1 //po4a: entry man manual
3 Copyright (c) 1996-2004 Andries Brouwer
4 Copyright (C) 2006-2012 Karel Zak <kzak@redhat.com>
6 This page is somewhat derived from a page that was
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8 and had been heavily modified by Rik Faith and myself.
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10 Fragments of text were written by Werner Almesberger, Remy Card,
11 Stephen Tweedie and Eric Youngdale.
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34 :man manual: System Administration
35 :man source: util-linux {release-version}
42 mount - mount a filesystem
48 *mount* [*-l*] [*-t* _fstype_]
50 *mount* *-a* [*-fFnrsvw*] [*-t* _fstype_] [*-O* _optlist_]
52 *mount* [*-fnrsvw*] [*-o* _options_] _device_|_mountpoint_
54 *mount* [*-fnrsvw*] [*-t* _fstype_] [*-o* _options_] _device mountpoint_
56 *mount* *--bind*|*--rbind*|*--move* _olddir newdir_
58 *mount* *--make-*[*shared*|*slave*|*private*|*unbindable*|*rshared*|*rslave*|*rprivate*|*runbindable*] _mountpoint_
62 All files accessible in a Unix system are arranged in one big tree, the file hierarchy, rooted at _/_. These files can be spread out over several devices. The *mount* command serves to attach the filesystem found on some device to the big file tree. Conversely, the *umount*(8) command will detach it again. The filesystem is used to control how data is stored on the device or provided in a virtual way by network or other services.
64 The standard form of the *mount* command is:
67 *mount -t* _type device dir_
70 This tells the kernel to attach the filesystem found on _device_ (which is of type _type_) at the directory _dir_. The option *-t* _type_ is optional. The *mount* command is usually able to detect a filesystem. The root permissions are necessary to mount a filesystem by default. See section "Non-superuser mounts" below for more details. The previous contents (if any) and owner and mode of _dir_ become invisible, and as long as this filesystem remains mounted, the pathname _dir_ refers to the root of the filesystem on _device_.
72 If only the directory or the device is given, for example:
78 then *mount* looks for a mountpoint (and if not found then for a device) in the _/etc/fstab_ file. It's possible to use the *--target* or *--source* options to avoid ambiguous interpretation of the given argument. For example:
81 *mount --target* _/mountpoint_
84 The same filesystem may be mounted more than once, and in some cases (e.g., network filesystems) the same filesystem may be mounted on the same mountpoint multiple times. The *mount* command does not implement any policy to control this behavior. All behavior is controlled by the kernel and it is usually specific to the filesystem driver. The exception is *--all*, in this case already mounted filesystems are ignored (see *--all* below for more details).
86 === Listing the mounts
88 The listing mode is maintained for backward compatibility only.
90 For more robust and customizable output use *findmnt*(8), *especially in your scripts*. Note that control characters in the mountpoint name are replaced with '?'.
92 The following command lists all mounted filesystems (of type _type_):
95 *mount* [*-l*] [*-t* _type_]
98 The option *-l* adds labels to this listing. See below.
100 === Indicating the device and filesystem
102 Most devices are indicated by a filename (of a block special device), like _/dev/sda1_, but there are other possibilities. For example, in the case of an NFS mount, _device_ may look like _knuth.cwi.nl:/dir_.
104 The device names of disk partitions are unstable; hardware reconfiguration, and adding or removing a device can cause changes in names. This is the reason why it's strongly recommended to use filesystem or partition identifiers like UUID or LABEL. Currently supported identifiers (tags):
107 Human readable filesystem identifier. See also *-L*.
110 Filesystem universally unique identifier. The format of the UUID is usually a series of hex digits separated by hyphens. See also *-U*.
112 Note that *mount* uses UUIDs as strings. The UUIDs from the command line or from *fstab*(5) are not converted to internal binary representation. The string representation of the UUID should be based on lower case characters.
114 PARTLABEL=__label__::
115 Human readable partition identifier. This identifier is independent on filesystem and does not change by *mkfs* or *mkswap* operations. It's supported for example for GUID Partition Tables (GPT).
118 Partition universally unique identifier. This identifier is independent on filesystem and does not change by *mkfs* or *mkswap* operations. It's supported for example for GUID Partition Tables (GPT).
121 Hardware block device ID as generated by udevd. This identifier is usually based on WWN (unique storage identifier) and assigned by the hardware manufacturer. See *ls /dev/disk/by-id* for more details, this directory and running udevd is required. This identifier is not recommended for generic use as the identifier is not strictly defined and it depends on udev, udev rules and hardware.
123 The command *lsblk --fs* provides an overview of filesystems, LABELs and UUIDs on available block devices. The command *blkid -p <device>* provides details about a filesystem on the specified device.
125 Don't forget that there is no guarantee that UUIDs and labels are really unique, especially if you move, share or copy the device. Use *lsblk -o +UUID,PARTUUID* to verify that the UUIDs are really unique in your system.
127 The recommended setup is to use tags (e.g. *UUID*=_uuid_) rather than _/dev/disk/by-{label,uuid,id,partuuid,partlabel}_ udev symlinks in the _/etc/fstab_ file. Tags are more readable, robust and portable. The *mount*(8) command internally uses udev symlinks, so the use of symlinks in _/etc/fstab_ has no advantage over tags. For more details see *libblkid*(3).
129 The _proc_ filesystem is not associated with a special device, and when mounting it, an arbitrary keyword - for example, __proc__ - can be used instead of a device specification. (The customary choice _none_ is less fortunate: the error message 'none already mounted' from *mount* can be confusing.)
131 === The files /etc/fstab, /etc/mtab and /proc/mounts
133 The file _/etc/fstab_ (see *fstab*(5)), may contain lines describing what devices are usually mounted where, using which options. The default location of the *fstab*(5) file can be overridden with the *--fstab* _path_ command-line option (see below for more details).
138 *mount -a* [*-t* _type_] [*-O* _optlist_]
141 (usually given in a bootscript) causes all filesystems mentioned in _fstab_ (of the proper type and/or having or not having the proper options) to be mounted as indicated, except for those whose line contains the *noauto* keyword. Adding the *-F* option will make *mount* fork, so that the filesystems are mounted in parallel.
143 When mounting a filesystem mentioned in _fstab_ or _mtab_, it suffices to specify on the command line only the device, or only the mount point.
145 The programs *mount* and *umount*(8) traditionally maintained a list of currently mounted filesystems in the file _/etc/mtab_. The support for regular classic _/etc/mtab_ is completely disabled at compile time by default, because on current Linux systems it is better to make _/etc/mtab_ a symlink to _/proc/mounts_ instead. The regular _mtab_ file maintained in userspace cannot reliably work with namespaces, containers and other advanced Linux features. If the regular _mtab_ support is enabled, then it's possible to use the file as well as the symlink.
147 If no arguments are given to *mount*, the list of mounted filesystems is printed.
149 If you want to override mount options from _/etc/fstab_, you have to use the *-o* option:
152 *mount* __device__|__dir__ *-o* _options_
155 and then the mount options from the command line will be appended to the list of options from _/etc/fstab_. This default behaviour can be changed using the *--options-mode* command-line option. The usual behavior is that the last option wins if there are conflicting ones.
157 The *mount* program does not read the _/etc/fstab_ file if both _device_ (or LABEL, UUID, ID, PARTUUID or PARTLABEL) and _dir_ are specified. For example, to mount device *foo* at */dir*:
160 *mount /dev/foo /dir*
163 This default behaviour can be changed by using the *--options-source-force* command-line option to always read configuration from _fstab_. For non-root users *mount* always reads the _fstab_ configuration.
165 === Non-superuser mounts
167 Normally, only the superuser can mount filesystems. However, when _fstab_ contains the *user* option on a line, anybody can mount the corresponding filesystem.
172 */dev/cdrom /cd iso9660 ro,user,noauto,unhide*
175 any user can mount the iso9660 filesystem found on an inserted CDROM using the command:
181 Note that *mount* is very strict about non-root users and all paths specified on command line are verified before _fstab_ is parsed or a helper program is executed. It's strongly recommended to use a valid mountpoint to specify filesystem, otherwise *mount* may fail. For example it's a bad idea to use NFS or CIFS source on command line.
183 Since util-linux 2.35, *mount* does not exit when user permissions are inadequate according to libmount's internal security rules. Instead, it drops suid permissions and continues as regular non-root user. This behavior supports use-cases where root permissions are not necessary (e.g., fuse filesystems, user namespaces, etc).
185 For more details, see *fstab*(5). Only the user that mounted a filesystem can unmount it again. If any user should be able to unmount it, then use *users* instead of *user* in the _fstab_ line. The *owner* option is similar to the *user* option, with the restriction that the user must be the owner of the special file. This may be useful e.g. for _/dev/fd_ if a login script makes the console user owner of this device. The *group* option is similar, with the restriction that the user must be a member of the group of the special file.
187 === Bind mount operation
189 Remount part of the file hierarchy somewhere else. The call is:
192 *mount --bind* _olddir newdir_
195 or by using this _fstab_ entry:
198 **/**__olddir__ **/**__newdir__ *none bind*
201 After this call the same contents are accessible in two places.
203 It is important to understand that "bind" does not create any second-class or special node in the kernel VFS. The "bind" is just another operation to attach a filesystem. There is nowhere stored information that the filesystem has been attached by a "bind" operation. The _olddir_ and _newdir_ are independent and the _olddir_ may be unmounted.
205 One can also remount a single file (on a single file). It's also possible to use a bind mount to create a mountpoint from a regular directory, for example:
208 *mount --bind foo foo*
211 The bind mount call attaches only (part of) a single filesystem, not possible submounts. The entire file hierarchy including submounts can be attached a second place by using:
214 *mount --rbind* _olddir newdir_
217 Note that the filesystem mount options maintained by the kernel will remain the same as those on the original mount point. The userspace mount options (e.g., _netdev) will not be copied by *mount* and it's necessary to explicitly specify the options on the *mount* command line.
219 Since util-linux 2.27 *mount* permits changing the mount options by passing the relevant options along with *--bind*. For example:
222 *mount -o bind,ro foo foo*
225 This feature is not supported by the Linux kernel; it is implemented in userspace by an additional *mount*(2) remounting system call. This solution is not atomic.
227 The alternative (classic) way to create a read-only bind mount is to use the remount operation, for example:
230 *mount --bind* _olddir newdir_
232 *mount -o remount,bind,ro* _olddir newdir_
235 Note that a read-only bind will create a read-only mountpoint (VFS entry), but the original filesystem superblock will still be writable, meaning that the _olddir_ will be writable, but the _newdir_ will be read-only.
237 It's also possible to change nosuid, nodev, noexec, noatime, nodiratime, relatime and nosymfollow VFS entry flags via a "remount,bind" operation. The other flags (for example filesystem-specific flags) are silently ignored. The classic *mount*(2) system call does not allow to change mount options recursively (for example with *-o rbind,ro*). The recursive semantic is possible with a new *mount_setattr*(2) kernel system call and it's supported since libmount from util-linux v2.39 by a new experimental "recursive" option argument (e.g. *-o rbind,ro=recursive*). For more details see the *FILESYSTEM-INDEPENDENT MOUNT OPTIONS* section.
239 Since util-linux 2.31, *mount* ignores the *bind* flag from _/etc/fstab_ on a *remount* operation (if *-o remount* is specified on command line). This is necessary to fully control mount options on remount by command line. In previous versions the bind flag has been always applied and it was impossible to re-define mount options without interaction with the bind semantic. This *mount* behavior does not affect situations when "remount,bind" is specified in the _/etc/fstab_ file.
241 === The move operation
243 Move a *mounted tree* to another place (atomically). The call is:
246 *mount --move* _olddir newdir_
249 This will cause the contents which previously appeared under _olddir_ to now be accessible under _newdir_. The physical location of the files is not changed. Note that _olddir_ has to be a mountpoint.
251 Note also that moving a mount residing under a shared mount is invalid and unsupported. Use *findmnt -o TARGET,PROPAGATION* to see the current propagation flags.
253 === Shared subtree operations
255 Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared, private, slave or unbindable. A shared mount provides the ability to create mirrors of that mount such that mounts and unmounts within any of the mirrors propagate to the other mirror. A slave mount receives propagation from its master, but not vice versa. A private mount carries no propagation abilities. An unbindable mount is a private mount which cannot be cloned through a bind operation. The detailed semantics are documented in _Documentation/filesystems/sharedsubtree.txt_ file in the kernel source tree; see also *mount_namespaces*(7).
257 Supported operations are:
260 mount --make-shared mountpoint
261 mount --make-slave mountpoint
262 mount --make-private mountpoint
263 mount --make-unbindable mountpoint
266 The following commands allow one to recursively change the type of all the mounts under a given mountpoint.
269 mount --make-rshared mountpoint
270 mount --make-rslave mountpoint
271 mount --make-rprivate mountpoint
272 mount --make-runbindable mountpoint
275 *mount* *does not read* *fstab*(5) when a *--make-** operation is requested. All necessary information has to be specified on the command line.
277 Note that the Linux kernel does not allow changing multiple propagation flags with a single *mount*(2) system call, and the flags cannot be mixed with other mount options and operations.
279 Since util-linux 2.23 the *mount* command can be used to do more propagation (topology) changes by one *mount*(8) call and do it also together with other mount operations. The propagation flags are applied by additional *mount*(2) system calls when the preceding mount operations were successful. Note that this use case is not atomic. It is possible to specify the propagation flags in *fstab*(5) as mount options (*private*, *slave*, *shared*, *unbindable*, *rprivate*, *rslave*, *rshared*, *runbindable*).
284 mount --make-private --make-unbindable /dev/sda1 /foo
291 mount --make-private /foo
292 mount --make-unbindable /foo
295 == COMMAND-LINE OPTIONS
297 The full set of mount options used by an invocation of *mount* is determined by first extracting the mount options for the filesystem from the _fstab_ table, then applying any options specified by the *-o* argument, and finally applying a *-r* or *-w* option, when present.
299 The *mount* command does not pass all command-line options to the **/sbin/mount.**__suffix__ mount helpers. The interface between *mount* and the mount helpers is described below in the *EXTERNAL HELPERS* section.
301 Command-line options available for the *mount* command are:
304 Mount all filesystems (of the given types) mentioned in _fstab_ (except for those whose line contains the *noauto* keyword). The filesystems are mounted following their order in _fstab_. The *mount* command compares filesystem source, target (and fs root for bind mount or btrfs) to detect already mounted filesystems. The kernel table with already mounted filesystems is cached during *mount --all*. This means that all duplicated _fstab_ entries will be mounted.
306 The correct functionality depends on _/proc_ (to detect already mounted filesystems) and on _/sys_ (to evaluate filesystem tags like UUID= or LABEL=). It's strongly recommended to mount _/proc_ and _/sys_ filesystems before *mount -a* is executed, or keep /proc and /sys at the beginning of _fstab_.
308 The option *--all* is possible to use for remount operation too. In this case all filters (*-t* and *-O*) are applied to the table of already mounted filesystems.
310 Since version 2.35 it is possible to use the command line option *-o* to alter mount options from _fstab_ (see also *--options-mode*).
312 Note that it is a bad practice to use *mount -a* for _fstab_ checking. The recommended solution is *findmnt --verify*.
315 Remount a subtree somewhere else (so that its contents are available in both places). See above, under *Bind mount operation*.
317 *-c*, *--no-canonicalize*::
318 Don't canonicalize paths. The *mount* command canonicalizes all paths (from the command line or _fstab_) by default. This option can be used together with the *-f* flag for already canonicalized absolute paths. The option is designed for mount helpers which call *mount -i*. It is strongly recommended to not use this command-line option for normal mount operations.
320 Note that *mount* does not pass this option to the **/sbin/mount.**__type__ helpers.
323 (Used in conjunction with *-a*.) Fork off a new incarnation of *mount* for each device. This will do the mounts on different devices or different NFS servers in parallel. This has the advantage that it is faster; also NFS timeouts proceed in parallel. A disadvantage is that the order of the mount operations is undefined. Thus, you cannot use this option if you want to mount both _/usr_ and _/usr/spool_.
326 Causes everything to be done except for the actual system call; if it's not obvious, this "fakes" mounting the filesystem. This option is useful in conjunction with the *-v* flag to determine what the *mount* command is trying to do. It can also be used to add entries for devices that were mounted earlier with the *-n* option. The *-f* option checks for an existing record in _/etc/mtab_ and fails when the record already exists (with a regular non-fake mount, this check is done by the kernel).
328 *-i, --internal-only*::
329 Don't call the **/sbin/mount.**__filesystem__ helper even if it exists.
331 *-L*, *--label* _label_::
332 Mount the partition that has the specified _label_.
334 *-l*, *--show-labels*::
335 Add the labels in the mount output. *mount* must have permission to read the disk device (e.g. be set-user-ID root) for this to work. One can set such a label for ext2, ext3 or ext4 using the *e2label*(8) utility, or for XFS using *xfs_admin*(8), or for reiserfs using *reiserfstune*(8).
338 Move a subtree to some other place. See above, the subsection *The move operation*.
340 *-m*, **--mkdir**[=__mode__]::
341 Allow to make a target directory (mountpoint) if it does not exist yet. Alias to "-o X-mount.mkdir[=mode]", the default mode is 0755. For more details see *X-mount.mkdir* below.
343 *--map-groups*, *--map-users* _inner_:_outer_:_count_::
344 Add the specified user/group mapping to an *X-mount.idmap* map. These options can be given multiple times to build up complete mappings for users and groups. For more details see *X-mount.idmap* below.
346 *--map-users* /proc/_PID_/ns/user::
347 Use the specified user namespace for user and group mapping in an id-mapped mount. This is an alias for "-o X-mount.idmap=/proc/_PID_/ns/user" and cannot be used twice nor together with the _inner_:_outer_:_count_ option format above. For more details see *X-mount.idmap* below.
350 Mount without writing in _/etc/mtab_. This is necessary for example when _/etc_ is on a read-only filesystem.
352 *-N*, *--namespace* _ns_::
353 Perform the mount operation in the mount namespace specified by _ns_. _ns_ is either PID of process running in that namespace or special file representing that namespace.
355 *mount* switches to the mount namespace when it reads _/etc/fstab_, writes _/etc/mtab: (or writes to _/run/mount_) and calls *mount*(2), otherwise it runs in the original mount namespace. This means that the target namespace does not have to contain any libraries or other requirements necessary to execute the *mount*(2) call.
357 See *mount_namespaces*(7) for more information.
359 *-O*, *--test-opts* _opts_::
360 Limit the set of filesystems to which the *-a* option applies. In this regard it is like the *-t* option except that *-O* is useless without *-a*. For example, the command
362 *mount -a -O no_netdev*
364 mounts all filesystems except those which have the option _netdev_ specified in the options field in the _/etc/fstab_ file.
366 It is different from *-t* in that each option is matched exactly; a leading *no* at the beginning of one option does not negate the rest.
368 The *-t* and *-O* options are cumulative in effect; that is, the command
370 *mount -a -t ext2 -O _netdev*
372 mounts all ext2 filesystems with the _netdev option, not all filesystems that are either ext2 or have the _netdev option specified.
374 *-o*, *--options* _opts_::
375 Use the specified mount options. The _opts_ argument is a comma-separated list. For example:
377 *mount LABEL=mydisk -o noatime,nodev,nosuid*
379 Note that the order of the options matters, as the last option wins if there are conflicting ones. The options from the command line also overwrite options from fstab by default.
381 For more details, see the *FILESYSTEM-INDEPENDENT MOUNT OPTIONS* and *FILESYSTEM-SPECIFIC MOUNT OPTIONS* sections.
384 Forces mount command to check if the filesystem is already mounted. This behavior is the default for *--all*; otherwise, it depends on the kernel filesystem driver. Some filesystems may be mounted more than once on the same mount point (e.g. tmpfs).
386 *--options-mode* _mode_::
387 Controls how to combine options from _fstab_/_mtab_ with options from the command line. _mode_ can be one of *ignore*, *append*, *prepend* or *replace*. For example, *append* means that options from _fstab_ are appended to options from the command line. The default value is *prepend* -- it means command line options are evaluated after _fstab_ options. Note that the last option wins if there are conflicting ones.
389 *--options-source* _source_::
390 Source of default options. _source_ is a comma-separated list of *fstab*, *mtab* and *disable*. *disable* disables *fstab* and *mtab* and enables *--options-source-force*. The default value is *fstab,mtab*.
392 *--options-source-force*::
393 Use options from _fstab_/_mtab_ even if both _device_ and _dir_ are specified.
396 Remount a subtree and all possible submounts somewhere else (so that its contents are available in both places). See above, the subsection *Bind mount operation*.
398 *-r*, *--read-only*::
399 Mount the filesystem read-only. A synonym is *-o ro*.
401 Note that, depending on the filesystem type, state and kernel behavior, the system may still write to the device. For example, ext3 and ext4 will replay the journal if the filesystem is dirty. To prevent this kind of write access, you may want to mount an ext3 or ext4 filesystem with the *ro,noload* mount options or set the block device itself to read-only mode, see the *blockdev*(8) command.
404 Tolerate sloppy mount options rather than failing. This will ignore mount options not supported by a filesystem type. Not all filesystems support this option. Currently it's supported by the *mount.nfs* mount helper only.
406 *--source* _device_::
407 If only one argument for the *mount* command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount source.
409 *--target* _directory_::
410 If only one argument for the mount command is given, then the argument might be interpreted as the target (mountpoint) or source (device). This option allows you to explicitly define that the argument is the mount target.
412 *--target-prefix* _directory_::
413 Prepend the specified directory to all mount targets. This option can be used to follow _fstab_, but mount operations are done in another place, for example:
415 *mount --all --target-prefix /chroot -o X-mount.mkdir*
417 mounts all from system _fstab_ to _/chroot_, all missing mountpoint are created (due to X-mount.mkdir). See also *--fstab* to use an alternative _fstab_.
419 *-T*, *--fstab* _path_::
420 Specifies an alternative _fstab_ file. If _path_ is a directory, then the files in the directory are sorted by *strverscmp*(3); files that start with "." or without an _.fstab_ extension are ignored. The option can be specified more than once. This option is mostly designed for initramfs or chroot scripts where additional configuration is specified beyond standard system configuration.
422 Note that *mount* does not pass the option *--fstab* to the **/sbin/mount.**__type__ helpers, meaning that the alternative _fstab_ files will be invisible for the helpers. This is no problem for normal mounts, but user (non-root) mounts always require _fstab_ to verify the user's rights.
424 *-t*, *--types* _fstype_::
425 The argument following the *-t* is used to indicate the filesystem type. The filesystem types which are currently supported depend on the running kernel. See _/proc/filesystems_ and _/lib/modules/$(uname -r)/kernel/fs_ for a complete list of the filesystems. The most common are ext2, ext3, ext4, xfs, btrfs, vfat, sysfs, proc, nfs and cifs.
427 The programs *mount* and *umount*(8) support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For example 'fuse.sshfs'. It's recommended to use subtype notation rather than add any prefix to the mount source (for example 'sshfs#example.com' is deprecated).
429 If no *-t* option is given, or if the *auto* type is specified, *mount* will try to guess the desired type. *mount* uses the *libblkid*(3) library for guessing the filesystem type; if that does not turn up anything that looks familiar, *mount* will try to read the file _/etc/filesystems_, or, if that does not exist, _/proc/filesystems_. All of the filesystem types listed there will be tried, except for those that are labeled "nodev" (e.g. _devpts_, _proc_ and _nfs_). If _/etc/filesystems_ ends in a line with a single {asterisk}, mount will read _/proc/filesystems_ afterwards. While trying, all filesystem types will be mounted with the mount option *silent*.
430 //TRANSLATORS: Keep {asterisk} untranslated.
432 The *auto* type may be useful for user-mounted floppies. Creating a file _/etc/filesystems_ can be useful to change the probe order (e.g., to try vfat before msdos or ext3 before ext2) or if you use a kernel module autoloader.
434 More than one type may be specified in a comma-separated list, for the *-t* option as well as in an _/etc/fstab_ entry. The list of filesystem types for the *-t* option can be prefixed with *no* to specify the filesystem types on which no action should be taken. The prefix *no* has no effect when specified in an _/etc/fstab_ entry.
436 The prefix *no* can be meaningful with the *-a* option. For example, the command
438 *mount -a -t nomsdos,smbfs*
440 mounts all filesystems except those of type _msdos_ and _smbfs_.
442 For most types all the *mount* program has to do is issue a simple *mount*(2) system call, and no detailed knowledge of the filesystem type is required. For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems have a separate mount program. In order to make it possible to treat all types in a uniform way, *mount* will execute the program **/sbin/mount.**__type__ (if that exists) when called with type _type_. Since different versions of the *smbmount* program have different calling conventions, */sbin/mount.smbfs* may have to be a shell script that sets up the desired call.
444 *-U*, *--uuid* _uuid_::
445 Mount the partition that has the specified _uuid_.
450 *-w*, *--rw*, *--read-write*::
451 Mount the filesystem read/write. Read-write is the kernel default and the *mount* default is to try read-only if the previous *mount*(2) syscall with read-write flags on write-protected devices failed.
453 A synonym is *-o rw*.
455 Note that specifying *-w* on the command line forces *mount* to never try read-only mount on write-protected devices or already mounted read-only filesystems.
457 include::man-common/help-version.adoc[]
459 == FILESYSTEM-INDEPENDENT MOUNT OPTIONS
461 Some of these options are only useful when they appear in the _/etc/fstab_ file.
463 Some of these options could be enabled or disabled by default in the system kernel. To check the current setting see the options in _/proc/mounts_. Note that filesystems also have per-filesystem specific default mount options (see for example *tune2fs -l* output for ext__N__ filesystems).
465 The options *nosuid*, *noexec*, *nodiratime*, *relatime*, *noatime*, *strictatime*, and *nosymfollow* are interpreted only by the abstract VFS kernel layer and applied to the mountpoint node rather than to the filesystem itself. Try:
468 findmnt -o TARGET,VFS-OPTIONS,FS-OPTIONS
471 to get a complete overview of filesystems and VFS options.
473 The read-only setting (*ro* or *rw*) is interpreted by VFS and the filesystem
474 and depends on how the option is specified on the *mount*(8) command line. The
475 default is to interpret it on the filesystem level. The operation "-o bind,remount,ro"
476 is applied only to the VFS mountpoint, and operation "-o remount,ro" is applied to
477 VFS and filesystem superblock. This semantic allows create a read-only
478 mountpoint but keeps the filesystem writable from another mountpoint.
480 Since v2.39 libmount can use a new kernel mount interface to set the VFS
481 options recursive. For backward compatibility, this feature is not enabled by
482 default, although recursive operation (e.g. rbind) has been requested. The new
483 option argument "recursive" could be specified, for example:
486 mount -orbind,ro=recursive,noexec=recursive,nosuid /foo /bar
489 recursively binds filesystems from /foo to /bar, /bar, and all submounts will
490 be read-only and noexec, but only /bar itself will be "nosuid". The "recursive"
491 optional argument for VFS mount options is an EXPERIMENTAL feature.
493 The following options apply to any filesystem that is being mounted (but not every filesystem actually honors them - e.g., the *sync* option today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs):
496 All I/O to the filesystem should be done asynchronously. (See also the *sync* option.)
499 Do not use the *noatime* feature, so the inode access time is controlled by kernel defaults. See also the descriptions of the *relatime* and *strictatime* mount options.
502 Do not update inode access times on this filesystem (e.g. for faster access on the news spool to speed up news servers). This works for all inode types (directories too), so it implies *nodiratime*.
505 Can be mounted with the *-a* option.
508 Can only be mounted explicitly (i.e., the *-a* option will not cause the filesystem to be mounted).
510 **context=**__context__, **fscontext=**__context__, **defcontext=**__context__, and **rootcontext=**__context__::
511 The *context=* option is useful when mounting filesystems that do not support extended attributes, such as a floppy or hard disk formatted with VFAT, or systems that are not normally running under SELinux, such as an ext3 or ext4 formatted disk from a non-SELinux workstation. You can also use *context=* on filesystems you do not trust, such as a floppy. It also helps in compatibility with xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where xattrs are supported, you can save time not having to label every file by assigning the entire disk one security context.
513 A commonly used option for removable media is *context="system_u:object_r:removable_t*.
515 The *fscontext=* option works for all filesystems, regardless of their xattr support. The fscontext option sets the overarching filesystem label to a specific security context. This filesystem label is separate from the individual labels on the files. It represents the entire filesystem for certain kinds of permission checks, such as during mount or file creation. Individual file labels are still obtained from the xattrs on the files themselves. The context option actually sets the aggregate context that fscontext provides, in addition to supplying the same label for individual files.
517 You can set the default security context for unlabeled files using *defcontext=* option. This overrides the value set for unlabeled files in the policy and requires a filesystem that supports xattr labeling.
519 The *rootcontext=* option allows you to explicitly label the root inode of a FS being mounted before that FS or inode becomes visible to userspace. This was found to be useful for things like stateless Linux. The special value *@target* can be used to assign the current context of the target mountpoint location.
521 Note that the kernel rejects any remount request that includes the context option, *even* when unchanged from the current context.
523 *Warning: the* _context_ *value might contain commas*, in which case the value has to be properly quoted, otherwise *mount* will interpret the comma as a separator between mount options. Don't forget that the shell strips off quotes and thus *double quoting is required*. For example:
525 mount -t tmpfs none /mnt -o \
526 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
529 For more details, see *selinux*(8).
532 Use the default options: *rw*, *suid*, *dev*, *exec*, *auto*, *nouser*, and *async*.
534 Note that the real set of all default mount options depends on the kernel and filesystem type. See the beginning of this section for more details.
537 Interpret character or block special devices on the filesystem.
540 Do not interpret character or block special devices on the filesystem.
543 Update directory inode access times on this filesystem. This is the default. (This option is ignored when *noatime* is set.)
546 Do not update directory inode access times on this filesystem. (This option is implied when *noatime* is set.)
549 All directory updates within the filesystem should be done synchronously. This affects the following system calls: *creat*(2), *link*(2), *unlink*(2), *symlink*(2), *mkdir*(2), *rmdir*(2), *mknod*(2) and *rename*(2).
552 Permit execution of binaries and other executable files.
555 Do not permit direct execution of any binaries on the mounted filesystem.
558 Allow an ordinary user to mount the filesystem if one of that user's groups matches the group of the device. This option implies the options *nosuid* and *nodev* (unless overridden by subsequent options, as in the option line *group,dev,suid*).
561 Every time the inode is modified, the i_version field will be incremented.
564 Do not increment the i_version inode field.
567 Allow mandatory locks on this filesystem. See *fcntl*(2). This option was deprecated in Linux 5.15.
570 Do not allow mandatory locks on this filesystem.
573 The filesystem resides on a device that requires network access (used to prevent the system from attempting to mount these filesystems until the network has been enabled on the system).
576 Do not report errors for this device if it does not exist.
579 Update inode access times relative to modify or change time. Access time is only updated if the previous access time was earlier than or equal to the current modify or change time. (Similar to *noatime*, but it doesn't break *mutt*(1) or other applications that need to know if a file has been read since the last time it was modified.)
581 Since Linux 2.6.30, the kernel defaults to the behavior provided by this option (unless *noatime* was specified), and the *strictatime* option is required to obtain traditional semantics. In addition, since Linux 2.6.30, the file's last access time is always updated if it is more than 1 day old.
584 Do not use the *relatime* feature. See also the *strictatime* mount option.
587 Allows to explicitly request full atime updates. This makes it possible for the kernel to default to *relatime* or *noatime* but still allow userspace to override it. For more details about the default system mount options see _/proc/mounts_.
590 Use the kernel's default behavior for inode access time updates.
593 Only update times (atime, mtime, ctime) on the in-memory version of the file inode.
595 This mount option significantly reduces writes to the inode table for workloads that perform frequent random writes to preallocated files.
597 The on-disk timestamps are updated only when:
599 * the inode needs to be updated for some change unrelated to file timestamps
600 * the application employs *fsync*(2), *syncfs*(2), or *sync*(2)
601 * an undeleted inode is evicted from memory
602 * more than 24 hours have passed since the inode was written to disk.
605 Do not use the lazytime feature.
608 Honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem.
611 Do not honor set-user-ID and set-group-ID bits or file capabilities when executing programs from this filesystem. In addition, SELinux domain transitions require permission _nosuid_transition_, which in turn needs also policy capability _nnp_nosuid_transition_.
614 Turn on the silent flag.
617 Turn off the silent flag.
620 Allow an ordinary user to mount the filesystem if that user is the owner of the device. This option implies the options *nosuid* and *nodev* (unless overridden by subsequent options, as in the option line *owner,dev,suid*).
623 Attempt to remount an already-mounted filesystem. This is commonly used to change the mount flags for a filesystem, especially to make a readonly filesystem writable. It does not change device or mount point.
625 The remount operation together with the *bind* flag has special semantics. See above, the subsection *Bind mount operation*.
627 The default kernel behavior for VFS mount flags (nodev,nosuid,noexec,ro) is to
628 reset all unspecified flags on remount. That's why *mount*(8) tries to
629 keep the current setting according to _fstab_ or _/proc/self/mountinfo_. This
630 default behavior is possible to change by *--options-mode*. The recursive
631 change of the mount flags (supported since v2.39 on systems with *mount_setattr*(2)
632 syscall), for example, *mount -o remount,ro=recursive*, do not use
633 "reset-unspecified" behavior, and it works as a simple add/remove operation
634 and unspecified flags are not modified.
636 The remount functionality follows the standard way the *mount* command works with options from _fstab_. This means that *mount* does not read _fstab_ (or _mtab_) only when both _device_ and _dir_ are specified.
638 *mount -o remount,rw /dev/foo /dir*
640 After this call all old mount options are replaced and arbitrary stuff from _fstab_ (or _mtab_) is ignored, except the *loop=* option which is internally generated and maintained by the *mount* command.
642 *mount -o remount,rw /dir*
644 After this call, *mount* reads _fstab_ and merges these options with the options from the command line (*-o*). If no mountpoint is found in _fstab_, then it defaults to mount options from _/proc/self/mountinfo_.
647 *mount* allows the use of *--all* to remount all already mounted filesystems which match a specified filter (*-O* and *-t*). For example:
649 *mount --all -o remount,ro -t vfat*
651 remounts all already mounted vfat filesystems in read-only mode. Each of the filesystems is remounted by *mount -o remount,ro* _/dir_ semantic. This means the *mount* command reads _fstab_ or _mtab_ and merges these options with the options from the command line.
654 Mount the filesystem read-only.
657 Mount the filesystem read-write.
660 All I/O to the filesystem should be done synchronously. In the case of media with a limited number of write cycles (e.g. some flash drives), *sync* may cause life-cycle shortening.
663 Allow an ordinary user to mount the filesystem. The name of the mounting user is written to the _mtab_ file (or to the private libmount file in _/run/mount_ on systems without a regular _mtab_) so that this same user can unmount the filesystem again. This option implies the options *noexec*, *nosuid*, and *nodev* (unless overridden by subsequent options, as in the option line *user,exec,dev,suid*).
666 Forbid an ordinary user to mount the filesystem. This is the default; it does not imply any other options.
669 Allow any user to mount and to unmount the filesystem, even when some other ordinary user mounted it. This option implies the options *noexec*, *nosuid*, and *nodev* (unless overridden by subsequent options, as in the option line *users,exec,dev,suid*).
672 All options prefixed with "X-" are interpreted as comments or as userspace application-specific options. These options are not stored in user space (e.g., _mtab_ file), nor sent to the mount._type_ helpers nor to the *mount*(2) system call. The suggested format is **X-**__appname__._option_.
675 The same as *X-** options, but stored permanently in user space. This means the options are also available for *umount*(8) or other operations. Note that maintaining mount options in user space is tricky, because it's necessary use libmount-based tools and there is no guarantee that the options will be always available (for example after a move mount operation or in unshared namespace).
677 Note that before util-linux v2.30 the x-* options have not been maintained by libmount and stored in user space (functionality was the same as for X-* now), but due to the growing number of use-cases (in initrd, systemd etc.) the functionality has been extended to keep existing _fstab_ configurations usable without a change.
679 *X-mount.auto-fstypes*=_list_::
680 Specifies allowed or forbidden filesystem types for automatic filesystem
683 The _list_ is a comma-separated list of the filesystem names. The
684 automatic filesystem detection is triggered by the "auto" filesystem type or
685 when the filesystem type is not specified.
687 Thy _list_ follows how mount
688 evaluates type patterns (see *-t* for more details). Only specified filesystem
689 types are allowed, or all specified types are forbidden if the list is prefixed
692 For example, X-mount.auto-fstypes="ext4,btrfs" accepts only ext4 and
693 btrfs, and X-mount.auto-fstypes="novfat,xfs" accepts all filesystems except vfat
696 Note that comma is used as a separator between mount options, it means
697 that auto-fstypes values have to be properly quoted, don’t forget that the shell
698 strips off quotes and thus double quoting is required. For example:
700 mount -t auto -o'X-mount.auto-fstypes="noext2,ext3"' /dev/sdc1 /mnt/test
703 *X-mount.mkdir*[=_mode_]::
704 Allow to make a target directory (mountpoint) if it does not exist yet. The optional argument _mode_ specifies the filesystem access mode used for *mkdir*(2) in octal notation. The default mode is 0755. This functionality is supported only for root users or when *mount* is executed without suid permissions. The option is also supported as *x-mount.mkdir*, but this notation is deprecated since v2.30. See also *--mkdir* command line option.
706 **X-mount.subdir=**__directory__::
707 Allow mounting sub-directory from a filesystem instead of the root directory. For now, this feature is implemented by temporary filesystem root directory mount in unshared namespace and then bind the sub-directory to the final mount point and umount the root of the filesystem. The sub-directory mount shows up atomically for the rest of the system although it is implemented by multiple *mount*(2) syscalls.
709 Note that this feature will not work in session with an unshared private mount namespace (after *unshare --mount*) on old kernels or with *mount*(8) without support for file-descriptors-based mount kernel API. In this case, you need *unshare --mount --propagation shared*.
711 This feature is EXPERIMENTAL.
713 *X-mount.owner*=_username_|_UID_, *X-mount.group*=_group_|_GID_::
714 Set _mountpoint_'s ownership after mounting. Names resolved in the target mount namespace, see *-N*.
716 *X-mount.mode*=_mode_::
717 Set _mountpoint_'s mode after mounting.
719 *X-mount.idmap*=__id-type__:__id-mount__:__id-host__:__id-range__ [__id-type__:__id-mount__:__id-host__:__id-range__], *X-mount.idmap*=__file__::
720 Use this option to create an idmapped mount.
721 An idmapped mount allows to change ownership of all files located under a mount according to the ID-mapping associated with a user namespace.
722 The ownership change is tied to the lifetime and localized to the relevant mount.
723 The relevant ID-mapping can be specified in two ways:
725 * A user can specify the ID-mapping directly.
727 The ID-mapping must be specified using the syntax __id-type__:__id-mount__:__id-host__:__id-range__.
728 Specifying *u* as the __id-type__ prefix creates a UID-mapping, *g* creates a GID-mapping and omitting __id-type__ or specifying *b* creates both a UID- and GID-mapping.
729 The __id-mount__ parameter indicates the starting ID in the new mount.
730 The __id-host__ parameter indicates the starting ID in the filesystem.
731 The __id-range__ parameter indicates how many IDs are to be mapped.
732 It is possible to specify multiple ID-mappings.
733 The individual ID-mappings must be separated by spaces.
735 For example, the ID-mapping *X-mount.idmap=u:1000:0:1 g:1001:1:2 5000:1000:2* creates an idmapped mount where
736 UID 0 is mapped to UID 1000, GID 1 is mapped to GUID 1001, GID 2 is mapped to GID 1002, UID and GID 1000 are mapped to 5000, and UID and GID 1001 are mapped to 5001 in the mount.
738 When an ID-mapping is specified directly a new user namespace will be allocated with the requested ID-mapping.
739 The newly created user namespace will be attached to the mount.
740 * A user can specify a user namespace file.
742 The user namespace will then be attached to the mount and the ID-mapping of the user namespace will become the ID-mapping of the mount.
744 For example, *X-mount.idmap=/proc/PID/ns/user* will attach the user namespace of the process PID to the mount.
747 Do not follow symlinks when resolving paths. Symlinks can still be created, and *readlink*(1), *readlink*(2), *realpath*(1), and *realpath*(3) all still work properly.
749 == FILESYSTEM-SPECIFIC MOUNT OPTIONS
751 This section lists options that are specific to particular filesystems. Where possible, you should first consult filesystem-specific manual pages for details. Some of those pages are listed in the following table.
753 [cols=",",options="header",]
755 |*Filesystem(s)* |*Manual page*
757 |cifs |*mount.cifs*(8)
758 |ext2, ext3, ext4 |*ext4*(5)
765 Note that some of the pages listed above might be available only after you install the respective userland tools.
767 The following options apply only to certain filesystems. We sort them by filesystem. All options follow the *-o* flag.
769 What options are supported depends a bit on the running kernel. Further information may be available in filesystem-specific files in the kernel source subdirectory _Documentation/filesystems_.
771 === Mount options for adfs
773 **uid=**__value__ and **gid=**__value__::
774 Set the owner and group of the files in the filesystem (default: uid=gid=0).
776 **ownmask=**__value__ and **othmask=**__value__::
777 Set the permission mask for ADFS 'owner' permissions and 'other' permissions, respectively (default: 0700 and 0077, respectively). See also _/usr/src/linux/Documentation/filesystems/adfs.rst_.
779 === Mount options for affs
781 **uid=**__value__ and **gid=**__value__::
782 Set the owner and group of the root of the filesystem (default: uid=gid=0, but with option *uid* or *gid* without specified value, the UID and GID of the current process are taken).
784 **setuid=**__value__ and **setgid=**__value__::
785 Set the owner and group of all files.
788 Set the mode of all files to _value_ & 0777 disregarding the original permissions. Add search permission to directories that have read permission. The value is given in octal.
791 Do not allow any changes to the protection bits on the filesystem.
794 Set UID and GID of the root of the filesystem to the UID and GID of the mount point upon the first sync or umount, and then clear this option. Strange...
797 Print an informational message for each successful mount.
799 **prefix=**__string__::
800 Prefix used before volume name, when following a link.
802 **volume=**__string__::
803 Prefix (of length at most 30) used before '/' when following a symbolic link.
805 **reserved=**__value__::
806 (Default: 2.) Number of unused blocks at the start of the device.
809 Give explicitly the location of the root block.
812 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
814 **grpquota**|**noquota**|**quota**|*usrquota*::
815 These options are accepted but ignored. (However, quota utilities may react to such strings in _/etc/fstab_.)
817 === Mount options for debugfs
819 The debugfs filesystem is a pseudo filesystem, traditionally mounted on _/sys/kernel/debug_. As of kernel version 3.4, debugfs has the following options:
821 **uid=**__n__**, gid=**__n__::
822 Set the owner and group of the mountpoint.
825 Sets the mode of the mountpoint.
827 === Mount options for devpts
829 The devpts filesystem is a pseudo filesystem, traditionally mounted on _/dev/pts_. In order to acquire a pseudo terminal, a process opens _/dev/ptmx_; the number of the pseudo terminal is then made available to the process and the pseudo terminal slave can be accessed as _/dev/pts/_<number>.
831 **uid=**__value__ and **gid=**__value__::
832 This sets the owner or the group of newly created pseudo terminals to the specified values. When nothing is specified, they will be set to the UID and GID of the creating process. For example, if there is a tty group with GID 5, then *gid=5* will cause newly created pseudo terminals to belong to the tty group.
835 Set the mode of newly created pseudo terminals to the specified value. The default is 0600. A value of *mode=620* and *gid=5* makes "mesg y" the default on newly created pseudo terminals.
838 Create a private instance of the devpts filesystem, such that indices of pseudo terminals allocated in this new instance are independent of indices created in other instances of devpts.
840 All mounts of devpts without this *newinstance* option share the same set of pseudo terminal indices (i.e., legacy mode). Each mount of devpts with the *newinstance* option has a private set of pseudo terminal indices.
842 This option is mainly used to support containers in the Linux kernel. It is implemented in Linux kernel versions starting with 2.6.29. Further, this mount option is valid only if *CONFIG_DEVPTS_MULTIPLE_INSTANCES* is enabled in the kernel configuration.
844 To use this option effectively, _/dev/ptmx_ must be a symbolic link to _pts/ptmx_. See _Documentation/filesystems/devpts.txt_ in the Linux kernel source tree for details.
846 **ptmxmode=**__value__::
847 Set the mode for the new _ptmx_ device node in the devpts filesystem.
849 With the support for multiple instances of devpts (see *newinstance* option above), each instance has a private _ptmx_ node in the root of the devpts filesystem (typically _/dev/pts/ptmx_).
851 For compatibility with older versions of the kernel, the default mode of the new _ptmx_ node is 0000. **ptmxmode=**__value__ specifies a more useful mode for the _ptmx_ node and is highly recommended when the *newinstance* option is specified.
853 This option is only implemented in Linux kernel versions starting with 2.6.29. Further, this option is valid only if *CONFIG_DEVPTS_MULTIPLE_INSTANCES* is enabled in the kernel configuration.
855 === Mount options for fat
857 (Note: _fat_ is not a separate filesystem, but a common part of the _msdos_, _umsdos_ and _vfat_ filesystems.)
859 *blocksize=*{**512**|**1024**|*2048*}::
860 Set blocksize (default 512). This option is obsolete.
862 **uid=**__value__ and **gid=**__value__::
863 Set the owner and group of all files. (Default: the UID and GID of the current process.)
865 **umask=**__value__::
866 Set the umask (the bitmask of the permissions that are *not* present). The default is the umask of the current process. The value is given in octal.
868 **dmask=**__value__::
869 Set the umask applied to directories only. The default is the umask of the current process. The value is given in octal.
871 **fmask=**__value__::
872 Set the umask applied to regular files only. The default is the umask of the current process. The value is given in octal.
874 **allow_utime=**__value__::
875 This option controls the permission check of mtime/atime.
878 If current process is in group of file's group ID, you can change timestamp.
881 Other users can change timestamp.
883 The default is set from 'dmask' option. (If the directory is writable, *utime*(2) is also allowed. I.e. ~dmask & 022)
885 Normally *utime*(2) checks that the current process is owner of the file, or that it has the *CAP_FOWNER* capability. But FAT filesystems don't have UID/GID on disk, so the normal check is too inflexible. With this option you can relax it.
887 **check=**__value__::
888 Three different levels of pickiness can be chosen:
891 Upper and lower case are accepted and equivalent, long name parts are truncated (e.g. _verylongname.foobar_ becomes _verylong.foo_), leading and embedded spaces are accepted in each name part (name and extension).
894 Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are rejected. This is the default.
897 Like "normal", but names that contain long parts or special characters that are sometimes used on Linux but are not accepted by MS-DOS (+, =, etc.) are rejected.
899 **codepage=**__value__::
900 Sets the codepage for converting to shortname characters on FAT and VFAT filesystems. By default, codepage 437 is used.
903 This option is obsolete and may fail or be ignored.
905 **cvf_format=**__module__::
906 Forces the driver to use the CVF (Compressed Volume File) module cvf___module__ instead of auto-detection. If the kernel supports *kmod*, the **cvf_format=**__xxx__ option also controls on-demand CVF module loading. This option is obsolete.
908 **cvf_option=**__option__::
909 Option passed to the CVF module. This option is obsolete.
912 Turn on the _debug_ flag. A version string and a list of filesystem parameters will be printed (these data are also printed if the parameters appear to be inconsistent).
915 If set, causes discard/TRIM commands to be issued to the block device when blocks are freed. This is useful for SSD devices and sparse/thinly-provisioned LUNs.
918 If set, use a fallback default BIOS Parameter Block configuration, determined by backing device size. These static parameters match defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360 kiB floppies and floppy images.
920 *errors=*{**panic**|**continue**|*remount-ro*}::
921 Specify FAT behavior on critical errors: panic, continue without doing anything, or remount the partition in read-only mode (default behavior).
923 *fat=*{**12**|**16**|*32*}::
924 Specify a 12, 16 or 32 bit fat. This overrides the automatic FAT type detection routine. Use with caution!
926 **iocharset=**__value__::
927 Character set to use for converting between 8 bit characters and 16 bit Unicode characters. The default is iso8859-1. Long filenames are stored on disk in Unicode format.
929 *nfs=*{**stale_rw**|*nostale_ro*}::
930 Enable this only if you want to export the FAT filesystem over NFS.
932 *stale_rw*: This option maintains an index (cache) of directory inodes which is used by the nfs-related code to improve look-ups. Full file operations (read/write) over NFS are supported but with cache eviction at NFS server, this could result in spurious *ESTALE* errors.
934 *nostale_ro*: This option bases the inode number and file handle on the on-disk location of a file in the FAT directory entry. This ensures that *ESTALE* will not be returned after a file is evicted from the inode cache. However, it means that operations such as rename, create and unlink could cause file handles that previously pointed at one file to point at a different file, potentially causing data corruption. For this reason, this option also mounts the filesystem readonly.
936 To maintain backward compatibility, *-o nfs* is also accepted, defaulting to *stale_rw*.
939 This option disables the conversion of timestamps between local time (as used by Windows on FAT) and UTC (which Linux uses internally). This is particularly useful when mounting devices (like digital cameras) that are set to UTC in order to avoid the pitfalls of local time.
941 **time_offset=**__minutes__::
942 Set offset for conversion of timestamps from local time used by FAT to UTC. I.e., _minutes_ will be subtracted from each timestamp to convert it to UTC used internally by Linux. This is useful when the time zone set in the kernel via *settimeofday*(2) is not the time zone used by the filesystem. Note that this option still does not provide correct time stamps in all cases in presence of DST - time stamps in a different DST setting will be off by one hour.
945 Turn on the _quiet_ flag. Attempts to chown or chmod files do not return errors, although they fail. Use with caution!
948 FAT has the *ATTR_RO* (read-only) attribute. On Windows, the *ATTR_RO* of the directory will just be ignored, and is used only by applications as a flag (e.g. it's set for the customized folder).
950 If you want to use *ATTR_RO* as read-only flag even for the directory, set this option.
953 If set, the execute permission bits of the file will be allowed only if the extension part of the name is .EXE, .COM, or .BAT. Not set by default.
956 If set, *ATTR_SYS* attribute on FAT is handled as *IMMUTABLE* flag on Linux. Not set by default.
959 If set, the filesystem will try to flush to disk more early than normal. Not set by default.
962 Use the "free clusters" value stored on *FSINFO*. It'll be used to determine number of free clusters without scanning disk. But it's not used by default, because recent Windows don't update it correctly in some case. If you are sure the "free clusters" on *FSINFO* is correct, by this option you can avoid scanning disk.
964 *dots*, *nodots*, *dotsOK=*[**yes**|*no*]::
965 Various misguided attempts to force Unix or DOS conventions onto a FAT filesystem.
967 === Mount options for hfs
969 **creator=**__cccc__**, type=**__cccc__::
970 Set the creator/type values as shown by the MacOS finder used for creating new files. Default values: '????'.
972 **uid=**__n__**, gid=**__n__::
973 Set the owner and group of all files. (Default: the UID and GID of the current process.)
975 **dir_umask=**__n__**, file_umask=**__n__**, umask=**__n__::
976 Set the umask used for all directories, all regular files, or all files and directories. Defaults to the umask of the current process.
979 Select the CDROM session to mount. Defaults to leaving that decision to the CDROM driver. This option will fail with anything but a CDROM as underlying device.
982 Select partition number n from the device. Only makes sense for CDROMs. Defaults to not parsing the partition table at all.
985 Don't complain about invalid mount options.
987 === Mount options for hpfs
989 **uid=**__value__ and **gid=**__value__::
990 Set the owner and group of all files. (Default: the UID and GID of the current process.)
992 **umask=**__value__::
993 Set the umask (the bitmask of the permissions that are *not* present). The default is the umask of the current process. The value is given in octal.
995 *case=*{**lower**|*asis*}::
996 Convert all files names to lower case, or leave them. (Default: *case=lower*.)
999 This option is obsolete and may fail or being ignored.
1002 Do not abort mounting when certain consistency checks fail.
1004 === Mount options for iso9660
1006 ISO 9660 is a standard describing a filesystem structure to be used on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the _udf_ filesystem.)
1008 Normal _iso9660_ filenames appear in an 8.3 format (i.e., DOS-like restrictions on filename length), and in addition all characters are in upper case. Also there is no field for file ownership, protection, number of links, provision for block/character devices, etc.
1010 Rock Ridge is an extension to iso9660 that provides all of these UNIX-like features. Basically there are extensions to each directory record that supply all of the additional information, and when Rock Ridge is in use, the filesystem is indistinguishable from a normal UNIX filesystem (except that it is read-only, of course).
1013 Disable the use of Rock Ridge extensions, even if available. Cf. *map*.
1016 Disable the use of Microsoft Joliet extensions, even if available. Cf. *map*.
1018 *check=*{*r*[*elaxed*]|*s*[*trict*]}::
1019 With *check=relaxed*, a filename is first converted to lower case before doing the lookup. This is probably only meaningful together with *norock* and *map=normal*. (Default: *check=strict*.)
1021 **uid=**__value__ and **gid=**__value__::
1022 Give all files in the filesystem the indicated user or group id, possibly overriding the information found in the Rock Ridge extensions. (Default: *uid=0,gid=0*.)
1024 *map=*{*n*[*ormal*]|*o*[*ff*]|*a*[*corn*]}::
1025 For non-Rock Ridge volumes, normal name translation maps upper to lower case ASCII, drops a trailing ';1', and converts ';' to '.'. With *map=off* no name translation is done. See *norock*. (Default: *map=normal*.) *map=acorn* is like *map=normal* but also apply Acorn extensions if present.
1027 **mode=**__value__::
1028 For non-Rock Ridge volumes, give all files the indicated mode. (Default: read and execute permission for everybody.) Octal mode values require a leading 0.
1031 Also show hidden and associated files. (If the ordinary files and the associated or hidden files have the same filenames, this may make the ordinary files inaccessible.)
1033 *block=*{**512**|**1024**|*2048*}::
1034 Set the block size to the indicated value. (Default: *block=1024*.)
1037 This option is obsolete and may fail or being ignored.
1040 If the high byte of the file length contains other garbage, set this mount option to ignore the high order bits of the file length. This implies that a file cannot be larger than 16 MB.
1043 Select number of session on a multisession CD.
1045 **sbsector=**__xxx__::
1046 Session begins from sector xxx.
1048 The following options are the same as for vfat and specifying them only makes sense when using discs encoded using Microsoft's Joliet extensions.
1050 **iocharset=**__value__::
1051 Character set to use for converting 16 bit Unicode characters on CD to 8 bit characters. The default is iso8859-1.
1054 Convert 16 bit Unicode characters on CD to UTF-8.
1056 === Mount options for jfs
1058 **iocharset=**__name__::
1059 Character set to use for converting from Unicode to ASCII. The default is to do no conversion. Use *iocharset=utf8* for UTF8 translations. This requires *CONFIG_NLS_UTF8* to be set in the kernel _.config_ file.
1061 **resize=**__value__::
1062 Resize the volume to _value_ blocks. JFS only supports growing a volume, not shrinking it. This option is only valid during a remount, when the volume is mounted read-write. The *resize* keyword with no value will grow the volume to the full size of the partition.
1065 Do not write to the journal. The primary use of this option is to allow for higher performance when restoring a volume from backup media. The integrity of the volume is not guaranteed if the system abnormally ends.
1068 Default. Commit metadata changes to the journal. Use this option to remount a volume where the *nointegrity* option was previously specified in order to restore normal behavior.
1070 *errors=*{**continue**|**remount-ro**|*panic*}::
1071 Define the behavior when an error is encountered. (Either ignore errors and just mark the filesystem erroneous and continue, or remount the filesystem read-only, or panic and halt the system.)
1073 **noquota**|**quota**|**usrquota**|*grpquota*::
1074 These options are accepted but ignored.
1076 === Mount options for msdos
1078 See mount options for fat. If the _msdos_ filesystem detects an inconsistency, it reports an error and sets the file system read-only. The filesystem can be made writable again by remounting it.
1080 === Mount options for ncpfs
1082 Just like _nfs_, the _ncpfs_ implementation expects a binary argument (a _struct ncp_mount_data_) to the *mount*(2) system call. This argument is constructed by *ncpmount*(8) and the current version of *mount* (2.12) does not know anything about ncpfs.
1084 === Mount options for ntfs
1086 **iocharset=**__name__::
1087 Character set to use when returning file names. Unlike VFAT, NTFS suppresses names that contain nonconvertible characters. Deprecated.
1090 New name for the option earlier called _iocharset_.
1093 Use UTF-8 for converting file names.
1095 *uni_xlate=*{**0**|**1**|*2*}::
1096 For 0 (or 'no' or 'false'), do not use escape sequences for unknown Unicode characters. For 1 (or 'yes' or 'true') or 2, use vfat-style 4-byte escape sequences starting with ":". Here 2 gives a little-endian encoding and 1 a byteswapped bigendian encoding.
1099 If enabled (posix=1), the filesystem distinguishes between upper and lower case. The 8.3 alias names are presented as hard links instead of being suppressed. This option is obsolete.
1101 **uid=**__value__, **gid=**__value__ and **umask=**__value__::
1102 Set the file permission on the filesystem. The umask value is given in octal. By default, the files are owned by root and not readable by somebody else.
1104 === Mount options for overlay
1106 Since Linux 3.18 the overlay pseudo filesystem implements a union mount for other filesystems.
1108 An overlay filesystem combines two filesystems - an *upper* filesystem and a *lower* filesystem. When a name exists in both filesystems, the object in the upper filesystem is visible while the object in the lower filesystem is either hidden or, in the case of directories, merged with the upper object.
1110 The lower filesystem can be any filesystem supported by Linux and does not need to be writable. The lower filesystem can even be another overlayfs. The upper filesystem will normally be writable and if it is it must support the creation of trusted.* extended attributes, and must provide a valid d_type in readdir responses, so NFS is not suitable.
1112 A read-only overlay of two read-only filesystems may use any filesystem type. The options *lowerdir* and *upperdir* are combined into a merged directory by using:
1116 mount -t overlay overlay \
1117 -olowerdir=/lower,upperdir=/upper,workdir=/work /merged
1121 **lowerdir=**__directory__::
1122 Any filesystem, does not need to be on a writable filesystem.
1124 **upperdir=**__directory__::
1125 The upperdir is normally on a writable filesystem.
1127 **workdir=**__directory__::
1128 The workdir needs to be an empty directory on the same filesystem as upperdir.
1131 Use the "*user.overlay.*" xattr namespace instead of "*trusted.overlay.*". This is useful for unprivileged mounting of overlayfs.
1133 *redirect_dir=*{**on**|**off**|**follow**|**nofollow**}::
1134 If the _redirect_dir_ feature is enabled, then the directory will be copied up (but not the contents). Then the "{**trusted**|**user**}.overlay.redirect" extended attribute is set to the path of the original location from the root of the overlay. Finally the directory is moved to the new location.
1137 Redirects are enabled.
1140 Redirects are not created and only followed if "redirect_always_follow" feature is enabled in the kernel/module config.
1143 Redirects are not created, but followed.
1146 Redirects are not created and not followed (equivalent to "redirect_dir=off" if "redirect_always_follow" feature is not enabled).
1148 *index=*{**on**|**off**}::
1149 Inode index. If this feature is disabled and a file with multiple hard links is copied up, then this will "break" the link. Changes will not be propagated to other names referring to the same inode.
1151 *uuid=*{**on**|**off**}::
1152 Can be used to replace UUID of the underlying filesystem in file handles with null, and effectively disable UUID checks. This can be useful in case the underlying disk is copied and the UUID of this copy is changed. This is only applicable if all lower/upper/work directories are on the same filesystem, otherwise it will fallback to normal behaviour.
1154 *nfs_export=*{**on**|**off**}::
1155 When the underlying filesystems supports NFS export and the "nfs_export"
1156 feature is enabled, an overlay filesystem may be exported to NFS.
1158 With the "nfs_export" feature, on copy_up of any lower object, an index entry
1159 is created under the index directory. The index entry name is the hexadecimal
1160 representation of the copy up origin file handle. For a non-directory object,
1161 the index entry is a hard link to the upper inode. For a directory object, the
1162 index entry has an extended attribute "{**trusted**|**user**}.overlay.upper"
1163 with an encoded file handle of the upper directory inode.
1165 When encoding a file handle from an overlay filesystem object, the following rules apply;;
1167 * For a non-upper object, encode a lower file handle from lower inode
1168 * For an indexed object, encode a lower file handle from copy_up origin
1169 * For a pure-upper object and for an existing non-indexed upper object, encode an upper file handle from upper inode
1172 The encoded overlay file handle includes;;
1174 * Header including path type information (e.g. lower/upper)
1175 * UUID of the underlying filesystem
1176 * Underlying filesystem encoding of underlying inode
1179 This encoding format is identical to the encoding format of file handles that are stored in extended attribute "{**trusted**|**user**}.overlay.origin". When decoding an overlay file handle, the following steps are followed;;
1181 * Find underlying layer by UUID and path type information.
1182 * Decode the underlying filesystem file handle to underlying dentry.
1183 * For a lower file handle, lookup the handle in index directory by name.
1184 * If a whiteout is found in index, return **ESTALE**. This represents an overlay object that was deleted after its file handle was encoded.
1185 * For a non-directory, instantiate a disconnected overlay dentry from the decoded underlying dentry, the path type and index inode, if found.
1186 * For a directory, use the connected underlying decoded dentry, path type and index, to lookup a connected overlay dentry.
1190 Decoding a non-directory file handle may return a disconnected dentry. copy_up
1191 of that disconnected dentry will create an upper index entry with no upper
1194 When overlay filesystem has multiple lower layers, a middle layer directory may
1195 have a "redirect" to lower directory. Because middle layer "redirects" are not
1196 indexed, a lower file handle that was encoded from the "redirect" origin
1197 directory, cannot be used to find the middle or upper layer directory.
1198 Similarly, a lower file handle that was encoded from a descendant of the
1199 "redirect" origin directory, cannot be used to reconstruct a connected overlay
1200 path. To mitigate the cases of directories that cannot be decoded from a lower
1201 file handle, these directories are copied up on encode and encoded as an upper
1202 file handle. On an overlay filesystem with no upper layer this mitigation
1203 cannot be used NFS export in this setup requires turning off redirect follow
1204 (e.g. "__redirect_dir=nofollow__").
1206 The overlay filesystem does not support non-directory connectable file handles, so exporting with the _subtree_check_ exportfs configuration will cause failures to lookup files over NFS.
1208 When the NFS export feature is enabled, all directory index entries are verified on mount time to check that upper file handles are not stale. This verification may cause significant overhead in some cases.
1210 Note: the mount options __index=off,nfs_export=on__ are conflicting for a
1211 read-write mount and will result in an error.
1214 *xino=*{**on**|**off**|**auto**}::
1215 The "xino" feature composes a unique object identifier from the real object st_ino and an underlying fsid index. The "xino" feature uses the high inode number bits for fsid, because the underlying filesystems rarely use the high inode number bits. In case the underlying inode number does overflow into the high xino bits, overlay filesystem will fall back to the non xino behavior for that inode.
1217 For a detailed description of the effect of this option please refer to https://docs.kernel.org/filesystems/overlayfs.html
1219 *metacopy=*{**on**|**off**}::
1220 When metadata only copy up feature is enabled, overlayfs will only copy up metadata (as opposed to whole file), when a metadata specific operation like chown/chmod is performed. Full file will be copied up later when file is opened for WRITE operation.
1222 In other words, this is delayed data copy up operation and data is copied up when there is a need to actually modify data.
1225 Volatile mounts are not guaranteed to survive a crash. It is strongly recommended that volatile mounts are only used if data written to the overlay can be recreated without significant effort.
1227 The advantage of mounting with the "volatile" option is that all forms of sync calls to the upper filesystem are omitted.
1229 In order to avoid a giving a false sense of safety, the syncfs (and fsync) semantics of volatile mounts are slightly different than that of the rest of VFS. If any writeback error occurs on the upperdir’s filesystem after a volatile mount takes place, all sync functions will return an error. Once this condition is reached, the filesystem will not recover, and every subsequent sync call will return an error, even if the upperdir has not experience a new error since the last sync call.
1231 When overlay is mounted with "volatile" option, the directory "$workdir/work/incompat/volatile" is created. During next mount, overlay checks for this directory and refuses to mount if present. This is a strong indicator that user should throw away upper and work directories and create fresh one. In very limited cases where the user knows that the system has not crashed and contents of upperdir are intact, The "volatile" directory can be removed.
1233 === Mount options for reiserfs
1235 Reiserfs is a journaling filesystem.
1238 Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem, using the 3.6 format for newly created objects. This filesystem will no longer be compatible with reiserfs 3.5 tools.
1240 *hash=*{**rupasov**|**tea**|**r5**|*detect*}::
1241 Choose which hash function reiserfs will use to find files within directories.
1244 A hash invented by Yury Yu. Rupasov. It is fast and preserves locality, mapping lexicographically close file names to close hash values. This option should not be used, as it causes a high probability of hash collisions.
1247 A Davis-Meyer function implemented by Jeremy Fitzhardinge. It uses hash permuting bits in the name. It gets high randomness and, therefore, low probability of hash collisions at some CPU cost. This may be used if *EHASHCOLLISION* errors are experienced with the r5 hash.
1250 A modified version of the rupasov hash. It is used by default and is the best choice unless the filesystem has huge directories and unusual file-name patterns.
1253 Instructs *mount* to detect which hash function is in use by examining the filesystem being mounted, and to write this information into the reiserfs superblock. This is only useful on the first mount of an old format filesystem.
1255 *hashed_relocation*::
1256 Tunes the block allocator. This may provide performance improvements in some situations.
1258 *no_unhashed_relocation*::
1259 Tunes the block allocator. This may provide performance improvements in some situations.
1262 Disable the border allocator algorithm invented by Yury Yu. Rupasov. This may provide performance improvements in some situations.
1265 Disable journaling. This will provide slight performance improvements in some situations at the cost of losing reiserfs's fast recovery from crashes. Even with this option turned on, reiserfs still performs all journaling operations, save for actual writes into its journaling area. Implementation of _nolog_ is a work in progress.
1268 By default, reiserfs stores small files and 'file tails' directly into its tree. This confuses some utilities such as *lilo*(8). This option is used to disable packing of files into the tree.
1271 Replay the transactions which are in the journal, but do not actually mount the filesystem. Mainly used by _reiserfsck_.
1273 **resize=**__number__::
1274 A remount option which permits online expansion of reiserfs partitions. Instructs reiserfs to assume that the device has _number_ blocks. This option is designed for use with devices which are under logical volume management (LVM). There is a special _resizer_ utility which can be obtained from _ftp://ftp.namesys.com/pub/reiserfsprogs_.
1277 Enable Extended User Attributes. See the *attr*(1) manual page.
1280 Enable POSIX Access Control Lists. See the *acl*(5) manual page.
1282 *barrier=none* / *barrier=flush*::
1283 This disables / enables the use of write barriers in the journaling code. *barrier=none* disables, *barrier=flush* enables (default). This also requires an IO stack which can support barriers, and if reiserfs gets an error on a barrier write, it will disable barriers again with a warning. Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some performance penalty. If your disks are battery-backed in one way or another, disabling barriers may safely improve performance.
1285 === Mount options for ubifs
1287 UBIFS is a flash filesystem which works on top of UBI volumes. Note that *atime* is not supported and is always turned off.
1289 The device name may be specified as
1293 UBI device number *X*, volume number *Y*
1295 UBI device number *0*, volume number *Y*
1297 UBI device number *X*, volume with name *NAME*
1299 UBI device number *0*, volume with name *NAME*
1302 Alternative *!* separator may be used instead of *:*.
1304 The following mount options are available:
1307 Enable bulk-read. VFS read-ahead is disabled because it slows down the filesystem. Bulk-Read is an internal optimization. Some flashes may read faster if the data are read at one go, rather than at several read requests. For example, OneNAND can do "read-while-load" if it reads more than one NAND page.
1310 Do not bulk-read. This is the default.
1313 Check data CRC-32 checksums. This is the default.
1316 Do not check data CRC-32 checksums. With this option, the filesystem does not check CRC-32 checksum for data, but it does check it for the internal indexing information. This option only affects reading, not writing. CRC-32 is always calculated when writing the data.
1318 *compr=*{**none**|**lzo**|*zlib*}::
1319 Select the default compressor which is used when new files are written. It is still possible to read compressed files if mounted with the *none* option.
1321 === Mount options for udf
1323 UDF is the "Universal Disk Format" filesystem defined by OSTA, the Optical Storage Technology Association, and is often used for DVD-ROM, frequently in the form of a hybrid UDF/ISO-9660 filesystem. It is, however, perfectly usable by itself on disk drives, flash drives and other block devices. See also _iso9660_.
1326 Make all files in the filesystem belong to the given user. uid=forget can be specified independently of (or usually in addition to) uid=<user> and results in UDF not storing uids to the media. In fact the recorded uid is the 32-bit overflow uid -1 as defined by the UDF standard. The value is given as either <user> which is a valid user name or the corresponding decimal user id, or the special string "forget".
1329 Make all files in the filesystem belong to the given group. gid=forget can be specified independently of (or usually in addition to) gid=<group> and results in UDF not storing gids to the media. In fact the recorded gid is the 32-bit overflow gid -1 as defined by the UDF standard. The value is given as either <group> which is a valid group name or the corresponding decimal group id, or the special string "forget".
1332 Mask out the given permissions from all inodes read from the filesystem. The value is given in octal.
1335 If *mode=* is set the permissions of all non-directory inodes read from the filesystem will be set to the given mode. The value is given in octal.
1338 If *dmode=* is set the permissions of all directory inodes read from the filesystem will be set to the given dmode. The value is given in octal.
1341 Set the block size. Default value prior to kernel version 2.6.30 was 2048. Since 2.6.30 and prior to 4.11 it was logical device block size with fallback to 2048. Since 4.11 it is logical block size with fallback to any valid block size between logical device block size and 4096.
1343 For other details see the *mkudffs*(8) 2.0+ manpage, see the *COMPATIBILITY* and *BLOCK SIZE* sections.
1346 Show otherwise hidden files.
1349 Show deleted files in lists.
1352 Embed data in the inode. (default)
1355 Don't embed data in the inode.
1358 Use short UDF address descriptors.
1361 Use long UDF address descriptors. (default)
1364 Unset strict conformance.
1367 Set the NLS character set. This requires kernel compiled with *CONFIG_UDF_NLS* option.
1370 Set the UTF-8 character set.
1372 === Mount options for debugging and disaster recovery
1375 Ignore the Volume Recognition Sequence and attempt to mount anyway.
1378 Select the session number for multi-session recorded optical media. (default= last session)
1381 Override standard anchor location. (default= 256)
1384 Set the last block of the filesystem.
1386 === Unused historical mount options that may be encountered and should be removed
1389 Ignored, use uid=<user> instead.
1392 Ignored, use gid=<group> instead.
1395 Unimplemented and ignored.
1398 Unimplemented and ignored.
1401 Unimplemented and ignored.
1404 Unimplemented and ignored.
1406 === Mount options for ufs
1408 **ufstype=**__value__::
1409 UFS is a filesystem widely used in different operating systems. The problem are differences among implementations. Features of some implementations are undocumented, so its hard to recognize the type of ufs automatically. That's why the user must specify the type of ufs by mount option. Possible values are:
1412 Old format of ufs, this is the default, read only. (Don't forget to give the *-r* option.)
1415 For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD).
1418 Used in FreeBSD 5.x supported as read-write.
1424 For filesystems created by SunOS or Solaris on Sparc.
1427 For filesystems created by Solaris on x86.
1430 For filesystems created by HP-UX, read-only.
1433 For filesystems created by NeXTStep (on NeXT station) (currently read only).
1436 For NextStep CDROMs (block_size == 2048), read-only.
1439 For filesystems created by OpenStep (currently read only). The same filesystem type is also used by macOS.
1441 **onerror=**__value__::
1442 Set behavior on error:
1445 If an error is encountered, cause a kernel panic.
1447 [**lock**|**umount**|*repair*];;
1448 These mount options don't do anything at present; when an error is encountered only a console message is printed.
1450 === Mount options for umsdos
1452 See mount options for msdos. The *dotsOK* option is explicitly killed by _umsdos_.
1454 === Mount options for vfat
1456 First of all, the mount options for _fat_ are recognized. The *dotsOK* option is explicitly killed by _vfat_. Furthermore, there are
1459 Translate unhandled Unicode characters to special escaped sequences. This lets you backup and restore filenames that are created with any Unicode characters. Without this option, a '?' is used when no translation is possible. The escape character is ':' because it is otherwise invalid on the vfat filesystem. The escape sequence that gets used, where u is the Unicode character, is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
1462 Allow two files with names that only differ in case. This option is obsolete.
1465 First try to make a short name without sequence number, before trying _name~num.ext_.
1468 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the console. It can be enabled for the filesystem with this option or disabled with utf8=0, utf8=no or utf8=false. If _uni_xlate_ gets set, UTF8 gets disabled.
1470 **shortname=**__mode__::
1471 Defines the behavior for creation and display of filenames which fit into 8.3 characters. If a long name for a file exists, it will always be the preferred one for display. There are four __mode__s:
1474 Force the short name to lower case upon display; store a long name when the short name is not all upper case.
1477 Force the short name to upper case upon display; store a long name when the short name is not all upper case.
1480 Display the short name as is; store a long name when the short name is not all lower case or all upper case.
1483 Display the short name as is; store a long name when the short name is not all upper case. This mode is the default since Linux 2.6.32.
1485 === Mount options for usbfs
1487 **devuid=**__uid__ and **devgid=**__gid__ and **devmode=**__mode__::
1488 Set the owner and group and mode of the device files in the usbfs filesystem (default: uid=gid=0, mode=0644). The mode is given in octal.
1490 **busuid=**__uid__ and **busgid=**__gid__ and **busmode=**__mode__::
1491 Set the owner and group and mode of the bus directories in the usbfs filesystem (default: uid=gid=0, mode=0555). The mode is given in octal.
1493 **listuid=**__uid__ and **listgid=**__gid__ and **listmode=**__mode__::
1494 Set the owner and group and mode of the file _devices_ (default: uid=gid=0, mode=0444). The mode is given in octal.
1496 == DM-VERITY SUPPORT
1498 The device-mapper verity target provides read-only transparent integrity checking of block devices using kernel crypto API. The *mount* command can open the dm-verity device and do the integrity verification before the device filesystem is mounted. Requires libcryptsetup with in libmount (optionally via *dlopen*(3)). If libcryptsetup supports extracting the root hash of an already mounted device, existing devices will be automatically reused in case of a match. Mount options for dm-verity:
1500 **verity.hashdevice=**__path__::
1501 Path to the hash tree device associated with the source volume to pass to dm-verity.
1503 **verity.roothash=**__hex__::
1504 Hex-encoded hash of the root of _verity.hashdevice_. Mutually exclusive with _verity.roothashfile._
1506 **verity.roothashfile=**__path__::
1507 Path to file containing the hex-encoded hash of the root of _verity.hashdevice._ Mutually exclusive with _verity.roothash._
1509 **verity.hashoffset=**__offset__::
1510 If the hash tree device is embedded in the source volume, _offset_ (default: 0) is used by dm-verity to get to the tree.
1512 **verity.fecdevice=**__path__::
1513 Path to the Forward Error Correction (FEC) device associated with the source volume to pass to dm-verity. Optional. Requires kernel built with *CONFIG_DM_VERITY_FEC*.
1515 **verity.fecoffset=**__offset__::
1516 If the FEC device is embedded in the source volume, _offset_ (default: 0) is used by dm-verity to get to the FEC area. Optional.
1518 **verity.fecroots=**__value__::
1519 Parity bytes for FEC (default: 2). Optional.
1521 **verity.roothashsig=**__path__::
1522 Path to *pkcs7*(1ssl) signature of root hash hex string. Requires crypt_activate_by_signed_key() from cryptsetup and kernel built with *CONFIG_DM_VERITY_VERIFY_ROOTHASH_SIG*. For device reuse, signatures have to be either used by all mounts of a device or by none. Optional.
1524 **verity.oncorruption=**__ignore__|__restart__|__panic__::
1525 Instruct the kernel to ignore, reboot or panic when corruption is detected. By default the I/O operation simply fails. Requires Linux 4.1 or newer, and libcrypsetup 2.3.4 or newer. Optional.
1527 Supported since util-linux v2.35.
1529 For example commands:
1532 mksquashfs /etc /tmp/etc.squashfs
1533 dd if=/dev/zero of=/tmp/etc.hash bs=1M count=10
1534 veritysetup format /tmp/etc.squashfs /tmp/etc.hash
1535 openssl smime -sign -in <hash> -nocerts -inkey private.key \
1536 -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s
1537 mount -o verity.hashdevice=/tmp/etc.hash,verity.roothash=<hash>,\
1538 verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.squashfs /mnt
1541 create squashfs image from _/etc_ directory, verity hash device and mount verified filesystem image to _/mnt_. The kernel will verify that the root hash is signed by a key from the kernel keyring if roothashsig is used.
1543 == LOOP-DEVICE SUPPORT
1545 One further possible type is a mount via the loop device. For example, the command
1548 *mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3*
1551 will set up the loop device _/dev/loop3_ to correspond to the file _/tmp/disk.img_, and then mount this device on _/mnt_.
1553 If no explicit loop device is mentioned (but just an option '**-o loop**' is given), then *mount* will try to find some unused loop device and use that, for example
1556 *mount /tmp/disk.img /mnt -o loop*
1559 The *mount* command *automatically* creates a loop device from a regular file if a filesystem type is not specified or the filesystem is known for libblkid, for example:
1562 *mount /tmp/disk.img /mnt*
1564 *mount -t ext4 /tmp/disk.img /mnt*
1567 This type of mount knows about three options, namely *loop*, *offset* and *sizelimit*, that are really options to *losetup*(8). (These options can be used in addition to those specific to the filesystem type.)
1569 Since Linux 2.6.25 auto-destruction of loop devices is supported, meaning that any loop device allocated by *mount* will be freed by *umount* independently of _/etc/mtab_.
1571 You can also free a loop device by hand, using *losetup -d* or *umount -d*.
1573 Since util-linux v2.29, *mount* re-uses the loop device rather than initializing a new device if the same backing file is already used for some loop device with the same offset and sizelimit. This is necessary to avoid a filesystem corruption.
1577 *mount* has the following exit status values (the bits can be ORed):
1583 incorrect invocation or permissions
1586 system error (out of memory, cannot fork, no more loop devices)
1589 internal *mount* bug
1595 problems writing or locking _/etc/mtab_
1601 some mount succeeded
1603 The command *mount -a* returns 0 (all succeeded), 32 (all failed), or 64 (some failed, some succeeded).
1607 The syntax of external mount helpers is:
1609 **/sbin/mount.**__suffix__ _spec dir_ [*-sfnv*] [*-N* _namespace_] [*-o* _options_] [*-t* __type__**.**_subtype_]
1611 where the _suffix_ is the filesystem type and the *-sfnvoN* options have the same meaning as the normal mount options. The *-t* option is used for filesystems with subtypes support (for example */sbin/mount.fuse -t fuse.sshfs*).
1613 The command *mount* does not pass the mount options *unbindable*, *runbindable*, *private*, *rprivate*, *slave*, *rslave*, *shared*, *rshared*, *auto*, *noauto*, *comment*, *x-**, *loop*, *offset* and *sizelimit* to the mount.<suffix> helpers. All other options are used in a comma-separated list as an argument to the *-o* option.
1617 *LIBMOUNT_FSTAB*=<path>::
1618 overrides the default location of the _fstab_ file (ignored for suid)
1620 *LIBMOUNT_DEBUG*=all::
1621 enables libmount debug output
1623 *LIBBLKID_DEBUG*=all::
1624 enables libblkid debug output
1626 *LOOPDEV_DEBUG*=all::
1627 enables loop device setup debug output
1631 See also "*The files /etc/fstab, /etc/mtab and /proc/mounts*" section above.
1637 libmount private runtime directory
1640 table of mounted filesystems or symlink to _/proc/mounts_
1643 lock file (unused on systems with _mtab_ symlink)
1646 temporary file (unused on systems with _mtab_ symlink)
1648 _/etc/filesystems_::
1649 a list of filesystem types to try
1653 A *mount* command existed in Version 5 AT&T UNIX.
1657 It is possible for a corrupted filesystem to cause a crash.
1659 Some Linux filesystems don't support *-o sync* and *-o dirsync* (the ext2, ext3, ext4, fat and vfat filesystems _do_ support synchronous updates (a la BSD) when mounted with the *sync* option).
1661 The *-o remount* may not be able to change mount parameters (all _ext2fs_-specific parameters, except *sb*, are changeable with a remount, for example, but you can't change *gid* or *umask* for the _fatfs_).
1663 It is possible that the files _/etc/mtab_ and _/proc/mounts_ don't match on systems with a regular _mtab_ file. The first file is based only on the *mount* command options, but the content of the second file also depends on the kernel and others settings (e.g. on a remote NFS server -- in certain cases the *mount* command may report unreliable information about an NFS mount point and the _/proc/mount_ file usually contains more reliable information.) This is another reason to replace the _mtab_ file with a symlink to the _/proc/mounts_ file.
1665 Checking files on NFS filesystems referenced by file descriptors (i.e. the *fcntl* and *ioctl* families of functions) may lead to inconsistent results due to the lack of a consistency check in the kernel even if the *noac* mount option is used.
1667 The *loop* option with the *offset* or *sizelimit* options used may fail when using older kernels if the *mount* command can't confirm that the size of the block device has been configured as requested. This situation can be worked around by using the *losetup*(8) command manually before calling *mount* with the configured loop device.
1671 mailto:kzak@redhat.com[Karel Zak]
1681 *mount_namespaces*(7),
1695 include::man-common/bugreports.adoc[]
1697 include::man-common/footer.adoc[]
1699 ifdef::translation[]
1700 include::man-common/translation.adoc[]