1MOUNT(8)                     System Administration                    MOUNT(8)
2
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.
105           It’s 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
279
280          mount -o remount,bind,ro olddir newdir
281
282       Note that a read-only bind will create a read-only mountpoint (VFS
283       entry), but the original filesystem superblock will still be writable,
284       meaning that the olddir will be writable, but the newdir will be
285       read-only.
286
287       It’s also possible to change nosuid, nodev, noexec, noatime,
288       nodiratime, relatime and nosymfollow VFS entry flags via a
289       "remount,bind" operation. The other flags (for example
290       filesystem-specific flags) are silently ignored. It’s impossible to
291       change mount options recursively (for example with -o rbind,ro).
292
293       Since util-linux 2.31, mount ignores the bind flag from /etc/fstab on a
294       remount operation (if -o remount is specified on command line). This is
295       necessary to fully control mount options on remount by command line. In
296       previous versions the bind flag has been always applied and it was
297       impossible to re-define mount options without interaction with the bind
298       semantic. This mount behavior does not affect situations when
299       "remount,bind" is specified in the /etc/fstab file.
300
301   The move operation
302       Move a mounted tree to another place (atomically). The call is:
303
304          mount --move olddir newdir
305
306       This will cause the contents which previously appeared under olddir to
307       now be accessible under newdir. The physical location of the files is
308       not changed. Note that olddir has to be a mountpoint.
309
310       Note also that moving a mount residing under a shared mount is invalid
311       and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current
312       propagation flags.
313
314   Shared subtree operations
315       Since Linux 2.6.15 it is possible to mark a mount and its submounts as
316       shared, private, slave or unbindable. A shared mount provides the
317       ability to create mirrors of that mount such that mounts and unmounts
318       within any of the mirrors propagate to the other mirror. A slave mount
319       receives propagation from its master, but not vice versa. A private
320       mount carries no propagation abilities. An unbindable mount is a
321       private mount which cannot be cloned through a bind operation. The
322       detailed semantics are documented in
323       Documentation/filesystems/sharedsubtree.txt file in the kernel source
324       tree; see also mount_namespaces(7).
325
326       Supported operations are:
327
328           mount --make-shared mountpoint
329           mount --make-slave mountpoint
330           mount --make-private mountpoint
331           mount --make-unbindable mountpoint
332
333       The following commands allow one to recursively change the type of all
334       the mounts under a given mountpoint.
335
336           mount --make-rshared mountpoint
337           mount --make-rslave mountpoint
338           mount --make-rprivate mountpoint
339           mount --make-runbindable mountpoint
340
341       mount does not read fstab(5) when a --make-* operation is requested.
342       All necessary information has to be specified on the command line.
343
344       Note that the Linux kernel does not allow changing multiple propagation
345       flags with a single mount(2) system call, and the flags cannot be mixed
346       with other mount options and operations.
347
348       Since util-linux 2.23 the mount command can be used to do more
349       propagation (topology) changes by one mount(8) call and do it also
350       together with other mount operations. The propagation flags are applied
351       by additional mount(2) system calls when the preceding mount operations
352       were successful. Note that this use case is not atomic. It is possible
353       to specify the propagation flags in fstab(5) as mount options (private,
354       slave, shared, unbindable, rprivate, rslave, rshared, runbindable).
355
356       For example:
357
358           mount --make-private --make-unbindable /dev/sda1 /foo
359
360       is the same as:
361
362           mount /dev/sda1 /foo
363           mount --make-private /foo
364           mount --make-unbindable /foo
365

COMMAND-LINE OPTIONS

367       The full set of mount options used by an invocation of mount is
368       determined by first extracting the mount options for the filesystem
369       from the fstab table, then applying any options specified by the -o
370       argument, and finally applying a -r or -w option, when present.
371
372       The mount command does not pass all command-line options to the
373       /sbin/mount.suffix mount helpers. The interface between mount and the
374       mount helpers is described below in the EXTERNAL HELPERS section.
375
376       Command-line options available for the mount command are:
377
378       -a, --all
379           Mount all filesystems (of the given types) mentioned in fstab
380           (except for those whose line contains the noauto keyword). The
381           filesystems are mounted following their order in fstab. The mount
382           command compares filesystem source, target (and fs root for bind
383           mount or btrfs) to detect already mounted filesystems. The kernel
384           table with already mounted filesystems is cached during mount
385           --all. This means that all duplicated fstab entries will be
386           mounted.
387
388           The correct functionality depends on /proc (to detect already
389           mounted filesystems) and on /sys (to evaluate filesystem tags like
390           UUID= or LABEL=). It’s strongly recommended to mount /proc and /sys
391           filesystems before mount -a is executed, or keep /proc and /sys at
392           the beginning of fstab.
393
394           The option --all is possible to use for remount operation too. In
395           this case all filters (-t and -O) are applied to the table of
396           already mounted filesystems.
397
398           Since version 2.35 it is possible to use the command line option -o
399           to alter mount options from fstab (see also --options-mode).
400
401           Note that it is a bad practice to use mount -a for fstab checking.
402           The recommended solution is findmnt --verify.
403
404       -B, --bind
405           Remount a subtree somewhere else (so that its contents are
406           available in both places). See above, under Bind mounts.
407
408       -c, --no-canonicalize
409           Don’t canonicalize paths. The mount command canonicalizes all paths
410           (from the command line or fstab) by default. This option can be
411           used together with the -f flag for already canonicalized absolute
412           paths. The option is designed for mount helpers which call mount
413           -i. It is strongly recommended to not use this command-line option
414           for normal mount operations.
415
416           Note that mount does not pass this option to the /sbin/mount.type
417           helpers.
418
419       -F, --fork
420           (Used in conjunction with -a.) Fork off a new incarnation of mount
421           for each device. This will do the mounts on different devices or
422           different NFS servers in parallel. This has the advantage that it
423           is faster; also NFS timeouts proceed in parallel. A disadvantage is
424           that the order of the mount operations is undefined. Thus, you
425           cannot use this option if you want to mount both /usr and
426           /usr/spool.
427
428       -f, --fake
429           Causes everything to be done except for the actual system call; if
430           it’s not obvious, this "fakes" mounting the filesystem. This option
431           is useful in conjunction with the -v flag to determine what the
432           mount command is trying to do. It can also be used to add entries
433           for devices that were mounted earlier with the -n option. The -f
434           option checks for an existing record in /etc/mtab and fails when
435           the record already exists (with a regular non-fake mount, this
436           check is done by the kernel).
437
438       -i, --internal-only
439           Don’t call the /sbin/mount.filesystem helper even if it exists.
440
441       -L, --label label
442           Mount the partition that has the specified label.
443
444       -l, --show-labels
445           Add the labels in the mount output. mount must have permission to
446           read the disk device (e.g. be set-user-ID root) for this to work.
447           One can set such a label for ext2, ext3 or ext4 using the
448           e2label(8) utility, or for XFS using xfs_admin(8), or for reiserfs
449           using reiserfstune(8).
450
451       -M, --move
452           Move a subtree to some other place. See above, the subsection The
453           move operation.
454
455       -m, --mkdir[=mode]
456           Allow to make a target directory (mountpoint) if it does not exist
457           yet. Alias to "-o X-mount.mkdir[=mode]", the default mode is 0755.
458           For more details see X-mount.mkdir below.
459
460       -n, --no-mtab
461           Mount without writing in /etc/mtab. This is necessary for example
462           when /etc is on a read-only filesystem.
463
464       -N, --namespace ns
465           Perform the mount operation in the mount namespace specified by ns.
466           ns is either PID of process running in that namespace or special
467           file representing that namespace.
468
469           mount switches to the mount namespace when it reads /etc/fstab,
470           writes /etc/mtab: (or writes to _/run/mount) and calls mount(2),
471           otherwise it runs in the original mount namespace. This means that
472           the target namespace does not have to contain any libraries or
473           other requirements necessary to execute the mount(2) call.
474
475           See mount_namespaces(7) for more information.
476
477       -O, --test-opts opts
478           Limit the set of filesystems to which the -a option applies. In
479           this regard it is like the -t option except that -O is useless
480           without -a. For example, the command
481
482           mount -a -O no_netdev
483
484           mounts all filesystems except those which have the option netdev
485           specified in the options field in the /etc/fstab file.
486
487           It is different from -t in that each option is matched exactly; a
488           leading no at the beginning of one option does not negate the rest.
489
490           The -t and -O options are cumulative in effect; that is, the
491           command
492
493           mount -a -t ext2 -O  _netdev
494
495           mounts all ext2 filesystems with the _netdev option, not all
496           filesystems that are either ext2 or have the _netdev option
497           specified.
498
499       -o, --options opts
500           Use the specified mount options. The opts argument is a
501           comma-separated list. For example:
502
503           mount LABEL=mydisk -o noatime,nodev,nosuid
504
505           For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and
506           FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.
507
508       --options-mode mode
509           Controls how to combine options from fstab/mtab with options from
510           the command line. mode can be one of ignore, append, prepend or
511           replace. For example, append means that options from fstab are
512           appended to options from the command line. The default value is
513           prepend — it means command line options are evaluated after fstab
514           options. Note that the last option wins if there are conflicting
515           ones.
516
517       --options-source source
518           Source of default options. source is a comma-separated list of
519           fstab, mtab and disable. disable disables fstab and mtab and
520           enables --options-source-force. The default value is fstab,mtab.
521
522       --options-source-force
523           Use options from fstab/mtab even if both device and dir are
524           specified.
525
526       -R, --rbind
527           Remount a subtree and all possible submounts somewhere else (so
528           that its contents are available in both places). See above, the
529           subsection Bind mounts.
530
531       -r, --read-only
532           Mount the filesystem read-only. A synonym is -o ro.
533
534           Note that, depending on the filesystem type, state and kernel
535           behavior, the system may still write to the device. For example,
536           ext3 and ext4 will replay the journal if the filesystem is dirty.
537           To prevent this kind of write access, you may want to mount an ext3
538           or ext4 filesystem with the ro,noload mount options or set the
539           block device itself to read-only mode, see the blockdev(8) command.
540
541       -s
542           Tolerate sloppy mount options rather than failing. This will ignore
543           mount options not supported by a filesystem type. Not all
544           filesystems support this option. Currently it’s supported by the
545           mount.nfs mount helper only.
546
547       --source device
548           If only one argument for the mount command is given, then the
549           argument might be interpreted as the target (mountpoint) or source
550           (device). This option allows you to explicitly define that the
551           argument is the mount source.
552
553       --target directory
554           If only one argument for the mount command is given, then the
555           argument might be interpreted as the target (mountpoint) or source
556           (device). This option allows you to explicitly define that the
557           argument is the mount target.
558
559       --target-prefix directory
560           Prepend the specified directory to all mount targets. This option
561           can be used to follow fstab, but mount operations are done in
562           another place, for example:
563
564           mount --all --target-prefix /chroot -o X-mount.mkdir
565
566           mounts all from system fstab to /chroot, all missing mountpoint are
567           created (due to X-mount.mkdir). See also --fstab to use an
568           alternative fstab.
569
570       -T, --fstab path
571           Specifies an alternative fstab file. If path is a directory, then
572           the files in the directory are sorted by strverscmp(3); files that
573           start with "." or without an .fstab extension are ignored. The
574           option can be specified more than once. This option is mostly
575           designed for initramfs or chroot scripts where additional
576           configuration is specified beyond standard system configuration.
577
578           Note that mount does not pass the option --fstab to the
579           /sbin/mount.type helpers, meaning that the alternative fstab files
580           will be invisible for the helpers. This is no problem for normal
581           mounts, but user (non-root) mounts always require fstab to verify
582           the user’s rights.
583
584       -t, --types fstype
585           The argument following the -t is used to indicate the filesystem
586           type. The filesystem types which are currently supported depend on
587           the running kernel. See /proc/filesystems and /lib/modules/$(uname
588           -r)/kernel/fs for a complete list of the filesystems. The most
589           common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and
590           cifs.
591
592           The programs mount and umount(8) support filesystem subtypes. The
593           subtype is defined by a '.subtype' suffix. For example
594           'fuse.sshfs'. It’s recommended to use subtype notation rather than
595           add any prefix to the mount source (for example 'sshfs#example.com'
596           is deprecated).
597
598           If no -t option is given, or if the auto type is specified, mount
599           will try to guess the desired type. mount uses the libblkid(3)
600           library for guessing the filesystem type; if that does not turn up
601           anything that looks familiar, mount will try to read the file
602           /etc/filesystems, or, if that does not exist, /proc/filesystems.
603           All of the filesystem types listed there will be tried, except for
604           those that are labeled "nodev" (e.g. devpts, proc and nfs). If
605           /etc/filesystems ends in a line with a single *, mount will read
606           /proc/filesystems afterwards. While trying, all filesystem types
607           will be mounted with the mount option silent.
608
609           The auto type may be useful for user-mounted floppies. Creating a
610           file /etc/filesystems can be useful to change the probe order
611           (e.g., to try vfat before msdos or ext3 before ext2) or if you use
612           a kernel module autoloader.
613
614           More than one type may be specified in a comma-separated list, for
615           the -t option as well as in an /etc/fstab entry. The list of
616           filesystem types for the -t option can be prefixed with no to
617           specify the filesystem types on which no action should be taken.
618           The prefix no has no effect when specified in an /etc/fstab entry.
619
620           The prefix no can be meaningful with the -a option. For example,
621           the command
622
623           mount -a -t nomsdos,smbfs
624
625           mounts all filesystems except those of type msdos and smbfs.
626
627           For most types all the mount program has to do is issue a simple
628           mount(2) system call, and no detailed knowledge of the filesystem
629           type is required. For a few types however (like nfs, nfs4, cifs,
630           smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4, cifs,
631           smbfs, and ncpfs filesystems have a separate mount program. In
632           order to make it possible to treat all types in a uniform way,
633           mount will execute the program /sbin/mount.type (if that exists)
634           when called with type type. Since different versions of the
635           smbmount program have different calling conventions,
636           /sbin/mount.smbfs may have to be a shell script that sets up the
637           desired call.
638
639       -U, --uuid uuid
640           Mount the partition that has the specified uuid.
641
642       -v, --verbose
643           Verbose mode.
644
645       -w, --rw, --read-write
646           Mount the filesystem read/write. Read-write is the kernel default
647           and the mount default is to try read-only if the previous mount(2)
648           syscall with read-write flags on write-protected devices failed.
649
650           A synonym is -o rw.
651
652           Note that specifying -w on the command line forces mount to never
653           try read-only mount on write-protected devices or already mounted
654           read-only filesystems.
655
656       -h, --help
657           Display help text and exit.
658
659       -V, --version
660           Print version and exit.
661

FILESYSTEM-INDEPENDENT MOUNT OPTIONS

663       Some of these options are only useful when they appear in the
664       /etc/fstab file.
665
666       Some of these options could be enabled or disabled by default in the
667       system kernel. To check the current setting see the options in
668       /proc/mounts. Note that filesystems also have per-filesystem specific
669       default mount options (see for example tune2fs -l output for extN
670       filesystems).
671
672       The following options apply to any filesystem that is being mounted
673       (but not every filesystem actually honors them - e.g., the sync option
674       today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs):
675
676       async
677           All I/O to the filesystem should be done asynchronously. (See also
678           the sync option.)
679
680       atime
681           Do not use the noatime feature, so the inode access time is
682           controlled by kernel defaults. See also the descriptions of the
683           relatime and strictatime mount options.
684
685       noatime
686           Do not update inode access times on this filesystem (e.g. for
687           faster access on the news spool to speed up news servers). This
688           works for all inode types (directories too), so it implies
689           nodiratime.
690
691       auto
692           Can be mounted with the -a option.
693
694       noauto
695           Can only be mounted explicitly (i.e., the -a option will not cause
696           the filesystem to be mounted).
697
698       context=context, fscontext=context, defcontext=context, and
699       rootcontext=context
700           The context= option is useful when mounting filesystems that do not
701           support extended attributes, such as a floppy or hard disk
702           formatted with VFAT, or systems that are not normally running under
703           SELinux, such as an ext3 or ext4 formatted disk from a non-SELinux
704           workstation. You can also use context= on filesystems you do not
705           trust, such as a floppy. It also helps in compatibility with
706           xattr-supporting filesystems on earlier 2.4.<x> kernel versions.
707           Even where xattrs are supported, you can save time not having to
708           label every file by assigning the entire disk one security context.
709
710           A commonly used option for removable media is
711           context="system_u:object_r:removable_t.
712
713           The fscontext= option works for all filesystems, regardless of
714           their xattr support. The fscontext option sets the overarching
715           filesystem label to a specific security context. This filesystem
716           label is separate from the individual labels on the files. It
717           represents the entire filesystem for certain kinds of permission
718           checks, such as during mount or file creation. Individual file
719           labels are still obtained from the xattrs on the files themselves.
720           The context option actually sets the aggregate context that
721           fscontext provides, in addition to supplying the same label for
722           individual files.
723
724           You can set the default security context for unlabeled files using
725           defcontext= option. This overrides the value set for unlabeled
726           files in the policy and requires a filesystem that supports xattr
727           labeling.
728
729           The rootcontext= option allows you to explicitly label the root
730           inode of a FS being mounted before that FS or inode becomes visible
731           to userspace. This was found to be useful for things like stateless
732           Linux.
733
734           Note that the kernel rejects any remount request that includes the
735           context option, even when unchanged from the current context.
736
737           Warning: the context value might contain commas, in which case the
738           value has to be properly quoted, otherwise mount will interpret the
739           comma as a separator between mount options. Don’t forget that the
740           shell strips off quotes and thus double quoting is required. For
741           example:
742
743          mount -t tmpfs none /mnt -o \
744          'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
745
746       For more details, see selinux(8).
747
748       defaults
749           Use the default options: rw, suid, dev, exec, auto, nouser, and
750           async.
751
752           Note that the real set of all default mount options depends on the
753           kernel and filesystem type. See the beginning of this section for
754           more details.
755
756       dev
757           Interpret character or block special devices on the filesystem.
758
759       nodev
760           Do not interpret character or block special devices on the
761           filesystem.
762
763       diratime
764           Update directory inode access times on this filesystem. This is the
765           default. (This option is ignored when noatime is set.)
766
767       nodiratime
768           Do not update directory inode access times on this filesystem.
769           (This option is implied when noatime is set.)
770
771       dirsync
772           All directory updates within the filesystem should be done
773           synchronously. This affects the following system calls: creat(2),
774           link(2), unlink(2), symlink(2), mkdir(2), rmdir(2), mknod(2) and
775           rename(2).
776
777       exec
778           Permit execution of binaries and other executable files.
779
780       noexec
781           Do not permit direct execution of any binaries on the mounted
782           filesystem.
783
784       group
785           Allow an ordinary user to mount the filesystem if one of that
786           user’s groups matches the group of the device. This option implies
787           the options nosuid and nodev (unless overridden by subsequent
788           options, as in the option line group,dev,suid).
789
790       iversion
791           Every time the inode is modified, the i_version field will be
792           incremented.
793
794       noiversion
795           Do not increment the i_version inode field.
796
797       mand
798           Allow mandatory locks on this filesystem. See fcntl(2). This option
799           was deprecated in Linux 5.15.
800
801       nomand
802           Do not allow mandatory locks on this filesystem.
803
804       _netdev
805           The filesystem resides on a device that requires network access
806           (used to prevent the system from attempting to mount these
807           filesystems until the network has been enabled on the system).
808
809       nofail
810           Do not report errors for this device if it does not exist.
811
812       relatime
813           Update inode access times relative to modify or change time. Access
814           time is only updated if the previous access time was earlier than
815           the current modify or change time. (Similar to noatime, but it
816           doesn’t break mutt(1) or other applications that need to know if a
817           file has been read since the last time it was modified.)
818
819           Since Linux 2.6.30, the kernel defaults to the behavior provided by
820           this option (unless noatime was specified), and the strictatime
821           option is required to obtain traditional semantics. In addition,
822           since Linux 2.6.30, the file’s last access time is always updated
823           if it is more than 1 day old.
824
825       norelatime
826           Do not use the relatime feature. See also the strictatime mount
827           option.
828
829       strictatime
830           Allows to explicitly request full atime updates. This makes it
831           possible for the kernel to default to relatime or noatime but still
832           allow userspace to override it. For more details about the default
833           system mount options see /proc/mounts.
834
835       nostrictatime
836           Use the kernel’s default behavior for inode access time updates.
837
838       lazytime
839           Only update times (atime, mtime, ctime) on the in-memory version of
840           the file inode.
841
842           This mount option significantly reduces writes to the inode table
843           for workloads that perform frequent random writes to preallocated
844           files.
845
846           The on-disk timestamps are updated only when:
847
848           •   the inode needs to be updated for some change unrelated to file
849               timestamps
850
851           •   the application employs fsync(2), syncfs(2), or sync(2)
852
853           •   an undeleted inode is evicted from memory
854
855           •   more than 24 hours have passed since the inode was written to
856               disk.
857
858       nolazytime
859           Do not use the lazytime feature.
860
861       suid
862           Honor set-user-ID and set-group-ID bits or file capabilities when
863           executing programs from this filesystem.
864
865       nosuid
866           Do not honor set-user-ID and set-group-ID bits or file capabilities
867           when executing programs from this filesystem. In addition, SELinux
868           domain transitions require permission nosuid_transition, which in
869           turn needs also policy capability nnp_nosuid_transition.
870
871       silent
872           Turn on the silent flag.
873
874       loud
875           Turn off the silent flag.
876
877       owner
878           Allow an ordinary user to mount the filesystem if that user is the
879           owner of the device. This option implies the options nosuid and
880           nodev (unless overridden by subsequent options, as in the option
881           line owner,dev,suid).
882
883       remount
884           Attempt to remount an already-mounted filesystem. This is commonly
885           used to change the mount flags for a filesystem, especially to make
886           a readonly filesystem writable. It does not change device or mount
887           point.
888
889           The remount operation together with the bind flag has special
890           semantics. See above, the subsection Bind mounts.
891
892           The remount functionality follows the standard way the mount
893           command works with options from fstab. This means that mount does
894           not read fstab (or mtab) only when both device and dir are
895           specified.
896
897           mount -o remount,rw /dev/foo /dir
898
899           After this call all old mount options are replaced and arbitrary
900           stuff from fstab (or mtab) is ignored, except the loop= option
901           which is internally generated and maintained by the mount command.
902
903           mount -o remount,rw /dir
904
905           After this call, mount reads fstab and merges these options with
906           the options from the command line (-o). If no mountpoint is found
907           in fstab, then a remount with unspecified source is allowed.
908
909           mount allows the use of --all to remount all already mounted
910           filesystems which match a specified filter (-O and -t). For
911           example:
912
913           mount --all -o remount,ro -t vfat
914
915           remounts all already mounted vfat filesystems in read-only mode.
916           Each of the filesystems is remounted by mount -o remount,ro /dir
917           semantic. This means the mount command reads fstab or mtab and
918           merges these options with the options from the command line.
919
920       ro
921           Mount the filesystem read-only.
922
923       rw
924           Mount the filesystem read-write.
925
926       sync
927           All I/O to the filesystem should be done synchronously. In the case
928           of media with a limited number of write cycles (e.g. some flash
929           drives), sync may cause life-cycle shortening.
930
931       user
932           Allow an ordinary user to mount the filesystem. The name of the
933           mounting user is written to the mtab file (or to the private
934           libmount file in /run/mount on systems without a regular mtab) so
935           that this same user can unmount the filesystem again. This option
936           implies the options noexec, nosuid, and nodev (unless overridden by
937           subsequent options, as in the option line user,exec,dev,suid).
938
939       nouser
940           Forbid an ordinary user to mount the filesystem. This is the
941           default; it does not imply any other options.
942
943       users
944           Allow any user to mount and to unmount the filesystem, even when
945           some other ordinary user mounted it. This option implies the
946           options noexec, nosuid, and nodev (unless overridden by subsequent
947           options, as in the option line users,exec,dev,suid).
948
949       X-*
950           All options prefixed with "X-" are interpreted as comments or as
951           userspace application-specific options. These options are not
952           stored in user space (e.g., mtab file), nor sent to the mount.type
953           helpers nor to the mount(2) system call. The suggested format is
954           X-appname.option.
955
956       x-*
957           The same as X-* options, but stored permanently in user space. This
958           means the options are also available for umount(8) or other
959           operations. Note that maintaining mount options in user space is
960           tricky, because it’s necessary use libmount-based tools and there
961           is no guarantee that the options will be always available (for
962           example after a move mount operation or in unshared namespace).
963
964           Note that before util-linux v2.30 the x-* options have not been
965           maintained by libmount and stored in user space (functionality was
966           the same as for X-* now), but due to the growing number of
967           use-cases (in initrd, systemd etc.) the functionality has been
968           extended to keep existing fstab configurations usable without a
969           change.
970
971       X-mount.mkdir[=mode]
972           Allow to make a target directory (mountpoint) if it does not exist
973           yet. The optional argument mode specifies the filesystem access
974           mode used for mkdir(2) in octal notation. The default mode is 0755.
975           This functionality is supported only for root users or when mount
976           is executed without suid permissions. The option is also supported
977           as x-mount.mkdir, but this notation is deprecated since v2.30. See
978           also --mkdir command line option.
979
980       X-mount.subdir=directory
981           Allow mounting sub-directory from a filesystem instead of the root
982           directory. For now, this feature is implemented by temporary
983           filesystem root directory mount in unshared namespace and then bind
984           the sub-directory to the final mount point and umount the root of
985           the filesystem. The sub-directory mount shows up atomically for the
986           rest of the system although it is implemented by multiple mount(2)
987           syscalls. This feature is EXPERIMENTAL.
988
989       nosymfollow
990           Do not follow symlinks when resolving paths. Symlinks can still be
991           created, and readlink(1), readlink(2), realpath(1), and realpath(3)
992           all still work properly.
993

FILESYSTEM-SPECIFIC MOUNT OPTIONS

995       This section lists options that are specific to particular filesystems.
996       Where possible, you should first consult filesystem-specific manual
997       pages for details. Some of those pages are listed in the following
998       table.
999
1000       ┌─────────────────┬───────────────┐
1001       │                 │               │
1002Filesystem(s)    Manual page   
1003       ├─────────────────┼───────────────┤
1004       │                 │               │
1005       │btrfs            │ btrfs(5)
1006       ├─────────────────┼───────────────┤
1007       │                 │               │
1008       │cifs             │ mount.cifs(8)
1009       ├─────────────────┼───────────────┤
1010       │                 │               │
1011       │ext2, ext3, ext4 │ ext4(5)
1012       ├─────────────────┼───────────────┤
1013       │                 │               │
1014       │fuse             │ fuse(8)       │
1015       ├─────────────────┼───────────────┤
1016       │                 │               │
1017       │nfs              │ nfs(5)
1018       ├─────────────────┼───────────────┤
1019       │                 │               │
1020       │tmpfs            │ tmpfs(5)
1021       ├─────────────────┼───────────────┤
1022       │                 │               │
1023       │xfs              │ xfs(5)
1024       └─────────────────┴───────────────┘
1025
1026       Note that some of the pages listed above might be available only after
1027       you install the respective userland tools.
1028
1029       The following options apply only to certain filesystems. We sort them
1030       by filesystem. All options follow the -o flag.
1031
1032       What options are supported depends a bit on the running kernel. Further
1033       information may be available in filesystem-specific files in the kernel
1034       source subdirectory Documentation/filesystems.
1035
1036   Mount options for adfs
1037       uid=value and gid=value
1038           Set the owner and group of the files in the filesystem (default:
1039           uid=gid=0).
1040
1041       ownmask=value and othmask=value
1042           Set the permission mask for ADFS 'owner' permissions and 'other'
1043           permissions, respectively (default: 0700 and 0077, respectively).
1044           See also /usr/src/linux/Documentation/filesystems/adfs.rst.
1045
1046   Mount options for affs
1047       uid=value and gid=value
1048           Set the owner and group of the root of the filesystem (default:
1049           uid=gid=0, but with option uid or gid without specified value, the
1050           UID and GID of the current process are taken).
1051
1052       setuid=value and setgid=value
1053           Set the owner and group of all files.
1054
1055       mode=value
1056           Set the mode of all files to value & 0777 disregarding the original
1057           permissions. Add search permission to directories that have read
1058           permission. The value is given in octal.
1059
1060       protect
1061           Do not allow any changes to the protection bits on the filesystem.
1062
1063       usemp
1064           Set UID and GID of the root of the filesystem to the UID and GID of
1065           the mount point upon the first sync or umount, and then clear this
1066           option. Strange...
1067
1068       verbose
1069           Print an informational message for each successful mount.
1070
1071       prefix=string
1072           Prefix used before volume name, when following a link.
1073
1074       volume=string
1075           Prefix (of length at most 30) used before '/' when following a
1076           symbolic link.
1077
1078       reserved=value
1079           (Default: 2.) Number of unused blocks at the start of the device.
1080
1081       root=value
1082           Give explicitly the location of the root block.
1083
1084       bs=value
1085           Give blocksize. Allowed values are 512, 1024, 2048, 4096.
1086
1087       grpquota|noquota|quota|usrquota
1088           These options are accepted but ignored. (However, quota utilities
1089           may react to such strings in /etc/fstab.)
1090
1091   Mount options for debugfs
1092       The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1093       /sys/kernel/debug. As of kernel version 3.4, debugfs has the following
1094       options:
1095
1096       uid=n, gid=n
1097           Set the owner and group of the mountpoint.
1098
1099       mode=value
1100           Sets the mode of the mountpoint.
1101
1102   Mount options for devpts
1103       The devpts filesystem is a pseudo filesystem, traditionally mounted on
1104       /dev/pts. In order to acquire a pseudo terminal, a process opens
1105       /dev/ptmx; the number of the pseudo terminal is then made available to
1106       the process and the pseudo terminal slave can be accessed as
1107       /dev/pts/<number>.
1108
1109       uid=value and gid=value
1110           This sets the owner or the group of newly created pseudo terminals
1111           to the specified values. When nothing is specified, they will be
1112           set to the UID and GID of the creating process. For example, if
1113           there is a tty group with GID 5, then gid=5 will cause newly
1114           created pseudo terminals to belong to the tty group.
1115
1116       mode=value
1117           Set the mode of newly created pseudo terminals to the specified
1118           value. The default is 0600. A value of mode=620 and gid=5 makes
1119           "mesg y" the default on newly created pseudo terminals.
1120
1121       newinstance
1122           Create a private instance of the devpts filesystem, such that
1123           indices of pseudo terminals allocated in this new instance are
1124           independent of indices created in other instances of devpts.
1125
1126           All mounts of devpts without this newinstance option share the same
1127           set of pseudo terminal indices (i.e., legacy mode). Each mount of
1128           devpts with the newinstance option has a private set of pseudo
1129           terminal indices.
1130
1131           This option is mainly used to support containers in the Linux
1132           kernel. It is implemented in Linux kernel versions starting with
1133           2.6.29. Further, this mount option is valid only if
1134           CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1135           configuration.
1136
1137           To use this option effectively, /dev/ptmx must be a symbolic link
1138           to pts/ptmx. See Documentation/filesystems/devpts.txt in the Linux
1139           kernel source tree for details.
1140
1141       ptmxmode=value
1142           Set the mode for the new ptmx device node in the devpts filesystem.
1143
1144           With the support for multiple instances of devpts (see newinstance
1145           option above), each instance has a private ptmx node in the root of
1146           the devpts filesystem (typically /dev/pts/ptmx).
1147
1148           For compatibility with older versions of the kernel, the default
1149           mode of the new ptmx node is 0000. ptmxmode=value specifies a more
1150           useful mode for the ptmx node and is highly recommended when the
1151           newinstance option is specified.
1152
1153           This option is only implemented in Linux kernel versions starting
1154           with 2.6.29. Further, this option is valid only if
1155           CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1156           configuration.
1157
1158   Mount options for fat
1159       (Note: fat is not a separate filesystem, but a common part of the
1160       msdos, umsdos and vfat filesystems.)
1161
1162       blocksize={512|1024|2048}
1163           Set blocksize (default 512). This option is obsolete.
1164
1165       uid=value and gid=value
1166           Set the owner and group of all files. (Default: the UID and GID of
1167           the current process.)
1168
1169       umask=value
1170           Set the umask (the bitmask of the permissions that are not
1171           present). The default is the umask of the current process. The
1172           value is given in octal.
1173
1174       dmask=value
1175           Set the umask applied to directories only. The default is the umask
1176           of the current process. The value is given in octal.
1177
1178       fmask=value
1179           Set the umask applied to regular files only. The default is the
1180           umask of the current process. The value is given in octal.
1181
1182       allow_utime=value
1183           This option controls the permission check of mtime/atime.
1184
1185           20
1186               If current process is in group of file’s group ID, you can
1187               change timestamp.
1188
1189           2
1190               Other users can change timestamp.
1191
1192       The default is set from 'dmask' option. (If the directory is writable,
1193       utime(2) is also allowed. I.e. ~dmask & 022)
1194
1195       Normally utime(2) checks that the current process is owner of the file,
1196       or that it has the CAP_FOWNER capability. But FAT filesystems don’t
1197       have UID/GID on disk, so the normal check is too inflexible. With this
1198       option you can relax it.
1199
1200       check=value
1201           Three different levels of pickiness can be chosen:
1202
1203           r[elaxed]
1204               Upper and lower case are accepted and equivalent, long name
1205               parts are truncated (e.g. verylongname.foobar becomes
1206               verylong.foo), leading and embedded spaces are accepted in each
1207               name part (name and extension).
1208
1209           n[ormal]
1210               Like "relaxed", but many special characters (*, ?, <, spaces,
1211               etc.) are rejected. This is the default.
1212
1213           s[trict]
1214               Like "normal", but names that contain long parts or special
1215               characters that are sometimes used on Linux but are not
1216               accepted by MS-DOS (+, =, etc.) are rejected.
1217
1218       codepage=value
1219           Sets the codepage for converting to shortname characters on FAT and
1220           VFAT filesystems. By default, codepage 437 is used.
1221
1222       conv=mode
1223           This option is obsolete and may fail or be ignored.
1224
1225       cvf_format=module
1226           Forces the driver to use the CVF (Compressed Volume File) module
1227           cvf_module instead of auto-detection. If the kernel supports kmod,
1228           the cvf_format=xxx option also controls on-demand CVF module
1229           loading. This option is obsolete.
1230
1231       cvf_option=option
1232           Option passed to the CVF module. This option is obsolete.
1233
1234       debug
1235           Turn on the debug flag. A version string and a list of filesystem
1236           parameters will be printed (these data are also printed if the
1237           parameters appear to be inconsistent).
1238
1239       discard
1240           If set, causes discard/TRIM commands to be issued to the block
1241           device when blocks are freed. This is useful for SSD devices and
1242           sparse/thinly-provisioned LUNs.
1243
1244       dos1xfloppy
1245           If set, use a fallback default BIOS Parameter Block configuration,
1246           determined by backing device size. These static parameters match
1247           defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360
1248           kiB floppies and floppy images.
1249
1250       errors={panic|continue|remount-ro}
1251           Specify FAT behavior on critical errors: panic, continue without
1252           doing anything, or remount the partition in read-only mode (default
1253           behavior).
1254
1255       fat={12|16|32}
1256           Specify a 12, 16 or 32 bit fat. This overrides the automatic FAT
1257           type detection routine. Use with caution!
1258
1259       iocharset=value
1260           Character set to use for converting between 8 bit characters and 16
1261           bit Unicode characters. The default is iso8859-1. Long filenames
1262           are stored on disk in Unicode format.
1263
1264       nfs={stale_rw|nostale_ro}
1265           Enable this only if you want to export the FAT filesystem over NFS.
1266
1267           stale_rw: This option maintains an index (cache) of directory
1268           inodes which is used by the nfs-related code to improve look-ups.
1269           Full file operations (read/write) over NFS are supported but with
1270           cache eviction at NFS server, this could result in spurious ESTALE
1271           errors.
1272
1273           nostale_ro: This option bases the inode number and file handle on
1274           the on-disk location of a file in the FAT directory entry. This
1275           ensures that ESTALE will not be returned after a file is evicted
1276           from the inode cache. However, it means that operations such as
1277           rename, create and unlink could cause file handles that previously
1278           pointed at one file to point at a different file, potentially
1279           causing data corruption. For this reason, this option also mounts
1280           the filesystem readonly.
1281
1282           To maintain backward compatibility, -o nfs is also accepted,
1283           defaulting to stale_rw.
1284
1285       tz=UTC
1286           This option disables the conversion of timestamps between local
1287           time (as used by Windows on FAT) and UTC (which Linux uses
1288           internally). This is particularly useful when mounting devices
1289           (like digital cameras) that are set to UTC in order to avoid the
1290           pitfalls of local time.
1291
1292       time_offset=minutes
1293           Set offset for conversion of timestamps from local time used by FAT
1294           to UTC. I.e., minutes will be subtracted from each timestamp to
1295           convert it to UTC used internally by Linux. This is useful when the
1296           time zone set in the kernel via settimeofday(2) is not the time
1297           zone used by the filesystem. Note that this option still does not
1298           provide correct time stamps in all cases in presence of DST - time
1299           stamps in a different DST setting will be off by one hour.
1300
1301       quiet
1302           Turn on the quiet flag. Attempts to chown or chmod files do not
1303           return errors, although they fail. Use with caution!
1304
1305       rodir
1306           FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO
1307           of the directory will just be ignored, and is used only by
1308           applications as a flag (e.g. it’s set for the customized folder).
1309
1310           If you want to use ATTR_RO as read-only flag even for the
1311           directory, set this option.
1312
1313       showexec
1314           If set, the execute permission bits of the file will be allowed
1315           only if the extension part of the name is .EXE, .COM, or .BAT. Not
1316           set by default.
1317
1318       sys_immutable
1319           If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on
1320           Linux. Not set by default.
1321
1322       flush
1323           If set, the filesystem will try to flush to disk more early than
1324           normal. Not set by default.
1325
1326       usefree
1327           Use the "free clusters" value stored on FSINFO. It’ll be used to
1328           determine number of free clusters without scanning disk. But it’s
1329           not used by default, because recent Windows don’t update it
1330           correctly in some case. If you are sure the "free clusters" on
1331           FSINFO is correct, by this option you can avoid scanning disk.
1332
1333       dots, nodots, dotsOK=[yes|no]
1334           Various misguided attempts to force Unix or DOS conventions onto a
1335           FAT filesystem.
1336
1337   Mount options for hfs
1338       creator=cccc, type=cccc
1339           Set the creator/type values as shown by the MacOS finder used for
1340           creating new files. Default values: '????'.
1341
1342       uid=n, gid=n
1343           Set the owner and group of all files. (Default: the UID and GID of
1344           the current process.)
1345
1346       dir_umask=n, file_umask=n, umask=n
1347           Set the umask used for all directories, all regular files, or all
1348           files and directories. Defaults to the umask of the current
1349           process.
1350
1351       session=n
1352           Select the CDROM session to mount. Defaults to leaving that
1353           decision to the CDROM driver. This option will fail with anything
1354           but a CDROM as underlying device.
1355
1356       part=n
1357           Select partition number n from the device. Only makes sense for
1358           CDROMs. Defaults to not parsing the partition table at all.
1359
1360       quiet
1361           Don’t complain about invalid mount options.
1362
1363   Mount options for hpfs
1364       uid=value and gid=value
1365           Set the owner and group of all files. (Default: the UID and GID of
1366           the current process.)
1367
1368       umask=value
1369           Set the umask (the bitmask of the permissions that are not
1370           present). The default is the umask of the current process. The
1371           value is given in octal.
1372
1373       case={lower|asis}
1374           Convert all files names to lower case, or leave them. (Default:
1375           case=lower.)
1376
1377       conv=mode
1378           This option is obsolete and may fail or being ignored.
1379
1380       nocheck
1381           Do not abort mounting when certain consistency checks fail.
1382
1383   Mount options for iso9660
1384       ISO 9660 is a standard describing a filesystem structure to be used on
1385       CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1386       udf filesystem.)
1387
1388       Normal iso9660 filenames appear in an 8.3 format (i.e., DOS-like
1389       restrictions on filename length), and in addition all characters are in
1390       upper case. Also there is no field for file ownership, protection,
1391       number of links, provision for block/character devices, etc.
1392
1393       Rock Ridge is an extension to iso9660 that provides all of these
1394       UNIX-like features. Basically there are extensions to each directory
1395       record that supply all of the additional information, and when Rock
1396       Ridge is in use, the filesystem is indistinguishable from a normal UNIX
1397       filesystem (except that it is read-only, of course).
1398
1399       norock
1400           Disable the use of Rock Ridge extensions, even if available. Cf.
1401           map.
1402
1403       nojoliet
1404           Disable the use of Microsoft Joliet extensions, even if available.
1405           Cf. map.
1406
1407       check={r[elaxed]|s[trict]}
1408           With check=relaxed, a filename is first converted to lower case
1409           before doing the lookup. This is probably only meaningful together
1410           with norock and map=normal. (Default: check=strict.)
1411
1412       uid=value and gid=value
1413           Give all files in the filesystem the indicated user or group id,
1414           possibly overriding the information found in the Rock Ridge
1415           extensions. (Default: uid=0,gid=0.)
1416
1417       map={n[ormal]|o[ff]|a[corn]}
1418           For non-Rock Ridge volumes, normal name translation maps upper to
1419           lower case ASCII, drops a trailing ';1', and converts ';' to '.'.
1420           With map=off no name translation is done. See norock. (Default:
1421           map=normal.) map=acorn is like map=normal but also apply Acorn
1422           extensions if present.
1423
1424       mode=value
1425           For non-Rock Ridge volumes, give all files the indicated mode.
1426           (Default: read and execute permission for everybody.) Octal mode
1427           values require a leading 0.
1428
1429       unhide
1430           Also show hidden and associated files. (If the ordinary files and
1431           the associated or hidden files have the same filenames, this may
1432           make the ordinary files inaccessible.)
1433
1434       block={512|1024|2048}
1435           Set the block size to the indicated value. (Default: block=1024.)
1436
1437       conv=mode
1438           This option is obsolete and may fail or being ignored.
1439
1440       cruft
1441           If the high byte of the file length contains other garbage, set
1442           this mount option to ignore the high order bits of the file length.
1443           This implies that a file cannot be larger than 16 MB.
1444
1445       session=x
1446           Select number of session on a multisession CD.
1447
1448       sbsector=xxx
1449           Session begins from sector xxx.
1450
1451       The following options are the same as for vfat and specifying them only
1452       makes sense when using discs encoded using Microsoft’s Joliet
1453       extensions.
1454
1455       iocharset=value
1456           Character set to use for converting 16 bit Unicode characters on CD
1457           to 8 bit characters. The default is iso8859-1.
1458
1459       utf8
1460           Convert 16 bit Unicode characters on CD to UTF-8.
1461
1462   Mount options for jfs
1463       iocharset=name
1464           Character set to use for converting from Unicode to ASCII. The
1465           default is to do no conversion. Use iocharset=utf8 for UTF8
1466           translations. This requires CONFIG_NLS_UTF8 to be set in the kernel
1467           .config file.
1468
1469       resize=value
1470           Resize the volume to value blocks. JFS only supports growing a
1471           volume, not shrinking it. This option is only valid during a
1472           remount, when the volume is mounted read-write. The resize keyword
1473           with no value will grow the volume to the full size of the
1474           partition.
1475
1476       nointegrity
1477           Do not write to the journal. The primary use of this option is to
1478           allow for higher performance when restoring a volume from backup
1479           media. The integrity of the volume is not guaranteed if the system
1480           abnormally ends.
1481
1482       integrity
1483           Default. Commit metadata changes to the journal. Use this option to
1484           remount a volume where the nointegrity option was previously
1485           specified in order to restore normal behavior.
1486
1487       errors={continue|remount-ro|panic}
1488           Define the behavior when an error is encountered. (Either ignore
1489           errors and just mark the filesystem erroneous and continue, or
1490           remount the filesystem read-only, or panic and halt the system.)
1491
1492       noquota|quota|usrquota|grpquota
1493           These options are accepted but ignored.
1494
1495   Mount options for msdos
1496       See mount options for fat. If the msdos filesystem detects an
1497       inconsistency, it reports an error and sets the file system read-only.
1498       The filesystem can be made writable again by remounting it.
1499
1500   Mount options for ncpfs
1501       Just like nfs, the ncpfs implementation expects a binary argument (a
1502       struct ncp_mount_data) to the mount(2) system call. This argument is
1503       constructed by ncpmount(8) and the current version of mount (2.12) does
1504       not know anything about ncpfs.
1505
1506   Mount options for ntfs
1507       iocharset=name
1508           Character set to use when returning file names. Unlike VFAT, NTFS
1509           suppresses names that contain nonconvertible characters.
1510           Deprecated.
1511
1512       nls=name
1513           New name for the option earlier called iocharset.
1514
1515       utf8
1516           Use UTF-8 for converting file names.
1517
1518       uni_xlate={0|1|2}
1519           For 0 (or 'no' or 'false'), do not use escape sequences for unknown
1520           Unicode characters. For 1 (or 'yes' or 'true') or 2, use vfat-style
1521           4-byte escape sequences starting with ":". Here 2 gives a
1522           little-endian encoding and 1 a byteswapped bigendian encoding.
1523
1524       posix=[0|1]
1525           If enabled (posix=1), the filesystem distinguishes between upper
1526           and lower case. The 8.3 alias names are presented as hard links
1527           instead of being suppressed. This option is obsolete.
1528
1529       uid=value, gid=value and umask=value
1530           Set the file permission on the filesystem. The umask value is given
1531           in octal. By default, the files are owned by root and not readable
1532           by somebody else.
1533
1534   Mount options for overlay
1535       Since Linux 3.18 the overlay pseudo filesystem implements a union mount
1536       for other filesystems.
1537
1538       An overlay filesystem combines two filesystems - an upper filesystem
1539       and a lower filesystem. When a name exists in both filesystems, the
1540       object in the upper filesystem is visible while the object in the lower
1541       filesystem is either hidden or, in the case of directories, merged with
1542       the upper object.
1543
1544       The lower filesystem can be any filesystem supported by Linux and does
1545       not need to be writable. The lower filesystem can even be another
1546       overlayfs. The upper filesystem will normally be writable and if it is
1547       it must support the creation of trusted.* extended attributes, and must
1548       provide a valid d_type in readdir responses, so NFS is not suitable.
1549
1550       A read-only overlay of two read-only filesystems may use any filesystem
1551       type. The options lowerdir and upperdir are combined into a merged
1552       directory by using:
1553
1554              mount -t overlay  overlay  \
1555                -olowerdir=/lower,upperdir=/upper,workdir=/work  /merged
1556
1557       lowerdir=directory
1558           Any filesystem, does not need to be on a writable filesystem.
1559
1560       upperdir=directory
1561           The upperdir is normally on a writable filesystem.
1562
1563       workdir=directory
1564           The workdir needs to be an empty directory on the same filesystem
1565           as upperdir.
1566
1567       userxattr
1568           Use the "user.overlay." xattr namespace instead of
1569           "trusted.overlay.". This is useful for unprivileged mounting of
1570           overlayfs.
1571
1572       redirect_dir={on|off|follow|nofollow}
1573           If the redirect_dir feature is enabled, then the directory will be
1574           copied up (but not the contents). Then the
1575           "{trusted|user}.overlay.redirect" extended attribute is set to the
1576           path of the original location from the root of the overlay. Finally
1577           the directory is moved to the new location.
1578
1579           on
1580               Redirects are enabled.
1581
1582           off
1583               Redirects are not created and only followed if
1584               "redirect_always_follow" feature is enabled in the
1585               kernel/module config.
1586
1587           follow
1588               Redirects are not created, but followed.
1589
1590           nofollow
1591               Redirects are not created and not followed (equivalent to
1592               "redirect_dir=off" if "redirect_always_follow" feature is not
1593               enabled).
1594
1595       index={on|off}
1596           Inode index. If this feature is disabled and a file with multiple
1597           hard links is copied up, then this will "break" the link. Changes
1598           will not be propagated to other names referring to the same inode.
1599
1600       uuid={on|off}
1601           Can be used to replace UUID of the underlying filesystem in file
1602           handles with null, and effectively disable UUID checks. This can be
1603           useful in case the underlying disk is copied and the UUID of this
1604           copy is changed. This is only applicable if all lower/upper/work
1605           directories are on the same filesystem, otherwise it will fallback
1606           to normal behaviour.
1607
1608       nfs_export={on|off}
1609           When the underlying filesystems supports NFS export and the
1610           "nfs_export" feature is enabled, an overlay filesystem may be
1611           exported to NFS.
1612
1613           With the "nfs_export" feature, on copy_up of any lower object, an
1614           index entry is created under the index directory. The index entry
1615           name is the hexadecimal representation of the copy up origin file
1616           handle. For a non-directory object, the index entry is a hard link
1617           to the upper inode. For a directory object, the index entry has an
1618           extended attribute "{trusted|user}.overlay.upper" with an encoded
1619           file handle of the upper directory inode.
1620
1621           When encoding a file handle from an overlay filesystem object, the
1622           following rules apply
1623
1624               •   For a non-upper object, encode a lower file handle from
1625                   lower inode
1626
1627               •   For an indexed object, encode a lower file handle from
1628                   copy_up origin
1629
1630               •   For a pure-upper object and for an existing non-indexed
1631                   upper object, encode an upper file handle from upper inode
1632
1633           The encoded overlay file handle includes
1634
1635               •   Header including path type information (e.g. lower/upper)
1636
1637               •   UUID of the underlying filesystem
1638
1639               •   Underlying filesystem encoding of underlying inode
1640
1641           This encoding format is identical to the encoding format of file
1642           handles that are stored in extended attribute
1643           "{trusted|user}.overlay.origin". When decoding an overlay file
1644           handle, the following steps are followed
1645
1646               •   Find underlying layer by UUID and path type information.
1647
1648               •   Decode the underlying filesystem file handle to underlying
1649                   dentry.
1650
1651               •   For a lower file handle, lookup the handle in index
1652                   directory by name.
1653
1654               •   If a whiteout is found in index, return ESTALE. This
1655                   represents an overlay object that was deleted after its
1656                   file handle was encoded.
1657
1658               •   For a non-directory, instantiate a disconnected overlay
1659                   dentry from the decoded underlying dentry, the path type
1660                   and index inode, if found.
1661
1662               •   For a directory, use the connected underlying decoded
1663                   dentry, path type and index, to lookup a connected overlay
1664                   dentry.
1665
1666           Decoding a non-directory file handle may return a disconnected
1667           dentry. copy_up of that disconnected dentry will create an upper
1668           index entry with no upper alias.
1669
1670           When overlay filesystem has multiple lower layers, a middle layer
1671           directory may have a "redirect" to lower directory. Because middle
1672           layer "redirects" are not indexed, a lower file handle that was
1673           encoded from the "redirect" origin directory, cannot be used to
1674           find the middle or upper layer directory. Similarly, a lower file
1675           handle that was encoded from a descendant of the "redirect" origin
1676           directory, cannot be used to reconstruct a connected overlay path.
1677           To mitigate the cases of directories that cannot be decoded from a
1678           lower file handle, these directories are copied up on encode and
1679           encoded as an upper file handle. On an overlay filesystem with no
1680           upper layer this mitigation cannot be used NFS export in this setup
1681           requires turning off redirect follow (e.g.
1682           "redirect_dir=nofollow").
1683
1684           The overlay filesystem does not support non-directory connectable
1685           file handles, so exporting with the subtree_check exportfs
1686           configuration will cause failures to lookup files over NFS.
1687
1688           When the NFS export feature is enabled, all directory index entries
1689           are verified on mount time to check that upper file handles are not
1690           stale. This verification may cause significant overhead in some
1691           cases.
1692
1693           Note: the mount options index=off,nfs_export=on are conflicting for
1694           a read-write mount and will result in an error.
1695
1696       xino={on|off|auto}
1697           The "xino" feature composes a unique object identifier from the
1698           real object st_ino and an underlying fsid index. The "xino" feature
1699           uses the high inode number bits for fsid, because the underlying
1700           filesystems rarely use the high inode number bits. In case the
1701           underlying inode number does overflow into the high xino bits,
1702           overlay filesystem will fall back to the non xino behavior for that
1703           inode.
1704
1705           For a detailed description of the effect of this option please
1706           refer to
1707           https://www.kernel.org/doc/html/latest/filesystems/overlayfs.html?highlight=overlayfs
1708
1709       metacopy={on|off}
1710           When metadata only copy up feature is enabled, overlayfs will only
1711           copy up metadata (as opposed to whole file), when a metadata
1712           specific operation like chown/chmod is performed. Full file will be
1713           copied up later when file is opened for WRITE operation.
1714
1715           In other words, this is delayed data copy up operation and data is
1716           copied up when there is a need to actually modify data.
1717
1718       volatile
1719           Volatile mounts are not guaranteed to survive a crash. It is
1720           strongly recommended that volatile mounts are only used if data
1721           written to the overlay can be recreated without significant effort.
1722
1723           The advantage of mounting with the "volatile" option is that all
1724           forms of sync calls to the upper filesystem are omitted.
1725
1726           In order to avoid a giving a false sense of safety, the syncfs (and
1727           fsync) semantics of volatile mounts are slightly different than
1728           that of the rest of VFS. If any writeback error occurs on the
1729           upperdir’s filesystem after a volatile mount takes place, all sync
1730           functions will return an error. Once this condition is reached, the
1731           filesystem will not recover, and every subsequent sync call will
1732           return an error, even if the upperdir has not experience a new
1733           error since the last sync call.
1734
1735           When overlay is mounted with "volatile" option, the directory
1736           "$workdir/work/incompat/volatile" is created. During next mount,
1737           overlay checks for this directory and refuses to mount if present.
1738           This is a strong indicator that user should throw away upper and
1739           work directories and create fresh one. In very limited cases where
1740           the user knows that the system has not crashed and contents of
1741           upperdir are intact, The "volatile" directory can be removed.
1742
1743   Mount options for reiserfs
1744       Reiserfs is a journaling filesystem.
1745
1746       conv
1747           Instructs version 3.6 reiserfs software to mount a version 3.5
1748           filesystem, using the 3.6 format for newly created objects. This
1749           filesystem will no longer be compatible with reiserfs 3.5 tools.
1750
1751       hash={rupasov|tea|r5|detect}
1752           Choose which hash function reiserfs will use to find files within
1753           directories.
1754
1755           rupasov
1756               A hash invented by Yury Yu. Rupasov. It is fast and preserves
1757               locality, mapping lexicographically close file names to close
1758               hash values. This option should not be used, as it causes a
1759               high probability of hash collisions.
1760
1761           tea
1762               A Davis-Meyer function implemented by Jeremy Fitzhardinge. It
1763               uses hash permuting bits in the name. It gets high randomness
1764               and, therefore, low probability of hash collisions at some CPU
1765               cost. This may be used if EHASHCOLLISION errors are experienced
1766               with the r5 hash.
1767
1768           r5
1769               A modified version of the rupasov hash. It is used by default
1770               and is the best choice unless the filesystem has huge
1771               directories and unusual file-name patterns.
1772
1773           detect
1774               Instructs mount to detect which hash function is in use by
1775               examining the filesystem being mounted, and to write this
1776               information into the reiserfs superblock. This is only useful
1777               on the first mount of an old format filesystem.
1778
1779       hashed_relocation
1780           Tunes the block allocator. This may provide performance
1781           improvements in some situations.
1782
1783       no_unhashed_relocation
1784           Tunes the block allocator. This may provide performance
1785           improvements in some situations.
1786
1787       noborder
1788           Disable the border allocator algorithm invented by Yury Yu.
1789           Rupasov. This may provide performance improvements in some
1790           situations.
1791
1792       nolog
1793           Disable journaling. This will provide slight performance
1794           improvements in some situations at the cost of losing reiserfs’s
1795           fast recovery from crashes. Even with this option turned on,
1796           reiserfs still performs all journaling operations, save for actual
1797           writes into its journaling area. Implementation of nolog is a work
1798           in progress.
1799
1800       notail
1801           By default, reiserfs stores small files and 'file tails' directly
1802           into its tree. This confuses some utilities such as lilo(8). This
1803           option is used to disable packing of files into the tree.
1804
1805       replayonly
1806           Replay the transactions which are in the journal, but do not
1807           actually mount the filesystem. Mainly used by reiserfsck.
1808
1809       resize=number
1810           A remount option which permits online expansion of reiserfs
1811           partitions. Instructs reiserfs to assume that the device has number
1812           blocks. This option is designed for use with devices which are
1813           under logical volume management (LVM). There is a special resizer
1814           utility which can be obtained from
1815           ftp://ftp.namesys.com/pub/reiserfsprogs.
1816
1817       user_xattr
1818           Enable Extended User Attributes. See the attr(1) manual page.
1819
1820       acl
1821           Enable POSIX Access Control Lists. See the acl(5) manual page.
1822
1823       barrier=none / barrier=flush
1824           This disables / enables the use of write barriers in the journaling
1825           code. barrier=none disables, barrier=flush enables (default). This
1826           also requires an IO stack which can support barriers, and if
1827           reiserfs gets an error on a barrier write, it will disable barriers
1828           again with a warning. Write barriers enforce proper on-disk
1829           ordering of journal commits, making volatile disk write caches safe
1830           to use, at some performance penalty. If your disks are
1831           battery-backed in one way or another, disabling barriers may safely
1832           improve performance.
1833
1834   Mount options for ubifs
1835       UBIFS is a flash filesystem which works on top of UBI volumes. Note
1836       that atime is not supported and is always turned off.
1837
1838       The device name may be specified as
1839
1840          ubiX_Y
1841              UBI device number X, volume number Y
1842
1843          ubiY
1844              UBI device number 0, volume number Y
1845
1846          ubiX:NAME
1847              UBI device number X, volume with name NAME
1848
1849          ubi:NAME
1850              UBI device number 0, volume with name NAME
1851
1852       Alternative ! separator may be used instead of :.
1853
1854       The following mount options are available:
1855
1856       bulk_read
1857           Enable bulk-read. VFS read-ahead is disabled because it slows down
1858           the filesystem. Bulk-Read is an internal optimization. Some flashes
1859           may read faster if the data are read at one go, rather than at
1860           several read requests. For example, OneNAND can do
1861           "read-while-load" if it reads more than one NAND page.
1862
1863       no_bulk_read
1864           Do not bulk-read. This is the default.
1865
1866       chk_data_crc
1867           Check data CRC-32 checksums. This is the default.
1868
1869       no_chk_data_crc
1870           Do not check data CRC-32 checksums. With this option, the
1871           filesystem does not check CRC-32 checksum for data, but it does
1872           check it for the internal indexing information. This option only
1873           affects reading, not writing. CRC-32 is always calculated when
1874           writing the data.
1875
1876       compr={none|lzo|zlib}
1877           Select the default compressor which is used when new files are
1878           written. It is still possible to read compressed files if mounted
1879           with the none option.
1880
1881   Mount options for udf
1882       UDF is the "Universal Disk Format" filesystem defined by OSTA, the
1883       Optical Storage Technology Association, and is often used for DVD-ROM,
1884       frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is,
1885       however, perfectly usable by itself on disk drives, flash drives and
1886       other block devices. See also iso9660.
1887
1888       uid=
1889           Make all files in the filesystem belong to the given user.
1890           uid=forget can be specified independently of (or usually in
1891           addition to) uid=<user> and results in UDF not storing uids to the
1892           media. In fact the recorded uid is the 32-bit overflow uid -1 as
1893           defined by the UDF standard. The value is given as either <user>
1894           which is a valid user name or the corresponding decimal user id, or
1895           the special string "forget".
1896
1897       gid=
1898           Make all files in the filesystem belong to the given group.
1899           gid=forget can be specified independently of (or usually in
1900           addition to) gid=<group> and results in UDF not storing gids to the
1901           media. In fact the recorded gid is the 32-bit overflow gid -1 as
1902           defined by the UDF standard. The value is given as either <group>
1903           which is a valid group name or the corresponding decimal group id,
1904           or the special string "forget".
1905
1906       umask=
1907           Mask out the given permissions from all inodes read from the
1908           filesystem. The value is given in octal.
1909
1910       mode=
1911           If mode= is set the permissions of all non-directory inodes read
1912           from the filesystem will be set to the given mode. The value is
1913           given in octal.
1914
1915       dmode=
1916           If dmode= is set the permissions of all directory inodes read from
1917           the filesystem will be set to the given dmode. The value is given
1918           in octal.
1919
1920       bs=
1921           Set the block size. Default value prior to kernel version 2.6.30
1922           was 2048. Since 2.6.30 and prior to 4.11 it was logical device
1923           block size with fallback to 2048. Since 4.11 it is logical block
1924           size with fallback to any valid block size between logical device
1925           block size and 4096.
1926
1927           For other details see the mkudffs(8) 2.0+ manpage, see the
1928           COMPATIBILITY and BLOCK SIZE sections.
1929
1930       unhide
1931           Show otherwise hidden files.
1932
1933       undelete
1934           Show deleted files in lists.
1935
1936       adinicb
1937           Embed data in the inode. (default)
1938
1939       noadinicb
1940           Don’t embed data in the inode.
1941
1942       shortad
1943           Use short UDF address descriptors.
1944
1945       longad
1946           Use long UDF address descriptors. (default)
1947
1948       nostrict
1949           Unset strict conformance.
1950
1951       iocharset=
1952           Set the NLS character set. This requires kernel compiled with
1953           CONFIG_UDF_NLS option.
1954
1955       utf8
1956           Set the UTF-8 character set.
1957
1958   Mount options for debugging and disaster recovery
1959       novrs
1960           Ignore the Volume Recognition Sequence and attempt to mount anyway.
1961
1962       session=
1963           Select the session number for multi-session recorded optical media.
1964           (default= last session)
1965
1966       anchor=
1967           Override standard anchor location. (default= 256)
1968
1969       lastblock=
1970           Set the last block of the filesystem.
1971
1972   Unused historical mount options that may be encountered and should be
1973       removed
1974       uid=ignore
1975           Ignored, use uid=<user> instead.
1976
1977       gid=ignore
1978           Ignored, use gid=<group> instead.
1979
1980       volume=
1981           Unimplemented and ignored.
1982
1983       partition=
1984           Unimplemented and ignored.
1985
1986       fileset=
1987           Unimplemented and ignored.
1988
1989       rootdir=
1990           Unimplemented and ignored.
1991
1992   Mount options for ufs
1993       ufstype=value
1994           UFS is a filesystem widely used in different operating systems. The
1995           problem are differences among implementations. Features of some
1996           implementations are undocumented, so its hard to recognize the type
1997           of ufs automatically. That’s why the user must specify the type of
1998           ufs by mount option. Possible values are:
1999
2000           old
2001               Old format of ufs, this is the default, read only. (Don’t
2002               forget to give the -r option.)
2003
2004           44bsd
2005               For filesystems created by a BSD-like system (NetBSD, FreeBSD,
2006               OpenBSD).
2007
2008           ufs2
2009               Used in FreeBSD 5.x supported as read-write.
2010
2011           5xbsd
2012               Synonym for ufs2.
2013
2014           sun
2015               For filesystems created by SunOS or Solaris on Sparc.
2016
2017           sunx86
2018               For filesystems created by Solaris on x86.
2019
2020           hp
2021               For filesystems created by HP-UX, read-only.
2022
2023           nextstep
2024               For filesystems created by NeXTStep (on NeXT station)
2025               (currently read only).
2026
2027           nextstep-cd
2028               For NextStep CDROMs (block_size == 2048), read-only.
2029
2030           openstep
2031               For filesystems created by OpenStep (currently read only). The
2032               same filesystem type is also used by macOS.
2033
2034       onerror=value
2035           Set behavior on error:
2036
2037           panic
2038               If an error is encountered, cause a kernel panic.
2039
2040           [lock|umount|repair]
2041               These mount options don’t do anything at present; when an error
2042               is encountered only a console message is printed.
2043
2044   Mount options for umsdos
2045       See mount options for msdos. The dotsOK option is explicitly killed by
2046       umsdos.
2047
2048   Mount options for vfat
2049       First of all, the mount options for fat are recognized. The dotsOK
2050       option is explicitly killed by vfat. Furthermore, there are
2051
2052       uni_xlate
2053           Translate unhandled Unicode characters to special escaped
2054           sequences. This lets you backup and restore filenames that are
2055           created with any Unicode characters. Without this option, a '?' is
2056           used when no translation is possible. The escape character is ':'
2057           because it is otherwise invalid on the vfat filesystem. The escape
2058           sequence that gets used, where u is the Unicode character, is: ':',
2059           (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
2060
2061       posix
2062           Allow two files with names that only differ in case. This option is
2063           obsolete.
2064
2065       nonumtail
2066           First try to make a short name without sequence number, before
2067           trying name~num.ext.
2068
2069       utf8
2070           UTF8 is the filesystem safe 8-bit encoding of Unicode that is used
2071           by the console. It can be enabled for the filesystem with this
2072           option or disabled with utf8=0, utf8=no or utf8=false. If uni_xlate
2073           gets set, UTF8 gets disabled.
2074
2075       shortname=mode
2076           Defines the behavior for creation and display of filenames which
2077           fit into 8.3 characters. If a long name for a file exists, it will
2078           always be the preferred one for display. There are four modes:
2079
2080           lower
2081               Force the short name to lower case upon display; store a long
2082               name when the short name is not all upper case.
2083
2084           win95
2085               Force the short name to upper case upon display; store a long
2086               name when the short name is not all upper case.
2087
2088           winnt
2089               Display the short name as is; store a long name when the short
2090               name is not all lower case or all upper case.
2091
2092           mixed
2093               Display the short name as is; store a long name when the short
2094               name is not all upper case. This mode is the default since
2095               Linux 2.6.32.
2096
2097   Mount options for usbfs
2098       devuid=uid and devgid=gid and devmode=mode
2099           Set the owner and group and mode of the device files in the usbfs
2100           filesystem (default: uid=gid=0, mode=0644). The mode is given in
2101           octal.
2102
2103       busuid=uid and busgid=gid and busmode=mode
2104           Set the owner and group and mode of the bus directories in the
2105           usbfs filesystem (default: uid=gid=0, mode=0555). The mode is given
2106           in octal.
2107
2108       listuid=uid and listgid=gid and listmode=mode
2109           Set the owner and group and mode of the file devices (default:
2110           uid=gid=0, mode=0444). The mode is given in octal.
2111

DM-VERITY SUPPORT

2113       The device-mapper verity target provides read-only transparent
2114       integrity checking of block devices using kernel crypto API. The mount
2115       command can open the dm-verity device and do the integrity verification
2116       before the device filesystem is mounted. Requires libcryptsetup with in
2117       libmount (optionally via dlopen(3)). If libcryptsetup supports
2118       extracting the root hash of an already mounted device, existing devices
2119       will be automatically reused in case of a match. Mount options for
2120       dm-verity:
2121
2122       verity.hashdevice=path
2123           Path to the hash tree device associated with the source volume to
2124           pass to dm-verity.
2125
2126       verity.roothash=hex
2127           Hex-encoded hash of the root of verity.hashdevice. Mutually
2128           exclusive with verity.roothashfile.
2129
2130       verity.roothashfile=path
2131           Path to file containing the hex-encoded hash of the root of
2132           verity.hashdevice. Mutually exclusive with verity.roothash.
2133
2134       verity.hashoffset=offset
2135           If the hash tree device is embedded in the source volume, offset
2136           (default: 0) is used by dm-verity to get to the tree.
2137
2138       verity.fecdevice=path
2139           Path to the Forward Error Correction (FEC) device associated with
2140           the source volume to pass to dm-verity. Optional. Requires kernel
2141           built with CONFIG_DM_VERITY_FEC.
2142
2143       verity.fecoffset=offset
2144           If the FEC device is embedded in the source volume, offset
2145           (default: 0) is used by dm-verity to get to the FEC area. Optional.
2146
2147       verity.fecroots=value
2148           Parity bytes for FEC (default: 2). Optional.
2149
2150       verity.roothashsig=path
2151           Path to pkcs7(1ssl) signature of root hash hex string. Requires
2152           crypt_activate_by_signed_key() from cryptsetup and kernel built
2153           with CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG. For device reuse,
2154           signatures have to be either used by all mounts of a device or by
2155           none. Optional.
2156
2157       verity.oncorruption=ignore|restart|panic
2158           Instruct the kernel to ignore, reboot or panic when corruption is
2159           detected. By default the I/O operation simply fails. Requires Linux
2160           4.1 or newer, and libcrypsetup 2.3.4 or newer. Optional.
2161
2162       Supported since util-linux v2.35.
2163
2164       For example commands:
2165
2166           mksquashfs /etc /tmp/etc.squashfs
2167           dd if=/dev/zero of=/tmp/etc.hash bs=1M count=10
2168           veritysetup format /tmp/etc.squashfs /tmp/etc.hash
2169           openssl smime -sign -in <hash> -nocerts -inkey private.key \
2170           -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s
2171           mount -o verity.hashdevice=/tmp/etc.hash,verity.roothash=<hash>,\
2172           verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.squashfs /mnt
2173
2174       create squashfs image from /etc directory, verity hash device and mount
2175       verified filesystem image to /mnt. The kernel will verify that the root
2176       hash is signed by a key from the kernel keyring if roothashsig is used.
2177

LOOP-DEVICE SUPPORT

2179       One further possible type is a mount via the loop device. For example,
2180       the command
2181
2182          mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3
2183
2184       will set up the loop device /dev/loop3 to correspond to the file
2185       /tmp/disk.img, and then mount this device on /mnt.
2186
2187       If no explicit loop device is mentioned (but just an option '-o loop'
2188       is given), then mount will try to find some unused loop device and use
2189       that, for example
2190
2191          mount /tmp/disk.img /mnt -o loop
2192
2193       The mount command automatically creates a loop device from a regular
2194       file if a filesystem type is not specified or the filesystem is known
2195       for libblkid, for example:
2196
2197          mount /tmp/disk.img /mnt
2198
2199          mount -t ext4 /tmp/disk.img /mnt
2200
2201       This type of mount knows about three options, namely loop, offset and
2202       sizelimit, that are really options to losetup(8). (These options can be
2203       used in addition to those specific to the filesystem type.)
2204
2205       Since Linux 2.6.25 auto-destruction of loop devices is supported,
2206       meaning that any loop device allocated by mount will be freed by umount
2207       independently of /etc/mtab.
2208
2209       You can also free a loop device by hand, using losetup -d or umount -d.
2210
2211       Since util-linux v2.29, mount re-uses the loop device rather than
2212       initializing a new device if the same backing file is already used for
2213       some loop device with the same offset and sizelimit. This is necessary
2214       to avoid a filesystem corruption.
2215

EXIT STATUS

2217       mount has the following exit status values (the bits can be ORed):
2218
2219       0
2220           success
2221
2222       1
2223           incorrect invocation or permissions
2224
2225       2
2226           system error (out of memory, cannot fork, no more loop devices)
2227
2228       4
2229           internal mount bug
2230
2231       8
2232           user interrupt
2233
2234       16
2235           problems writing or locking /etc/mtab
2236
2237       32
2238           mount failure
2239
2240       64
2241           some mount succeeded
2242
2243           The command mount -a returns 0 (all succeeded), 32 (all failed), or
2244           64 (some failed, some succeeded).
2245

EXTERNAL HELPERS

2247       The syntax of external mount helpers is:
2248
2249       /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t
2250       type.subtype]
2251
2252       where the suffix is the filesystem type and the -sfnvoN options have
2253       the same meaning as the normal mount options. The -t option is used for
2254       filesystems with subtypes support (for example /sbin/mount.fuse -t
2255       fuse.sshfs).
2256
2257       The command mount does not pass the mount options unbindable,
2258       runbindable, private, rprivate, slave, rslave, shared, rshared, auto,
2259       noauto, comment, x-*, loop, offset and sizelimit to the mount.<suffix>
2260       helpers. All other options are used in a comma-separated list as an
2261       argument to the -o option.
2262

ENVIRONMENT

2264       LIBMOUNT_FSTAB=<path>
2265           overrides the default location of the fstab file (ignored for suid)
2266
2267       LIBMOUNT_MTAB=<path>
2268           overrides the default location of the mtab file (ignored for suid)
2269
2270       LIBMOUNT_DEBUG=all
2271           enables libmount debug output
2272
2273       LIBBLKID_DEBUG=all
2274           enables libblkid debug output
2275
2276       LOOPDEV_DEBUG=all
2277           enables loop device setup debug output
2278

FILES

2280       See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section
2281       above.
2282
2283       /etc/fstab
2284           filesystem table
2285
2286       /run/mount
2287           libmount private runtime directory
2288
2289       /etc/mtab
2290           table of mounted filesystems or symlink to /proc/mounts
2291
2292       /etc/mtab~
2293           lock file (unused on systems with mtab symlink)
2294
2295       /etc/mtab.tmp
2296           temporary file (unused on systems with mtab symlink)
2297
2298       /etc/filesystems
2299           a list of filesystem types to try
2300

HISTORY

2302       A mount command existed in Version 5 AT&T UNIX.
2303

BUGS

2305       It is possible for a corrupted filesystem to cause a crash.
2306
2307       Some Linux filesystems don’t support -o sync and -o dirsync (the ext2,
2308       ext3, ext4, fat and vfat filesystems do support synchronous updates (a
2309       la BSD) when mounted with the sync option).
2310
2311       The -o remount may not be able to change mount parameters (all
2312       ext2fs-specific parameters, except sb, are changeable with a remount,
2313       for example, but you can’t change gid or umask for the fatfs).
2314
2315       It is possible that the files /etc/mtab and /proc/mounts don’t match on
2316       systems with a regular mtab file. The first file is based only on the
2317       mount command options, but the content of the second file also depends
2318       on the kernel and others settings (e.g. on a remote NFS server — in
2319       certain cases the mount command may report unreliable information about
2320       an NFS mount point and the /proc/mount file usually contains more
2321       reliable information.) This is another reason to replace the mtab file
2322       with a symlink to the /proc/mounts file.
2323
2324       Checking files on NFS filesystems referenced by file descriptors (i.e.
2325       the fcntl and ioctl families of functions) may lead to inconsistent
2326       results due to the lack of a consistency check in the kernel even if
2327       the noac mount option is used.
2328
2329       The loop option with the offset or sizelimit options used may fail when
2330       using older kernels if the mount command can’t confirm that the size of
2331       the block device has been configured as requested. This situation can
2332       be worked around by using the losetup(8) command manually before
2333       calling mount with the configured loop device.
2334

AUTHORS

2336       Karel Zak <kzak@redhat.com>
2337

SEE ALSO

2339       mount(2), umount(2), filesystems(5), fstab(5), nfs(5), xfs(5),
2340       mount_namespaces(7), xattr(7), e2label(8), findmnt(8), losetup(8),
2341       lsblk(8), mke2fs(8), mountd(8), nfsd(8), swapon(8), tune2fs(8),
2342       umount(8), xfs_admin(8)
2343

REPORTING BUGS

2345       For bug reports, use the issue tracker at
2346       https://github.com/util-linux/util-linux/issues.
2347

AVAILABILITY

2349       The mount command is part of the util-linux package which can be
2350       downloaded from Linux Kernel Archive
2351       <https://www.kernel.org/pub/linux/utils/util-linux/>.
2352
2353
2354
2355util-linux 2.38                   2022-02-17                          MOUNT(8)
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