#Bash 的 mount 命令

MOUNT(8)                     System Administration                    MOUNT(8)

NAME
       mount - mount a filesystem

SYNOPSIS
       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

       mount
       --make-[shared|slave|private|unbindable|rshared|rslave|rprivate|runbindable]
       mountpoint

DESCRIPTION
       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 details).

   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 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 knuth.cwi.nl:/dir.

       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):

       LABEL=label
           Human readable filesystem identifier. See also -L.

       UUID=uuid
           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.

       PARTLABEL=label
           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).

       PARTUUID=uuid
           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).

       ID=id
           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 device.

       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 line.

       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
       FILESYSTEM-INDEPENDENT MOUNT OPTIONS section.

       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.

   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 mountpoint.

       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

COMMAND-LINE OPTIONS
       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 section.

       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 --options-mode).

           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 operation.

       -c, --no-canonicalize
           Don’t canonicalize paths. The mount command canonicalizes all paths
           (from the command line or fstab) by default. This option can be
           used together with the -f flag for already canonicalized absolute
           paths. The option is designed for mount helpers which call mount
           -i. It is strongly recommended to not use this command-line option
           for normal mount operations.

           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 exists.

       -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.

       -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
           command

           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
           specified.

       -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 default.

           For more details, see the FILESYSTEM-INDEPENDENT MOUNT OPTIONS and
           FILESYSTEM-SPECIFIC MOUNT OPTIONS sections.

       --onlyonce
           Forces mount command to check if the filesystem is already mounted.
           This behavior is the default for --all; otherwise, it depends on
           the kernel filesystem driver. Some filesystems may be mounted more
           than once on the same mount point (e.g. tmpfs).

       --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 fstab,mtab.

       --options-source-force
           Use options from fstab/mtab even if both device and dir are
           specified.

       -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.

       -s
           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 'sshfs#example.com'
           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.

FILESYSTEM-INDEPENDENT MOUNT OPTIONS
       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):

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

       atime
           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.

       noatime
           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.

       auto
           Can be mounted with the -a option.

       noauto
           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
       rootcontext=context
           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
           context="system_u:object_r:removable_t.

           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 location.

           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 \
          'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'

       For more details, see selinux(8).

       defaults
           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.

       dev
           Interpret character or block special devices on the filesystem.

       nodev
           Do not interpret character or block special devices on the
           filesystem.

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

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

       dirsync
           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).

       exec
           Permit execution of binaries and other executable files.

       noexec
           Do not permit direct execution of any binaries on the mounted
           filesystem.

       group
           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).

       iversion
           Every time the inode is modified, the i_version field will be
           incremented.

       noiversion
           Do not increment the i_version inode field.

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

       nomand
           Do not allow mandatory locks on this filesystem.

       _netdev
           The filesystem resides on a device that requires network access
           (used to prevent the system from attempting to mount these
           filesystems until the network has been enabled on the system).

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

       relatime
           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.

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

       strictatime
           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.

       nostrictatime
           Use the kernel’s default behavior for inode access time updates.

       lazytime
           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.

       nolazytime
           Do not use the lazytime feature.

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

       nosuid
           Do not honor set-user-ID and set-group-ID bits or file capabilities
           when executing programs from this filesystem. In addition, SELinux
           domain transitions require permission nosuid_transition, which in
           turn needs also policy capability nnp_nosuid_transition.

       silent
           Turn on the silent flag.

       loud
           Turn off the silent flag.

       owner
           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).

       remount
           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
           /proc/self/mountinfo.

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

           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.

       ro
           Mount the filesystem read-only.

       rw
           Mount the filesystem read-write.

       sync
           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.

       user
           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).

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

       users
           Allow any user to mount and to unmount the filesystem, even when
           some other ordinary user mounted it. This option implies the
           options noexec, nosuid, and nodev (unless overridden by subsequent
           options, as in the option line users,exec,dev,suid).

       X-*
           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.

       x-*
           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.

       X-mount.auto-fstypes=list
           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, X-mount.auto-fstypes="ext4,btrfs" accepts only ext4
           and btrfs, and X-mount.auto-fstypes="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’X-mount.auto-fstypes="noext2,ext3"'
          /dev/sdc1 /mnt/test

       X-mount.mkdir[=mode]
           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.

       X-mount.subdir=directory
           Allow mounting sub-directory from a filesystem instead of the root
           directory. For now, this feature is implemented by temporary
           filesystem root directory mount in unshared namespace and then bind
           the sub-directory to the final mount point and umount the root of
           the filesystem. The sub-directory mount shows up atomically for the
           rest of the system although it is implemented by multiple mount(2)
           syscalls.

           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.

       X-mount.owner=username|UID, X-mount.group=group|GID
           Set mountpoint's ownership after mounting. Names resolved in the
           target mount namespace, see -N.

       X-mount.mode=mode
           Set mountpoint's mode after mounting.

       X-mount.idmap=id-type:id-mount:id-host:id-range
       [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.

       nosymfollow
           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.

FILESYSTEM-SPECIFIC MOUNT OPTIONS
       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 /usr/src/linux/Documentation/filesystems/adfs.rst.

   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 taken).

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

       mode=value
           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.

       protect
           Do not allow any changes to the protection bits on the filesystem.

       usemp
           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...

       verbose
           Print an informational message for each successful mount.

       prefix=string
           Prefix used before volume name, when following a link.

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

       reserved=value
           (Default: 2.) Number of unused blocks at the start of the device.

       root=value
           Give explicitly the location of the root block.

       bs=value
           Give blocksize. Allowed values are 512, 1024, 2048, 4096.

       grpquota|noquota|quota|usrquota
           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.

       mode=value
           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.

       mode=value
           Set the mode of newly created pseudo terminals to the specified
           value. The default is 0600. A value of mode=620 and gid=5 makes
           "mesg y" the default on newly created pseudo terminals.

       newinstance
           Create a private instance of the devpts filesystem, such that
           indices of pseudo terminals allocated in this new instance are
           independent of indices created in other instances of devpts.

           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
           configuration.

           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.

       ptmxmode=value
           Set the mode for the new ptmx device node in the devpts filesystem.

           With the support for multiple instances of devpts (see newinstance
           option above), each instance has a private ptmx node in the root of
           the devpts filesystem (typically /dev/pts/ptmx).

           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
           configuration.

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

       blocksize={512|1024|2048}
           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.)

       umask=value
           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.

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

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

       allow_utime=value
           This option controls the permission check of mtime/atime.

           20
               If current process is in group of file’s group ID, you can
               change timestamp.

           2
               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.

       check=value
           Three different levels of pickiness can be chosen:

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

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

           s[trict]
               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.

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

       conv=mode
           This option is obsolete and may fail or be ignored.

       cvf_format=module
           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.

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

       debug
           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).

       discard
           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.

       dos1xfloppy
           If set, use a fallback default BIOS Parameter Block configuration,
           determined by backing device size. These static parameters match
           defaults assumed by DOS 1.x for 160 kiB, 180 kiB, 320 kiB, and 360
           kiB floppies and floppy images.

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

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

       iocharset=value
           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.

       nfs={stale_rw|nostale_ro}
           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.

       tz=UTC
           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.

       time_offset=minutes
           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.

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

       rodir
           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.

       showexec
           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.

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

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

       usefree
           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.

       session=n
           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.

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

       quiet
           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.)

       umask=value
           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.

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

       conv=mode
           This option is obsolete and may fail or being ignored.

       nocheck
           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).

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

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

       check={r[elaxed]|s[trict]}
           With check=relaxed, a filename is first converted to lower case
           before doing the lookup. This is probably only meaningful together
           with norock and map=normal. (Default: check=strict.)

       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.)

       map={n[ormal]|o[ff]|a[corn]}
           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.

       mode=value
           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.

       unhide
           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.)

       block={512|1024|2048}
           Set the block size to the indicated value. (Default: block=1024.)

       conv=mode
           This option is obsolete and may fail or being ignored.

       cruft
           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.

       session=x
           Select number of session on a multisession CD.

       sbsector=xxx
           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.

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

       utf8
           Convert 16 bit Unicode characters on CD to UTF-8.

   Mount options for jfs
       iocharset=name
           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=value
           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.

       nointegrity
           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.

       integrity
           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.

       errors={continue|remount-ro|panic}
           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.)

       noquota|quota|usrquota|grpquota
           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
       iocharset=name
           Character set to use when returning file names. Unlike VFAT, NTFS
           suppresses names that contain nonconvertible characters.
           Deprecated.

       nls=name
           New name for the option earlier called iocharset.

       utf8
           Use UTF-8 for converting file names.

       uni_xlate={0|1|2}
           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.

       posix=[0|1]
           If enabled (posix=1), the filesystem distinguishes between upper
           and lower case. The 8.3 alias names are presented as hard links
           instead of being suppressed. This option is obsolete.

       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

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

       upperdir=directory
           The upperdir is normally on a writable filesystem.

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

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

       redirect_dir={on|off|follow|nofollow}
           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.

           on
               Redirects are enabled.

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

           follow
               Redirects are not created, but followed.

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

       index={on|off}
           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.

       uuid={on|off}
           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.

       nfs_export={on|off}
           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. lower/upper)

               •   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 information.

               •   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.
           "redirect_dir=nofollow").

           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 error.

       xino={on|off|auto}
           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 https://docs.kernel.org/filesystems/overlayfs.html

       metacopy={on|off}
           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 data.

       volatile
           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.

       conv
           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.

       hash={rupasov|tea|r5|detect}
           Choose which hash function reiserfs will use to find files within
           directories.

           rupasov
               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.

           tea
               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.

           r5
               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.

           detect
               Instructs mount to detect which hash function is in use by
               examining the filesystem being mounted, and to write this
               information into the reiserfs superblock. This is only useful
               on the first mount of an old format filesystem.

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

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

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

       nolog
           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.

       notail
           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.

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

       resize=number
           A remount option which permits online expansion of reiserfs
           partitions. Instructs reiserfs to assume that the device has number
           blocks. This option is designed for use with devices which are
           under logical volume management (LVM). There is a special resizer
           utility which can be obtained from
           ftp://ftp.namesys.com/pub/reiserfsprogs.

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

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

       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

          ubiX_Y
              UBI device number X, volume number Y

          ubiY
              UBI device number 0, volume number Y

          ubiX:NAME
              UBI device number X, volume with name NAME

          ubi:NAME
              UBI device number 0, volume with name NAME

       Alternative ! separator may be used instead of :.

       The following mount options are available:

       bulk_read
           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.

       no_bulk_read
           Do not bulk-read. This is the default.

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

       no_chk_data_crc
           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.

       compr={none|lzo|zlib}
           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.

       uid=
           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".

       gid=
           Make all files in the filesystem belong to the given group.
           gid=forget can be specified independently of (or usually in
           addition to) gid=<group> and results in UDF not storing gids to the
           media. In fact the recorded gid is the 32-bit overflow gid -1 as
           defined by the UDF standard. The value is given as either <group>
           which is a valid group name or the corresponding decimal group id,
           or the special string "forget".

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

       mode=
           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.

       dmode=
           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.

       bs=
           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.

       unhide
           Show otherwise hidden files.

       undelete
           Show deleted files in lists.

       adinicb
           Embed data in the inode. (default)

       noadinicb
           Don’t embed data in the inode.

       shortad
           Use short UDF address descriptors.

       longad
           Use long UDF address descriptors. (default)

       nostrict
           Unset strict conformance.

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

       utf8
           Set the UTF-8 character set.

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

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

       anchor=
           Override standard anchor location. (default= 256)

       lastblock=
           Set the last block of the filesystem.

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

       gid=ignore
           Ignored, use gid=<group> instead.

       volume=
           Unimplemented and ignored.

       partition=
           Unimplemented and ignored.

       fileset=
           Unimplemented and ignored.

       rootdir=
           Unimplemented and ignored.

   Mount options for ufs
       ufstype=value
           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
               Old format of ufs, this is the default, read only. (Don’t
               forget to give the -r option.)

           44bsd
               For filesystems created by a BSD-like system (NetBSD, FreeBSD,
               OpenBSD).

           ufs2
               Used in FreeBSD 5.x supported as read-write.

           5xbsd
               Synonym for ufs2.

           sun
               For filesystems created by SunOS or Solaris on Sparc.

           sunx86
               For filesystems created by Solaris on x86.

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

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

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

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

       onerror=value
           Set behavior on error:

           panic
               If an error is encountered, cause a kernel panic.

           [lock|umount|repair]
               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 are

       uni_xlate
           Translate unhandled Unicode characters to special escaped
           sequences. This lets you backup and restore filenames that are
           created with any Unicode characters. Without this option, a '?' is
           used when no translation is possible. The escape character is ':'
           because it is otherwise invalid on the vfat filesystem. The escape
           sequence that gets used, where u is the Unicode character, is: ':',
           (u & 0x3f), ((u>>6) & 0x3f), (u>>12).

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

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

       utf8
           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.

       shortname=mode
           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:

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

           win95
               Force the short name to upper case upon display; store a long
               name when the short name is not all upper case.

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

           mixed
               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.

DM-VERITY SUPPORT
       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:

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

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

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

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

       verity.fecdevice=path
           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.

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

       verity.fecroots=value
           Parity bytes for FEC (default: 2). Optional.

       verity.roothashsig=path
           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.

       verity.oncorruption=ignore|restart|panic
           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.squashfs
           dd if=/dev/zero of=/tmp/etc.hash bs=1M count=10
           veritysetup format /tmp/etc.squashfs /tmp/etc.hash
           openssl smime -sign -in <hash> -nocerts -inkey private.key \
           -signer private.crt -noattr -binary -outform der -out /tmp/etc.roothash.p7s
           mount -o verity.hashdevice=/tmp/etc.hash,verity.roothash=<hash>,\
           verity.roothashsig=/tmp/etc.roothash.p7s /tmp/etc.squashfs /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.

LOOP-DEVICE SUPPORT
       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
       mount has the following exit status values (the bits can be ORed):

       0
           success

       1
           incorrect invocation or permissions

       2
           system error (out of memory, cannot fork, no more loop devices)

       4
           internal mount bug

       8
           user interrupt

       16
           problems writing or locking /etc/mtab

       32
           mount failure

       64
           some mount succeeded

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

EXTERNAL HELPERS
       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
       LIBMOUNT_FORCE_MOUNT2={always|never|auto}
           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.

       LIBMOUNT_FSTAB=<path>
           overrides the default location of the fstab file (ignored for suid)

       LIBMOUNT_DEBUG=all
           enables libmount debug output

       LIBBLKID_DEBUG=all
           enables libblkid debug output

       LOOPDEV_DEBUG=all
           enables loop device setup debug output

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

       /etc/fstab
           filesystem table

       /run/mount
           libmount private runtime directory

       /etc/mtab
           table of mounted filesystems or symlink to /proc/mounts

       /etc/mtab~
           lock file (unused on systems with mtab symlink)

       /etc/mtab.tmp
           temporary file (unused on systems with mtab symlink)

       /etc/filesystems
           a list of filesystem types to try

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

BUGS
       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 fatfs).

       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
       Karel Zak <[email protected]>

SEE ALSO
       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
       For bug reports, use the issue tracker at
       https://github.com/util-linux/util-linux/issues.

AVAILABILITY
       The mount command is part of the util-linux package which can be
       downloaded from Linux Kernel Archive
       <https://www.kernel.org/pub/linux/utils/util-linux/>.

util-linux 2.39.3                 2023-12-01                          MOUNT(8)