1MOUNT(8) System Administration MOUNT(8)
2
6 mount - mount a filesystem
7
9 mount [-h|-V]
10 mount [-l] [-t fstype]
12 mount -a [-fFnrsvw] [-t fstype] [-O optlist]
14 mount [-fnrsvw] [-o options] device|mountpoint
16 mount [-fnrsvw] [-t fstype] [-o options] device mountpoint
18 mount --bind|--rbind|--move olddir newdir
20 mount
22 --make-[shared|slave|private|unbindable|rshared|rslave|rprivate|runbindable]
23 mountpoint
24
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 The standard form of the mount command is:
35 mount -t type device dir
37 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 If only the directory or the device is given, for example:
48 mount /dir
50 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 mount --target /mountpoint
57 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 Listing the mounts
67 The listing mode is maintained for backward compatibility only.
68 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 The following command lists all mounted filesystems (of type type):
74 mount [-l] [-t type]
76 The option -l adds labels to this listing. See below.
78 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 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 LABEL=label
91 Human readable filesystem identifier. See also -L.
92 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 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 PARTLABEL=label
103 Human readable partition identifier. This identifier is independent
104 on filesystem and does not change by mkfs or mkswap operations It’s
105 supported for example for GUID Partition Tables (GPT).
106 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 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 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 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 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 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 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 The command
150 mount -a [-t type] [-O optlist]
152 (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 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 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 If no arguments are given to mount, the list of mounted filesystems is
173 printed.
174 If you want to override mount options from /etc/fstab, you have to use
176 the -o option:
177 mount device**|dir -o options
179 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 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 mount /dev/foo /dir
190 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 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 Thus, given a line
202 /dev/cdrom /cd iso9660 ro,user,noauto,unhide
204 any user can mount the iso9660 filesystem found on an inserted CDROM
206 using the command:
207 mount /cd
209 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 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 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 Bind mount operation
232 Remount part of the file hierarchy somewhere else. The call is:
233 mount --bind olddir newdir
235 or by using this fstab entry:
237 /olddir /newdir none bind
239 After this call the same contents are accessible in two places.
241 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 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 mount --bind foo foo
254 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 mount --rbind olddir newdir
260 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 Since util-linux 2.27 mount permits changing the mount options by
267 passing the relevant options along with --bind. For example:
268 mount -o bind,ro foo foo
270 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 The alternative (classic) way to create a read-only bind mount is to
276 use the remount operation, for example:
277 mount --bind olddir newdir mount -o remount,bind,ro olddir
279 newdir
280 Note that a read-only bind will create a read-only mountpoint (VFS
282 entry), but the original filesystem superblock will still be writable,
283 meaning that the olddir will be writable, but the newdir will be
284 read-only.
285 It’s also possible to change nosuid, nodev, noexec, noatime, nodiratime
287 and relatime VFS entry flags via a "remount,bind" operation. The other
288 flags (for example filesystem-specific flags) are silently ignored.
289 It’s impossible to change mount options recursively (for example with
290 -o rbind,ro).
291 Since util-linux 2.31, mount ignores the bind flag from /etc/fstab on a
293 remount operation (if "-o remount" is specified on command line). This
294 is necessary to fully control mount options on remount by command line.
295 In previous versions the bind flag has been always applied and it was
296 impossible to re-define mount options without interaction with the bind
297 semantic. This mount behavior does not affect situations when
298 "remount,bind" is specified in the /etc/fstab file.
299 The move operation
301 Move a mounted tree to another place (atomically). The call is:
302 mount --move olddir newdir
304 This will cause the contents which previously appeared under olddir to
306 now be accessible under newdir. The physical location of the files is
307 not changed. Note that olddir has to be a mountpoint.
308 Note also that moving a mount residing under a shared mount is invalid
310 and unsupported. Use findmnt -o TARGET,PROPAGATION to see the current
311 propagation flags.
312 Shared subtree operations
314 Since Linux 2.6.15 it is possible to mark a mount and its submounts as
315 shared, private, slave or unbindable. A shared mount provides the
316 ability to create mirrors of that mount such that mounts and unmounts
317 within any of the mirrors propagate to the other mirror. A slave mount
318 receives propagation from its master, but not vice versa. A private
319 mount carries no propagation abilities. An unbindable mount is a
320 private mount which cannot be cloned through a bind operation. The
321 detailed semantics are documented in
322 Documentation/filesystems/sharedsubtree.txt file in the kernel source
323 tree; see also mount_namespaces(7).
324 Supported operations are:
326 mount --make-shared mountpoint
328 mount --make-slave mountpoint
329 mount --make-private mountpoint
330 mount --make-unbindable mountpoint
331 The following commands allow one to recursively change the type of all
333 the mounts under a given mountpoint.
334 mount --make-rshared mountpoint
336 mount --make-rslave mountpoint
337 mount --make-rprivate mountpoint
338 mount --make-runbindable mountpoint
339 mount(8) does not read fstab(5) when a --make-* operation is requested.
341 All necessary information has to be specified on the command line.
342 Note that the Linux kernel does not allow changing multiple propagation
344 flags with a single mount(2) system call, and the flags cannot be mixed
345 with other mount options and operations.
346 Since util-linux 2.23 the mount command can be used to do more
348 propagation (topology) changes by one mount(8) call and do it also
349 together with other mount operations. The propagation flags are applied
350 by additional mount(2) system calls when the preceding mount operations
351 were successful. Note that this use case is not atomic. It is possible
352 to specify the propagation flags in fstab(5) as mount options (private,
353 slave, shared, unbindable, rprivate, rslave, rshared, runbindable).
354 For example:
356 mount --make-private --make-unbindable /dev/sda1 /foo
358 is the same as:
360 mount /dev/sda1 /foo
362 mount --make-private /foo
363 mount --make-unbindable /foo
364
366 The full set of mount options used by an invocation of mount is
367 determined by first extracting the mount options for the filesystem
368 from the fstab table, then applying any options specified by the -o
369 argument, and finally applying a -r or -w option, when present.
370 The mount command does not pass all command-line options to the
372 /sbin/mount.suffix mount helpers. The interface between mount and the
373 mount helpers is described below in the section EXTERNAL HELPERS.
374 Command-line options available for the mount command are:
376 -a, --all
378 Mount all filesystems (of the given types) mentioned in fstab
379 (except for those whose line contains the noauto keyword). The
380 filesystems are mounted following their order in fstab. The mount
381 command compares filesystem source, target (and fs root for bind
382 mount or btrfs) to detect already mounted filesystems. The kernel
383 table with already mounted filesystems is cached during mount
384 --all. This means that all duplicated fstab entries will be
385 mounted.
386 The option --all is possible to use for remount operation too. In
388 this case all filters (-t and -O) are applied to the table of
389 already mounted filesystems.
390 Since version 2.35 is possible to use the command line option -o to
392 alter mount options from fstab (see also --options-mode).
393 Note that it is a bad practice to use mount -a for fstab checking.
395 The recommended solution is findmnt --verify.
396 -B, --bind
398 Remount a subtree somewhere else (so that its contents are
399 available in both places). See above, under Bind mounts.
400 -c, --no-canonicalize
402 Don’t canonicalize paths. The mount command canonicalizes all paths
403 (from the command line or fstab) by default. This option can be
404 used together with the -f flag for already canonicalized absolute
405 paths. The option is designed for mount helpers which call mount
406 -i. It is strongly recommended to not use this command-line option
407 for normal mount operations.
408 Note that mount does not pass this option to the /sbin/mount.type
410 helpers.
411 -F, --fork
413 (Used in conjunction with -a.) Fork off a new incarnation of mount
414 for each device. This will do the mounts on different devices or
415 different NFS servers in parallel. This has the advantage that it
416 is faster; also NFS timeouts proceed in parallel. A disadvantage is
417 that the order of the mount operations is undefined. Thus, you
418 cannot use this option if you want to mount both /usr and
419 /usr/spool.
420 -f, --fake
422 Causes everything to be done except for the actual system call; if
423 it’s not obvious, this "fakes" mounting the filesystem. This option
424 is useful in conjunction with the -v flag to determine what the
425 mount command is trying to do. It can also be used to add entries
426 for devices that were mounted earlier with the -n option. The -f
427 option checks for an existing record in /etc/mtab and fails when
428 the record already exists (with a regular non-fake mount, this
429 check is done by the kernel).
430 -i, --internal-only
432 Don’t call the /sbin/mount.filesystem helper even if it exists.
433 -L, --label label
435 Mount the partition that has the specified label.
436 -l, --show-labels
438 Add the labels in the mount output. mount must have permission to
439 read the disk device (e.g. be set-user-ID root) for this to work.
440 One can set such a label for ext2, ext3 or ext4 using the
441 e2label(8) utility, or for XFS using xfs_admin(8), or for reiserfs
442 using reiserfstune(8).
443 -M, --move
445 Move a subtree to some other place. See above, the subsection The
446 move operation.
447 -n, --no-mtab
449 Mount without writing in /etc/mtab. This is necessary for example
450 when /etc is on a read-only filesystem.
451 -N, --namespace ns
453 Perform the mount operation in the mount namespace specified by ns.
454 ns is either PID of process running in that namespace or special
455 file representing that namespace.
456 mount switches to the mount namespace when it reads /etc/fstab,
458 writes /etc/mtab: (or writes to _/run/mount) and calls the mount(2)
459 system call, otherwise it runs in the original mount namespace.
460 This means that the target namespace does not have to contain any
461 libraries or other requirements necessary to execute the mount(2)
462 call.
463 See mount_namespaces(7) for more information.
465 -O, --test-opts opts
467 Limit the set of filesystems to which the -a option applies. In
468 this regard it is like the -t option except that -O is useless
469 without -a. For example, the command
470 mount -a -O no_netdev
472 mounts all filesystems except those which have the option netdev
474 specified in the options field in the /etc/fstab file.
475 It is different from -t in that each option is matched exactly; a
477 leading no at the beginning of one option does not negate the rest.
478 The -t and -O options are cumulative in effect; that is, the
480 command
481 mount -a -t ext2 -O _netdev
483 mounts all ext2 filesystems with the _netdev option, not all
485 filesystems that are either ext2 or have the _netdev option
486 specified.
487 -o, --options opts
489 Use the specified mount options. The opts argument is a
490 comma-separated list. For example:
491 mount LABEL=mydisk -o noatime,nodev,nosuid
493 For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and
495 FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.
496 --options-mode mode
498 Controls how to combine options from fstab/mtab with options from
499 the command line. mode can be one of ignore, append, prepend or
500 replace. For example, append means that options from fstab are
501 appended to options from the command line. The default value is
502 prepend — it means command line options are evaluated after fstab
503 options. Note that the last option wins if there are conflicting
504 ones.
505 --options-source source
507 Source of default options. source is a comma-separated list of
508 fstab, mtab and disable. disable disables fstab and mtab and
509 disables --options-source-force. The default value is fstab,mtab.
510 --options-source-force
512 Use options from fstab/mtab even if both device and dir are
513 specified.
514 -R, --rbind
516 Remount a subtree and all possible submounts somewhere else (so
517 that its contents are available in both places). See above, the
518 subsection Bind mounts.
519 -r, --read-only
521 Mount the filesystem read-only. A synonym is -o ro.
522 Note that, depending on the filesystem type, state and kernel
524 behavior, the system may still write to the device. For example,
525 ext3 and ext4 will replay the journal if the filesystem is dirty.
526 To prevent this kind of write access, you may want to mount an ext3
527 or ext4 filesystem with the ro,noload mount options or set the
528 block device itself to read-only mode, see the blockdev(8) command.
529 -s
531 Tolerate sloppy mount options rather than failing. This will ignore
532 mount options not supported by a filesystem type. Not all
533 filesystems support this option. Currently it’s supported by the
534 mount.nfs mount helper only.
535 --source device
537 If only one argument for the mount command is given, then the
538 argument might be interpreted as the target (mountpoint) or source
539 (device). This option allows you to explicitly define that the
540 argument is the mount source.
541 --target directory
543 If only one argument for the mount command is given, then the
544 argument might be interpreted as the target (mountpoint) or source
545 (device). This option allows you to explicitly define that the
546 argument is the mount target.
547 --target-prefix directory
549 Prepend the specified directory to all mount targets. This option
550 can be used to follow fstab, but mount operations are done in
551 another place, for example:
552 mount --all --target-prefix /chroot -o X-mount.mkdir
554 mounts all from system fstab to /chroot, all missing mountpoint are
556 created (due to X-mount.mkdir). See also --fstab to use an
557 alternative fstab.
558 -T, --fstab path
560 Specifies an alternative fstab file. If path is a directory, then
561 the files in the directory are sorted by strverscmp(3); files that
562 start with "." or without an .fstab extension are ignored. The
563 option can be specified more than once. This option is mostly
564 designed for initramfs or chroot scripts where additional
565 configuration is specified beyond standard system configuration.
566 Note that mount does not pass the option --fstab to the
568 /sbin/mount.type helpers, meaning that the alternative fstab files
569 will be invisible for the helpers. This is no problem for normal
570 mounts, but user (non-root) mounts always require fstab to verify
571 the user’s rights.
572 -t, --types fstype
574 The argument following the -t is used to indicate the filesystem
575 type. The filesystem types which are currently supported depend on
576 the running kernel. See /proc/filesystems and /lib/modules/$(uname
577 -r)/kernel/fs for a complete list of the filesystems. The most
578 common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and
579 cifs.
580 The programs mount and umount(8) support filesystem subtypes. The
582 subtype is defined by a '.subtype' suffix. For example
583 'fuse.sshfs'. It’s recommended to use subtype notation rather than
584 add any prefix to the mount source (for example 'sshfs#example.com'
585 is deprecated).
586 If no -t option is given, or if the auto type is specified, mount
588 will try to guess the desired type. mount uses the libblkid(3)
589 library for guessing the filesystem type; if that does not turn up
590 anything that looks familiar, mount will try to read the file
591 /etc/filesystems, or, if that does not exist, /proc/filesystems.
592 All of the filesystem types listed there will be tried, except for
593 those that are labeled "nodev" (e.g. devpts, proc and nfs). If
594 /etc/filesystems ends in a line with a single *, mount will read
595 /proc/filesystems afterwards. While trying, all filesystem types
596 will be mounted with the mount option silent.
597 The auto type may be useful for user-mounted floppies. Creating a
599 file /etc/filesystems can be useful to change the probe order
600 (e.g., to try vfat before msdos or ext3 before ext2) or if you use
601 a kernel module autoloader.
602 More than one type may be specified in a comma-separated list, for
604 the -t option as well as in an /etc/fstab entry. The list of
605 filesystem types for the -t option can be prefixed with no to
606 specify the filesystem types on which no action should be taken.
607 The prefix no has no effect when specified in an /etc/fstab entry.
608 The prefix no can be meaningful with the -a option. For example,
610 the command
611 mount -a -t nomsdos,smbfs
613 mounts all filesystems except those of type msdos and smbfs.
615 For most types all the mount program has to do is issue a simple
617 mount(2) system call, and no detailed knowledge of the filesystem
618 type is required. For a few types however (like nfs, nfs4, cifs,
619 smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4, cifs,
620 smbfs, and ncpfs filesystems have a separate mount program. In
621 order to make it possible to treat all types in a uniform way,
622 mount will execute the program /sbin/mount.type (if that exists)
623 when called with type type. Since different versions of the
624 smbmount program have different calling conventions,
625 /sbin/mount.smbfs may have to be a shell script that sets up the
626 desired call.
627 -U, --uuid uuid
629 Mount the partition that has the specified uuid.
630 -v, --verbose
632 Verbose mode.
633 -w, --rw, --read-write
635 Mount the filesystem read/write. Read-write is the kernel default
636 and the mount default is to try read-only if the previous mount
637 syscall with read-write flags on write-protected devices of
638 filesystems failed.
639 A synonym is -o rw.
641 Note that specifying -w on the command line forces mount to never
643 try read-only mount on write-protected devices or already mounted
644 read-only filesystems.
645 -V, --version
647 Display version information and exit.
648 -h, --help
650 Display help text and exit.
651
653 Some of these options are only useful when they appear in the
654 /etc/fstab file.
655 Some of these options could be enabled or disabled by default in the
657 system kernel. To check the current setting see the options in
658 /proc/mounts. Note that filesystems also have per-filesystem specific
659 default mount options (see for example tune2fs -l output for ext_N_
660 filesystems).
661 The following options apply to any filesystem that is being mounted
663 (but not every filesystem actually honors them - e.g., the sync option
664 today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs):
665 async
667 All I/O to the filesystem should be done asynchronously. (See also
668 the sync option.)
669 atime
671 Do not use the noatime feature, so the inode access time is
672 controlled by kernel defaults. See also the descriptions of the
673 relatime and strictatime mount options.
674 noatime
676 Do not update inode access times on this filesystem (e.g. for
677 faster access on the news spool to speed up news servers). This
678 works for all inode types (directories too), so it implies
679 nodiratime.
680 auto
682 Can be mounted with the -a option.
683 noauto
685 Can only be mounted explicitly (i.e., the -a option will not cause
686 the filesystem to be mounted).
687 context=context, fscontext=context, defcontext=context, and
689 rootcontext=context
690 The context= option is useful when mounting filesystems that do not
691 support extended attributes, such as a floppy or hard disk
692 formatted with VFAT, or systems that are not normally running under
693 SELinux, such as an ext3 or ext4 formatted disk from a non-SELinux
694 workstation. You can also use context= on filesystems you do not
695 trust, such as a floppy. It also helps in compatibility with
696 xattr-supporting filesystems on earlier 2.4.<x> kernel versions.
697 Even where xattrs are supported, you can save time not having to
698 label every file by assigning the entire disk one security context.
699 A commonly used option for removable media is
701 context="system_u:object_r:removable_t.
702 The fscontext= option works for all filesystems, regardless of
704 their xattr support. The fscontext option sets the overarching
705 filesystem label to a specific security context. This filesystem
706 label is separate from the individual labels on the files. It
707 represents the entire filesystem for certain kinds of permission
708 checks, such as during mount or file creation. Individual file
709 labels are still obtained from the xattrs on the files themselves.
710 The context option actually sets the aggregate context that
711 fscontext provides, in addition to supplying the same label for
712 individual files.
713 You can set the default security context for unlabeled files using
715 defcontext= option. This overrides the value set for unlabeled
716 files in the policy and requires a filesystem that supports xattr
717 labeling.
718 The rootcontext= option allows you to explicitly label the root
720 inode of a FS being mounted before that FS or inode becomes visible
721 to userspace. This was found to be useful for things like stateless
722 Linux.
723 Note that the kernel rejects any remount request that includes the
725 context option, even when unchanged from the current context.
726 Warning: the context value might contain commas, in which case the
728 value has to be properly quoted, otherwise mount will interpret the
729 comma as a separator between mount options. Don’t forget that the
730 shell strips off quotes and thus double quoting is required. For
731 example:
732 mount -t tmpfs none /mnt -o \
734 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
735 For more details, see selinux(8).
737 defaults
739 Use the default options: rw, suid, dev, exec, auto, nouser, and
740 async.
741 Note that the real set of all default mount options depends on the
743 kernel and filesystem type. See the beginning of this section for
744 more details.
745 dev
747 Interpret character or block special devices on the filesystem.
748 nodev
750 Do not interpret character or block special devices on the
751 filesystem.
752 diratime
754 Update directory inode access times on this filesystem. This is the
755 default. (This option is ignored when noatime is set.)
756 nodiratime
758 Do not update directory inode access times on this filesystem.
759 (This option is implied when noatime is set.)
760 dirsync
762 All directory updates within the filesystem should be done
763 synchronously. This affects the following system calls: creat(2),
764 link(2), unlink(2), symlink(2), mkdir(2), rmdir(2), mknod(2) and
765 rename(2).
766 exec
768 Permit execution of binaries.
769 noexec
771 Do not permit direct execution of any binaries on the mounted
772 filesystem.
773 group
775 Allow an ordinary user to mount the filesystem if one of that
776 user’s groups matches the group of the device. This option implies
777 the options nosuid and nodev (unless overridden by subsequent
778 options, as in the option line group,dev,suid).
779 iversion
781 Every time the inode is modified, the i_version field will be
782 incremented.
783 noiversion
785 Do not increment the i_version inode field.
786 mand
788 Allow mandatory locks on this filesystem. See fcntl(2).
789 nomand
791 Do not allow mandatory locks on this filesystem.
792 _netdev
794 The filesystem resides on a device that requires network access
795 (used to prevent the system from attempting to mount these
796 filesystems until the network has been enabled on the system).
797 nofail
799 Do not report errors for this device if it does not exist.
800 relatime
802 Update inode access times relative to modify or change time. Access
803 time is only updated if the previous access time was earlier than
804 the current modify or change time. (Similar to noatime, but it
805 doesn’t break mutt(1) or other applications that need to know if a
806 file has been read since the last time it was modified.)
807 Since Linux 2.6.30, the kernel defaults to the behavior provided by
809 this option (unless noatime was specified), and the strictatime
810 option is required to obtain traditional semantics. In addition,
811 since Linux 2.6.30, the file’s last access time is always updated
812 if it is more than 1 day old.
813 norelatime
815 Do not use the relatime feature. See also the strictatime mount
816 option.
817 strictatime
819 Allows to explicitly request full atime updates. This makes it
820 possible for the kernel to default to relatime or noatime but still
821 allow userspace to override it. For more details about the default
822 system mount options see /proc/mounts.
823 nostrictatime
825 Use the kernel’s default behavior for inode access time updates.
826 lazytime
828 Only update times (atime, mtime, ctime) on the in-memory version of
829 the file inode.
830 This mount option significantly reduces writes to the inode table
832 for workloads that perform frequent random writes to preallocated
833 files.
834 The on-disk timestamps are updated only when:
836 • the inode needs to be updated for some change unrelated to file
838 timestamps
839 • the application employs fsync(2), syncfs(2), or sync(2)
841 • an undeleted inode is evicted from memory
843 • more than 24 hours have passed since the inode was written to
845 disk.
846 nolazytime
848 Do not use the lazytime feature.
849 suid
851 Honor set-user-ID and set-group-ID bits or file capabilities when
852 executing programs from this filesystem.
853 nosuid
855 Do not honor set-user-ID and set-group-ID bits or file capabilities
856 when executing programs from this filesystem. In addition, SELinux
857 domain transitions require permission nosuid_transition, which in
858 turn needs also policy capability nnp_nosuid_transition.
859 silent
861 Turn on the silent flag.
862 loud
864 Turn off the silent flag.
865 owner
867 Allow an ordinary user to mount the filesystem if that user is the
868 owner of the device. This option implies the options nosuid and
869 nodev (unless overridden by subsequent options, as in the option
870 line owner,dev,suid).
871 remount
873 Attempt to remount an already-mounted filesystem. This is commonly
874 used to change the mount flags for a filesystem, especially to make
875 a readonly filesystem writable. It does not change device or mount
876 point.
877 The remount operation together with the bind flag has special
879 semantics. See above, the subsection Bind mounts.
880 The remount functionality follows the standard way the mount
882 command works with options from fstab. This means that mount does
883 not read fstab (or mtab) only when both device and dir are
884 specified.
885 mount -o remount,rw /dev/foo /dir
887 After this call all old mount options are replaced and arbitrary
889 stuff from fstab (or mtab) is ignored, except the loop= option
890 which is internally generated and maintained by the mount command.
891 mount -o remount,rw /dir
893 After this call, mount reads fstab and merges these options with
895 the options from the command line (-o). If no mountpoint is found
896 in fstab, then a remount with unspecified source is allowed.
897 mount allows the use of --all to remount all already mounted
899 filesystems which match a specified filter (-O and -t). For
900 example:
901 mount --all -o remount,ro -t vfat
903 remounts all already mounted vfat filesystems in read-only mode.
905 Each of the filesystems is remounted by mount -o remount,ro /dir
906 semantic. This means the mount command reads fstab or mtab and
907 merges these options with the options from the command line.
908 ro
910 Mount the filesystem read-only.
911 rw
913 Mount the filesystem read-write.
914 sync
916 All I/O to the filesystem should be done synchronously. In the case
917 of media with a limited number of write cycles (e.g. some flash
918 drives), sync may cause life-cycle shortening.
919 user
921 Allow an ordinary user to mount the filesystem. The name of the
922 mounting user is written to the mtab file (or to the private
923 libmount file in /run/mount on systems without a regular mtab) so
924 that this same user can unmount the filesystem again. This option
925 implies the options noexec, nosuid, and nodev (unless overridden by
926 subsequent options, as in the option line user,exec,dev,suid).
927 nouser
929 Forbid an ordinary user to mount the filesystem. This is the
930 default; it does not imply any other options.
931 users
933 Allow any user to mount and to unmount the filesystem, even when
934 some other ordinary user mounted it. This option implies the
935 options noexec, nosuid, and nodev (unless overridden by subsequent
936 options, as in the option line users,exec,dev,suid).
937 X-*
939 All options prefixed with "X-" are interpreted as comments or as
940 userspace application-specific options. These options are not
941 stored in user space (e.g., mtab file), nor sent to the mount.type
942 helpers nor to the mount(2) system call. The suggested format is
943 X-appname.option.
944 x-*
946 The same as X-* options, but stored permanently in user space. This
947 means the options are also available for umount(8) or other
948 operations. Note that maintaining mount options in user space is
949 tricky, because it’s necessary use libmount-based tools and there
950 is no guarantee that the options will be always available (for
951 example after a move mount operation or in unshared namespace).
952 Note that before util-linux v2.30 the x-* options have not been
954 maintained by libmount and stored in user space (functionality was
955 the same as for X-* now), but due to the growing number of
956 use-cases (in initrd, systemd etc.) the functionality has been
957 extended to keep existing fstab configurations usable without a
958 change.
959 X-mount.mkdir[=mode]
961 Allow to make a target directory (mountpoint) if it does not exit
962 yet. The optional argument mode specifies the filesystem access
963 mode used for mkdir(2) in octal notation. The default mode is 0755.
964 This functionality is supported only for root users or when mount
965 executed without suid permissions. The option is also supported as
966 x-mount.mkdir, this notation is deprecated since v2.30.
967 nosymfollow
969 Do not follow symlinks when resolving paths. Symlinks can still be
970 created, and readlink(1), readlink(2), realpath(1), and realpath(3)
971 all still work properly.
972
974 This section lists options that are specific to particular filesystems.
975 Where possible, you should first consult filesystem-specific manual
976 pages for details. Some of those pages are listed in the following
977 table.
978 ┌─────────────────┬───────────────┐
980 │ │ │
981 │Filesystem(s) │ Manual page │
982 ├─────────────────┼───────────────┤
983 │ │ │
984 │btrfs │ btrfs(5) │
985 ├─────────────────┼───────────────┤
986 │ │ │
987 │cifs │ mount.cifs(8) │
988 ├─────────────────┼───────────────┤
989 │ │ │
990 │ext2, ext3, ext4 │ ext4(5) │
991 ├─────────────────┼───────────────┤
992 │ │ │
993 │fuse │ fuse(8) │
994 ├─────────────────┼───────────────┤
995 │ │ │
996 │nfs │ nfs(5) │
997 ├─────────────────┼───────────────┤
998 │ │ │
999 │tmpfs │ tmpfs(5) │
1000 ├─────────────────┼───────────────┤
1001 │ │ │
1002 │xfs │ xfs(5) │
1003 └─────────────────┴───────────────┘
1004 Note that some of the pages listed above might be available only after
1006 you install the respective userland tools.
1007 The following options apply only to certain filesystems. We sort them
1009 by filesystem. All options follow the -o flag.
1010 What options are supported depends a bit on the running kernel. Further
1012 information may be available in filesystem-specific files in the kernel
1013 source subdirectory Documentation/filesystems.
1014 Mount options for adfs
1016 uid=value and gid=value
1017 Set the owner and group of the files in the filesystem (default:
1018 uid=gid=0).
1019 ownmask=value and othmask=value
1021 Set the permission mask for ADFS 'owner' permissions and 'other'
1022 permissions, respectively (default: 0700 and 0077, respectively).
1023 See also /usr/src/linux/Documentation/filesystems/adfs.rst.
1024 Mount options for affs
1026 uid=value and gid=value
1027 Set the owner and group of the root of the filesystem (default:
1028 uid=gid=0, but with option uid or gid without specified value, the
1029 UID and GID of the current process are taken).
1030 setuid=value and setgid=value
1032 Set the owner and group of all files.
1033 mode=value
1035 Set the mode of all files to value & 0777 disregarding the original
1036 permissions. Add search permission to directories that have read
1037 permission. The value is given in octal.
1038 protect
1040 Do not allow any changes to the protection bits on the filesystem.
1041 usemp
1043 Set UID and GID of the root of the filesystem to the UID and GID of
1044 the mount point upon the first sync or umount, and then clear this
1045 option. Strange...
1046 verbose
1048 Print an informational message for each successful mount.
1049 prefix=string
1051 Prefix used before volume name, when following a link.
1052 volume=string
1054 Prefix (of length at most 30) used before '/' when following a
1055 symbolic link.
1056 reserved=value
1058 (Default: 2.) Number of unused blocks at the start of the device.
1059 root=value
1061 Give explicitly the location of the root block.
1062 bs=value
1064 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
1065 grpquota|noquota|quota|usrquota
1067 These options are accepted but ignored. (However, quota utilities
1068 may react to such strings in /etc/fstab.)
1069 Mount options for debugfs
1071 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1072 /sys/kernel/debug. As of kernel version 3.4, debugfs has the following
1073 options:
1074 uid=n, gid=n
1076 Set the owner and group of the mountpoint.
1077 mode=value
1079 Sets the mode of the mountpoint.
1080 Mount options for devpts
1082 The devpts filesystem is a pseudo filesystem, traditionally mounted on
1083 /dev/pts. In order to acquire a pseudo terminal, a process opens
1084 /dev/ptmx; the number of the pseudo terminal is then made available to
1085 the process and the pseudo terminal slave can be accessed as
1086 /dev/pts/<number>.
1087 uid=value and gid=value
1089 This sets the owner or the group of newly created pseudo terminals
1090 to the specified values. When nothing is specified, they will be
1091 set to the UID and GID of the creating process. For example, if
1092 there is a tty group with GID 5, then gid=5 will cause newly
1093 created pseudo terminals to belong to the tty group.
1094 mode=value
1096 Set the mode of newly created pseudo terminals to the specified
1097 value. The default is 0600. A value of mode=620 and gid=5 makes
1098 "mesg y" the default on newly created pseudo terminals.
1099 newinstance
1101 Create a private instance of the devpts filesystem, such that
1102 indices of pseudo terminals allocated in this new instance are
1103 independent of indices created in other instances of devpts.
1104 All mounts of devpts without this newinstance option share the same
1106 set of pseudo terminal indices (i.e., legacy mode). Each mount of
1107 devpts with the newinstance option has a private set of pseudo
1108 terminal indices.
1109 This option is mainly used to support containers in the Linux
1111 kernel. It is implemented in Linux kernel versions starting with
1112 2.6.29. Further, this mount option is valid only if
1113 CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1114 configuration.
1115 To use this option effectively, /dev/ptmx must be a symbolic link
1117 to pts/ptmx. See Documentation/filesystems/devpts.txt in the Linux
1118 kernel source tree for details.
1119 ptmxmode=value
1121 Set the mode for the new ptmx device node in the devpts filesystem.
1122 With the support for multiple instances of devpts (see newinstance
1124 option above), each instance has a private ptmx node in the root of
1125 the devpts filesystem (typically /dev/pts/ptmx).
1126 For compatibility with older versions of the kernel, the default
1128 mode of the new ptmx node is 0000. ptmxmode=value specifies a more
1129 useful mode for the ptmx node and is highly recommended when the
1130 newinstance option is specified.
1131 This option is only implemented in Linux kernel versions starting
1133 with 2.6.29. Further, this option is valid only if
1134 CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1135 configuration.
1136 Mount options for fat
1138 (Note: fat is not a separate filesystem, but a common part of the
1139 msdos, umsdos and vfat filesystems.)
1140 blocksize={512|1024|2048}
1142 Set blocksize (default 512). This option is obsolete.
1143 uid=value and gid=value
1145 Set the owner and group of all files. (Default: the UID and GID of
1146 the current process.)
1147 umask=value
1149 Set the umask (the bitmask of the permissions that are not
1150 present). The default is the umask of the current process. The
1151 value is given in octal.
1152 dmask=value
1154 Set the umask applied to directories only. The default is the umask
1155 of the current process. The value is given in octal.
1156 fmask=value
1158 Set the umask applied to regular files only. The default is the
1159 umask of the current process. The value is given in octal.
1160 allow_utime=value
1162 This option controls the permission check of mtime/atime.
1163 20
1165 If current process is in group of file’s group ID, you can
1166 change timestamp.
1167 2
1169 Other users can change timestamp.
1170 The default is set from 'dmask' option. (If the directory is writable,
1172 utime(2) is also allowed. I.e. ~dmask & 022)
1173 Normally utime(2) checks that the current process is owner of the file,
1175 or that it has the CAP_FOWNER capability. But FAT filesystems don’t
1176 have UID/GID on disk, so the normal check is too inflexible. With this
1177 option you can relax it.
1178 check=value
1180 Three different levels of pickiness can be chosen:
1181 r[elaxed]
1183 Upper and lower case are accepted and equivalent, long name
1184 parts are truncated (e.g. verylongname.foobar becomes
1185 verylong.foo), leading and embedded spaces are accepted in each
1186 name part (name and extension).
1187 n[ormal]
1189 Like "relaxed", but many special characters (*, ?, <, spaces,
1190 etc.) are rejected. This is the default.
1191 s[trict]
1193 Like "normal", but names that contain long parts or special
1194 characters that are sometimes used on Linux but are not
1195 accepted by MS-DOS (+, =, etc.) are rejected.
1196 codepage=value
1198 Sets the codepage for converting to shortname characters on FAT and
1199 VFAT filesystems. By default, codepage 437 is used.
1200 conv=mode
1202 This option is obsolete and may fail or be ignored.
1203 cvf_format=module
1205 Forces the driver to use the CVF (Compressed Volume File) module
1206 cvf__module_ instead of auto-detection. If the kernel supports
1207 kmod, the cvf_format=xxx option also controls on-demand CVF module
1208 loading. This option is obsolete.
1209 cvf_option=option
1211 Option passed to the CVF module. This option is obsolete.
1212 debug
1214 Turn on the debug flag. A version string and a list of filesystem
1215 parameters will be printed (these data are also printed if the
1216 parameters appear to be inconsistent).
1217 discard
1219 If set, causes discard/TRIM commands to be issued to the block
1220 device when blocks are freed. This is useful for SSD devices and
1221 sparse/thinly-provisioned LUNs.
1222 dos1xfloppy
1224 If set, use a fallback default BIOS Parameter Block configuration,
1225 determined by backing device size. These static parameters match
1226 defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360
1227 kiB floppies and floppy images.
1228 errors={panic|continue|remount-ro}
1230 Specify FAT behavior on critical errors: panic, continue without
1231 doing anything, or remount the partition in read-only mode (default
1232 behavior).
1233 fat={12|16|32}
1235 Specify a 12, 16 or 32 bit fat. This overrides the automatic FAT
1236 type detection routine. Use with caution!
1237 iocharset=value
1239 Character set to use for converting between 8 bit characters and 16
1240 bit Unicode characters. The default is iso8859-1. Long filenames
1241 are stored on disk in Unicode format.
1242 nfs={stale_rw|nostale_ro}
1244 Enable this only if you want to export the FAT filesystem over NFS.
1245 stale_rw: This option maintains an index (cache) of directory
1247 inodes which is used by the nfs-related code to improve look-ups.
1248 Full file operations (read/write) over NFS are supported but with
1249 cache eviction at NFS server, this could result in spurious ESTALE
1250 errors.
1251 nostale_ro: This option bases the inode number and file handle on
1253 the on-disk location of a file in the FAT directory entry. This
1254 ensures that ESTALE will not be returned after a file is evicted
1255 from the inode cache. However, it means that operations such as
1256 rename, create and unlink could cause file handles that previously
1257 pointed at one file to point at a different file, potentially
1258 causing data corruption. For this reason, this option also mounts
1259 the filesystem readonly.
1260 To maintain backward compatibility, -o nfs is also accepted,
1262 defaulting to stale_rw.
1263 tz=UTC
1265 This option disables the conversion of timestamps between local
1266 time (as used by Windows on FAT) and UTC (which Linux uses
1267 internally). This is particularly useful when mounting devices
1268 (like digital cameras) that are set to UTC in order to avoid the
1269 pitfalls of local time.
1270 time_offset=minutes
1272 Set offset for conversion of timestamps from local time used by FAT
1273 to UTC. I.e., minutes will be subtracted from each timestamp to
1274 convert it to UTC used internally by Linux. This is useful when the
1275 time zone set in the kernel via settimeofday(2) is not the time
1276 zone used by the filesystem. Note that this option still does not
1277 provide correct time stamps in all cases in presence of DST - time
1278 stamps in a different DST setting will be off by one hour.
1279 quiet
1281 Turn on the quiet flag. Attempts to chown or chmod files do not
1282 return errors, although they fail. Use with caution!
1283 rodir
1285 FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO
1286 of the directory will just be ignored, and is used only by
1287 applications as a flag (e.g. it’s set for the customized folder).
1288 If you want to use ATTR_RO as read-only flag even for the
1290 directory, set this option.
1291 showexec
1293 If set, the execute permission bits of the file will be allowed
1294 only if the extension part of the name is .EXE, .COM, or .BAT. Not
1295 set by default.
1296 sys_immutable
1298 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on
1299 Linux. Not set by default.
1300 flush
1302 If set, the filesystem will try to flush to disk more early than
1303 normal. Not set by default.
1304 usefree
1306 Use the "free clusters" value stored on FSINFO. It’ll be used to
1307 determine number of free clusters without scanning disk. But it’s
1308 not used by default, because recent Windows don’t update it
1309 correctly in some case. If you are sure the "free clusters" on
1310 FSINFO is correct, by this option you can avoid scanning disk.
1311 dots, nodots, dotsOK=[yes|no]
1313 Various misguided attempts to force Unix or DOS conventions onto a
1314 FAT filesystem.
1315 Mount options for hfs
1317 creator=cccc, type=cccc
1318 Set the creator/type values as shown by the MacOS finder used for
1319 creating new files. Default values: '????'.
1320 uid=n, gid=n
1322 Set the owner and group of all files. (Default: the UID and GID of
1323 the current process.)
1324 dir_umask=n, file_umask=n, umask=n
1326 Set the umask used for all directories, all regular files, or all
1327 files and directories. Defaults to the umask of the current
1328 process.
1329 session=n
1331 Select the CDROM session to mount. Defaults to leaving that
1332 decision to the CDROM driver. This option will fail with anything
1333 but a CDROM as underlying device.
1334 part=n
1336 Select partition number n from the device. Only makes sense for
1337 CDROMs. Defaults to not parsing the partition table at all.
1338 quiet
1340 Don’t complain about invalid mount options.
1341 Mount options for hpfs
1343 uid=value and gid=value
1344 Set the owner and group of all files. (Default: the UID and GID of
1345 the current process.)
1346 umask=value
1348 Set the umask (the bitmask of the permissions that are not
1349 present). The default is the umask of the current process. The
1350 value is given in octal.
1351 case={lower|asis}
1353 Convert all files names to lower case, or leave them. (Default:
1354 case=lower.)
1355 conv=mode
1357 This option is obsolete and may fail or being ignored.
1358 nocheck
1360 Do not abort mounting when certain consistency checks fail.
1361 Mount options for iso9660
1363 ISO 9660 is a standard describing a filesystem structure to be used on
1364 CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1365 udf filesystem.)
1366 Normal iso9660 filenames appear in an 8.3 format (i.e., DOS-like
1368 restrictions on filename length), and in addition all characters are in
1369 upper case. Also there is no field for file ownership, protection,
1370 number of links, provision for block/character devices, etc.
1371 Rock Ridge is an extension to iso9660 that provides all of these
1373 UNIX-like features. Basically there are extensions to each directory
1374 record that supply all of the additional information, and when Rock
1375 Ridge is in use, the filesystem is indistinguishable from a normal UNIX
1376 filesystem (except that it is read-only, of course).
1377 norock
1379 Disable the use of Rock Ridge extensions, even if available. Cf.
1380 map.
1381 nojoliet
1383 Disable the use of Microsoft Joliet extensions, even if available.
1384 Cf. map.
1385 check={r[elaxed]|s[trict]}
1387 With check=relaxed, a filename is first converted to lower case
1388 before doing the lookup. This is probably only meaningful together
1389 with norock and map=normal. (Default: check=strict.)
1390 uid=value and gid=value
1392 Give all files in the filesystem the indicated user or group id,
1393 possibly overriding the information found in the Rock Ridge
1394 extensions. (Default: uid=0,gid=0.)
1395 map={n[ormal]|o[ff]|a[corn]}
1397 For non-Rock Ridge volumes, normal name translation maps upper to
1398 lower case ASCII, drops a trailing ';1', and converts ';' to '.'.
1399 With map=off no name translation is done. See norock. (Default:
1400 map=normal.) map=acorn is like map=normal but also apply Acorn
1401 extensions if present.
1402 mode=value
1404 For non-Rock Ridge volumes, give all files the indicated mode.
1405 (Default: read and execute permission for everybody.) Octal mode
1406 values require a leading 0.
1407 unhide
1409 Also show hidden and associated files. (If the ordinary files and
1410 the associated or hidden files have the same filenames, this may
1411 make the ordinary files inaccessible.)
1412 block={512|1024|2048}
1414 Set the block size to the indicated value. (Default: block=1024.)
1415 conv=mode
1417 This option is obsolete and may fail or being ignored.
1418 cruft
1420 If the high byte of the file length contains other garbage, set
1421 this mount option to ignore the high order bits of the file length.
1422 This implies that a file cannot be larger than 16 MB.
1423 session=x
1425 Select number of session on a multisession CD.
1426 sbsector=xxx
1428 Session begins from sector xxx.
1429 The following options are the same as for vfat and specifying them only
1431 makes sense when using discs encoded using Microsoft’s Joliet
1432 extensions.
1433 iocharset=value
1435 Character set to use for converting 16 bit Unicode characters on CD
1436 to 8 bit characters. The default is iso8859-1.
1437 utf8
1439 Convert 16 bit Unicode characters on CD to UTF-8.
1440 Mount options for jfs
1442 iocharset=name
1443 Character set to use for converting from Unicode to ASCII. The
1444 default is to do no conversion. Use iocharset=utf8 for UTF8
1445 translations. This requires CONFIG_NLS_UTF8 to be set in the kernel
1446 .config file.
1447 resize=value
1449 Resize the volume to value blocks. JFS only supports growing a
1450 volume, not shrinking it. This option is only valid during a
1451 remount, when the volume is mounted read-write. The resize keyword
1452 with no value will grow the volume to the full size of the
1453 partition.
1454 nointegrity
1456 Do not write to the journal. The primary use of this option is to
1457 allow for higher performance when restoring a volume from backup
1458 media. The integrity of the volume is not guaranteed if the system
1459 abnormally ends.
1460 integrity
1462 Default. Commit metadata changes to the journal. Use this option to
1463 remount a volume where the nointegrity option was previously
1464 specified in order to restore normal behavior.
1465 errors={continue|remount-ro|panic}
1467 Define the behavior when an error is encountered. (Either ignore
1468 errors and just mark the filesystem erroneous and continue, or
1469 remount the filesystem read-only, or panic and halt the system.)
1470 noquota|quota|usrquota|grpquota
1472 These options are accepted but ignored.
1473 Mount options for msdos
1475 See mount options for fat. If the msdos filesystem detects an
1476 inconsistency, it reports an error and sets the file system read-only.
1477 The filesystem can be made writable again by remounting it.
1478 Mount options for ncpfs
1480 Just like nfs, the ncpfs implementation expects a binary argument (a
1481 struct ncp_mount_data) to the mount system call. This argument is
1482 constructed by ncpmount(8) and the current version of mount (2.12) does
1483 not know anything about ncpfs.
1484 Mount options for ntfs
1486 iocharset=name
1487 Character set to use when returning file names. Unlike VFAT, NTFS
1488 suppresses names that contain nonconvertible characters.
1489 Deprecated.
1490 nls=name
1492 New name for the option earlier called iocharset.
1493 utf8
1495 Use UTF-8 for converting file names.
1496 uni_xlate={0|1|2}
1498 For 0 (or 'no' or 'false'), do not use escape sequences for unknown
1499 Unicode characters. For 1 (or 'yes' or 'true') or 2, use vfat-style
1500 4-byte escape sequences starting with ":". Here 2 gives a
1501 little-endian encoding and 1 a byteswapped bigendian encoding.
1502 posix=[0|1]
1504 If enabled (posix=1), the filesystem distinguishes between upper
1505 and lower case. The 8.3 alias names are presented as hard links
1506 instead of being suppressed. This option is obsolete.
1507 uid=value, gid=value and umask=value
1509 Set the file permission on the filesystem. The umask value is given
1510 in octal. By default, the files are owned by root and not readable
1511 by somebody else.
1512 Mount options for overlay
1514 Since Linux 3.18 the overlay pseudo filesystem implements a union mount
1515 for other filesystems.
1516 An overlay filesystem combines two filesystems - an upper filesystem
1518 and a lower filesystem. When a name exists in both filesystems, the
1519 object in the upper filesystem is visible while the object in the lower
1520 filesystem is either hidden or, in the case of directories, merged with
1521 the upper object.
1522 The lower filesystem can be any filesystem supported by Linux and does
1524 not need to be writable. The lower filesystem can even be another
1525 overlayfs. The upper filesystem will normally be writable and if it is
1526 it must support the creation of trusted.* extended attributes, and must
1527 provide a valid d_type in readdir responses, so NFS is not suitable.
1528 A read-only overlay of two read-only filesystems may use any filesystem
1530 type. The options lowerdir and upperdir are combined into a merged
1531 directory by using:
1532 mount -t overlay overlay \
1534 -olowerdir=/lower,upperdir=/upper,workdir=/work /merged
1535 lowerdir=directory
1537 Any filesystem, does not need to be on a writable filesystem.
1538 upperdir=directory
1540 The upperdir is normally on a writable filesystem.
1541 workdir=directory
1543 The workdir needs to be an empty directory on the same filesystem
1544 as upperdir.
1545 userxattr
1547 Use the "user.overlay." xattr namespace instead of
1548 "trusted.overlay.". This is useful for unprivileged mounting of
1549 overlayfs.
1550 redirect_dir={on|off|follow|nofollow}
1552 If the redirect_dir feature is enabled, then the directory will be
1553 copied up (but not the contents). Then the
1554 "{trusted|user}.overlay.redirect" extended attribute is set to the
1555 path of the original location from the root of the overlay. Finally
1556 the directory is moved to the new location.
1557 on
1559 Redirects are enabled.
1560 off
1562 Redirects are not created and only followed if
1563 "redirect_always_follow" feature is enabled in the
1564 kernel/module config.
1565 follow
1567 Redirects are not created, but followed.
1568 nofollow
1570 Redirects are not created and not followed (equivalent to
1571 "redirect_dir=off" if "redirect_always_follow" feature is not
1572 enabled).
1573 index={on|off}
1575 Inode index. If this feature is disabled and a file with multiple
1576 hard links is copied up, then this will "break" the link. Changes
1577 will not be propagated to other names referring to the same inode.
1578 uuid={on|off}
1580 Can be used to replace UUID of the underlying filesystem in file
1581 handles with null, and effectively disable UUID checks. This can be
1582 useful in case the underlying disk is copied and the UUID of this
1583 copy is changed. This is only applicable if all lower/upper/work
1584 directories are on the same filesystem, otherwise it will fallback
1585 to normal behaviour.
1586 nfs_export={on|off}
1588 When the underlying filesystems supports NFS export and the
1589 "nfs_export" feature is enabled, an overlay filesystem may be
1590 exported to NFS.
1591 With the “nfs_export” feature, on copy_up of any lower object, an
1593 index entry is created under the index directory. The index entry
1594 name is the hexadecimal representation of the copy up origin file
1595 handle. For a non-directory object, the index entry is a hard link
1596 to the upper inode. For a directory object, the index entry has an
1597 extended attribute "{trusted|user}.overlay.upper" with an encoded
1598 file handle of the upper directory inode.
1599 When encoding a file handle from an overlay filesystem object, the
1601 following rules apply
1602 • For a non-upper object, encode a lower file handle from
1604 lower inode
1605 • For an indexed object, encode a lower file handle from
1607 copy_up origin
1608 • For a pure-upper object and for an existing non-indexed
1610 upper object, encode an upper file handle from upper inode
1611 The encoded overlay file handle includes
1613 • Header including path type information (e.g. lower/upper)
1615 • UUID of the underlying filesystem
1617 • Underlying filesystem encoding of underlying inode
1619 This encoding format is identical to the encoding format file
1621 handles that are stored in extended attribute
1622 "{trusted|user}.overlay.origin". When decoding an overlay file
1623 handle, the following steps are followed
1624 • Find underlying layer by UUID and path type information.
1626 • Decode the underlying filesystem file handle to underlying
1628 dentry.
1629 • For a lower file handle, lookup the handle in index
1631 directory by name.
1632 • If a whiteout is found in index, return ESTALE. This
1634 represents an overlay object that was deleted after its
1635 file handle was encoded.
1636 • For a non-directory, instantiate a disconnected overlay
1638 dentry from the decoded underlying dentry, the path type
1639 and index inode, if found.
1640 • For a directory, use the connected underlying decoded
1642 dentry, path type and index, to lookup a connected overlay
1643 dentry.
1644 Decoding a non-directory file handle may return a disconnected
1646 dentry. copy_up of that disconnected dentry will create an upper
1647 index entry with no upper alias.
1648 When overlay filesystem has multiple lower layers, a middle layer
1650 directory may have a "redirect" to lower directory. Because middle
1651 layer "redirects" are not indexed, a lower file handle that was
1652 encoded from the "redirect" origin directory, cannot be used to
1653 find the middle or upper layer directory. Similarly, a lower file
1654 handle that was encoded from a descendant of the "redirect" origin
1655 directory, cannot be used to reconstruct a connected overlay path.
1656 To mitigate the cases of directories that cannot be decoded from a
1657 lower file handle, these directories are copied up on encode and
1658 encoded as an upper file handle. On an overlay filesystem with no
1659 upper layer this mitigation cannot be used NFS export in this setup
1660 requires turning off redirect follow (e.g.
1661 "redirect_dir=nofollow").
1662 The overlay filesystem does not support non-directory connectable
1664 file handles, so exporting with the subtree_check exportfs
1665 configuration will cause failures to lookup files over NFS.
1666 When the NFS export feature is enabled, all directory index entries
1668 are verified on mount time to check that upper file handles are not
1669 stale. This verification may cause significant overhead in some
1670 cases.
1671 Note: the mount options index=off,nfs_export=on are conflicting for
1673 a read-write mount and will result in an error.
1674 xinfo={on|off|auto}
1676 The "xino" feature composes a unique object identifier from the
1677 real object st_ino and an underlying fsid index. The "xino" feature
1678 uses the high inode number bits for fsid, because the underlying
1679 filesystems rarely use the high inode number bits. In case the
1680 underlying inode number does overflow into the high xino bits,
1681 overlay filesystem will fall back to the non xino behavior for that
1682 inode.
1683 For a detailed description of the effect of this option please
1685 refer to
1686 https://www.kernel.org/doc/html/latest/filesystems/overlayfs.html?highlight=overlayfs
1687 metacopy={on|off}
1689 When metadata only copy up feature is enabled, overlayfs will only
1690 copy up metadata (as opposed to whole file), when a metadata
1691 specific operation like chown/chmod is performed. Full file will be
1692 copied up later when file is opened for WRITE operation.
1693 In other words, this is delayed data copy up operation and data is
1695 copied up when there is a need to actually modify data.
1696 volatile
1698 Volatile mounts are not guaranteed to survive a crash. It is
1699 strongly recommended that volatile mounts are only used if data
1700 written to the overlay can be recreated without significant effort.
1701 The advantage of mounting with the "volatile" option is that all
1703 forms of sync calls to the upper filesystem are omitted.
1704 In order to avoid a giving a false sense of safety, the syncfs (and
1706 fsync) semantics of volatile mounts are slightly different than
1707 that of the rest of VFS. If any writeback error occurs on the
1708 upperdir’s filesystem after a volatile mount takes place, all sync
1709 functions will return an error. Once this condition is reached, the
1710 filesystem will not recover, and every subsequent sync call will
1711 return an error, even if the upperdir has not experience a new
1712 error since the last sync call.
1713 When overlay is mounted with "volatile" option, the directory
1715 "$workdir/work/incompat/volatile" is created. During next mount,
1716 overlay checks for this directory and refuses to mount if present.
1717 This is a strong indicator that user should throw away upper and
1718 work directories and create fresh one. In very limited cases where
1719 the user knows that the system has not crashed and contents of
1720 upperdir are intact, The "volatile" directory can be removed.
1721 Mount options for reiserfs
1723 Reiserfs is a journaling filesystem.
1724 conv
1726 Instructs version 3.6 reiserfs software to mount a version 3.5
1727 filesystem, using the 3.6 format for newly created objects. This
1728 filesystem will no longer be compatible with reiserfs 3.5 tools.
1729 hash={rupasov|tea|r5|detect}
1731 Choose which hash function reiserfs will use to find files within
1732 directories.
1733 rupasov
1735 A hash invented by Yury Yu. Rupasov. It is fast and preserves
1736 locality, mapping lexicographically close file names to close
1737 hash values. This option should not be used, as it causes a
1738 high probability of hash collisions.
1739 tea
1741 A Davis-Meyer function implemented by Jeremy Fitzhardinge. It
1742 uses hash permuting bits in the name. It gets high randomness
1743 and, therefore, low probability of hash collisions at some CPU
1744 cost. This may be used if EHASHCOLLISION errors are experienced
1745 with the r5 hash.
1746 r5
1748 A modified version of the rupasov hash. It is used by default
1749 and is the best choice unless the filesystem has huge
1750 directories and unusual file-name patterns.
1751 detect
1753 Instructs mount to detect which hash function is in use by
1754 examining the filesystem being mounted, and to write this
1755 information into the reiserfs superblock. This is only useful
1756 on the first mount of an old format filesystem.
1757 hashed_relocation
1759 Tunes the block allocator. This may provide performance
1760 improvements in some situations.
1761 no_unhashed_relocation
1763 Tunes the block allocator. This may provide performance
1764 improvements in some situations.
1765 noborder
1767 Disable the border allocator algorithm invented by Yury Yu.
1768 Rupasov. This may provide performance improvements in some
1769 situations.
1770 nolog
1772 Disable journaling. This will provide slight performance
1773 improvements in some situations at the cost of losing reiserfs’s
1774 fast recovery from crashes. Even with this option turned on,
1775 reiserfs still performs all journaling operations, save for actual
1776 writes into its journaling area. Implementation of nolog is a work
1777 in progress.
1778 notail
1780 By default, reiserfs stores small files and 'file tails' directly
1781 into its tree. This confuses some utilities such as lilo(8). This
1782 option is used to disable packing of files into the tree.
1783 replayonly
1785 Replay the transactions which are in the journal, but do not
1786 actually mount the filesystem. Mainly used by reiserfsck.
1787 resize=number
1789 A remount option which permits online expansion of reiserfs
1790 partitions. Instructs reiserfs to assume that the device has number
1791 blocks. This option is designed for use with devices which are
1792 under logical volume management (LVM). There is a special resizer
1793 utility which can be obtained from
1794 ftp://ftp.namesys.com/pub/reiserfsprogs.
1795 user_xattr
1797 Enable Extended User Attributes. See the attr(1) manual page.
1798 acl
1800 Enable POSIX Access Control Lists. See the acl(5) manual page.
1801 barrier=none / barrier=flush
1803 This disables / enables the use of write barriers in the journaling
1804 code. barrier=none disables, barrier=flush enables (default). This
1805 also requires an IO stack which can support barriers, and if
1806 reiserfs gets an error on a barrier write, it will disable barriers
1807 again with a warning. Write barriers enforce proper on-disk
1808 ordering of journal commits, making volatile disk write caches safe
1809 to use, at some performance penalty. If your disks are
1810 battery-backed in one way or another, disabling barriers may safely
1811 improve performance.
1812 Mount options for ubifs
1814 UBIFS is a flash filesystem which works on top of UBI volumes. Note
1815 that atime is not supported and is always turned off.
1816 The device name may be specified as
1818 ubiX_Y
1820 UBI device number X, volume number Y
1821 ubiY
1823 UBI device number 0, volume number Y
1824 ubiX:NAME
1826 UBI device number X, volume with name NAME
1827 ubi:NAME
1829 UBI device number 0, volume with name NAME
1830 Alternative ! separator may be used instead of :.
1832 The following mount options are available:
1834 bulk_read
1836 Enable bulk-read. VFS read-ahead is disabled because it slows down
1837 the filesystem. Bulk-Read is an internal optimization. Some flashes
1838 may read faster if the data are read at one go, rather than at
1839 several read requests. For example, OneNAND can do
1840 "read-while-load" if it reads more than one NAND page.
1841 no_bulk_read
1843 Do not bulk-read. This is the default.
1844 chk_data_crc
1846 Check data CRC-32 checksums. This is the default.
1847 no_chk_data_crc
1849 Do not check data CRC-32 checksums. With this option, the
1850 filesystem does not check CRC-32 checksum for data, but it does
1851 check it for the internal indexing information. This option only
1852 affects reading, not writing. CRC-32 is always calculated when
1853 writing the data.
1854 compr={none|lzo|zlib}
1856 Select the default compressor which is used when new files are
1857 written. It is still possible to read compressed files if mounted
1858 with the none option.
1859 Mount options for udf
1861 UDF is the "Universal Disk Format" filesystem defined by OSTA, the
1862 Optical Storage Technology Association, and is often used for DVD-ROM,
1863 frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is,
1864 however, perfectly usable by itself on disk drives, flash drives and
1865 other block devices. See also iso9660.
1866 uid=
1868 Make all files in the filesystem belong to the given user.
1869 uid=forget can be specified independently of (or usually in
1870 addition to) uid=<user> and results in UDF not storing uids to the
1871 media. In fact the recorded uid is the 32-bit overflow uid -1 as
1872 defined by the UDF standard. The value is given as either <user>
1873 which is a valid user name or the corresponding decimal user id, or
1874 the special string "forget".
1875 gid=
1877 Make all files in the filesystem belong to the given group.
1878 gid=forget can be specified independently of (or usually in
1879 addition to) gid=<group> and results in UDF not storing gids to the
1880 media. In fact the recorded gid is the 32-bit overflow gid -1 as
1881 defined by the UDF standard. The value is given as either <group>
1882 which is a valid group name or the corresponding decimal group id,
1883 or the special string "forget".
1884 umask=
1886 Mask out the given permissions from all inodes read from the
1887 filesystem. The value is given in octal.
1888 mode=
1890 If mode= is set the permissions of all non-directory inodes read
1891 from the filesystem will be set to the given mode. The value is
1892 given in octal.
1893 dmode=
1895 If dmode= is set the permissions of all directory inodes read from
1896 the filesystem will be set to the given dmode. The value is given
1897 in octal.
1898 bs=
1900 Set the block size. Default value prior to kernel version 2.6.30
1901 was 2048. Since 2.6.30 and prior to 4.11 it was logical device
1902 block size with fallback to 2048. Since 4.11 it is logical block
1903 size with fallback to any valid block size between logical device
1904 block size and 4096.
1905 For other details see the mkudffs(8) 2.0+ manpage, sections
1907 COMPATIBILITY and BLOCK SIZE.
1908 unhide
1910 Show otherwise hidden files.
1911 undelete
1913 Show deleted files in lists.
1914 adinicb
1916 Embed data in the inode. (default)
1917 noadinicb
1919 Don’t embed data in the inode.
1920 shortad
1922 Use short UDF address descriptors.
1923 longad
1925 Use long UDF address descriptors. (default)
1926 nostrict
1928 Unset strict conformance.
1929 iocharset=
1931 Set the NLS character set. This requires kernel compiled with
1932 CONFIG_UDF_NLS option.
1933 utf8
1935 Set the UTF-8 character set.
1936 Mount options for debugging and disaster recovery
1938 novrs
1939 Ignore the Volume Recognition Sequence and attempt to mount anyway.
1940 session=
1942 Select the session number for multi-session recorded optical media.
1943 (default= last session)
1944 anchor=
1946 Override standard anchor location. (default= 256)
1947 lastblock=
1949 Set the last block of the filesystem.
1950 Unused historical mount options that may be encountered and should be
1952 removed
1953 uid=ignore
1954 Ignored, use uid=<user> instead.
1955 gid=ignore
1957 Ignored, use gid=<group> instead.
1958 volume=
1960 Unimplemented and ignored.
1961 partition=
1963 Unimplemented and ignored.
1964 fileset=
1966 Unimplemented and ignored.
1967 rootdir=
1969 Unimplemented and ignored.
1970 Mount options for ufs
1972 ufstype=value
1973 UFS is a filesystem widely used in different operating systems. The
1974 problem are differences among implementations. Features of some
1975 implementations are undocumented, so its hard to recognize the type
1976 of ufs automatically. That’s why the user must specify the type of
1977 ufs by mount option. Possible values are:
1978 old
1980 Old format of ufs, this is the default, read only. (Don’t
1981 forget to give the -r option.)
1982 44bsd
1984 For filesystems created by a BSD-like system (NetBSD, FreeBSD,
1985 OpenBSD).
1986 ufs2
1988 Used in FreeBSD 5.x supported as read-write.
1989 5xbsd
1991 Synonym for ufs2.
1992 sun
1994 For filesystems created by SunOS or Solaris on Sparc.
1995 sunx86
1997 For filesystems created by Solaris on x86.
1998 hp
2000 For filesystems created by HP-UX, read-only.
2001 nextstep
2003 For filesystems created by NeXTStep (on NeXT station)
2004 (currently read only).
2005 nextstep-cd
2007 For NextStep CDROMs (block_size == 2048), read-only.
2008 openstep
2010 For filesystems created by OpenStep (currently read only). The
2011 same filesystem type is also used by Mac OS X.
2012 onerror=value
2014 Set behavior on error:
2015 panic
2017 If an error is encountered, cause a kernel panic.
2018 [lock|umount|repair]
2020 These mount options don’t do anything at present; when an error
2021 is encountered only a console message is printed.
2022 Mount options for umsdos
2024 See mount options for msdos. The dotsOK option is explicitly killed by
2025 umsdos.
2026 Mount options for vfat
2028 First of all, the mount options for fat are recognized. The dotsOK
2029 option is explicitly killed by vfat. Furthermore, there are
2030 uni_xlate
2032 Translate unhandled Unicode characters to special escaped
2033 sequences. This lets you backup and restore filenames that are
2034 created with any Unicode characters. Without this option, a '?' is
2035 used when no translation is possible. The escape character is ':'
2036 because it is otherwise invalid on the vfat filesystem. The escape
2037 sequence that gets used, where u is the Unicode character, is: ':',
2038 (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
2039 posix
2041 Allow two files with names that only differ in case. This option is
2042 obsolete.
2043 nonumtail
2045 First try to make a short name without sequence number, before
2046 trying name~num.ext.
2047 utf8
2049 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used
2050 by the console. It can be enabled for the filesystem with this
2051 option or disabled with utf8=0, utf8=no or utf8=false. If uni_xlate
2052 gets set, UTF8 gets disabled.
2053 shortname=mode
2055 Defines the behavior for creation and display of filenames which
2056 fit into 8.3 characters. If a long name for a file exists, it will
2057 always be the preferred one for display. There are four modes:
2058 lower
2060 Force the short name to lower case upon display; store a long
2061 name when the short name is not all upper case.
2062 win95
2064 Force the short name to upper case upon display; store a long
2065 name when the short name is not all upper case.
2066 winnt
2068 Display the short name as is; store a long name when the short
2069 name is not all lower case or all upper case.
2070 mixed
2072 Display the short name as is; store a long name when the short
2073 name is not all upper case. This mode is the default since
2074 Linux 2.6.32.
2075 Mount options for usbfs
2077 devuid=uid and devgid=gid and devmode=mode
2078 Set the owner and group and mode of the device files in the usbfs
2079 filesystem (default: uid=gid=0, mode=0644). The mode is given in
2080 octal.
2081 busuid=uid and busgid=gid and busmode=mode
2083 Set the owner and group and mode of the bus directories in the
2084 usbfs filesystem (default: uid=gid=0, mode=0555). The mode is given
2085 in octal.
2086 listuid=uid and listgid=gid and listmode=mode
2088 Set the owner and group and mode of the file devices (default:
2089 uid=gid=0, mode=0444). The mode is given in octal.
2090
2092 The device-mapper verity target provides read-only transparent
2093 integrity checking of block devices using kernel crypto API. The mount
2094 command can open the dm-verity device and do the integrity verification
2095 before on the device filesystem is mounted. Requires libcryptsetup with
2096 in libmount (optionally via dlopen(3)). If libcryptsetup supports
2097 extracting the root hash of an already mounted device, existing devices
2098 will be automatically reused in case of a match. Mount options for
2099 dm-verity:
2100 verity.hashdevice=path
2102 Path to the hash tree device associated with the source volume to
2103 pass to dm-verity.
2104 verity.roothash=hex
2106 Hex-encoded hash of the root of verity.hashdevice. Mutually
2107 exclusive with verity.roothashfile.
2108 verity.roothashfile=path
2110 Path to file containing the hex-encoded hash of the root of
2111 verity.hashdevice. Mutually exclusive with verity.roothash.
2112 verity.hashoffset=offset
2114 If the hash tree device is embedded in the source volume, offset
2115 (default: 0) is used by dm-verity to get to the tree.
2116 verity.fecdevice=path
2118 Path to the Forward Error Correction (FEC) device associated with
2119 the source volume to pass to dm-verity. Optional. Requires kernel
2120 built with CONFIG_DM_VERITY_FEC.
2121 verity.fecoffset=offset
2123 If the FEC device is embedded in the source volume, offset
2124 (default: 0) is used by dm-verity to get to the FEC area. Optional.
2125 verity.fecroots=value
2127 Parity bytes for FEC (default: 2). Optional.
2128 verity.roothashsig=path
2130 Path to pkcs7(1ssl) signature of root hash hex string. Requires
2131 crypt_activate_by_signed_key() from cryptsetup and kernel built
2132 with CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG. For device reuse,
2133 signatures have to be either used by all mounts of a device or by
2134 none. Optional.
2135 Supported since util-linux v2.35.
2137 For example commands:
2139 mksquashfs /etc /tmp/etc.squashfs
2141 dd if=/dev/zero of=/tmp/etc.hash bs=1M count=10
2142 veritysetup format /tmp/etc.squashfs /tmp/etc.hash
2143 openssl smime -sign -in <hash> -nocerts -inkey private.key \
2144 -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s
2145 mount -o verity.hashdevice=/tmp/etc.hash,verity.roothash=<hash>,\
2146 verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.squashfs /mnt
2147 create squashfs image from /etc directory, verity hash device and mount
2149 verified filesystem image to /mnt. The kernel will verify that the root
2150 hash is signed by a key from the kernel keyring if roothashsig is used.
2151
2153 One further possible type is a mount via the loop device. For example,
2154 the command
2155 mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3
2157 will set up the loop device /dev/loop3 to correspond to the file
2159 /tmp/disk.img, and then mount this device on /mnt.
2160 If no explicit loop device is mentioned (but just an option '-o loop'
2162 is given), then mount will try to find some unused loop device and use
2163 that, for example
2164 mount /tmp/disk.img /mnt -o loop
2166 The mount command automatically creates a loop device from a regular
2168 file if a filesystem type is not specified or the filesystem is known
2169 for libblkid, for example:
2170 mount /tmp/disk.img /mnt
2172 mount -t ext4 /tmp/disk.img /mnt
2174 This type of mount knows about three options, namely loop, offset and
2176 sizelimit, that are really options to losetup(8). (These options can be
2177 used in addition to those specific to the filesystem type.)
2178 Since Linux 2.6.25 auto-destruction of loop devices is supported,
2180 meaning that any loop device allocated by mount will be freed by umount
2181 independently of /etc/mtab.
2182 You can also free a loop device by hand, using losetup -d or umount -d.
2184 Since util-linux v2.29, mount re-uses the loop device rather than
2186 initializing a new device if the same backing file is already used for
2187 some loop device with the same offset and sizelimit. This is necessary
2188 to avoid a filesystem corruption.
2189
2191 mount has the following exit status values (the bits can be ORed):
2192 0
2194 success
2195 1
2197 incorrect invocation or permissions
2198 2
2200 system error (out of memory, cannot fork, no more loop devices)
2201 4
2203 internal mount bug
2204 8
2206 user interrupt
2207 16
2209 problems writing or locking /etc/mtab
2210 32
2212 mount failure
2213 64
2215 some mount succeeded
2216 The command mount -a returns 0 (all succeeded), 32 (all failed), or
2218 64 (some failed, some succeeded).
2219
2221 The syntax of external mount helpers is:
2222 /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options] [-t
2224 type.subtype]
2225 where the suffix is the filesystem type and the -sfnvoN options have
2227 the same meaning as the normal mount options. The -t option is used for
2228 filesystems with subtypes support (for example /sbin/mount.fuse -t
2229 fuse.sshfs).
2230 The command mount does not pass the mount options unbindable,
2232 runbindable, private, rprivate, slave, rslave, shared, rshared, auto,
2233 noauto, comment, x-*, loop, offset and sizelimit to the mount.<suffix>
2234 helpers. All other options are used in a comma-separated list as an
2235 argument to the -o option.
2236
2238 LIBMOUNT_FSTAB=<path>
2239 overrides the default location of the fstab file (ignored for suid)
2240 LIBMOUNT_MTAB=<path>
2242 overrides the default location of the mtab file (ignored for suid)
2243 LIBMOUNT_DEBUG=all
2245 enables libmount debug output
2246 LIBBLKID_DEBUG=all
2248 enables libblkid debug output
2249 LOOPDEV_DEBUG=all
2251 enables loop device setup debug output
2252
2254 See also "The files /etc/fstab, /etc/mtab and /proc/mounts" section
2255 above.
2256 /etc/fstab
2258 filesystem table
2259 /run/mount
2261 libmount private runtime directory
2262 /etc/mtab
2264 table of mounted filesystems or symlink to /proc/mounts
2265 /etc/mtab~
2267 lock file (unused on systems with mtab symlink)
2268 /etc/mtab.tmp
2270 temporary file (unused on systems with mtab symlink)
2271 /etc/filesystems
2273 a list of filesystem types to try
2274
2276 A mount command existed in Version 5 AT&T UNIX.
2277
2279 It is possible for a corrupted filesystem to cause a crash.
2280 Some Linux filesystems don’t support -o sync and -o dirsync (the ext2,
2282 ext3, ext4, fat and vfat filesystems do support synchronous updates (a
2283 la BSD) when mounted with the sync option).
2284 The -o remount may not be able to change mount parameters (all
2286 ext2fs-specific parameters, except sb, are changeable with a remount,
2287 for example, but you can’t change gid or umask for the fatfs).
2288 It is possible that the files /etc/mtab and /proc/mounts don’t match on
2290 systems with a regular mtab file. The first file is based only on the
2291 mount command options, but the content of the second file also depends
2292 on the kernel and others settings (e.g. on a remote NFS server — in
2293 certain cases the mount command may report unreliable information about
2294 an NFS mount point and the /proc/mount file usually contains more
2295 reliable information.) This is another reason to replace the mtab file
2296 with a symlink to the /proc/mounts file.
2297 Checking files on NFS filesystems referenced by file descriptors (i.e.
2299 the fcntl and ioctl families of functions) may lead to inconsistent
2300 results due to the lack of a consistency check in the kernel even if
2301 the noac mount option is used.
2302 The loop option with the offset or sizelimit options used may fail when
2304 using older kernels if the mount command can’t confirm that the size of
2305 the block device has been configured as requested. This situation can
2306 be worked around by using the losetup(8) command manually before
2307 calling mount with the configured loop device.
2308
2310 Karel Zak <kzak@redhat.com>
2311
2313 mount(2), umount(2), filesystems(5), fstab(5), nfs(5), xfs(5),
2314 mount_namespaces(7), xattr(7), e2label(8), findmnt(8), losetup(8),
2315 lsblk(8), mke2fs(8), mountd(8), nfsd(8), swapon(8), tune2fs(8),
2316 umount(8), xfs_admin(8)
2317
2319 For bug reports, use the issue tracker at
2320 https://github.com/karelzak/util-linux/issues.
2321
2323 The mount command is part of the util-linux package which can be
2324 downloaded from Linux Kernel Archive
2325 <https://www.kernel.org/pub/linux/utils/util-linux/>.
2326util-linux 2.37.2 2021-08-16 MOUNT(8)