors. (default)
1926
1927       nostrict
1928           Unset strict conformance.
1929
1930       iocharset=
1931           Set the NLS character set. This requires kernel compiled with
1932           CONFIG_UDF_NLS option.
1933
1934       utf8
1935           Set the UTF-8 character set.
1936
1937   Mount options for debugging and disaster recovery
1938       novrs
1939           Ignore the Volume Recognition Sequence and attempt to mount anyway.
1940
1941       session=
1942           Select the session number for multi-session recorded optical media.
1943           (default= last session)
1944
1945       anchor=
1946           Override standard anchor location. (default= 256)
1947
1948       lastblock=
1949           Set the last block of the filesystem.
1950
1951   Unused historical mount options that may be encountered and should be
1952       removed
1953       uid=ignore
1954           Ignored, use uid=<user> instead.
1955
1956       gid=ignore
1957           Ignored, use gid=<group> instead.
1958
1959       volume=
1960           Unimplemented and ignored.
1961
1962       partition=
1963           Unimplemented and ignored.
1964
1965       fileset=
1966           Unimplemented and ignored.
1967
1968       rootdir=
1969           Unimplemented and ignored.
1970
1971   Mount options for ufs
1972       ufstype=value
1973           UFS is a filesystem widely used in different operating systems. The
1974           problem are differences among implementations. Features of some
1975           implementations are undocumented, so its hard to recognize the type
1976           of ufs automatically. That’s why the user must specify the type of
1977           ufs by mount option. Possible values are:
1978
1979           old
1980               Old format of ufs, this is the default, read only. (Don’t
1981               forget to give the -r option.)
1982
1983           44bsd
1984               For filesystems created by a BSD-like system (NetBSD, FreeBSD,
1985               OpenBSD).
1986
1987           ufs2
1988               Used in FreeBSD 5.x supported as read-write.
1989
1990           5xbsd
1991               Synonym for ufs2.
1992
1993           sun
1994               For filesystems created by SunOS or Solaris on Sparc.
1995
1996           sunx86
1997               For filesystems created by Solaris on x86.
1998
1999           hp
2000               For filesystems created by HP-UX, read-only.
2001
2002           nextstep
2003               For filesystems created by NeXTStep (on NeXT station)
2004               (currently read only).
2005
2006           nextstep-cd
2007               For NextStep CDROMs (block_size == 2048), read-only.
2008
2009           openstep
2010               For filesystems created by OpenStep (currently read only). The
2011               same filesystem type is also used by Mac OS X.
2012
2013       onerror=value
2014           Set behavior on error:
2015
2016           panic
2017               If an error is encountered, cause a kernel panic.
2018
2019           [lock|umount|repair]
2020               These mount options don’t do anything at present; when an error
2021               is encountered only a console message is printed.
2022
2023   Mount options for umsdos
2024       See mount options for msdos. The dotsOK option is explicitly killed by
2025       umsdos.
2026
2027   Mount options for vfat
2028       First of all, the mount options for fat are recognized. The dotsOK
2029       option is explicitly killed by vfat. Furthermore, there are
2030
2031       uni_xlate
2032           Translate unhandled Unicode characters to special escaped
2033           sequences. This lets you backup and restore filenames that are
2034           created with any Unicode characters. Without this option, a '?' is
2035           used when no translation is possible. The escape character is ':'
2036           because it is otherwise invalid on the vfat filesystem. The escape
2037           sequence that gets used, where u is the Unicode character, is: ':',
2038           (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
2039
2040       posix
2041           Allow two files with names that only differ in case. This option is
2042           obsolete.
2043
2044       nonumtail
2045           First try to make a short name without sequence number, before
2046           trying name~num.ext.
2047
2048       utf8
2049           UTF8 is the filesystem safe 8-bit encoding of Unicode that is used
2050           by the console. It can be enabled for the filesystem with this
2051           option or disabled with utf8=0, utf8=no or utf8=false. If uni_xlate
2052           gets set, UTF8 gets disabled.
2053
2054       shortname=mode
2055           Defines the behavior for creation and display of filenames which
2056           fit into 8.3 characters. If a long name for a file exists, it will
2057           always be the preferred one for display. There are four modes:
2058
2059           lower
2060               Force the short name to lower case upon display; store a long
2061               name when the short name is not all upper case.
2062
2063           win95
2064               Force the short name to upper case upon display; store a long
2065               name when the short name is not all upper case.
2066
2067           winnt
2068               Display the short name as is; store a long name when the short
2069               name is not all lower case or all upper case.
2070
2071           mixed
2072               Display the short name as is; store a long name when the short
2073               name is not all upper case. This mode is the default since
2074               Linux 2.6.32.
2075
2076   Mount options for usbfs
2077       devuid=uid and devgid=gid and devmode=mode
2078           Set the owner and group and mode of the device files in the usbfs
2079           filesystem (default: uid=gid=0, mode=0644). The mode is given in
2080           octal.
2081
2082       busuid=uid and busgid=gid and busmode=mode
2083           Set the owner and group and mode of the bus directories in the
2084           usbfs filesystem (default: uid=gid=0, mode=0555). The mode is given
2085           in octal.
2086
2087       listuid=uid and listgid=gid and listmode=mode
2088           Set the owner and group and mode of the file devices (default:
2089           uid=gid=0, mode=0444). The mode is given in octal.
2090

DM-VERITY SUPPORT (EXPERIMENTAL)

2092       The device-mapper verity target provides read-only transparent
2093       integrity checking of block devices using kernel crypto API. The mount
2094       command can open the dm-verity device and do the integrity verification
2095       before on the device filesystem is mounted. Requires libcryptsetup with
2096       in libmount (optionally via dlopen(3)). If libcryptsetup supports
2097       extracting the root hash of an already mounted device, existing devices
2098       will be automatically reused in case of a match. Mount options for
2099       dm-verity:
2100
2101       verity.hashdevice=path
2102           Path to the hash tree device associated with the source volume to
2103           pass to dm-verity.
2104
2105       verity.roothash=hex
2106           Hex-encoded hash of the root of verity.hashdevice. Mutually
2107           exclusive with verity.roothashfile.
2108
2109       verity.roothashfile=path
2110           Path to file containing the hex-encoded hash of the root of
2111           verity.hashdevice. Mutually exclusive with verity.roothash.
2112
2113       verity.hashoffset=offset
2114           If the hash tree device is embedded in the source volume, offset
2115           (default: 0) is used by dm-verity to get to the tree.
2116
2117       verity.fecdevice=path
2118           Path to the Forward Error Correction (FEC) device associated with
2119           the source volume to pass to dm-verity. Optional. Requires kernel
2120           built with CONFIG_DM_VERITY_FEC.
2121
2122       verity.fecoffset=offset
2123           If the FEC device is embedded in the source volume, offset
2124           (default: 0) is used by dm-verity to get to the FEC area. Optional.
2125
2126       verity.fecroots=value
2127           Parity bytes for FEC (default: 2). Optional.
2128
2129       verity.roothashsig=path
2130           Path to pkcs7(1ssl) signature of root hash hex string. Requires
2131           crypt_activate_by_signed_key() from cryptsetup and kernel built
2132           with CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG. For device reuse,
2133           signatures have to be either used by all mounts of a device or by
2134           none. Optional.
2135
2136       Supported since util-linux v2.35.
2137
2138       For example commands:
2139
2140           mksquashfs /etc /tmp/etc.squashfs
2141           dd if=/dev/zero of=/tmp/etc.hash bs=1M count=10
2142           veritysetup format /tmp/etc.squashfs /tmp/etc.hash
2143           openssl smime -sign -in <hash> -nocerts -inkey private.key \
2144           -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s
2145           mount -o verity.hashdevice=/tmp/etc.hash,verity.roothash=<hash>,\
2146           verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.squashfs /mnt
2147
2148       create squashfs image from /etc directory, verity hash device and mount
2149       verified filesystem image to /mnt. The kernel will verify that the root
2150       hash is signed by a key from the kernel keyring if roothashsig is used.
2151

LOOP-DEVICE SUPPORT

2153       One further possible type is a mount via the loop device. For example,
2154       the command
2155
2156          mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3
2157
2158       will set up the loop device /dev/loop3 to correspond to the file
2159       /tmp/disk.img, and then mount this device on /mnt.
2160
2161       If no explicit loop device is mentioned (but just an option '-o loop'
2162       is given), then mount will try to find some unused loop device and use
2163       that, for example
2164
2165          mount /tmp/disk.img /mnt -o loop
2166
2167       The mount command automatically creates a loop device from a regular
2168       file if a filesystem type is not specified or the filesystem is known
2169       for libblkid, for example:
2170
2171          mount /tmp/disk.img /mnt
2172
2173          mount -t ext4 /tmp/disk.img /mnt
2174
2175       This type of mount knows about three options, namely loop, offset and
2176       sizelimit, that are really options to losetup(8). (These options can be
2177       used in addition to those specific to the filesystem type.)
2178
2179       Since Linux 2.6.25 auto-destruction of loop devices is supported,
2180       meaning that any loop device allocated by mount will be freed by umount
2181       independently of /etc/mtab.
2182
2183       You can also free a loop device by hand, using losetup -d or umount -d.
2184
2185       Since util-linux v2.29, mount re-uses the loop device rather than
2186       initializing a new device if the same backing file is already used for
2187       some loop device with the same offset and sizelimit. This is necessary
2188       to avoid a filesystem corruption.
2189

EXIT STATUS

2191       mount has the following exit status values (the bits can be ORed):
2192
2193       0
2194           success
2195
2196       1
2197           incorrect invocation or permissions
2198
2199       2
2200           system error (out of memory, cannot fork, no more loop devices)
2201
2202       4
2203           internal mount bug
2204
2205       8
2206           user interrupt
2207
2208       16
2209           problems writing or locking /etc/mtab
2210
2211       32
2212           mount failure
2213
2214       64
2215           some mount succeeded
2216
2217           The command mount -a returns 0 (all succeeded), 32 (all failed), or
2218           64 (some failed, some succeeded).
2219

EXTERNAL HELPERS

2221       The syntax of external mount helpers is:
2222
2223       /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t
2224       type.subtype]
2225
2226       where the suffix is the filesystem type and the -sfnvoN options have
2227       the same meaning as the normal mount options. The -t option is used for
2228       filesystems with subtypes support (for example /sbin/mount.fuse -t
2229       fuse.sshfs).
2230
2231       The command mount does not pass the mount options unbindable,
2232       runbindable, private, rprivate, slave, rslave, shared, rshared, auto,
2233       noauto, comment, x-*, loop, offset and sizelimit to the mount.<suffix>
2234       helpers. All other options are used in a comma-separated list as an
2235       argument to the -o option.
2236

ENVIRONMENT

2238       LIBMOUNT_FSTAB=<path>
2239           overrides the default location of the fstab file (ignored for suid)
2240
2241       LIBMOUNT_MTAB=<path>
2242           overrides the default location of the mtab file (ignored for suid)
2243
2244       LIBMOUNT_DEBUG=all
2245           enables libmount debug output
2246
2247       LIBBLKID_DEBUG=all
2248           enables libblkid debug output
2249
2250       LOOPDEV_DEBUG=all
2251           enables loop device setup debug output
2252

FILES

2254       See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section
2255       above.
2256
2257       /etc/fstab
2258           filesystem table
2259
2260       /run/mount
2261           libmount private runtime directory
2262
2263       /etc/mtab
2264           table of mounted filesystems or symlink to /proc/mounts
2265
2266       /etc/mtab~
2267           lock file (unused on systems with mtab symlink)
2268
2269       /etc/mtab.tmp
2270           temporary file (unused on systems with mtab symlink)
2271
2272       /etc/filesystems
2273           a list of filesystem types to try
2274

HISTORY

2276       A mount command existed in Version 5 AT&T UNIX.
2277

BUGS

2279       It is possible for a corrupted filesystem to cause a crash.
2280
2281       Some Linux filesystems don’t support -o sync and -o dirsync (the ext2,
2282       ext3, ext4, fat and vfat filesystems do support synchronous updates (a
2283       la BSD) when mounted with the sync option).
2284
2285       The -o remount may not be able to change mount parameters (all
2286       ext2fs-specific parameters, except sb, are changeable with a remount,
2287       for example, but you can’t change gid or umask for the fatfs).
2288
2289       It is possible that the files /etc/mtab and /proc/mounts don’t match on
2290       systems with a regular mtab file. The first file is based only on the
2291       mount command options, but the content of the second file also depends
2292       on the kernel and others settings (e.g. on a remote NFS server — in
2293       certain cases the mount command may report unreliable information about
2294       an NFS mount point and the /proc/mount file usually contains more
2295       reliable information.) This is another reason to replace the mtab file
2296       with a symlink to the /proc/mounts file.
2297
2298       Checking files on NFS filesystems referenced by file descriptors (i.e.
2299       the fcntl and ioctl families of functions) may lead to inconsistent
2300       results due to the lack of a consistency check in the kernel even if
2301       the noac mount option is used.
2302
2303       The loop option with the offset or sizelimit options used may fail when
2304       using older kernels if the mount command can’t confirm that the size of
2305       the block device has been configured as requested. This situation can
2306       be worked around by using the losetup(8) command manually before
2307       calling mount with the configured loop device.
2308

AUTHORS

2310       Karel Zak <kzak@redhat.com>
2311

SEE ALSO

2313       mount(2), umount(2), filesystems(5), fstab(5), nfs(5), xfs(5),
2314       mount_namespaces(7), xattr(7), e2label(8), findmnt(8), losetup(8),
2315       lsblk(8), mke2fs(8), mountd(8), nfsd(8), swapon(8), tune2fs(8),
2316       umount(8), xfs_admin(8)
2317

REPORTING BUGS

2319       For bug reports, use the issue tracker at
2320       https://github.com/karelzak/util-linux/issues.
2321

AVAILABILITY

2323       The mount command is part of the util-linux package which can be
2324       downloaded from Linux Kernel Archive
2325       <https://www.kernel.org/pub/linux/utils/util-linux/>.
2326
2327
2328
2329util-linux 2.37.2                 2021-08-16                          MOUNT(8)
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