mount(8) — Linux manual page


MOUNT(8)                  System Administration                 MOUNT(8)

NAME         top

       mount - mount a filesystem

SYNOPSIS         top

       mount [-h|-V]

       mount [-l] [-t fstype]

       mount -a [-fFnrsvw] [-t fstype] [-O optlist]

       mount [-fnrsvw] [-o options] device|mountpoint

       mount [-fnrsvw] [-t fstype] [-o options] device mountpoint

       mount --bind|--rbind|--move olddir newdir


DESCRIPTION         top

       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.

       The standard form of the mount command is:

          mount -t type device dir

       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.

       If only the directory or the device is given, for example:

          mount /dir

       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:

          mount --target /mountpoint

       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

   Listing the mounts
       The listing mode is maintained for backward compatibility only.

       For more robust and customizable output use findmnt(8),
       especially in your scripts. Note that control characters in the
       mountpoint name are replaced with '?'.

       The following command lists all mounted filesystems (of type

          mount [-l] [-t type]

       The option -l adds labels to this listing. See below.

   Indicating the device and filesystem
       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

       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):

           Human readable filesystem identifier. See also -L.

           Filesystem universally unique identifier. The format of the
           UUID is usually a series of hex digits separated by hyphens.
           See also -U.

           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.

           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).

           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).

           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.

       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

       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.

       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).

       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.)

   The files /etc/fstab, /etc/mtab and /proc/mounts
       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).

       The command

          mount -a [-t type] [-O optlist]

       (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.

       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.

       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.

       If no arguments are given to mount, the list of mounted
       filesystems is printed.

       If you want to override mount options from /etc/fstab, you have
       to use the -o option:

          mount device|dir -o options

       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.

       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:

          mount /dev/foo /dir

       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.

   Non-superuser mounts
       Normally, only the superuser can mount filesystems. However, when
       fstab contains the user option on a line, anybody can mount the
       corresponding filesystem.

       Thus, given a line

          /dev/cdrom /cd iso9660 ro,user,noauto,unhide

       any user can mount the iso9660 filesystem found on an inserted
       CDROM using the command:

          mount /cd

       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

       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).

       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.

       The user mount option is accepted if no username is specified. If
       used in the format user=someone, the option is silently ignored
       and visible only for external mount helpers (/sbin/mount.<type>)
       for compatibility with some network filesystems.

   Bind mount operation
       Remount part of the file hierarchy somewhere else. The call is:

          mount --bind olddir newdir

       or by using this fstab entry:

          /olddir /newdir none bind

       After this call the same contents are accessible in two places.

       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.

       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:

          mount --bind foo foo

       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:

          mount --rbind olddir newdir

       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.

       Since util-linux 2.27 mount permits changing the mount options by
       passing the relevant options along with --bind. For example:

          mount -o bind,ro foo foo

       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.

       The alternative (classic) way to create a read-only bind mount is
       to use the remount operation, for example:

          mount --bind olddir newdir

          mount -o remount,bind,ro olddir newdir

       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.

       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

       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.

       Since util-linux 2.40, mount does not canonicalize the mountpoint
       path on bind operation if the target is a symlink. This feature
       is usable (only) with the new kernel mount API where bind mount
       over symlinks is supported.

   The move operation
       Move a mounted tree to another place (atomically). The call is:

          mount --move olddir newdir

       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

       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.

   Shared subtree operations
       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).

       Supported operations are:

           mount --make-shared mountpoint
           mount --make-slave mountpoint
           mount --make-private mountpoint
           mount --make-unbindable mountpoint

       The following commands allow one to recursively change the type
       of all the mounts under a given mountpoint.

           mount --make-rshared mountpoint
           mount --make-rslave mountpoint
           mount --make-rprivate mountpoint
           mount --make-runbindable mountpoint

       mount does not read fstab(5) when a --make-* operation is
       requested. All necessary information has to be specified on the
       command line.

       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.

       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).

       For example:

           mount --make-private --make-unbindable /dev/sda1 /foo

       is the same as:

           mount /dev/sda1 /foo
           mount --make-private /foo
           mount --make-unbindable /foo


       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.

       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

       Command-line options available for the mount command are:

       -a, --all
           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.

           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.

           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.

           Since version 2.35 it is possible to use the command line
           option -o to alter mount options from fstab (see also

           Note that it is a bad practice to use mount -a for fstab
           checking. The recommended solution is findmnt --verify.

       -B, --bind
           Remount a subtree somewhere else (so that its contents are
           available in both places). See above, under Bind mount

       -c, --no-canonicalize
           Don’t canonicalize paths. The mount command canonicalizes all
           paths (from the command line or fstab) by default. 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.

           Since util-linux 2.40, mount does not canonicalize the
           mountpoint path on bind operation if the target is a symlink
           (see "Bind mount operation" section for more details).

           Note that mount does not pass this option to the
           /sbin/mount.type helpers.

       -F, --fork
           (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.

       -f, --fake
           Causes everything to be done except for the mount-related
           system calls. The --fake option was originally designed to
           write an entry to /etc/mtab without actually mounting.

           The /etc/mtab is no longer maintained in userspace, and
           starting from version 2.39, the mount operation can be a
           complex chain of operations with dependencies between the
           syscalls. The --fake option forces libmount to skip all mount
           source preparation, mount option analysis, and the actual
           mounting process.

           The difference between fake and non-fake execution is huge.
           This is the reason why the --fake option has minimal
           significance for the current mount(8) implementation and it
           is maintained mostly for backward compatibility.

       -i, --internal-only
           Don’t call the /sbin/mount.filesystem helper even if it

       -L, --label label
           Mount the partition that has the specified label.

       -l, --show-labels
           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).

       -M, --move
           Move a subtree to some other place. See above, the subsection
           The move operation.

       -m, --mkdir[=mode]
           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.

       --map-groups, --map-users inner:_outer_:_count_
           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.

       --map-users /proc/PID/ns/user
           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.

       -n, --no-mtab
           Mount without writing in /etc/mtab. This is necessary for
           example when /etc is on a read-only filesystem.

       -N, --namespace ns
           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.

           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.

           See mount_namespaces(7) for more information.

       -O, --test-opts opts
           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

           mount -a -O no_netdev

           mounts all filesystems except those which have the option
           netdev specified in the options field in the /etc/fstab file.

           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.

           The -t and -O options are cumulative in effect; that is, the

           mount -a -t ext2 -O  _netdev

           mounts all ext2 filesystems with the _netdev option, not all
           filesystems that are either ext2 or have the _netdev option

       -o, --options opts
           Use the specified mount options. The opts argument is a
           comma-separated list. For example:

           mount LABEL=mydisk -o noatime,nodev,nosuid

           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

           For more details, see the FILESYSTEM-INDEPENDENT MOUNT

           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.

       --options-mode mode
           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.

       --options-source source
           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

           Use options from fstab/mtab even if both device and dir are

       -R, --rbind
           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.

       -r, --read-only
           Mount the filesystem read-only. A synonym is -o ro.

           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.

           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.

       --source device
           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.

       --target directory
           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.

       --target-prefix directory
           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:

           mount --all --target-prefix /chroot -o X-mount.mkdir

           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.

       -T, --fstab path
           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.

           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.

       -t, --types fstype
           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.

           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
           '' is deprecated).

           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 *, mount will read /proc/filesystems
           afterwards. While trying, all filesystem types will be
           mounted with the mount option silent.

           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.

           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.

           The prefix no can be meaningful with the -a option. For
           example, the command

           mount -a -t nomsdos,smbfs

           mounts all filesystems except those of type msdos and smbfs.

           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.

       -U, --uuid uuid
           Mount the partition that has the specified uuid.

       -v, --verbose
           Verbose mode.

       -w, --rw, --read-write
           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.

           A synonym is -o rw.

           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.

       -h, --help
           Display help text and exit.

       -V, --version
           Print version and exit.


       Some of these options are only useful when they appear in the
       /etc/fstab file.

       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 extN filesystems).

       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:

              findmnt -o TARGET,VFS-OPTIONS,FS-OPTIONS

       to get a complete overview of filesystems and VFS options.

       The read-only setting (ro or rw) is interpreted by VFS and the
       filesystem and depends on how the option is specified on the
       mount(8) command line. The default is to interpret it on the
       filesystem level. The operation "-o bind,remount,ro" is applied
       only to the VFS mountpoint, and operation "-o remount,ro" is
       applied to VFS and filesystem superblock. This semantic allows
       create a read-only mountpoint but keeps the filesystem writable
       from another mountpoint.

       Since v2.39 libmount can use a new kernel mount interface to set
       the VFS options recursive. For backward compatibility, this
       feature is not enabled by default, although recursive operation
       (e.g. rbind) has been requested. The new option argument
       "recursive" could be specified, for example:

              mount -orbind,ro=recursive,noexec=recursive,nosuid /foo /bar

       recursively binds filesystems from /foo to /bar, /bar, and all
       submounts will be read-only and noexec, but only /bar itself will
       be "nosuid". The "recursive" optional argument for VFS mount
       options is an EXPERIMENTAL feature.

       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):

           All I/O to the filesystem should be done asynchronously. (See
           also the sync option.)

           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.

           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.

           Can be mounted with the -a option.

           Can only be mounted explicitly (i.e., the -a option will not
           cause the filesystem to be mounted).

       context=context, fscontext=context, defcontext=context, and
           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.

           A commonly used option for removable media is

           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.

           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.

           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

           Note that the kernel rejects any remount request that
           includes the context option, even when unchanged from the
           current context.

           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:

                  mount -t tmpfs none /mnt -o \

       For more details, see selinux(8).

           Use the default options: rw, suid, dev, exec, auto, nouser,
           and async.

           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.

           Interpret character or block special devices on the

           Do not interpret character or block special devices on the

           Update directory inode access times on this filesystem. This
           is the default. (This option is ignored when noatime is set.)

           Do not update directory inode access times on this
           filesystem. (This option is implied when noatime is set.)

           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).

           Permit execution of binaries and other executable files.

           Do not permit direct execution of any binaries on the mounted

           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).

           Every time the inode is modified, the i_version field will be

           Do not increment the i_version inode field.

           Allow mandatory locks on this filesystem. See fcntl(2). This
           option was deprecated in Linux 5.15.

           Do not allow mandatory locks on this filesystem.

           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

           Do not report errors for this device if it does not exist.

           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.)

           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.

           Do not use the relatime feature. See also the strictatime
           mount option.

           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.

           Use the kernel’s default behavior for inode access time

           Only update times (atime, mtime, ctime) on the in-memory
           version of the file inode.

           This mount option significantly reduces writes to the inode
           table for workloads that perform frequent random writes to
           preallocated files.

           The on-disk timestamps are updated only when:

           •   the inode needs to be updated for some change unrelated
               to file timestamps

           •   the application employs fsync(2), syncfs(2), or sync(2)

           •   an undeleted inode is evicted from memory

           •   more than 24 hours have passed since the inode was
               written to disk.

           Do not use the lazytime feature.

           Honor set-user-ID and set-group-ID bits or file capabilities
           when executing programs from this filesystem.

           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

           Turn on the silent flag.

           Turn off the silent flag.

           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).

           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.

           The remount operation together with the bind flag has special
           semantics. See above, the subsection Bind mount operation.

           The default kernel behavior for VFS mount flags
           (nodev,nosuid,noexec,ro) is to reset all unspecified flags on
           remount. That’s why mount(8) tries to keep the current
           setting according to fstab or /proc/self/mountinfo. This
           default behavior is possible to change by --options-mode. The
           recursive change of the mount flags (supported since v2.39 on
           systems with mount_setattr(2) syscall), for example, mount -o
           remount,ro=recursive, do not use "reset-unspecified"
           behavior, and it works as a simple add/remove operation and
           unspecified flags are not modified.

           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.

           mount -o remount,rw /dev/foo /dir

           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.

           mount -o remount,rw /dir

           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

           mount allows the use of --all to remount all already mounted
           filesystems which match a specified filter (-O and -t). For

           mount --all -o remount,ro -t vfat

           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.

           Mount the filesystem read-only.

           Mount the filesystem read-write.

           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.

           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).

           Forbid an ordinary user to mount the filesystem. This is the
           default; it does not imply any other options.

           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

           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.

           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).

           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.
           Specifies allowed or forbidden filesystem types for automatic
           filesystem detection.

           The list is a comma-separated list of the filesystem names.
           The automatic filesystem detection is triggered by the "auto"
           filesystem type or when the filesystem type is not specified.

           Thy list follows how mount evaluates type patterns (see -t
           for more details). Only specified filesystem types are
           allowed, or all specified types are forbidden if the list is
           prefixed by "no".

           For example,"ext4,btrfs" accepts only
           ext4 and btrfs, and"novfat,xfs" accepts
           all filesystems except vfat and xfs.

           Note that comma is used as a separator between mount options,
           it means that auto-fstypes values have to be properly quoted,
           don’t forget that the shell strips off quotes and thus double
           quoting is required. For example:

          mount -t auto -o’"noext2,ext3"'
          /dev/sdc1 /mnt/test

           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.

           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)

           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.

           This feature is EXPERIMENTAL.

           Set mountpoint's ownership after mounting. Names resolved in
           the target mount namespace, see -N.

           Set mountpoint's mode after mounting.

       [id-type:id-mount:id-host:id-range], X-mount.idmap=file
           Use this option to create an idmapped mount. An idmapped
           mount allows to change ownership of all files located under a
           mount according to the ID-mapping associated with a user
           namespace. The ownership change is tied to the lifetime and
           localized to the relevant mount. The relevant ID-mapping can
           be specified in two ways:

           •   A user can specify the ID-mapping directly.

               The ID-mapping must be specified using the syntax
               id-type:id-mount:id-host:id-range. 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. The id-mount parameter
               indicates the starting ID in the new mount. The id-host
               parameter indicates the starting ID in the filesystem.
               The id-range parameter indicates how many IDs are to be
               mapped. It is possible to specify multiple ID-mappings.
               The individual ID-mappings must be separated by spaces.

               For example, the ID-mapping X-mount.idmap=u:1000:0:1
               g:1001:1:2 5000:1000:2 creates an idmapped mount where
               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.

               When an ID-mapping is specified directly a new user
               namespace will be allocated with the requested
               ID-mapping. The newly created user namespace will be
               attached to the mount.

           •   A user can specify a user namespace file.

               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.

               For example, X-mount.idmap=/proc/PID/ns/user will attach
               the user namespace of the process PID to the mount.

           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.


       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.
       │                  │               │
       │ Filesystem(s)    Manual page   │
       │                  │               │
       │ btrfs            │ btrfs(5)      │
       │                  │               │
       │ cifs             │ mount.cifs(8) │
       │                  │               │
       │ ext2, ext3, ext4 │ ext4(5)       │
       │                  │               │
       │ fuse             │ fuse(8)       │
       │                  │               │
       │ nfs              │ nfs(5)        │
       │                  │               │
       │ tmpfs            │ tmpfs(5)      │
       │                  │               │
       │ xfs              │ xfs(5)        │

       Note that some of the pages listed above might be available only
       after you install the respective userland tools.

       The following options apply only to certain filesystems. We sort
       them by filesystem. All options follow the -o flag.

       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.

   Mount options for adfs
       uid=value and gid=value
           Set the owner and group of the files in the filesystem
           (default: uid=gid=0).

       ownmask=value and othmask=value
           Set the permission mask for ADFS 'owner' permissions and
           'other' permissions, respectively (default: 0700 and 0077,
           respectively). See also

   Mount options for affs
       uid=value and gid=value
           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

       setuid=value and setgid=value
           Set the owner and group of all files.

           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.

           Do not allow any changes to the protection bits on the

           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...

           Print an informational message for each successful mount.

           Prefix used before volume name, when following a link.

           Prefix (of length at most 30) used before '/' when following
           a symbolic link.

           (Default: 2.) Number of unused blocks at the start of the

           Give explicitly the location of the root block.

           Give blocksize. Allowed values are 512, 1024, 2048, 4096.

           These options are accepted but ignored. (However, quota
           utilities may react to such strings in /etc/fstab.)

   Mount options for debugfs
       The debugfs filesystem is a pseudo filesystem, traditionally
       mounted on /sys/kernel/debug. As of kernel version 3.4, debugfs
       has the following options:

       uid=n, gid=n
           Set the owner and group of the mountpoint.

           Sets the mode of the mountpoint.

   Mount options for devpts
       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>.

       uid=value and gid=value
           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.

           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

           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

           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.

           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

           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.

           Set the mode for the new ptmx device node in the devpts

           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

           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.

           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

   Mount options for fat
       (Note: fat is not a separate filesystem, but a common part of the
       msdos, umsdos and vfat filesystems.)

           Set blocksize (default 512). This option is obsolete.

       uid=value and gid=value
           Set the owner and group of all files. (Default: the UID and
           GID of the current process.)

           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.

           Set the umask applied to directories only. The default is the
           umask of the current process. The value is given in octal.

           Set the umask applied to regular files only. The default is
           the umask of the current process. The value is given in

           This option controls the permission check of mtime/atime.

               If current process is in group of file’s group ID, you
               can change timestamp.

               Other users can change timestamp.

       The default is set from 'dmask' option. (If the directory is
       writable, utime(2) is also allowed. I.e. ~dmask & 022)

       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.

           Three different levels of pickiness can be chosen:

               Upper and lower case are accepted and equivalent, long
               name parts are truncated (e.g. verylongname.foobar
               becomes, leading and embedded spaces are
               accepted in each name part (name and extension).

               Like "relaxed", but many special characters (*, ?, <,
               spaces, etc.) are rejected. This is the default.

               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.

           Sets the codepage for converting to shortname characters on
           FAT and VFAT filesystems. By default, codepage 437 is used.

           This option is obsolete and may fail or be ignored.

           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.

           Option passed to the CVF module. This option is obsolete.

           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).

           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.

           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

           Specify FAT behavior on critical errors: panic, continue
           without doing anything, or remount the partition in read-only
           mode (default behavior).

           Specify a 12, 16 or 32 bit fat. This overrides the automatic
           FAT type detection routine. Use with caution!

           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.

           Enable this only if you want to export the FAT filesystem
           over NFS.

           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.

           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.

           To maintain backward compatibility, -o nfs is also accepted,
           defaulting to stale_rw.

           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.

           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.

           Turn on the quiet flag. Attempts to chown or chmod files do
           not return errors, although they fail. Use with caution!

           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).

           If you want to use ATTR_RO as read-only flag even for the
           directory, set this option.

           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.

           If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE
           flag on Linux. Not set by default.

           If set, the filesystem will try to flush to disk more early
           than normal. Not set by default.

           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.

       dots, nodots, dotsOK=[yes|no]
           Various misguided attempts to force Unix or DOS conventions
           onto a FAT filesystem.

   Mount options for hfs
       creator=cccc, type=cccc
           Set the creator/type values as shown by the MacOS finder used
           for creating new files. Default values: '????'.

       uid=n, gid=n
           Set the owner and group of all files. (Default: the UID and
           GID of the current process.)

       dir_umask=n, file_umask=n, umask=n
           Set the umask used for all directories, all regular files, or
           all files and directories. Defaults to the umask of the
           current process.

           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.

           Select partition number n from the device. Only makes sense
           for CDROMs. Defaults to not parsing the partition table at

           Don’t complain about invalid mount options.

   Mount options for hpfs
       uid=value and gid=value
           Set the owner and group of all files. (Default: the UID and
           GID of the current process.)

           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.

           Convert all files names to lower case, or leave them.
           (Default: case=lower.)

           This option is obsolete and may fail or being ignored.

           Do not abort mounting when certain consistency checks fail.

   Mount options for iso9660
       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.)

       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.

       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).

           Disable the use of Rock Ridge extensions, even if available.
           Cf. map.

           Disable the use of Microsoft Joliet extensions, even if
           available. Cf. map.

           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:

       uid=value and gid=value
           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.)

           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.

           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.

           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.)

           Set the block size to the indicated value. (Default:

           This option is obsolete and may fail or being ignored.

           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.

           Select number of session on a multisession CD.

           Session begins from sector xxx.

       The following options are the same as for vfat and specifying
       them only makes sense when using discs encoded using Microsoft’s
       Joliet extensions.

           Character set to use for converting 16 bit Unicode characters
           on CD to 8 bit characters. The default is iso8859-1.

           Convert 16 bit Unicode characters on CD to UTF-8.

   Mount options for jfs
           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.

           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.

           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.

           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.

           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.)

           These options are accepted but ignored.

   Mount options for msdos
       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.

   Mount options for ncpfs
       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.

   Mount options for ntfs
           Character set to use when returning file names. Unlike VFAT,
           NTFS suppresses names that contain nonconvertible characters.

           New name for the option earlier called iocharset.

           Use UTF-8 for converting file names.

           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.

           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

       uid=value, gid=value and umask=value
           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.

   Mount options for overlay
       Since Linux 3.18 the overlay pseudo filesystem implements a union
       mount for other filesystems.

       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.

       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.

       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:

              mount -t overlay  overlay  \
                -olowerdir=/lower,upperdir=/upper,workdir=/work  /merged

           Any filesystem, does not need to be on a writable filesystem.

           The upperdir is normally on a writable filesystem.

           The workdir needs to be an empty directory on the same
           filesystem as upperdir.

           Use the "user.overlay." xattr namespace instead of
           "trusted.overlay.". This is useful for unprivileged mounting
           of overlayfs.

           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.

               Redirects are enabled.

               Redirects are not created and only followed if
               "redirect_always_follow" feature is enabled in the
               kernel/module config.

               Redirects are not created, but followed.

               Redirects are not created and not followed (equivalent to
               "redirect_dir=off" if "redirect_always_follow" feature is
               not enabled).

           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.

           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.

           When the underlying filesystems supports NFS export and the
           "nfs_export" feature is enabled, an overlay filesystem may be
           exported to NFS.

           With the "nfs_export" feature, on copy_up of any lower
           object, an index entry is created under the index directory.
           The index entry name is the hexadecimal representation of the
           copy up origin file handle. For a non-directory object, the
           index entry is a hard link to the upper inode. For a
           directory object, the index entry has an extended attribute
           "{trusted|user}.overlay.upper" with an encoded file handle of
           the upper directory inode.

           When encoding a file handle from an overlay filesystem
           object, the following rules apply

               •   For a non-upper object, encode a lower file handle
                   from lower inode

               •   For an indexed object, encode a lower file handle
                   from copy_up origin

               •   For a pure-upper object and for an existing
                   non-indexed upper object, encode an upper file handle
                   from upper inode

           The encoded overlay file handle includes

               •   Header including path type information (e.g.

               •   UUID of the underlying filesystem

               •   Underlying filesystem encoding of underlying inode

           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

               •   Find underlying layer by UUID and path type

               •   Decode the underlying filesystem file handle to
                   underlying dentry.

               •   For a lower file handle, lookup the handle in index
                   directory by name.

               •   If a whiteout is found in index, return ESTALE. This
                   represents an overlay object that was deleted after
                   its file handle was encoded.

               •   For a non-directory, instantiate a disconnected
                   overlay dentry from the decoded underlying dentry,
                   the path type and index inode, if found.

               •   For a directory, use the connected underlying decoded
                   dentry, path type and index, to lookup a connected
                   overlay dentry.

           Decoding a non-directory file handle may return a
           disconnected dentry. copy_up of that disconnected dentry will
           create an upper index entry with no upper alias.

           When overlay filesystem has multiple lower layers, a middle
           layer directory may have a "redirect" to lower directory.
           Because middle layer "redirects" are not indexed, a lower
           file handle that was encoded from the "redirect" origin
           directory, cannot be used to find the middle or upper layer
           directory. Similarly, a lower file handle that was encoded
           from a descendant of the "redirect" origin directory, cannot
           be used to reconstruct a connected overlay path. To mitigate
           the cases of directories that cannot be decoded from a lower
           file handle, these directories are copied up on encode and
           encoded as an upper file handle. On an overlay filesystem
           with no upper layer this mitigation cannot be used NFS export
           in this setup requires turning off redirect follow (e.g.

           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.

           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.

           Note: the mount options index=off,nfs_export=on are
           conflicting for a read-write mount and will result in an

           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.

           For a detailed description of the effect of this option
           please refer to

           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.

           In other words, this is delayed data copy up operation and
           data is copied up when there is a need to actually modify

           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.

           The advantage of mounting with the "volatile" option is that
           all forms of sync calls to the upper filesystem are omitted.

           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.

           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.

   Mount options for reiserfs
       Reiserfs is a journaling filesystem.

           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.

           Choose which hash function reiserfs will use to find files
           within directories.

               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.

               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.

               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.

               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

           Tunes the block allocator. This may provide performance
           improvements in some situations.

           Tunes the block allocator. This may provide performance
           improvements in some situations.

           Disable the border allocator algorithm invented by Yury Yu.
           Rupasov. This may provide performance improvements in some

           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.

           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.

           Replay the transactions which are in the journal, but do not
           actually mount the filesystem. Mainly used by reiserfsck.

           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

           Enable Extended User Attributes. See the attr(1) manual page.

           Enable POSIX Access Control Lists. See the acl(5) manual

       barrier=none / barrier=flush
           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.

   Mount options for ubifs
       UBIFS is a flash filesystem which works on top of UBI volumes.
       Note that atime is not supported and is always turned off.

       The device name may be specified as

              UBI device number X, volume number Y

              UBI device number 0, volume number Y

              UBI device number X, volume with name NAME

              UBI device number 0, volume with name NAME

       Alternative ! separator may be used instead of :.

       The following mount options are available:

           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.

           Do not bulk-read. This is the default.

           Check data CRC-32 checksums. This is the default.

           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.

           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.

   Mount options for udf
       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.

           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".

           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

           Mask out the given permissions from all inodes read from the
           filesystem. The value is given in octal.

           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.

           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.

           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.

           For other details see the mkudffs(8) 2.0+ manpage, see the
           COMPATIBILITY and BLOCK SIZE sections.

           Show otherwise hidden files.

           Show deleted files in lists.

           Embed data in the inode. (default)

           Don’t embed data in the inode.

           Use short UDF address descriptors.

           Use long UDF address descriptors. (default)

           Unset strict conformance.

           Set the NLS character set. This requires kernel compiled with
           CONFIG_UDF_NLS option.

           Set the UTF-8 character set.

   Mount options for debugging and disaster recovery
           Ignore the Volume Recognition Sequence and attempt to mount

           Select the session number for multi-session recorded optical
           media. (default= last session)

           Override standard anchor location. (default= 256)

           Set the last block of the filesystem.

   Unused historical mount options that may be encountered and should be
           Ignored, use uid=<user> instead.

           Ignored, use gid=<group> instead.

           Unimplemented and ignored.

           Unimplemented and ignored.

           Unimplemented and ignored.

           Unimplemented and ignored.

   Mount options for ufs
           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:

               Old format of ufs, this is the default, read only. (Don’t
               forget to give the -r option.)

               For filesystems created by a BSD-like system (NetBSD,
               FreeBSD, OpenBSD).

               Used in FreeBSD 5.x supported as read-write.

               Synonym for ufs2.

               For filesystems created by SunOS or Solaris on Sparc.

               For filesystems created by Solaris on x86.

               For filesystems created by HP-UX, read-only.

               For filesystems created by NeXTStep (on NeXT station)
               (currently read only).

               For NextStep CDROMs (block_size == 2048), read-only.

               For filesystems created by OpenStep (currently read
               only). The same filesystem type is also used by macOS.

           Set behavior on error:

               If an error is encountered, cause a kernel panic.

               These mount options don’t do anything at present; when an
               error is encountered only a console message is printed.

   Mount options for umsdos
       See mount options for msdos. The dotsOK option is explicitly
       killed by umsdos.

   Mount options for vfat
       First of all, the mount options for fat are recognized. The
       dotsOK option is explicitly killed by vfat. Furthermore, there

           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),

           Allow two files with names that only differ in case. This
           option is obsolete.

           First try to make a short name without sequence number,
           before trying name~num.ext.

           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.

           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 modes:

               Force the short name to lower case upon display; store a
               long name when the short name is not all upper case.

               Force the short name to upper case upon display; store a
               long name when the short name is not all upper case.

               Display the short name as is; store a long name when the
               short name is not all lower case or all upper case.

               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.

   Mount options for usbfs
       devuid=uid and devgid=gid and devmode=mode
           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.

       busuid=uid and busgid=gid and busmode=mode
           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.

       listuid=uid and listgid=gid and listmode=mode
           Set the owner and group and mode of the file devices
           (default: uid=gid=0, mode=0444). The mode is given in octal.


       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:

           Path to the hash tree device associated with the source
           volume to pass to dm-verity.

           Hex-encoded hash of the root of verity.hashdevice. Mutually
           exclusive with verity.roothashfile.

           Path to file containing the hex-encoded hash of the root of
           verity.hashdevice. Mutually exclusive with verity.roothash.

           If the hash tree device is embedded in the source volume,
           offset (default: 0) is used by dm-verity to get to the tree.

           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.

           If the FEC device is embedded in the source volume, offset
           (default: 0) is used by dm-verity to get to the FEC area.

           Parity bytes for FEC (default: 2). Optional.

           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.

           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.

       Supported since util-linux v2.35.

       For example commands:

           mksquashfs /etc /tmp/etc.raw
           veritysetup format /tmp/etc.raw /tmp/etc.verity --root-hash-file=/tmp/etc.roothash
           openssl smime -sign -in /tmp/etc.roothash -nocerts -inkey private.key \
           -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s
           mount -o verity.hashdevice=/tmp/etc.verity,verity.roothashfile=/tmp/etc.roothash,\
           verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.raw /mnt

       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.


       One further possible type is a mount via the loop device. For
       example, the command

          mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop3

       will set up the loop device /dev/loop3 to correspond to the file
       /tmp/disk.img, and then mount this device on /mnt.

       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

          mount /tmp/disk.img /mnt -o loop

       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:

          mount /tmp/disk.img /mnt

          mount -t ext4 /tmp/disk.img /mnt

       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.)

       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.

       You can also free a loop device by hand, using losetup -d or
       umount -d.

       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.

EXIT STATUS         top

       mount has the following exit status values (the bits can be


           incorrect invocation or permissions

           system error (out of memory, cannot fork, no more loop

           internal mount bug

           user interrupt

           problems writing or locking /etc/mtab

           mount failure

           some mount succeeded

           The command mount -a returns 0 (all succeeded), 32 (all
           failed), or 64 (some failed, some succeeded).


       The syntax of external mount helpers is:

       /sbin/mount.suffix spec dir [-sfnv] [-N namespace] [-o options]
       [-t type.subtype]

       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).

       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.

ENVIRONMENT         top

           force to use classic mount(2) system call (requires support
           for new file descriptors based mount API). The default is
           auto; in this case, libmount tries to be smart and use
           classic mount(2) only for well-known issues. If the new mount
           API is unavailable, libmount can still use traditional
           mount(2), although LIBMOUNT_FORCE_MOUNT2 is set to never.

           overrides the default location of the fstab file (ignored for

           enables libmount debug output

           enables libblkid debug output

           enables loop device setup debug output

FILES         top

       See also "The files /etc/fstab, /etc/mtab and /proc/mounts"
       section above.

           filesystem table

           libmount private runtime directory

           table of mounted filesystems or symlink to /proc/mounts

           lock file (unused on systems with mtab symlink)

           temporary file (unused on systems with mtab symlink)

           a list of filesystem types to try

HISTORY         top

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

BUGS         top

       It is possible for a corrupted filesystem to cause a crash.

       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).

       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

       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.

       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.

       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.

AUTHORS         top

       Karel Zak <>

SEE ALSO         top

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

REPORTING BUGS         top

       For bug reports, use the issue tracker at

AVAILABILITY         top

       The mount command is part of the util-linux package which can be
       downloaded from Linux Kernel Archive
       <>. This page
       is part of the util-linux (a random collection of Linux
       utilities) project. Information about the project can be found at
       ⟨⟩. If you have
       a bug report for this manual page, send it to This page was obtained from the
       project's upstream Git repository
       ⟨git://⟩ on
       2023-12-22. (At that time, the date of the most recent commit
       that was found in the repository was 2023-12-14.) If you discover
       any rendering problems in this HTML version of the page, or you
       believe there is a better or more up-to-date source for the page,
       or you have corrections or improvements to the information in
       this COLOPHON (which is not part of the original manual page),
       send a mail to

util-linux 2.39.594-1e0ad      2023-08-25                       MOUNT(8)

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