Adding upstream version 2.33.1.upstream/2.33.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+.\" Copyright (c) 1996-2004 Andries Brouwer
+.\" Copyright (C) 2006-2012 Karel Zak <kzak@redhat.com>
+.\"
+.\" This page is somewhat derived from a page that was
+.\" (c) 1980, 1989, 1991 The Regents of the University of California
+.\" and had been heavily modified by Rik Faith and myself.
+.\" (Probably no BSD text remains.)
+.\" Fragments of text were written by Werner Almesberger, Remy Card,
+.\" Stephen Tweedie and Eric Youngdale.
+.\"
+.\" This is free documentation; you can redistribute it and/or
+.\" modify it under the terms of the GNU General Public License as
+.\" published by the Free Software Foundation; either version 2 of
+.\" the License, or (at your option) any later version.
+.\"
+.\" The GNU General Public License's references to "object code"
+.\" and "executables" are to be interpreted as the output of any
+.\" document formatting or typesetting system, including
+.\" intermediate and printed output.
+.\"
+.\" This manual is distributed in the hope that it will be useful,
+.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
+.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+.\" GNU General Public License for more details.
+.\"
+.\" You should have received a copy of the GNU General Public License along
+.\" with this program; if not, write to the Free Software Foundation, Inc.,
+.\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+.\"
+.TH MOUNT 8 "August 2015" "util-linux" "System Administration"
+.SH NAME
+mount \- mount a filesystem
+.SH SYNOPSIS
+.B mount
+.RB [ \-l | \-h | \-V ]
+.LP
+.B mount \-a
+.RB [ \-fFnrsvw ]
+.RB [ \-t
+.IR fstype ]
+.RB [ \-O
+.IR optlist ]
+.LP
+.B mount
+.RB [ \-fnrsvw ]
+.RB [ \-o
+.IR options ]
+.IR device | dir
+.LP
+.B mount
+.RB [ \-fnrsvw ]
+.RB [ \-t
+.IB fstype ]
+.RB [ \-o
+.IR options ]
+.I device dir
+.SH DESCRIPTION
+All files accessible in a Unix system are arranged in one big
+tree, the file hierarchy, rooted at
+.IR / .
+These files can be spread out over several devices.  The
+.B mount
+command serves to attach the filesystem found on some device
+to the big file tree.  Conversely, the
+.BR 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 another services.
+
+The standard form of the
+.B mount
+command is:
+.RS
+
+.br
+.BI "mount \-t" " type device dir"
+.br
+
+.RE
+This tells the kernel to attach the filesystem found on
+.I device
+(which is of type
+.IR type )
+at the directory
+.IR dir .
+The option \fB\-t \fItype\fR is optional.  The
+.B 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
+.I dir
+become invisible, and as long as this filesystem remains mounted,
+the pathname
+.I dir
+refers to the root of the filesystem on
+.IR device .
+
+If only the directory or the device is given, for example:
+.RS
+.sp
+.B mount /dir
+.sp
+.RE
+then \fBmount\fR looks for a mountpoint (and if not found then for a device) in the
+.I /etc/fstab
+file.  It's possible to use the
+.B \-\-target
+or
+.B \-\-source
+options to avoid ambivalent interpretation of the given argument.  For example:
+.RS
+.sp
+.B mount \-\-target /mountpoint
+.sp
+.RE
+
+The same filesystem may be mounted more than once, and in some cases (e.g.
+network filesystems) the same filesystem maybe be mounted on the same
+mountpoint more times. The mount command does not implement any policy to
+control this behavior. All behavior is controlled by kernel and it is usually
+specific to filesystem driver. The exception is \fB\-\-all\fR, in this case
+already mounted filesystems are ignored (see \fB\-\-all\fR below for more details).
+
+.SS Listing the mounts
+The listing mode is maintained for backward compatibility only.
+
+For more robust and customizable output use
+.BR findmnt (8),
+\fBespecially in your scripts\fP.  Note that control characters in the
+mountpoint name are replaced with '?'.
+
+The following command lists all mounted filesystems (of type
+.IR type ):
+.RS
+.sp
+.BR "mount " [ \-l "] [" "\-t \fItype\/\fP" ]
+.sp
+.RE
+The option \fB\-l\fR adds labels to this listing.  See below.
+
+.SS Indicating the device and filesystem
+Most devices are indicated by a filename (of a block special device), like
+.IR /dev/sda1 ,
+but there are other possibilities.  For example, in the case of an NFS mount,
+.I device
+may look like
+.IR knuth.cwi.nl:/dir .
+It is also possible to indicate a block special device using its filesystem label
+or UUID (see the \fB\-L\fR and \fB\-U\fR options below), or its partition label
+or UUID.  Partition identifiers are supported for example for GUID Partition
+Tables (GPT).
+
+The device name of disk partitions are unstable; hardware reconfiguration,
+adding or removing a device can cause change in names. This is reason why it's
+strongly recommended to use filesystem or partition identificators like UUID or
+LABEL.
+
+The command \fBlsblk --fs\fR provides overview of filesystems, LABELs and UUIDs
+on available block devices.  The command \fBblkid -p <device>\fR 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
+.B "lsblk \-o +UUID,PARTUUID"
+to verify that the UUIDs are really unique in your system.
+
+The recommended setup is to use tags (e.g.\& \fBUUID=\fIuuid\fR) rather than
+.I /dev/disk/by-{label,uuid,partuuid,partlabel}
+udev symlinks in the
+.I /etc/fstab
+file.  Tags are
+more readable, robust and portable.  The
+.BR mount (8)
+command internally uses udev
+symlinks, so the use of symlinks in /etc/fstab has no advantage over tags.
+For more details see
+.BR libblkid (3).
+
+Note that
+.BR mount (8)
+uses UUIDs as strings.  The UUIDs from the command line or from
+.BR fstab (5)
+are not converted to internal binary representation.  The string representation
+of the UUID should be based on lower case characters.
+
+The
+.I proc
+filesystem is not associated with a special device, and when
+mounting it, an arbitrary keyword, such as
+.I proc
+can be used instead of a device specification.
+(The customary choice
+.I none
+is less fortunate: the error message `none already mounted' from
+.B mount
+can be confusing.)
+
+.SS The files /etc/fstab, /etc/mtab and /proc/mounts
+The file
+.I /etc/fstab
+(see
+.BR fstab (5)),
+may contain lines describing what devices are usually
+mounted where, using which options.  The default location of the
+.BR fstab (5)
+file can be overridden with the
+.BI \-\-fstab " path"
+command-line option (see below for more details).
+.LP
+The command
+.RS
+.sp
+.B mount \-a
+.RB [ \-t
+.IR type ]
+.RB [ \-O
+.IR optlist ]
+.sp
+.RE
+(usually given in a bootscript) causes all filesystems mentioned in
+.I 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
+.B noauto
+keyword.  Adding the
+.B \-F
+option will make \fBmount\fR fork, so that the
+filesystems are mounted simultaneously.
+.LP
+When mounting a filesystem mentioned in
+.I fstab
+or
+.IR mtab ,
+it suffices to specify on the command line only the device, or only the mount point.
+.sp
+The programs
+.B mount
+and
+.B umount
+traditionally maintained a list of currently mounted filesystems in the file
+.IR /etc/mtab .
+The support for regular classic
+.I /etc/mtab
+is completely disabled in compile time by default, because on current Linux
+systems it is better to make it a symlink to
+.I /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 than it's possible to
+use the file as well as the symlink.
+.sp
+If no arguments are given to
+.BR mount ,
+the list of mounted filesystems is printed.
+.sp
+If you want to override mount options from
+.I /etc/fstab
+you have to use the \fB\-o\fR option:
+.RS
+.sp
+.BI mount " device" \fR| "dir " \-o " options"
+.sp
+.RE
+and then the mount options from the command line will be appended to
+the list of options from
+.IR /etc/fstab .
+This default behaviour is possible to change by command line
+option \fB\-\-options\-mode\fR.
+The usual behavior is that the last option wins if there are conflicting
+ones.
+.sp
+The
+.B mount
+program does not read the
+.I /etc/fstab
+file if both
+.I device
+(or LABEL, UUID, PARTUUID or PARTLABEL) and
+.I dir
+are specified.  For example, to mount device
+.BR foo " at " /dir :
+.RS
+.sp
+.B "mount /dev/foo /dir"
+.sp
+.RE
+This default behaviour is possible to change by command line option
+\fB\-\-options\-source\-force\fR to always read configuration from fstab. For
+non-root users
+.B mount
+always read fstab configuration.
+
+.SS Non-superuser mounts
+Normally, only the superuser can mount filesystems.
+However, when
+.I fstab
+contains the
+.B user
+option on a line, anybody can mount the corresponding filesystem.
+.LP
+Thus, given a line
+.RS
+.sp
+.B "/dev/cdrom  /cd  iso9660  ro,user,noauto,unhide"
+.sp
+.RE
+any user can mount the iso9660 filesystem found on an inserted CDROM
+using the command:
+.RS
+.B "mount /cd"
+.sp
+.RE
+Note that \fBmount\fR 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 \fBmount\fR may fail. For example it's bad idea
+to use NFS or CIFS source on command line.
+.PP
+For more details, see
+.BR fstab (5).
+Only the user that mounted a filesystem can unmount it again.
+If any user should be able to unmount it, then use
+.B users
+instead of
+.B user
+in the
+.I fstab
+line.
+The
+.B owner
+option is similar to the
+.B user
+option, with the restriction that the user must be the owner
+of the special file.  This may be useful e.g.\& for
+.I /dev/fd
+if a login script makes the console user owner of this device.
+The
+.B group
+option is similar, with the restriction that the user must be
+member of the group of the special file.
+
+.SS Bind mount operation
+Remount part of the file hierarchy somewhere else.  The call is:
+
+.RS
+.br
+.B mount \-\-bind
+.I olddir newdir
+.RE
+
+or by using this fstab entry:
+
+.RS
+.br
+.BI / olddir
+.BI / newdir
+.B none bind
+.RE
+
+After this call the same contents are accessible in two places.
+
+It is important to understand that "bind" does not to 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 "bind" operation. The \fIolddir\fR and \fInewdir\fR are
+independent and the \fIolddir\fR maybe be umounted.
+
+One can also remount a single file (on a single file).  It's also
+possible to use the bind mount to create a mountpoint from a regular
+directory, for example:
+
+.RS
+.br
+.B mount \-\-bind foo foo
+.RE
+
+The bind mount call attaches only (part of) a single filesystem, not possible
+submounts.  The entire file hierarchy including submounts is attached
+a second place by using:
+
+.RS
+.br
+.B mount \-\-rbind
+.I olddir newdir
+.RE
+
+Note that the filesystem mount options maintained by kernel will remain the same as those
+on the original mount point.  The userspace mount options (e.g. _netdev) will not be copied
+by
+.BR mount (8)
+and it's necessary explicitly specify the options on mount command line.
+
+.BR mount (8)
+since v2.27 allows to change the mount options by passing the
+relevant options along with
+.BR \-\-bind .
+For example:
+
+.RS
+.br
+.B mount -o bind,ro foo foo
+.RE
+
+This feature is not supported by the Linux kernel; it is implemented in userspace
+by an additional \fBmount\fR(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:
+
+.RS
+.br
+.B mount \-\-bind
+.I olddir newdir
+.br
+.B mount \-o remount,bind,ro
+.I olddir newdir
+.RE
+
+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
+.I olddir
+will be writable, but the
+.I newdir
+will be read-only.
+
+It's also possible to change nosuid, nodev, noexec, noatime, nodiratime and
+relatime VFS entry flags by "remount,bind" operation.  The another (for example
+filesystem specific flags) are silently ignored.  It's impossible to change mount
+options recursively (for example with \fB-o rbind,ro\fR).
+
+.BR mount (8)
+since v2.31 ignores the \fBbind\fR flag from
+.I /etc/fstab
+on
+.B remount operation
+(if "-o remount" specified on command line). This is necessary to fully control
+mount options on remount by command line. In the 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
+.BR mount (8)
+behavior does not affect situations when "remount,bind" is specified in the
+.I /etc/fstab
+file.
+.RE
+
+.SS The move operation
+Move a
+.B mounted tree
+to another place (atomically).  The call is:
+
+.RS
+.br
+.B mount \-\-move
+.I olddir newdir
+.RE
+
+This will cause the contents which previously appeared under
+.I olddir
+to now be accessible under
+.IR newdir .
+The physical location of the files is not changed.
+Note that
+.I olddir
+has to be a mountpoint.
+
+Note also that moving a mount residing under a shared mount is invalid and
+unsupported.  Use
+.B findmnt \-o TARGET,PROPAGATION
+to see the current propagation flags.
+
+.SS 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
+.I Documentation/filesystems/sharedsubtree.txt
+file in the kernel source tree.
+
+Supported operations are:
+
+.RS
+.nf
+.BI "mount \-\-make\-shared " mountpoint
+.BI "mount \-\-make\-slave " mountpoint
+.BI "mount \-\-make\-private " mountpoint
+.BI "mount \-\-make\-unbindable " mountpoint
+.fi
+.RE
+
+The following commands allow one to recursively change the type of all the
+mounts under a given mountpoint.
+
+.RS
+.nf
+.BI "mount \-\-make\-rshared " mountpoint
+.BI "mount \-\-make\-rslave " mountpoint
+.BI "mount \-\-make\-rprivate " mountpoint
+.BI "mount \-\-make\-runbindable " mountpoint
+.fi
+.RE
+
+.BR mount (8)
+.B does not read
+.BR fstab (5)
+when a \fB\-\-make-\fR* operation is requested.  All necessary information has to be
+specified on the command line.
+
+Note that the Linux kernel does not allow to change multiple propagation flags
+with a single
+.BR mount (2)
+system call, and the flags cannot be mixed with other mount options and operations.
+
+Since util-linux 2.23 the \fBmount\fR command allows to do more propagation
+(topology) changes by one mount(8) call and do it also together with other
+mount operations.  This feature is EXPERIMENTAL.  The propagation flags are applied
+by additional \fBmount\fR(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
+.BR fstab (5)
+as mount options
+.RB ( private ,
+.BR slave ,
+.BR shared ,
+.BR unbindable ,
+.BR rprivate ,
+.BR rslave ,
+.BR rshared ,
+.BR runbindable ).
+
+For example:
+
+.RS
+.nf
+.B mount \-\-make\-private \-\-make\-unbindable /dev/sda1 /foo
+.fi
+.RE
+
+is the same as:
+
+.RS
+.nf
+.B mount /dev/sda1 /foox
+.B mount \-\-make\-private /foo
+.B mount \-\-make\-unbindable /foo
+.fi
+.RE
+
+.SH COMMAND-LINE OPTIONS
+The full set of mount options used by an invocation of
+.B mount
+is determined by first extracting the
+mount options for the filesystem from the
+.I fstab
+table, then applying any options specified by the
+.B \-o
+argument, and finally applying a
+.BR \-r " or " \-w
+option, when present.
+
+The command \fBmount\fR does not pass all command-line options to the
+\fB/sbin/mount.\fIsuffix\fR mount helpers.  The interface between \fBmount\fR
+and the mount helpers is described below in the section \fBEXTERNAL HELPERS\fR.
+.sp
+Command-line options available for the
+.B mount
+command are:
+.TP
+.BR \-a , " \-\-all"
+Mount all filesystems (of the given types) mentioned in
+.I fstab
+(except for those whose line contains the
+.B noauto
+keyword).  The filesystems are mounted following their order in
+.IR 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 \fBmount \-\-all\fR. It means
+that all duplicated fstab entries will be mounted.
+.sp
+Note that it is a bad practice to use \fBmount \-a\fR for
+.I fstab
+checking. The recommended solution is \fBfindmnt \-\-verify\fR.
+.TP
+.BR \-B , " \-\-bind"
+Remount a subtree somewhere else (so that its contents are available
+in both places).  See above, under \fBBind mounts\fR.
+.TP
+.BR \-c , " \-\-no\-canonicalize"
+Don't canonicalize paths.  The mount command canonicalizes all paths
+(from command line or fstab) by default.  This option can be used
+together with the
+.B \-f
+flag for already canonicalized absolute paths.  The option is designed for mount
+helpers which call \fBmount -i\fR.  It is strongly recommended to not use this
+command-line option for normal mount operations.
+.sp
+Note that \fBmount\fR(8) does not pass this option to the
+\fB/sbin/mount.\fItype\fR helpers.
+.TP
+.BR \-F , " \-\-fork"
+(Used in conjunction with
+.BR \-a .)
+Fork off a new incarnation of \fBmount\fR 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 go in
+parallel.  A disadvantage is that the mounts are done in undefined order.
+Thus, you cannot use this option if you want to mount both
+.I /usr
+and
+.IR /usr/spool .
+.IP "\fB\-f, \-\-fake\fP"
+Causes everything to be done except for the actual system call; if it's not
+obvious, this ``fakes'' mounting the filesystem.  This option is useful in
+conjunction with the
+.B \-v
+flag to determine what the
+.B mount
+command is trying to do.  It can also be used to add entries for devices
+that were mounted earlier with the \fB\-n\fR option.  The \fB\-f\fR option
+checks for an existing record in /etc/mtab and fails when the record already
+exists (with a regular non-fake mount, this check is done by the kernel).
+.IP "\fB\-i, \-\-internal\-only\fP"
+Don't call the \fB/sbin/mount.\fIfilesystem\fR helper even if it exists.
+.TP
+.BR \-L , " \-\-label " \fIlabel
+Mount the partition that has the specified
+.IR label .
+.TP
+.BR \-l , " \-\-show\-labels"
+Add the labels in the mount output.  \fBmount\fR 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
+.BR e2label (8)
+utility, or for XFS using
+.BR xfs_admin (8),
+or for reiserfs using
+.BR reiserfstune (8).
+.TP
+.BR \-M , " \-\-move"
+Move a subtree to some other place.  See above, the subsection
+\fBThe move operation\fR.
+.TP
+.BR \-n , " \-\-no\-mtab"
+Mount without writing in
+.IR /etc/mtab .
+This is necessary for example when
+.I /etc
+is on a read-only filesystem.
+.TP
+.BR \-N , " \-\-namespace " \fIns
+Perform mount in namespace specified by \fIns\fR.
+\fIns\fR is either PID of process running in that namespace
+or special file representing that namespace.
+.sp
+.BR mount (8)
+switches to the namespace when it reads /etc/fstab, writes /etc/mtab (or writes to /run/mount) and calls
+.BR mount (2)
+system call, otherwise it runs in the original namespace. It means that the target namespace does not have
+to contain any libraries or another requirements necessary to execute
+.BR mount (2)
+command.
+.sp
+See \fBnamespaces\fR(7) for more information.
+.TP
+.BR \-O , " \-\-test\-opts " \fIopts
+Limit the set of filesystems to which the
+.B \-a
+option applies.  In this regard it is like the
+.B \-t
+option except that
+.B \-O
+is useless without
+.BR \-a .
+For example, the command:
+.RS
+.RS
+.sp
+.B "mount \-a \-O no_netdev"
+.sp
+.RE
+mounts all filesystems except those which have the option
+.I _netdev
+specified in the options field in the
+.I /etc/fstab
+file.
+
+It is different from
+.B \-t
+in that each option is matched exactly; a leading
+.B no
+at the beginning of one option does not negate the rest.
+
+The
+.B \-t
+and
+.B \-O
+options are cumulative in effect; that is, the command
+.RS
+.sp
+.B "mount \-a \-t ext2 \-O _netdev"
+.sp
+.RE
+mounts all ext2 filesystems with the _netdev option, not all filesystems
+that are either ext2 or have the _netdev option specified.
+.RE
+.TP
+.BR \-o , " \-\-options " \fIopts
+Use the specified mount options.  The \fIopts\fR argument is
+a comma-separated list.  For example:
+.RS
+.RS
+.sp
+.B "mount LABEL=mydisk \-o noatime,nodev,nosuid"
+.sp
+.RE
+
+For more details, see the
+.B FILESYSTEM-INDEPENDENT MOUNT OPTIONS
+and
+.B FILESYSTEM-SPECIFIC MOUNT OPTIONS
+sections.
+.RE
+
+.TP
+.BR "\-\-options\-mode " \fImode
+Controls how to combine options from fstab/mtab with options from command line.
+\fImode\fR can be one of
+.BR ignore ", " append ", " prepend " or " replace .
+For example \fBappend\fR means that options from fstab are appended to options from command line.
+Default value is \fBprepend\fR -- it means command line options are evaluated after fstab options.
+Note that the last option wins if there are conflicting ones.
+
+.TP
+.BR "\-\-options\-source " \fIsource
+Source of default options.
+\fIsource\fR is comma separated list of
+.BR fstab ", " mtab " and " disable .
+\fBdisable\fR disables
+.BR fstab " and " mtab
+and disables \fB\-\-options\-source\-force\fR.
+Default value is \fBfstab,mtab\fR.
+
+.TP
+.B \-\-options\-source\-force
+Use options from fstab/mtab even if both \fIdevice\fR and \fIdir\fR are specified.
+
+.TP
+.BR \-R , " \-\-rbind"
+Remount a subtree and all possible submounts somewhere else (so that its
+contents are available in both places).  See above, the subsection
+\fBBind mounts\fR.
+.TP
+.BR \-r , " \-\-read\-only"
+Mount the filesystem read-only.  A synonym is
+.BR "\-o ro" .
+.sp
+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 \fBro,noload\fR mount
+options or set the block device itself to read-only mode, see the
+.BR blockdev (8)
+command.
+.TP
+.B \-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 \fBmount.nfs\fR mount helper only.
+.TP
+.BI \-\-source " device"
+If only one argument for the mount command is given then the argument might be
+interpreted as target (mountpoint) or source (device).  This option allows to
+explicitly define that the argument is the mount source.
+.TP
+.BI \-\-target " directory"
+If only one argument for the mount command is given then the argument might be
+interpreted as target (mountpoint) or source (device).  This option allows to
+explicitly define that the argument is the mount target.
+.TP
+.BR \-T , " \-\-fstab " \fIpath
+Specifies an alternative fstab file.  If \fIpath\fP is a directory then the files
+in the directory are sorted by
+.BR 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.
+.sp
+Note that \fBmount\fR(8) does not pass the option \fB\-\-fstab\fP to the
+\fB/sbin/mount.\fItype\fR 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.
+.TP
+.BR \-t , " \-\-types " \fIfstype
+The argument following the
+.B \-t
+is used to indicate the filesystem type.  The filesystem types which are
+currently supported depend on the running kernel.  See
+.I /proc/filesystems
+and
+.I /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.
+.sp
+The programs
+.B mount
+and
+.B umount
+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
+.B \-t
+option is given, or if the
+.B auto
+type is specified, mount will try to guess the desired type.
+Mount uses the blkid library for guessing the filesystem
+type; if that does not turn up anything that looks familiar,
+mount will try to read the file
+.IR /etc/filesystems ,
+or, if that does not exist,
+.IR /proc/filesystems .
+All of the filesystem types listed there will be tried,
+except for those that are labeled "nodev" (e.g.\&
+.IR devpts ,
+.I proc
+and
+.IR nfs ).
+If
+.I /etc/filesystems
+ends in a line with a single *, mount will read
+.I /proc/filesystems
+afterwards.  While trying, all filesystem types will be
+mounted with the mount option \fBsilent\fR.
+.sp
+The
+.B auto
+type may be useful for user-mounted floppies.
+Creating a file
+.I /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.
+.sp
+More than one type may be specified in a comma-separated
+list, for option
+.B \-t
+as well as in an
+.I /etc/fstab
+entry.  The list of filesystem types for option
+.B \-t
+can be prefixed with
+.B no
+to specify the filesystem types on which no action should be taken.
+The prefix
+.B no
+has no effect when specified in an
+.I /etc/fstab
+entry.
+.sp
+The prefix
+.B no
+can be meaningful with the
+.B \-a
+option.  For example, the command
+.RS
+.RS
+.sp
+.B "mount \-a \-t nomsdos,smbfs"
+.sp
+.RE
+mounts all filesystems except those of type
+.I msdos
+and
+.IR smbfs .
+.sp
+For most types all the
+.B mount
+program has to do is issue a simple
+.BR 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, \fBmount\fR will execute the program
+.BI /sbin/mount. type
+(if that exists) when called with type
+.IR type .
+Since different versions of the
+.B smbmount
+program have different calling conventions,
+.B /sbin/mount.smbfs
+may have to be a shell script that sets up the desired call.
+.RE
+.TP
+.BR \-U , " \-\-uuid " \fIuuid
+Mount the partition that has the specified
+.IR uuid .
+.TP
+.BR \-v , " \-\-verbose"
+Verbose mode.
+.TP
+.BR \-w , " \-\-rw" , " \-\-read\-write"
+Mount the filesystem read/write. The read-write is kernel default.  A synonym is
+.BR "\-o rw" .
+
+Note that specify \fB\-w\fR on command line forces \fBmount\fR command
+to never try read-only mount on write-protected devices. The default is
+try read-only if the previous mount syscall with read-write flags failed.
+.TP
+.BR \-V , " \-\-version"
+Display version information and exit.
+.TP
+.BR \-h , " \-\-help"
+Display help text and exit.
+
+.SH FILESYSTEM-INDEPENDENT MOUNT OPTIONS
+Some of these options are only useful when they appear in the
+.I /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 \fBtune2fs \-l\fP
+output for extN filesystems).
+
+The following options apply to any filesystem that is being
+mounted (but not every filesystem actually honors them \(en e.g.\&, the
+.B sync
+option today has an effect only for ext2, ext3, ext4, fat, vfat and ufs):
+
+.TP
+.B async
+All I/O to the filesystem should be done asynchronously.  (See also the
+.B sync
+option.)
+.TP
+.B atime
+Do not use the \fBnoatime\fR feature, so the inode access time is controlled
+by kernel defaults.  See also the descriptions of the \fB\%relatime\fR and
+.B strictatime
+mount options.
+.TP
+.B 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 \fB\%nodiratime\fR.
+.TP
+.B auto
+Can be mounted with the
+.B \-a
+option.
+.TP
+.B noauto
+Can only be mounted explicitly (i.e., the
+.B \-a
+option will not cause the filesystem to be mounted).
+.TP
+.na
+.BR context=\fIcontext ", " fscontext=\fIcontext ", " defcontext=\fIcontext ", and " \%rootcontext=\fIcontext
+.ad
+The
+.B 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
+.B 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
+.BR \%context="system_u:object_r:removable_t" .
+
+Two other options are
+.B fscontext=
+and
+.BR defcontext= ,
+both of which are mutually exclusive of the context option.  This means you
+can use fscontext and defcontext with each other, but neither can be used with
+context.
+
+The
+.B 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
+.B defcontext=
+option.  This overrides the value set for unlabeled files in the policy and requires a
+filesystem that supports xattr labeling.
+
+The
+.B 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.
+
+Note that the kernel rejects any remount request that includes the context
+option, \fBeven\fP when unchanged from the current context.
+
+.BR "Warning: the \fIcontext\fP value might contain commas" ,
+in which case the value has to be properly quoted, otherwise
+.BR mount (8)
+will interpret the comma as a separator between mount options.  Don't forget that
+the shell strips off quotes and thus
+.BR "double quoting is required" .
+For example:
+.RS
+.RS
+.sp
+.nf
+.B mount \-t tmpfs none /mnt \-o \e
+.B \ \ 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
+.fi
+.sp
+.RE
+For more details, see
+.BR selinux (8).
+.RE
+
+.TP
+.B defaults
+Use the default options:
+.BR rw ", " suid ", " dev ", " exec ", " auto ", " nouser ", and " async .
+
+Note that the real set of all default mount options depends on kernel
+and filesystem type.  See the beginning of this section for more details.
+.TP
+.B dev
+Interpret character or block special devices on the filesystem.
+.TP
+.B nodev
+Do not interpret character or block special devices on the file
+system.
+.TP
+.B diratime
+Update directory inode access times on this filesystem.  This is the default.
+(This option is ignored when \fBnoatime\fR is set.)
+.TP
+.B nodiratime
+Do not update directory inode access times on this filesystem.
+(This option is implied when \fBnoatime\fR is set.)
+.TP
+.B dirsync
+All directory updates within the filesystem should be done synchronously.
+This affects the following system calls: creat, link, unlink, symlink,
+mkdir, rmdir, mknod and rename.
+.TP
+.B exec
+Permit execution of binaries.
+.TP
+.B noexec
+Do not permit direct execution of any binaries on the mounted filesystem.
+.TP
+.B 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
+.BR nosuid " and " nodev
+(unless overridden by subsequent options, as in the option line
+.BR group,dev,suid ).
+.TP
+.B iversion
+Every time the inode is modified, the i_version field will be incremented.
+.TP
+.B noiversion
+Do not increment the i_version inode field.
+.TP
+.B mand
+Allow mandatory locks on this filesystem.  See
+.BR fcntl (2).
+.TP
+.B nomand
+Do not allow mandatory locks on this filesystem.
+.TP
+.B _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).
+.TP
+.B nofail
+Do not report errors for this device if it does not exist.
+.TP
+.B relatime
+Update inode access times relative to modify or change time.  Access
+time is only updated if the previous access time was earlier than the
+current modify or change time.  (Similar to \fB\%noatime\fR, but it doesn't
+break \fBmutt\fR 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
+.B \%noatime
+was specified), and the
+.B \%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.
+.TP
+.B norelatime
+Do not use the
+.B relatime
+feature.  See also the
+.B strictatime
+mount option.
+.TP
+.B strictatime
+Allows to explicitly request full atime updates.  This makes it
+possible for the kernel to default to
+.B \%relatime
+or
+.B \%noatime
+but still allow userspace to override it.  For more details about the default
+system mount options see /proc/mounts.
+.TP
+.B nostrictatime
+Use the kernel's default behavior for inode access time updates.
+.TP
+.B 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:
+.sp
+.RS
+- the inode needs to be updated for some change unrelated to file timestamps
+.sp
+- the application employs
+.BR fsync (2),
+.BR syncfs (2),
+or
+.BR sync (2)
+.sp
+- an undeleted inode is evicted from memory
+.sp
+- more than 24 hours have passed since the i-node was written to disk.
+.RE
+.sp
+.TP
+.B nolazytime
+Do not use the lazytime feature.
+.TP
+.B suid
+Allow set-user-ID or set-group-ID bits to take
+effect.
+.TP
+.B nosuid
+Do not allow set-user-ID or set-group-ID bits to take
+effect.
+.TP
+.B silent
+Turn on the silent flag.
+.TP
+.B loud
+Turn off the silent flag.
+.TP
+.B owner
+Allow an ordinary user to mount the filesystem if that
+user is the owner of the device.
+This option implies the options
+.BR nosuid " and " nodev
+(unless overridden by subsequent options, as in the option line
+.BR owner,dev,suid ).
+.TP
+.B 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
+.B bind
+flag has special semantic. See above, the subsection \fBBind mounts\fR.
+
+The remount functionality follows the standard way the mount command works
+with options from fstab.  This means that \fBmount\fR does not
+read fstab (or mtab) only when both
+.I device
+and
+.I dir
+are specified.
+.sp
+.in +4
+.B "mount \-o remount,rw /dev/foo /dir"
+.in
+.sp
+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.
+.sp
+.in +4
+.B "mount \-o remount,rw  /dir"
+.in
+.sp
+After this call, mount reads fstab and merges these options with
+the options from the command line (\fB\-o\fR).
+If no mountpoint is found in fstab, then a remount with unspecified source is
+allowed.
+.TP
+.B ro
+Mount the filesystem read-only.
+.TP
+.B rw
+Mount the filesystem read-write.
+.TP
+.B 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), \fBsync\fR may cause life-cycle shortening.
+.TP
+.B 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
+.BR noexec ", " nosuid ", and " nodev
+(unless overridden by subsequent options, as in the option line
+.BR user,exec,dev,suid ).
+.TP
+.B nouser
+Forbid an ordinary user to mount the filesystem.
+This is the default; it does not imply any other options.
+.TP
+.B users
+Allow any user to mount and to unmount the filesystem, even
+when some other ordinary user mounted it.
+This option implies the options
+.BR noexec ", " nosuid ", and " nodev
+(unless overridden by subsequent options, as in the option line
+.BR users,exec,dev,suid ).
+.TP
+.B X-*
+All options prefixed with "X-" are interpreted as comments or as userspace
+application-specific options.  These options are not stored in the user space (e.g. mtab file),
+nor sent to the mount.\fItype\fR helpers nor to the
+.BR mount (2)
+system call.  The suggested format is \fBX-\fIappname\fR.\fIoption\fR.
+.TP
+.B x-*
+The same as \fBX-*\fR options, but stored permanently in the user space. It
+means the options are also available for umount or another operations.  Note
+that maintain 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 have X-* now),
+but due to growing number of use-cases (in initrd, systemd etc.) the
+functionality have been extended to keep existing fstab configurations usable
+without a change.
+.TP
+.BR X-mount.mkdir [ = \fImode\fR ]
+Allow to make a target directory (mountpoint).  The optional argument
+.I mode
+specifies the filesystem access mode used for
+.BR mkdir (2)
+in octal notation.  The default mode is 0755.  This functionality is supported
+only for root users.  The option is also supported as x-mount.mkdir, this notation
+is deprecated for mount.mkdir since v2.30.
+
+.SH "FILESYSTEM-SPECIFIC MOUNT OPTIONS"
+You should consult the respective man page for the filesystem first.
+If you want to know what options the ext4 filesystem supports, then check the
+.BR ext4 (5)
+man page.
+If that doesn't exist, you can also check the corresponding mount page like
+.BR mount.cifs (8).
+Note that you might have to install the respective userland tools.
+.sp
+The following options apply only to certain filesystems.
+We sort them by filesystem.  They all follow the
+.B \-o
+flag.
+.sp
+What options are supported depends a bit on the running kernel.
+More info may be found in the kernel source subdirectory
+.IR Documentation/filesystems .
+
+.SS "Mount options for adfs"
+.TP
+\fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
+Set the owner and group of the files in the filesystem (default: uid=gid=0).
+.TP
+\fBownmask=\fP\,\fIvalue\fP and \fBothmask=\fP\,\fIvalue\fP
+Set the permission mask for ADFS 'owner' permissions and 'other' permissions,
+respectively (default: 0700 and 0077, respectively).
+See also
+.IR /usr/src/linux/Documentation/filesystems/adfs.txt .
+
+.SS "Mount options for affs"
+.TP
+\fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
+Set the owner and group of the root of the filesystem (default: uid=gid=0,
+but with option
+.B uid
+or
+.B gid
+without specified value, the UID and GID of the current process are taken).
+.TP
+\fBsetuid=\fP\,\fIvalue\fP and \fBsetgid=\fP\,\fIvalue\fP
+Set the owner and group of all files.
+.TP
+.BI mode= value
+Set the mode of all files to
+.IR value " & 0777"
+disregarding the original permissions.
+Add search permission to directories that have read permission.
+The value is given in octal.
+.TP
+.B protect
+Do not allow any changes to the protection bits on the filesystem.
+.TP
+.B 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...
+.TP
+.B verbose
+Print an informational message for each successful mount.
+.TP
+.BI prefix= string
+Prefix used before volume name, when following a link.
+.TP
+.BI volume= string
+Prefix (of length at most 30) used before '/' when following a symbolic link.
+.TP
+.BI reserved= value
+(Default: 2.) Number of unused blocks at the start of the device.
+.TP
+.BI root= value
+Give explicitly the location of the root block.
+.TP
+.BI bs= value
+Give blocksize.  Allowed values are 512, 1024, 2048, 4096.
+.TP
+.BR grpquota | noquota | quota | usrquota
+These options are accepted but ignored.
+(However, quota utilities may react to such strings in
+.IR /etc/fstab .)
+
+.SS "Mount options for debugfs"
+The debugfs filesystem is a pseudo filesystem, traditionally mounted on
+.IR /sys/kernel/debug .
+.\" or just /debug
+.\" present since 2.6.11
+As of kernel version 3.4, debugfs has the following options:
+.TP
+.BI uid= n ", gid=" n
+Set the owner and group of the mountpoint.
+.TP
+.BI mode= value
+Sets the mode of the mountpoint.
+
+.SS "Mount options for devpts"
+The devpts filesystem is a pseudo filesystem, traditionally mounted on
+.IR /dev/pts .
+In order to acquire a pseudo terminal, a process opens
+.IR /dev/ptmx ;
+the number of the pseudo terminal is then made available to the process
+and the pseudo terminal slave can be accessed as
+.IR /dev/pts/ <number>.
+.TP
+\fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
+This sets the owner or the group of newly created PTYs 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
+.B gid=5
+will cause newly created PTYs to belong to the tty group.
+.TP
+.BI mode= value
+Set the mode of newly created PTYs to the specified value.
+The default is 0600.
+A value of
+.B mode=620
+and
+.B gid=5
+makes "mesg y" the default on newly created PTYs.
+.TP
+\fBnewinstance
+Create a private instance of devpts filesystem, such that
+indices of ptys allocated in this new instance are
+independent of indices created in other instances of devpts.
+
+All mounts of devpts without this
+.B newinstance
+option share the same set of pty indices (i.e. legacy mode).
+Each mount of devpts with the
+.B newinstance
+option has a private set of pty 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,
+.I /dev/ptmx
+must be a symbolic link to
+.I pts/ptmx.
+See
+.I Documentation/filesystems/devpts.txt
+in the linux kernel source tree for details.
+.TP
+.BI ptmxmode= value
+
+Set the mode for the new
+.I ptmx
+device node in the devpts filesystem.
+
+With the support for multiple instances of devpts (see
+.B newinstance
+option above), each instance has a private
+.I ptmx
+node in the root of the devpts filesystem (typically
+.IR /dev/pts/ptmx ).
+
+For compatibility with older versions of the kernel, the
+default mode of the new
+.I ptmx
+node is 0000.
+.BI ptmxmode= value
+specifies a more useful mode for the
+.I ptmx
+node and is highly recommended when the
+.B 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.
+
+.SS "Mount options for fat"
+(Note:
+.I fat
+is not a separate filesystem, but a common part of the
+.IR msdos ,
+.I umsdos
+and
+.I vfat
+filesystems.)
+.TP
+.BR blocksize= { 512 | 1024 | 2048 }
+Set blocksize (default 512).  This option is obsolete.
+.TP
+\fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
+Set the owner and group of all files.
+(Default: the UID and GID of the current process.)
+.TP
+.BI umask= value
+Set the umask (the bitmask of the permissions that are
+.B not
+present).  The default is the umask of the current process.
+The value is given in octal.
+.TP
+.BI dmask= value
+Set the umask applied to directories only.
+The default is the umask of the current process.
+The value is given in octal.
+.TP
+.BI 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.
+.TP
+.BI allow_utime= value
+This option controls the permission check of mtime/atime.
+.RS
+.TP
+.B 20
+If current process is in group of file's group ID, you can change timestamp.
+.TP
+.B 2
+Other users can change timestamp.
+.PP
+The default is set from `dmask' option. (If the directory is writable,
+.BR utime (2)
+is also allowed.  I.e.\& \s+3~\s0dmask & 022)
+
+Normally
+.BR utime (2)
+checks current process is owner of the file, or it has
+CAP_FOWNER capability.  But FAT filesystem doesn't have UID/GID on disk, so
+normal check is too inflexible.  With this option you can relax it.
+.RE
+.TP
+.BI check= value
+Three different levels of pickiness can be chosen:
+.RS
+.TP
+.BR r [ elaxed ]
+Upper and lower case are accepted and equivalent, long name parts are
+truncated (e.g.\&
+.I verylongname.foobar
+becomes
+.IR verylong.foo ),
+leading and embedded spaces are accepted in each name part (name and extension).
+.TP
+.BR n [ ormal ]
+Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are
+rejected.  This is the default.
+.TP
+.BR 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.
+.RE
+.TP
+.BI codepage= value
+Sets the codepage for converting to shortname characters on FAT
+and VFAT filesystems.  By default, codepage 437 is used.
+.TP
+.BI conv= mode
+This option is obsolete and may fail or being ignored.
+.TP
+.BI cvf_format= module
+Forces the driver to use the CVF (Compressed Volume File) module
+.RI 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.
+.TP
+.BI cvf_option= option
+Option passed to the CVF module.  This option is obsolete.
+.TP
+.B debug
+Turn on the
+.I 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).
+.TP
+.B 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.
+.TP
+.B 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.
+.TP
+.BR 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).
+.TP
+.BR fat= { 12 | 16 | 32 }
+Specify a 12, 16 or 32 bit fat.  This overrides
+the automatic FAT type detection routine.  Use with caution!
+.TP
+.BI 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.
+.TP
+.BR nfs= { stale_rw | nostale_ro }
+Enable this only if you want to export the FAT filesystem over NFS.
+
+.BR 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
+.B ESTALE
+errors.
+
+.BR 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
+.B 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
+.BR stale_rw .
+.TP
+.B 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.
+.TP
+.BI time_offset= minutes
+Set offset for conversion of timestamps from local time used by FAT to UTC.
+I.e.,
+.I 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
+.BR 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.
+.TP
+.B quiet
+Turn on the
+.I quiet
+flag.  Attempts to chown or chmod files do not return errors,
+although they fail.  Use with caution!
+.TP
+.B 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.
+.TP
+.B 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.
+.TP
+.B sys_immutable
+If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux.
+Not set by default.
+.TP
+.B flush
+If set, the filesystem will try to flush to disk more early than normal.
+Not set by default.
+.TP
+.B 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.
+.TP
+.BR dots ", " nodots ", " dotsOK= [ yes | no ]
+Various misguided attempts to force Unix or DOS conventions
+onto a FAT filesystem.
+
+.SS "Mount options for hfs"
+.TP
+.BI creator= cccc ", type=" cccc
+Set the creator/type values as shown by the MacOS finder
+used for creating new files.  Default values: '????'.
+.TP
+.BI uid= n ", gid=" n
+Set the owner and group of all files.
+(Default: the UID and GID of the current process.)
+.TP
+.BI 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.
+.TP
+.BI 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.
+.TP
+.BI part= n
+Select partition number n from the device.
+Only makes sense for CDROMs.
+Defaults to not parsing the partition table at all.
+.TP
+.B quiet
+Don't complain about invalid mount options.
+
+.SS "Mount options for hpfs"
+.TP
+\fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
+Set the owner and group of all files. (Default: the UID and GID
+of the current process.)
+.TP
+.BI umask= value
+Set the umask (the bitmask of the permissions that are
+.B not
+present).  The default is the umask of the current process.
+The value is given in octal.
+.TP
+.BR case= { lower | asis }
+Convert all files names to lower case, or leave them.
+(Default:
+.BR case=lower .)
+.TP
+.BI conv= mode
+This option is obsolete and may fail or being ignored.
+.TP
+.B nocheck
+Do not abort mounting when certain consistency checks fail.
+
+.SS "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
+.I udf
+filesystem.)
+
+Normal
+.I 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).
+.TP
+.B norock
+Disable the use of Rock Ridge extensions, even if available.  Cf.\&
+.BR map .
+.TP
+.B nojoliet
+Disable the use of Microsoft Joliet extensions, even if available.  Cf.\&
+.BR map .
+.TP
+.BR check= { r [ elaxed ]| s [ trict ]}
+With
+.BR check=relaxed ,
+a filename is first converted to lower case before doing the lookup.
+This is probably only meaningful together with
+.B norock
+and
+.BR map=normal .
+(Default:
+.BR check=strict .)
+.TP
+\fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
+Give all files in the filesystem the indicated user or group id,
+possibly overriding the information found in the Rock Ridge extensions.
+(Default:
+.BR uid=0,gid=0 .)
+.TP
+.BR 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
+.B map=off
+no name translation is done.  See
+.BR norock .
+(Default:
+.BR map=normal .)
+.B map=acorn
+is like
+.B map=normal
+but also apply Acorn extensions if present.
+.TP
+.BI 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.
+.TP
+.B 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.)
+.TP
+.BR block= { 512 | 1024 | 2048 }
+Set the block size to the indicated value.
+(Default:
+.BR block=1024 .)
+.TP
+.BI conv= mode
+This option is obsolete and may fail or being ignored.
+.TP
+.B 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.
+.TP
+.BI session= x
+Select number of session on multisession CD.
+.TP
+.BI sbsector= xxx
+Session begins from sector xxx.
+.LP
+The following options are the same as for vfat and specifying them only makes
+sense when using discs encoded using Microsoft's Joliet extensions.
+.TP
+.BI iocharset= value
+Character set to use for converting 16 bit Unicode characters on CD
+to 8 bit characters.  The default is iso8859-1.
+.TP
+.B utf8
+Convert 16 bit Unicode characters on CD to UTF-8.
+
+.SS "Mount options for jfs"
+.TP
+.BI iocharset= name
+Character set to use for converting from Unicode to ASCII.  The default is
+to do no conversion.  Use
+.B iocharset=utf8
+for UTF8 translations.  This requires CONFIG_NLS_UTF8 to be set in
+the kernel
+.I ".config"
+file.
+.TP
+.BI resize= value
+Resize the volume to
+.I 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
+.B resize
+keyword with no value will grow the volume to the full size of the partition.
+.TP
+.B 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.
+.TP
+.B integrity
+Default.  Commit metadata changes to the journal.  Use this option to remount
+a volume where the
+.B nointegrity
+option was previously specified in order to restore normal behavior.
+.TP
+.BR 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.)
+.TP
+.BR noquota | quota | usrquota | grpquota
+These options are accepted but ignored.
+
+.SS "Mount options for msdos"
+See mount options for fat.
+If the
+.I 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.
+
+.SS "Mount options for ncpfs"
+Just like
+.IR nfs ", the " ncpfs
+implementation expects a binary argument (a
+.IR "struct ncp_mount_data" )
+to the mount system call.  This argument is constructed by
+.BR ncpmount (8)
+and the current version of
+.B mount
+(2.12) does not know anything about ncpfs.
+
+.SS "Mount options for ntfs"
+.TP
+.BI iocharset= name
+Character set to use when returning file names.
+Unlike VFAT, NTFS suppresses names that contain
+nonconvertible characters.  Deprecated.
+.TP
+.BI nls= name
+New name for the option earlier called
+.IR iocharset .
+.TP
+.B utf8
+Use UTF-8 for converting file names.
+.TP
+.BR 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 give a little-endian encoding
+and 1 a byteswapped bigendian encoding.
+.TP
+.B 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.
+.TP
+\fBuid=\fP\,\fIvalue\fP, \fBgid=\fP\,\fIvalue\fP and \fBumask=\fP\,\fIvalue\fP
+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.
+
+.SS "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 \fBupper\fR filesystem and
+a \fBlower\fR 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 \fBlowerdir\fR and \fBupperdir\fR are combined into a merged
+directory by using:
+
+.RS
+.br
+.nf
+.B "mount \-t overlay  overlay  \e"
+.B "  \-olowerdir=/lower,upperdir=/upper,workdir=/work  /merged"
+.fi
+.br
+.RE
+
+.TP
+.BI lowerdir= directory
+Any filesystem, does not need to be on a writable filesystem.
+.TP
+.BI upperdir= directory
+The upperdir is normally on a writable filesystem.
+.TP
+.BI workdir= directory
+The workdir needs to be an empty directory on the same filesystem as upperdir.
+
+.SS "Mount options for reiserfs"
+Reiserfs is a journaling filesystem.
+.TP
+.B 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.
+.TP
+.BR hash= { rupasov | tea | r5 | detect }
+Choose which hash function reiserfs will use to find files within directories.
+.RS
+.TP
+.B 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.
+.TP
+.B 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.
+.TP
+.B 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.
+.TP
+.B detect
+Instructs
+.I 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.
+.RE
+.TP
+.B hashed_relocation
+Tunes the block allocator.  This may provide performance improvements
+in some situations.
+.TP
+.B no_unhashed_relocation
+Tunes the block allocator.  This may provide performance improvements
+in some situations.
+.TP
+.B noborder
+Disable the border allocator algorithm invented by Yury Yu.\& Rupasov.
+This may provide performance improvements in some situations.
+.TP
+.B 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
+.I nolog
+is a work in progress.
+.TP
+.B notail
+By default, reiserfs stores small files and `file tails' directly into its
+tree.  This confuses some utilities such as
+.BR LILO (8).
+This option is used to disable packing of files into the tree.
+.TP
+.B replayonly
+Replay the transactions which are in the journal, but do not actually
+mount the filesystem.  Mainly used by
+.IR reiserfsck .
+.TP
+.BI resize= number
+A remount option which permits online expansion of reiserfs partitions.
+Instructs reiserfs to assume that the device has
+.I number
+blocks.
+This option is designed for use with devices which are under logical
+volume management (LVM).
+There is a special
+.I resizer
+utility which can be obtained from
+.IR ftp://ftp.namesys.com/pub/reiserfsprogs .
+.TP
+.B user_xattr
+Enable Extended User Attributes.  See the
+.BR attr (5)
+manual page.
+.TP
+.B acl
+Enable POSIX Access Control Lists.  See the
+.BR acl (5)
+manual page.
+.TP
+.BR 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.
+
+.SS "Mount options for ubifs"
+UBIFS is a flash filesystem which works on top of UBI volumes.  Note that
+\fBatime\fR is not supported and is always turned off.
+.TP
+The device name may be specified as
+.RS
+.B ubiX_Y
+UBI device number
+.BR X ,
+volume number
+.B Y
+.TP
+.B ubiY
+UBI device number
+.BR 0 ,
+volume number
+.B Y
+.TP
+.B ubiX:NAME
+UBI device number
+.BR X ,
+volume with name
+.B NAME
+.TP
+.B ubi:NAME
+UBI device number
+.BR 0 ,
+volume with name
+.B NAME
+.RE
+Alternative
+.B !
+separator may be used instead of
+.BR : .
+.TP
+The following mount options are available:
+.TP
+.B bulk_read
+Enable bulk-read.  VFS read-ahead is disabled because it slows down the file
+system.  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.
+.TP
+.B no_bulk_read
+Do not bulk-read.  This is the default.
+.TP
+.B chk_data_crc
+Check data CRC-32 checksums.  This is the default.
+.TP
+.BR 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.
+.TP
+.BR 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
+.B none
+option.
+
+.SS "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
+.IR iso9660 .
+.TP
+.B 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".
+.TP
+.B 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".
+.TP
+.B umask=
+Mask out the given permissions from all inodes read from the filesystem.
+The value is given in octal.
+.TP
+.B 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.
+.TP
+.B 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.
+.TP
+.B 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 \fBmkudffs\fP(8) 2.0+ manpage, sections
+\fBCOMPATIBILITY\fP and \fBBLOCK SIZE\fP.
+.TP
+.B unhide
+Show otherwise hidden files.
+.TP
+.B undelete
+Show deleted files in lists.
+.TP
+.B adinicb
+Embed data in the inode. (default)
+.TP
+.B noadinicb
+Don't embed data in the inode.
+.TP
+.B shortad
+Use short UDF address descriptors.
+.TP
+.B longad
+Use long UDF address descriptors. (default)
+.TP
+.B nostrict
+Unset strict conformance.
+.TP
+.B iocharset=
+Set the NLS character set. This requires kernel compiled with CONFIG_UDF_NLS option.
+.TP
+.B utf8
+Set the UTF-8 character set.
+.SS Mount options for debugging and disaster recovery
+.TP
+.B novrs
+Ignore the Volume Recognition Sequence and attempt to mount anyway.
+.TP
+.B session=
+Select the session number for multi-session recorded optical media. (default= last session)
+.TP
+.B anchor=
+Override standard anchor location. (default= 256)
+.TP
+.B lastblock=
+Set the last block of the filesystem.
+.SS Unused historical mount options that may be encountered and should be removed
+.TP
+.B uid=ignore
+Ignored, use uid=<user> instead.
+.TP
+.B gid=ignore
+Ignored, use gid=<group> instead.
+.TP
+.B volume=
+Unimplemented and ignored.
+.TP
+.B partition=
+Unimplemented and ignored.
+.TP
+.B fileset=
+Unimplemented and ignored.
+.TP
+.B rootdir=
+Unimplemented and ignored.
+
+.SS "Mount options for ufs"
+.TP
+.BI 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:
+.RS
+.TP
+.B old
+Old format of ufs, this is the default, read only.
+(Don't forget to give the \-r option.)
+.TP
+.B 44bsd
+For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD).
+.TP
+.B ufs2
+Used in FreeBSD 5.x supported as read-write.
+.TP
+.B 5xbsd
+Synonym for ufs2.
+.TP
+.B sun
+For filesystems created by SunOS or Solaris on Sparc.
+.TP
+.B sunx86
+For filesystems created by Solaris on x86.
+.TP
+.B hp
+For filesystems created by HP-UX, read-only.
+.TP
+.B nextstep
+For filesystems created by NeXTStep (on NeXT station) (currently read only).
+.TP
+.B nextstep-cd
+For NextStep CDROMs (block_size == 2048), read-only.
+.TP
+.B openstep
+For filesystems created by OpenStep (currently read only).
+The same filesystem type is also used by Mac OS X.
+.RE
+
+.TP
+.BI onerror= value
+Set behavior on error:
+.RS
+.TP
+.B panic
+If an error is encountered, cause a kernel panic.
+.TP
+.RB [ lock | umount | repair ]
+These mount options don't do anything at present;
+when an error is encountered only a console message is printed.
+.RE
+
+.SS "Mount options for umsdos"
+See mount options for msdos.
+The
+.B dotsOK
+option is explicitly killed by
+.IR umsdos .
+
+.SS "Mount options for vfat"
+First of all, the mount options for
+.I fat
+are recognized.
+The
+.B dotsOK
+option is explicitly killed by
+.IR vfat .
+Furthermore, there are
+.TP
+.B 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).
+.TP
+.B posix
+Allow two files with names that only differ in case.
+This option is obsolete.
+.TP
+.B nonumtail
+First try to make a short name without sequence number,
+before trying
+.IR name\s+3~\s0num.ext .
+.TP
+.B 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.
+.TP
+.BI 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 \fImode\fRs:
+.RS
+.TP
+.B lower
+Force the short name to lower case upon display; store a long name when
+the short name is not all upper case.
+.TP
+.B win95
+Force the short name to upper case upon display; store a long name when
+the short name is not all upper case.
+.TP
+.B winnt
+Display the short name as is; store a long name when the short name is
+not all lower case or all upper case.
+.TP
+.B 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.
+.RE
+
+.SS "Mount options for usbfs"
+.TP
+\fBdevuid=\fP\,\fIuid\fP and \fBdevgid=\fP\,\fIgid\fP and \fBdevmode=\fP\,\fImode\fP
+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.
+.TP
+\fBbusuid=\fP\,\fIuid\fP and \fBbusgid=\fP\,\fIgid\fP and \fBbusmode=\fP\,\fImode\fP
+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.
+.TP
+\fBlistuid=\fP\,\fIuid\fP and \fBlistgid=\fP\,\fIgid\fP and \fBlistmode=\fP\,\fImode\fP
+Set the owner and group and mode of the file
+.I devices
+(default: uid=gid=0, mode=0444).  The mode is given in octal.
+
+.SH "THE LOOP DEVICE"
+One further possible type is a mount via the loop device.  For example,
+the command
+.RS
+.sp
+.B "mount /tmp/disk.img /mnt \-t vfat \-o loop=/dev/loop3"
+.sp
+.RE
+will set up the loop device
+.I /dev/loop3
+to correspond to the file
+.IR /tmp/disk.img ,
+and then mount this device on
+.IR /mnt .
+
+If no explicit loop device is mentioned
+(but just an option `\fB\-o loop\fP' is given), then
+.B mount
+will try to find some unused loop device and use that, for example
+.RS
+.sp
+.B "mount /tmp/disk.img /mnt \-o loop"
+.sp
+.RE
+The mount command
+.B 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:
+.RS
+.sp
+.B "mount /tmp/disk.img /mnt"
+.sp
+.B "mount \-t ext4 /tmp/disk.img /mnt"
+.sp
+.RE
+This type of mount knows about three options, namely
+.BR loop ", " offset " and " sizelimit ,
+that are really options to
+.BR \%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
+.B mount
+will be freed by
+.B umount
+independently of
+.IR /etc/mtab .
+
+You can also free a loop device by hand, using
+.BR "losetup \-d " or " umount \-d" .
+
+Since util-linux v2.29 mount command re-uses the loop device rather than
+initialize 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.
+
+.SH RETURN CODES
+.B mount
+has the following return codes (the bits can be ORed):
+.TP
+.B 0
+success
+.TP
+.B 1
+incorrect invocation or permissions
+.TP
+.B 2
+system error (out of memory, cannot fork, no more loop devices)
+.TP
+.B 4
+internal
+.B mount
+bug
+.TP
+.B 8
+user interrupt
+.TP
+.B 16
+problems writing or locking /etc/mtab
+.TP
+.B 32
+mount failure
+.TP
+.B 64
+some mount succeeded
+.RE
+
+The command \fBmount \-a\fR returns 0 (all succeeded), 32 (all failed), or 64 (some
+failed, some succeeded).
+
+.SH "EXTERNAL HELPERS"
+The syntax of external mount helpers is:
+.sp
+.in +4
+.BI /sbin/mount. suffix
+.I spec dir
+.RB [ \-sfnv ]
+.RB [ \-N
+.IR namespace ]
+.RB [ \-o
+.IR options ]
+.RB [ \-t
+.IR type \fB. subtype ]
+.in
+.sp
+where the \fIsuffix\fR is the filesystem type and the \fB\-sfnvoN\fR options have
+the same meaning as the normal mount options.  The \fB\-t\fR option is used for
+filesystems with subtypes support (for example
+.BR "/sbin/mount.fuse \-t fuse.sshfs" ).
+
+The command \fBmount\fR does not pass the mount options
+.BR unbindable ,
+.BR runbindable ,
+.BR private ,
+.BR rprivate ,
+.BR slave ,
+.BR rslave ,
+.BR shared ,
+.BR rshared ,
+.BR auto ,
+.BR noauto ,
+.BR comment ,
+.BR x-* ,
+.BR loop ,
+.B offset
+and
+.B sizelimit
+to the mount.<suffix> helpers.  All other options are used in a
+comma-separated list as argument to the \fB\-o\fR option.
+
+.SH FILES
+See also "\fBThe files /etc/fstab, /etc/mtab and /proc/mounts\fR" section above.
+.TP 18n
+.I /etc/fstab
+filesystem table
+.TP
+.I /run/mount
+libmount private runtime directory
+.TP
+.I /etc/mtab
+table of mounted filesystems or symlink to /proc/mounts
+.TP
+.I /etc/mtab\s+3~\s0
+lock file (unused on systems with mtab symlink)
+.TP
+.I /etc/mtab.tmp
+temporary file (unused on systems with mtab symlink)
+.TP
+.I /etc/filesystems
+a list of filesystem types to try
+.SH ENVIRONMENT
+.IP LIBMOUNT_FSTAB=<path>
+overrides the default location of the fstab file (ignored for suid)
+.IP LIBMOUNT_MTAB=<path>
+overrides the default location of the mtab file (ignored for suid)
+.IP LIBMOUNT_DEBUG=all
+enables libmount debug output
+.IP LIBBLKID_DEBUG=all
+enables libblkid debug output
+.IP LOOPDEV_DEBUG=all
+enables loop device setup debug output
+.SH "SEE ALSO"
+.na
+.BR mount (2),
+.BR umount (2),
+.BR umount (8),
+.BR fstab (5),
+.BR nfs (5),
+.BR xfs (5),
+.BR e2label (8),
+.BR findmnt (8),
+.BR losetup (8),
+.BR mke2fs (8),
+.BR mountd (8),
+.BR nfsd (8),
+.BR swapon (8),
+.BR tune2fs (8),
+.BR xfs_admin (8)
+.ad
+.SH BUGS
+It is possible for a corrupted filesystem to cause a crash.
+.PP
+Some Linux filesystems don't support
+.BR "\-o sync " nor " \-o dirsync"
+(the ext2, ext3, ext4, fat and vfat filesystems
+.I do
+support synchronous updates (a la BSD) when mounted with the
+.B sync
+option).
+.PP
+The
+.B "\-o remount"
+may not be able to change mount parameters (all
+.IR ext2fs -specific
+parameters, except
+.BR sb ,
+are changeable with a remount, for example, but you can't change
+.B gid
+or
+.B umask
+for the
+.IR fatfs ).
+.PP
+It is possible that the files
+.I /etc/mtab
+and
+.I /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/mounts file usually contains more reliable information.)  This is
+another reason to replace the mtab file with a symlink to the
+.I /proc/mounts
+file.
+.PP
+Checking files on NFS filesystems referenced by file descriptors (i.e.\& the
+.B fcntl
+and
+.B ioctl
+families of functions) may lead to inconsistent results due to the lack of
+a consistency check in the kernel even if noac is used.
+.PP
+The
+.B loop
+option with the
+.B offset
+or
+.B sizelimit
+options used may fail when using older kernels if the
+.B 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
+.B losetup
+command manually before calling
+.B mount
+with the configured loop device.
+.SH HISTORY
+A
+.B mount
+command existed in Version 5 AT&T UNIX.
+.SH AUTHORS
+.nf
+Karel Zak <kzak@redhat.com>
+.fi
+.SH AVAILABILITY
+The mount command is part of the util-linux package and is available from
+https://www.kernel.org/pub/linux/utils/util-linux/.