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30 .TH MOUNT 8 "August 2015" "util-linux" "System Administration"
32 mount \- mount a filesystem
35 .RB [ \-l | \-h | \-V ]
58 All files accessible in a Unix system are arranged in one big
59 tree, the file hierarchy, rooted at
61 These files can be spread out over several devices. The
63 command serves to attach the filesystem found on some device
64 to the big file tree. Conversely, the
66 command will detach it again. The filesystem is used to control how data is
67 stored on the device or provided in a virtual way by network or another services.
69 The standard form of the
75 .BI "mount \-t" " type device dir"
79 This tells the kernel to attach the filesystem found on
85 The option \fB\-t \fItype\fR is optional. The
87 command is usually able to detect a filesystem. The root permissions are necessary
88 to mount a filesystem by default. See section "Non-superuser mounts" below for more details.
89 The previous contents (if any) and owner and mode of
91 become invisible, and as long as this filesystem remains mounted,
94 refers to the root of the filesystem on
97 If only the directory or the device is given, for example:
103 then \fBmount\fR looks for a mountpoint (and if not found then for a device) in the
105 file. It's possible to use the
109 options to avoid ambivalent interpretation of the given argument. For example:
112 .B mount \-\-target /mountpoint
116 The same filesystem may be mounted more than once, and in some cases (e.g.
117 network filesystems) the same filesystem may be mounted on the same
118 mountpoint more times. The mount command does not implement any policy to
119 control this behavior. All behavior is controlled by the kernel and it is usually
120 specific to the filesystem driver. The exception is \fB\-\-all\fR, in this case
121 already mounted filesystems are ignored (see \fB\-\-all\fR below for more details).
123 .SS Listing the mounts
124 The listing mode is maintained for backward compatibility only.
126 For more robust and customizable output use
128 \fBespecially in your scripts\fP. Note that control characters in the
129 mountpoint name are replaced with '?'.
131 The following command lists all mounted filesystems (of type
135 .BR "mount " [ \-l "] [" "\-t \fItype\/\fP" ]
138 The option \fB\-l\fR adds labels to this listing. See below.
140 .SS Indicating the device and filesystem
141 Most devices are indicated by a filename (of a block special device), like
143 but there are other possibilities. For example, in the case of an NFS mount,
146 .IR knuth.cwi.nl:/dir .
147 It is also possible to indicate a block special device using its filesystem label
148 or UUID (see the \fB\-L\fR and \fB\-U\fR options below), or its partition label
149 or UUID. Partition identifiers are supported for example for GUID Partition
152 The device names of disk partitions are unstable; hardware reconfiguration,
153 adding or removing a device can cause changes in names. This is the reason why it's
154 strongly recommended to use filesystem or partition identifiers like UUID or
157 The command \fBlsblk --fs\fR provides an overview of filesystems, LABELs and UUIDs
158 on available block devices. The command \fBblkid -p <device>\fR provides details about
159 a filesystem on the specified device.
161 Don't forget that there is no guarantee that UUIDs and labels are really
162 unique, especially if you move, share or copy the device. Use
163 .B "lsblk \-o +UUID,PARTUUID"
164 to verify that the UUIDs are really unique in your system.
166 The recommended setup is to use tags (e.g.\& \fBUUID=\fIuuid\fR) rather than
167 .I /dev/disk/by-{label,uuid,partuuid,partlabel}
171 more readable, robust and portable. The
173 command internally uses udev
174 symlinks, so the use of symlinks in /etc/fstab has no advantage over tags.
180 uses UUIDs as strings. The UUIDs from the command line or from
182 are not converted to internal binary representation. The string representation
183 of the UUID should be based on lower case characters.
187 filesystem is not associated with a special device, and when
188 mounting it, an arbitrary keyword, such as
190 can be used instead of a device specification.
191 (The customary choice
193 is less fortunate: the error message `none already mounted' from
197 .SS The files /etc/fstab, /etc/mtab and /proc/mounts
202 may contain lines describing what devices are usually
203 mounted where, using which options. The default location of the
205 file can be overridden with the
206 .BI \-\-fstab " path"
207 command-line option (see below for more details).
219 (usually given in a bootscript) causes all filesystems mentioned in
221 (of the proper type and/or having or not having the proper options)
222 to be mounted as indicated, except for those whose line contains the
226 option will make \fBmount\fR fork, so that the
227 filesystems are mounted simultaneously.
229 When mounting a filesystem mentioned in
233 it suffices to specify on the command line only the device, or only the mount point.
239 traditionally maintained a list of currently mounted filesystems in the file
241 The support for regular classic
243 is completely disabled in compile time by default, because on current Linux
244 systems it is better to make it a symlink to
246 instead. The regular mtab file maintained in userspace cannot reliably
247 work with namespaces, containers and other advanced Linux features.
248 If the regular mtab support is enabled than it's possible to
249 use the file as well as the symlink.
251 If no arguments are given to
253 the list of mounted filesystems is printed.
255 If you want to override mount options from
257 you have to use the \fB\-o\fR option:
260 .BI mount " device" \fR| "dir " \-o " options"
263 and then the mount options from the command line will be appended to
264 the list of options from
266 This default behaviour is possible to change by command line
267 option \fB\-\-options\-mode\fR.
268 The usual behavior is that the last option wins if there are conflicting
273 program does not read the
277 (or LABEL, UUID, PARTUUID or PARTLABEL) and
279 are specified. For example, to mount device
280 .BR foo " at " /dir :
283 .B "mount /dev/foo /dir"
286 This default behaviour is possible to change by command line option
287 \fB\-\-options\-source\-force\fR to always read configuration from fstab. For
290 always read fstab configuration.
292 .SS Non-superuser mounts
293 Normally, only the superuser can mount filesystems.
298 option on a line, anybody can mount the corresponding filesystem.
303 .B "/dev/cdrom /cd iso9660 ro,user,noauto,unhide"
306 any user can mount the iso9660 filesystem found on an inserted CDROM
312 Note that \fBmount\fR is very strict about non-root users and all paths
313 specified on command line are verified before fstab is parsed or a helper
314 program is executed. It's strongly recommended to use a valid mountpoint to
315 specify filesystem, otherwise \fBmount\fR may fail. For example it's bad idea
316 to use NFS or CIFS source on command line.
318 Since version 2.35 \fBmount\fR command does not exit when user permissions are
319 inadequate by internal libmount security rules. It drops suid permissions
320 and continue as regular non-root user. It allows to support use-cases where
321 root permissions are not necessary (e.g. fuse filesystems, user namespaces,
324 For more details, see
326 Only the user that mounted a filesystem can unmount it again.
327 If any user should be able to unmount it, then use
336 option is similar to the
338 option, with the restriction that the user must be the owner
339 of the special file. This may be useful e.g.\& for
341 if a login script makes the console user owner of this device.
344 option is similar, with the restriction that the user must be
345 member of the group of the special file.
347 .SS Bind mount operation
348 Remount part of the file hierarchy somewhere else. The call is:
356 or by using this fstab entry:
365 After this call the same contents are accessible in two places.
367 It is important to understand that "bind" does not to create any second-class
368 or special node in the kernel VFS. The "bind" is just another operation to
369 attach a filesystem. There is nowhere stored information that the filesystem
370 has been attached by "bind" operation. The \fIolddir\fR and \fInewdir\fR are
371 independent and the \fIolddir\fR may be umounted.
373 One can also remount a single file (on a single file). It's also
374 possible to use the bind mount to create a mountpoint from a regular
375 directory, for example:
379 .B mount \-\-bind foo foo
382 The bind mount call attaches only (part of) a single filesystem, not possible
383 submounts. The entire file hierarchy including submounts is attached
384 a second place by using:
392 Note that the filesystem mount options maintained by kernel will remain the same as those
393 on the original mount point. The userspace mount options (e.g. _netdev) will not be copied
396 and it's necessary explicitly specify the options on mount command line.
399 since v2.27 allows to change the mount options by passing the
400 relevant options along with
406 .B mount -o bind,ro foo foo
409 This feature is not supported by the Linux kernel; it is implemented in userspace
410 by an additional \fBmount\fR(2) remounting system call.
411 This solution is not atomic.
413 The alternative (classic) way to create a read-only bind mount is to use the remount
414 operation, for example:
421 .B mount \-o remount,bind,ro
425 Note that a read-only bind will create a read-only mountpoint (VFS entry),
426 but the original filesystem superblock will still be writable, meaning that the
428 will be writable, but the
432 It's also possible to change nosuid, nodev, noexec, noatime, nodiratime and
433 relatime VFS entry flags by "remount,bind" operation. The another (for example
434 filesystem specific flags) are silently ignored. It's impossible to change mount
435 options recursively (for example with \fB-o rbind,ro\fR).
438 since v2.31 ignores the \fBbind\fR flag from
442 (if "-o remount" specified on command line). This is necessary to fully control
443 mount options on remount by command line. In the previous versions the bind
444 flag has been always applied and it was impossible to re-define mount options
445 without interaction with the bind semantic. This
447 behavior does not affect situations when "remount,bind" is specified in the
451 .SS The move operation
454 to another place (atomically). The call is:
462 This will cause the contents which previously appeared under
464 to now be accessible under
466 The physical location of the files is not changed.
469 has to be a mountpoint.
471 Note also that moving a mount residing under a shared mount is invalid and
473 .B findmnt \-o TARGET,PROPAGATION
474 to see the current propagation flags.
476 .SS Shared subtree operations
477 Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared,
478 private, slave or unbindable. A shared mount provides the ability to create mirrors
479 of that mount such that mounts and unmounts within any of the mirrors propagate
480 to the other mirror. A slave mount receives propagation from its master, but
481 not vice versa. A private mount carries no propagation abilities. An
482 unbindable mount is a private mount which cannot be cloned through a bind
483 operation. The detailed semantics are documented in
484 .I Documentation/filesystems/sharedsubtree.txt
485 file in the kernel source tree.
487 Supported operations are:
491 .BI "mount \-\-make\-shared " mountpoint
492 .BI "mount \-\-make\-slave " mountpoint
493 .BI "mount \-\-make\-private " mountpoint
494 .BI "mount \-\-make\-unbindable " mountpoint
498 The following commands allow one to recursively change the type of all the
499 mounts under a given mountpoint.
503 .BI "mount \-\-make\-rshared " mountpoint
504 .BI "mount \-\-make\-rslave " mountpoint
505 .BI "mount \-\-make\-rprivate " mountpoint
506 .BI "mount \-\-make\-runbindable " mountpoint
513 when a \fB\-\-make-\fR* operation is requested. All necessary information has to be
514 specified on the command line.
516 Note that the Linux kernel does not allow to change multiple propagation flags
519 system call, and the flags cannot be mixed with other mount options and operations.
521 Since util-linux 2.23 the \fBmount\fR command allows to do more propagation
522 (topology) changes by one mount(8) call and do it also together with other
523 mount operations. This feature is EXPERIMENTAL. The propagation flags are applied
524 by additional \fBmount\fR(2) system calls when the preceding mount operations
525 were successful. Note that this use case is not atomic. It is possible to
526 specify the propagation flags in
542 .B mount \-\-make\-private \-\-make\-unbindable /dev/sda1 /foo
550 .B mount /dev/sda1 /foox
551 .B mount \-\-make\-private /foo
552 .B mount \-\-make\-unbindable /foo
556 .SH COMMAND-LINE OPTIONS
557 The full set of mount options used by an invocation of
559 is determined by first extracting the
560 mount options for the filesystem from the
562 table, then applying any options specified by the
564 argument, and finally applying a
566 option, when present.
568 The command \fBmount\fR does not pass all command-line options to the
569 \fB/sbin/mount.\fIsuffix\fR mount helpers. The interface between \fBmount\fR
570 and the mount helpers is described below in the section \fBEXTERNAL HELPERS\fR.
572 Command-line options available for the
577 Mount all filesystems (of the given types) mentioned in
579 (except for those whose line contains the
581 keyword). The filesystems are mounted following their order in
583 The mount command compares filesystem source, target (and fs root for bind
584 mount or btrfs) to detect already mounted filesystems. The kernel table with
585 already mounted filesystems is cached during \fBmount \-\-all\fR. It means
586 that all duplicated fstab entries will be mounted.
588 The option \fB\-\-all\fR is possible to use for remount operation too. In this
589 case all filters (\fB\-t\fR and \fB\-O\fR) are applied to the table of already
592 Since version 2.35 is possible to use the command line option \fB\-o\fR to
593 alter mount options from fstab (see also \fB\-\-options\-mode\fR).
595 Note that it is a bad practice to use \fBmount \-a\fR for
597 checking. The recommended solution is \fBfindmnt \-\-verify\fR.
599 .BR \-B , " \-\-bind"
600 Remount a subtree somewhere else (so that its contents are available
601 in both places). See above, under \fBBind mounts\fR.
603 .BR \-c , " \-\-no\-canonicalize"
604 Don't canonicalize paths. The mount command canonicalizes all paths
605 (from command line or fstab) by default. This option can be used
608 flag for already canonicalized absolute paths. The option is designed for mount
609 helpers which call \fBmount -i\fR. It is strongly recommended to not use this
610 command-line option for normal mount operations.
612 Note that \fBmount\fR(8) does not pass this option to the
613 \fB/sbin/mount.\fItype\fR helpers.
615 .BR \-F , " \-\-fork"
616 (Used in conjunction with
618 Fork off a new incarnation of \fBmount\fR for each device.
619 This will do the mounts on different devices or different NFS servers
621 This has the advantage that it is faster; also NFS timeouts go in
622 parallel. A disadvantage is that the mounts are done in undefined order.
623 Thus, you cannot use this option if you want to mount both
627 .IP "\fB\-f, \-\-fake\fP"
628 Causes everything to be done except for the actual system call; if it's not
629 obvious, this ``fakes'' mounting the filesystem. This option is useful in
632 flag to determine what the
634 command is trying to do. It can also be used to add entries for devices
635 that were mounted earlier with the \fB\-n\fR option. The \fB\-f\fR option
636 checks for an existing record in /etc/mtab and fails when the record already
637 exists (with a regular non-fake mount, this check is done by the kernel).
638 .IP "\fB\-i, \-\-internal\-only\fP"
639 Don't call the \fB/sbin/mount.\fIfilesystem\fR helper even if it exists.
641 .BR \-L , " \-\-label " \fIlabel
642 Mount the partition that has the specified
645 .BR \-l , " \-\-show\-labels"
646 Add the labels in the mount output. \fBmount\fR must have
647 permission to read the disk device (e.g.\& be set-user-ID root) for this to work.
648 One can set such a label for ext2, ext3 or ext4 using the
650 utility, or for XFS using
652 or for reiserfs using
653 .BR reiserfstune (8).
655 .BR \-M , " \-\-move"
656 Move a subtree to some other place. See above, the subsection
657 \fBThe move operation\fR.
659 .BR \-n , " \-\-no\-mtab"
660 Mount without writing in
662 This is necessary for example when
664 is on a read-only filesystem.
666 .BR \-N , " \-\-namespace " \fIns
667 Perform mount in namespace specified by \fIns\fR.
668 \fIns\fR is either PID of process running in that namespace
669 or special file representing that namespace.
672 switches to the namespace when it reads /etc/fstab, writes /etc/mtab (or writes to /run/mount) and calls
674 system call, otherwise it runs in the original namespace. It means that the target namespace does not have
675 to contain any libraries or another requirements necessary to execute
679 See \fBnamespaces\fR(7) for more information.
681 .BR \-O , " \-\-test\-opts " \fIopts
682 Limit the set of filesystems to which the
684 option applies. In this regard it is like the
690 For example, the command:
694 .B "mount \-a \-O no_netdev"
697 mounts all filesystems except those which have the option
699 specified in the options field in the
705 in that each option is matched exactly; a leading
707 at the beginning of one option does not negate the rest.
713 options are cumulative in effect; that is, the command
716 .B "mount \-a \-t ext2 \-O _netdev"
719 mounts all ext2 filesystems with the _netdev option, not all filesystems
720 that are either ext2 or have the _netdev option specified.
723 .BR \-o , " \-\-options " \fIopts
724 Use the specified mount options. The \fIopts\fR argument is
725 a comma-separated list. For example:
729 .B "mount LABEL=mydisk \-o noatime,nodev,nosuid"
733 For more details, see the
734 .B FILESYSTEM-INDEPENDENT MOUNT OPTIONS
736 .B FILESYSTEM-SPECIFIC MOUNT OPTIONS
741 .BR "\-\-options\-mode " \fImode
742 Controls how to combine options from fstab/mtab with options from command line.
743 \fImode\fR can be one of
744 .BR ignore ", " append ", " prepend " or " replace .
745 For example \fBappend\fR means that options from fstab are appended to options from command line.
746 Default value is \fBprepend\fR -- it means command line options are evaluated after fstab options.
747 Note that the last option wins if there are conflicting ones.
750 .BR "\-\-options\-source " \fIsource
751 Source of default options.
752 \fIsource\fR is comma separated list of
753 .BR fstab ", " mtab " and " disable .
754 \fBdisable\fR disables
755 .BR fstab " and " mtab
756 and disables \fB\-\-options\-source\-force\fR.
757 Default value is \fBfstab,mtab\fR.
760 .B \-\-options\-source\-force
761 Use options from fstab/mtab even if both \fIdevice\fR and \fIdir\fR are specified.
764 .BR \-R , " \-\-rbind"
765 Remount a subtree and all possible submounts somewhere else (so that its
766 contents are available in both places). See above, the subsection
769 .BR \-r , " \-\-read\-only"
770 Mount the filesystem read-only. A synonym is
773 Note that, depending on the filesystem type, state and kernel behavior, the
774 system may still write to the device. For example, ext3 and ext4 will replay the
775 journal if the filesystem is dirty. To prevent this kind of write access, you
776 may want to mount an ext3 or ext4 filesystem with the \fBro,noload\fR mount
777 options or set the block device itself to read-only mode, see the
782 Tolerate sloppy mount options rather than failing. This will ignore mount
783 options not supported by a filesystem type. Not all filesystems support this
784 option. Currently it's supported by the \fBmount.nfs\fR mount helper only.
786 .BI \-\-source " device"
787 If only one argument for the mount command is given then the argument might be
788 interpreted as target (mountpoint) or source (device). This option allows to
789 explicitly define that the argument is the mount source.
791 .BI \-\-target " directory"
792 If only one argument for the mount command is given then the argument might be
793 interpreted as target (mountpoint) or source (device). This option allows to
794 explicitly define that the argument is the mount target.
796 .BI \-\-target\-prefix " directory"
797 Prepend specified directory to all mount targets. This option allows to follow
798 fstab, but mount operations is done on another place, for example:
802 .B "mount \-\-all \-\-target\-prefix /chroot \-o X\-mount.mkdir
805 mounts all from system fstab to /chroot, all missing muontpoint are created
806 (due to X-mount.mkdir). See also \fB\-\-fstab\fP to use an alternative fstab.
809 .BR \-T , " \-\-fstab " \fIpath
810 Specifies an alternative fstab file. If \fIpath\fP is a directory then the files
811 in the directory are sorted by
813 files that start with "."\& or without an \&.fstab extension are ignored. The option
814 can be specified more than once. This option is mostly designed for initramfs
815 or chroot scripts where additional configuration is specified beyond standard
816 system configuration.
818 Note that \fBmount\fR(8) does not pass the option \fB\-\-fstab\fP to the
819 \fB/sbin/mount.\fItype\fR helpers, meaning that the alternative fstab files will be
820 invisible for the helpers. This is no problem for normal mounts, but user
821 (non-root) mounts always require fstab to verify the user's rights.
823 .BR \-t , " \-\-types " \fIfstype
824 The argument following the
826 is used to indicate the filesystem type. The filesystem types which are
827 currently supported depend on the running kernel. See
830 .I /lib/modules/$(uname -r)/kernel/fs
831 for a complete list of the filesystems. The most common are ext2, ext3, ext4,
832 xfs, btrfs, vfat, sysfs, proc, nfs and cifs.
838 support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For
839 example 'fuse.sshfs'. It's recommended to use subtype notation rather than add
840 any prefix to the mount source (for example 'sshfs#example.com' is
845 option is given, or if the
847 type is specified, mount will try to guess the desired type.
848 Mount uses the blkid library for guessing the filesystem
849 type; if that does not turn up anything that looks familiar,
850 mount will try to read the file
851 .IR /etc/filesystems ,
852 or, if that does not exist,
853 .IR /proc/filesystems .
854 All of the filesystem types listed there will be tried,
855 except for those that are labeled "nodev" (e.g.\&
862 ends in a line with a single *, mount will read
864 afterwards. While trying, all filesystem types will be
865 mounted with the mount option \fBsilent\fR.
869 type may be useful for user-mounted floppies.
872 can be useful to change the probe order (e.g., to try vfat before msdos
873 or ext3 before ext2) or if you use a kernel module autoloader.
875 More than one type may be specified in a comma-separated
880 entry. The list of filesystem types for option
884 to specify the filesystem types on which no action should be taken.
887 has no effect when specified in an
893 can be meaningful with the
895 option. For example, the command
899 .B "mount \-a \-t nomsdos,smbfs"
902 mounts all filesystems except those of type
907 For most types all the
909 program has to do is issue a simple
911 system call, and no detailed knowledge of the filesystem type is required.
912 For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is
913 necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems
914 have a separate mount program. In order to make it possible to
915 treat all types in a uniform way, \fBmount\fR will execute the program
916 .BI /sbin/mount. type
917 (if that exists) when called with type
919 Since different versions of the
921 program have different calling conventions,
923 may have to be a shell script that sets up the desired call.
926 .BR \-U , " \-\-uuid " \fIuuid
927 Mount the partition that has the specified
930 .BR \-v , " \-\-verbose"
933 .BR \-w , " \-\-rw" , " \-\-read\-write"
934 Mount the filesystem read/write. The read-write is kernel default. A synonym is
937 Note that specify \fB\-w\fR on command line forces \fBmount\fR command
938 to never try read-only mount on write-protected devices. The default is
939 try read-only if the previous mount syscall with read-write flags failed.
941 .BR \-V , " \-\-version"
942 Display version information and exit.
944 .BR \-h , " \-\-help"
945 Display help text and exit.
947 .SH FILESYSTEM-INDEPENDENT MOUNT OPTIONS
948 Some of these options are only useful when they appear in the
952 Some of these options could be enabled or disabled by default
953 in the system kernel. To check the current setting see the options
954 in /proc/mounts. Note that filesystems also have per-filesystem
955 specific default mount options (see for example \fBtune2fs \-l\fP
956 output for extN filesystems).
958 The following options apply to any filesystem that is being
959 mounted (but not every filesystem actually honors them \(en e.g.\&, the
961 option today has an effect only for ext2, ext3, ext4, fat, vfat, ufs and xfs):
965 All I/O to the filesystem should be done asynchronously. (See also the
970 Do not use the \fBnoatime\fR feature, so the inode access time is controlled
971 by kernel defaults. See also the descriptions of the \fB\%relatime\fR and
976 Do not update inode access times on this filesystem (e.g.\& for faster
977 access on the news spool to speed up news servers). This works for all
978 inode types (directories too), so it implies \fB\%nodiratime\fR.
981 Can be mounted with the
986 Can only be mounted explicitly (i.e., the
988 option will not cause the filesystem to be mounted).
991 .BR context=\fIcontext ", " fscontext=\fIcontext ", " defcontext=\fIcontext ", and " \%rootcontext=\fIcontext
995 option is useful when mounting filesystems that do not support
996 extended attributes, such as a floppy or hard disk formatted with VFAT, or
997 systems that are not normally running under SELinux, such as an ext3 or ext4 formatted
999 disk from a non-SELinux workstation. You can also use
1001 on filesystems you do not trust, such as a floppy. It also helps in compatibility with
1002 xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where
1003 xattrs are supported, you can save time not having to label every file by
1004 assigning the entire disk one security context.
1006 A commonly used option for removable media is
1007 .BR \%context="system_u:object_r:removable_t" .
1009 Two other options are
1013 both of which are mutually exclusive of the context option. This means you
1014 can use fscontext and defcontext with each other, but neither can be used with
1019 option works for all filesystems, regardless of their xattr
1020 support. The fscontext option sets the overarching filesystem label to a
1021 specific security context. This filesystem label is separate from the
1022 individual labels on the files. It represents the entire filesystem for
1023 certain kinds of permission checks, such as during mount or file creation.
1024 Individual file labels are still obtained from the xattrs on the files
1025 themselves. The context option actually sets the aggregate context that
1026 fscontext provides, in addition to supplying the same label for individual
1029 You can set the default security context for unlabeled files using
1031 option. This overrides the value set for unlabeled files in the policy and requires a
1032 filesystem that supports xattr labeling.
1036 option allows you to explicitly label the root inode of a FS being mounted
1037 before that FS or inode becomes visible to userspace. This was found to be
1038 useful for things like stateless linux.
1040 Note that the kernel rejects any remount request that includes the context
1041 option, \fBeven\fP when unchanged from the current context.
1043 .BR "Warning: the \fIcontext\fP value might contain commas" ,
1044 in which case the value has to be properly quoted, otherwise
1046 will interpret the comma as a separator between mount options. Don't forget that
1047 the shell strips off quotes and thus
1048 .BR "double quoting is required" .
1054 .B mount \-t tmpfs none /mnt \-o \e
1055 .B \ \ 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
1059 For more details, see
1065 Use the default options:
1066 .BR rw ", " suid ", " dev ", " exec ", " auto ", " nouser ", and " async .
1068 Note that the real set of all default mount options depends on kernel
1069 and filesystem type. See the beginning of this section for more details.
1072 Interpret character or block special devices on the filesystem.
1075 Do not interpret character or block special devices on the file
1079 Update directory inode access times on this filesystem. This is the default.
1080 (This option is ignored when \fBnoatime\fR is set.)
1083 Do not update directory inode access times on this filesystem.
1084 (This option is implied when \fBnoatime\fR is set.)
1087 All directory updates within the filesystem should be done synchronously.
1088 This affects the following system calls: creat, link, unlink, symlink,
1089 mkdir, rmdir, mknod and rename.
1092 Permit execution of binaries.
1095 Do not permit direct execution of any binaries on the mounted filesystem.
1098 Allow an ordinary user to mount the filesystem if one
1099 of that user's groups matches the group of the device.
1100 This option implies the options
1101 .BR nosuid " and " nodev
1102 (unless overridden by subsequent options, as in the option line
1103 .BR group,dev,suid ).
1106 Every time the inode is modified, the i_version field will be incremented.
1109 Do not increment the i_version inode field.
1112 Allow mandatory locks on this filesystem. See
1116 Do not allow mandatory locks on this filesystem.
1119 The filesystem resides on a device that requires network access
1120 (used to prevent the system from attempting to mount these filesystems
1121 until the network has been enabled on the system).
1124 Do not report errors for this device if it does not exist.
1127 Update inode access times relative to modify or change time. Access
1128 time is only updated if the previous access time was earlier than the
1129 current modify or change time. (Similar to \fB\%noatime\fR, but it doesn't
1130 break \fBmutt\fR or other applications that need to know if a file has been
1131 read since the last time it was modified.)
1133 Since Linux 2.6.30, the kernel defaults to the behavior provided by this
1136 was specified), and the
1138 option is required to obtain traditional semantics. In addition, since Linux
1139 2.6.30, the file's last access time is always updated if it is more than 1
1145 feature. See also the
1150 Allows to explicitly request full atime updates. This makes it
1151 possible for the kernel to default to
1155 but still allow userspace to override it. For more details about the default
1156 system mount options see /proc/mounts.
1159 Use the kernel's default behavior for inode access time updates.
1162 Only update times (atime, mtime, ctime) on the in-memory version of the file inode.
1164 This mount option significantly reduces writes to the inode table for
1165 workloads that perform frequent random writes to preallocated files.
1167 The on-disk timestamps are updated only when:
1170 - the inode needs to be updated for some change unrelated to file timestamps
1172 - the application employs
1178 - an undeleted inode is evicted from memory
1180 - more than 24 hours have passed since the i-node was written to disk.
1185 Do not use the lazytime feature.
1188 Honor set-user-ID and set-group-ID bits or file capabilities when
1189 executing programs from this filesystem.
1192 Do not honor set-user-ID and set-group-ID bits or file capabilities when
1193 executing programs from this filesystem.
1196 Turn on the silent flag.
1199 Turn off the silent flag.
1202 Allow an ordinary user to mount the filesystem if that
1203 user is the owner of the device.
1204 This option implies the options
1205 .BR nosuid " and " nodev
1206 (unless overridden by subsequent options, as in the option line
1207 .BR owner,dev,suid ).
1210 Attempt to remount an already-mounted filesystem. This is commonly
1211 used to change the mount flags for a filesystem, especially to make a
1212 readonly filesystem writable. It does not change device or mount point.
1214 The remount operation together with the
1216 flag has special semantic. See above, the subsection \fBBind mounts\fR.
1218 The remount functionality follows the standard way the mount command works
1219 with options from fstab. This means that \fBmount\fR does not
1220 read fstab (or mtab) only when both
1227 .B "mount \-o remount,rw /dev/foo /dir"
1230 After this call all old mount options are replaced and arbitrary stuff from
1231 fstab (or mtab) is ignored, except the loop= option which is internally
1232 generated and maintained by the mount command.
1235 .B "mount \-o remount,rw /dir"
1238 After this call, mount reads fstab and merges these options with
1239 the options from the command line (\fB\-o\fR).
1240 If no mountpoint is found in fstab, then a remount with unspecified source is
1243 mount(8) allows to use \fB\-\-all\fR to remount all already mounted filesystems
1244 which match a specified filter (\fB\-O\fR and \fB\-t\fR). For example:
1247 .B "mount \-\-all \-o remount,ro -t vfat"
1250 remounts all already mounted vfat filesystems in read-only mode. The each of the
1251 filesystems is remounted by "mount \-o remount,ro /dir" semantic. It means the
1252 mount command reads fstab or mtab and merges these options with the options
1253 from the command line.
1256 Mount the filesystem read-only.
1259 Mount the filesystem read-write.
1262 All I/O to the filesystem should be done synchronously. In the case of
1263 media with a limited number of write cycles
1264 (e.g.\& some flash drives), \fBsync\fR may cause life-cycle shortening.
1267 Allow an ordinary user to mount the filesystem.
1268 The name of the mounting user is written to the mtab file (or to the private
1269 libmount file in /run/mount on systems without a regular mtab) so that this
1270 same user can unmount the filesystem again.
1271 This option implies the options
1272 .BR noexec ", " nosuid ", and " nodev
1273 (unless overridden by subsequent options, as in the option line
1274 .BR user,exec,dev,suid ).
1277 Forbid an ordinary user to mount the filesystem.
1278 This is the default; it does not imply any other options.
1281 Allow any user to mount and to unmount the filesystem, even
1282 when some other ordinary user mounted it.
1283 This option implies the options
1284 .BR noexec ", " nosuid ", and " nodev
1285 (unless overridden by subsequent options, as in the option line
1286 .BR users,exec,dev,suid ).
1289 All options prefixed with "X-" are interpreted as comments or as userspace
1290 application-specific options. These options are not stored in the user space (e.g. mtab file),
1291 nor sent to the mount.\fItype\fR helpers nor to the
1293 system call. The suggested format is \fBX-\fIappname\fR.\fIoption\fR.
1296 The same as \fBX-*\fR options, but stored permanently in the user space. It
1297 means the options are also available for umount or another operations. Note
1298 that maintain mount options in user space is tricky, because it's necessary use
1299 libmount based tools and there is no guarantee that the options will be always
1300 available (for example after a move mount operation or in unshared namespace).
1302 Note that before util-linux v2.30 the x-* options have not been maintained by
1303 libmount and stored in user space (functionality was the same as have X-* now),
1304 but due to growing number of use-cases (in initrd, systemd etc.) the
1305 functionality have been extended to keep existing fstab configurations usable
1308 .BR X-mount.mkdir [ = \fImode\fR ]
1309 Allow to make a target directory (mountpoint). The optional argument
1311 specifies the filesystem access mode used for
1313 in octal notation. The default mode is 0755. This functionality is supported
1314 only for root users. The option is also supported as x-mount.mkdir, this notation
1315 is deprecated for mount.mkdir since v2.30.
1317 .SH "FILESYSTEM-SPECIFIC MOUNT OPTIONS"
1318 You should consult the respective man page for the filesystem first.
1319 If you want to know what options the ext4 filesystem supports, then check the
1322 If that doesn't exist, you can also check the corresponding mount page like
1324 Note that you might have to install the respective userland tools.
1326 The following options apply only to certain filesystems.
1327 We sort them by filesystem. They all follow the
1331 What options are supported depends a bit on the running kernel.
1332 More info may be found in the kernel source subdirectory
1333 .IR Documentation/filesystems .
1335 .SS "Mount options for adfs"
1337 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1338 Set the owner and group of the files in the filesystem (default: uid=gid=0).
1340 \fBownmask=\fP\,\fIvalue\fP and \fBothmask=\fP\,\fIvalue\fP
1341 Set the permission mask for ADFS 'owner' permissions and 'other' permissions,
1342 respectively (default: 0700 and 0077, respectively).
1344 .IR /usr/src/linux/Documentation/filesystems/adfs.txt .
1346 .SS "Mount options for affs"
1348 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1349 Set the owner and group of the root of the filesystem (default: uid=gid=0,
1354 without specified value, the UID and GID of the current process are taken).
1356 \fBsetuid=\fP\,\fIvalue\fP and \fBsetgid=\fP\,\fIvalue\fP
1357 Set the owner and group of all files.
1360 Set the mode of all files to
1362 disregarding the original permissions.
1363 Add search permission to directories that have read permission.
1364 The value is given in octal.
1367 Do not allow any changes to the protection bits on the filesystem.
1370 Set UID and GID of the root of the filesystem to the UID and GID
1371 of the mount point upon the first sync or umount, and then
1372 clear this option. Strange...
1375 Print an informational message for each successful mount.
1378 Prefix used before volume name, when following a link.
1381 Prefix (of length at most 30) used before '/' when following a symbolic link.
1384 (Default: 2.) Number of unused blocks at the start of the device.
1387 Give explicitly the location of the root block.
1390 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
1392 .BR grpquota | noquota | quota | usrquota
1393 These options are accepted but ignored.
1394 (However, quota utilities may react to such strings in
1397 .SS "Mount options for debugfs"
1398 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1399 .IR /sys/kernel/debug .
1401 .\" present since 2.6.11
1402 As of kernel version 3.4, debugfs has the following options:
1404 .BI uid= n ", gid=" n
1405 Set the owner and group of the mountpoint.
1408 Sets the mode of the mountpoint.
1410 .SS "Mount options for devpts"
1411 The devpts filesystem is a pseudo filesystem, traditionally mounted on
1413 In order to acquire a pseudo terminal, a process opens
1415 the number of the pseudo terminal is then made available to the process
1416 and the pseudo terminal slave can be accessed as
1417 .IR /dev/pts/ <number>.
1419 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1420 This sets the owner or the group of newly created PTYs to
1421 the specified values. When nothing is specified, they will
1422 be set to the UID and GID of the creating process.
1423 For example, if there is a tty group with GID 5, then
1425 will cause newly created PTYs to belong to the tty group.
1428 Set the mode of newly created PTYs to the specified value.
1429 The default is 0600.
1434 makes "mesg y" the default on newly created PTYs.
1437 Create a private instance of devpts filesystem, such that
1438 indices of ptys allocated in this new instance are
1439 independent of indices created in other instances of devpts.
1441 All mounts of devpts without this
1443 option share the same set of pty indices (i.e. legacy mode).
1444 Each mount of devpts with the
1446 option has a private set of pty indices.
1448 This option is mainly used to support containers in the
1449 linux kernel. It is implemented in linux kernel versions
1450 starting with 2.6.29. Further, this mount option is valid
1451 only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the
1452 kernel configuration.
1454 To use this option effectively,
1456 must be a symbolic link to
1459 .I Documentation/filesystems/devpts.txt
1460 in the linux kernel source tree for details.
1464 Set the mode for the new
1466 device node in the devpts filesystem.
1468 With the support for multiple instances of devpts (see
1470 option above), each instance has a private
1472 node in the root of the devpts filesystem (typically
1473 .IR /dev/pts/ptmx ).
1475 For compatibility with older versions of the kernel, the
1476 default mode of the new
1480 specifies a more useful mode for the
1482 node and is highly recommended when the
1484 option is specified.
1486 This option is only implemented in linux kernel versions
1487 starting with 2.6.29. Further, this option is valid only if
1488 CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1491 .SS "Mount options for fat"
1494 is not a separate filesystem, but a common part of the
1501 .BR blocksize= { 512 | 1024 | 2048 }
1502 Set blocksize (default 512). This option is obsolete.
1504 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1505 Set the owner and group of all files.
1506 (Default: the UID and GID of the current process.)
1509 Set the umask (the bitmask of the permissions that are
1511 present). The default is the umask of the current process.
1512 The value is given in octal.
1515 Set the umask applied to directories only.
1516 The default is the umask of the current process.
1517 The value is given in octal.
1520 Set the umask applied to regular files only.
1521 The default is the umask of the current process.
1522 The value is given in octal.
1524 .BI allow_utime= value
1525 This option controls the permission check of mtime/atime.
1529 If current process is in group of file's group ID, you can change timestamp.
1532 Other users can change timestamp.
1534 The default is set from `dmask' option. (If the directory is writable,
1536 is also allowed. I.e.\& \s+3~\s0dmask & 022)
1540 checks current process is owner of the file, or it has
1541 CAP_FOWNER capability. But FAT filesystem doesn't have UID/GID on disk, so
1542 normal check is too inflexible. With this option you can relax it.
1546 Three different levels of pickiness can be chosen:
1550 Upper and lower case are accepted and equivalent, long name parts are
1552 .I verylongname.foobar
1555 leading and embedded spaces are accepted in each name part (name and extension).
1558 Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are
1559 rejected. This is the default.
1562 Like "normal", but names that contain long parts or special characters
1563 that are sometimes used on Linux but are not accepted by MS-DOS
1564 (+, =, etc.) are rejected.
1568 Sets the codepage for converting to shortname characters on FAT
1569 and VFAT filesystems. By default, codepage 437 is used.
1572 This option is obsolete and may fail or being ignored.
1574 .BI cvf_format= module
1575 Forces the driver to use the CVF (Compressed Volume File) module
1577 instead of auto-detection. If the kernel supports kmod, the
1578 cvf_format=xxx option also controls on-demand CVF module loading.
1579 This option is obsolete.
1581 .BI cvf_option= option
1582 Option passed to the CVF module. This option is obsolete.
1587 flag. A version string and a list of filesystem parameters will be
1588 printed (these data are also printed if the parameters appear to be
1592 If set, causes discard/TRIM commands to be issued to the block device
1593 when blocks are freed. This is useful for SSD devices and
1594 sparse/thinly-provisioned LUNs.
1597 If set, use a fallback default BIOS Parameter Block configuration, determined
1598 by backing device size. These static parameters match defaults assumed by DOS
1599 1.x for 160 kiB, 180 kiB, 320 kiB, and 360 kiB floppies and floppy images.
1601 .BR errors= { panic | continue | remount-ro }
1602 Specify FAT behavior on critical errors: panic, continue without doing
1603 anything, or remount the partition in read-only mode (default behavior).
1605 .BR fat= { 12 | 16 | 32 }
1606 Specify a 12, 16 or 32 bit fat. This overrides
1607 the automatic FAT type detection routine. Use with caution!
1609 .BI iocharset= value
1610 Character set to use for converting between 8 bit characters
1611 and 16 bit Unicode characters. The default is iso8859-1.
1612 Long filenames are stored on disk in Unicode format.
1614 .BR nfs= { stale_rw | nostale_ro }
1615 Enable this only if you want to export the FAT filesystem over NFS.
1618 This option maintains an index (cache) of directory inodes which is used by the
1619 nfs-related code to improve look-ups. Full file operations (read/write) over
1620 NFS are supported but with cache eviction at NFS server, this could result in
1626 This option bases the inode number and file handle
1627 on the on-disk location of a file in the FAT directory entry.
1630 will not be returned after a file is
1631 evicted from the inode cache. However, it means that operations
1632 such as rename, create and unlink could cause file handles that
1633 previously pointed at one file to point at a different file,
1634 potentially causing data corruption. For this reason, this
1635 option also mounts the filesystem readonly.
1637 To maintain backward compatibility, '-o nfs' is also accepted,
1642 This option disables the conversion of timestamps
1643 between local time (as used by Windows on FAT) and UTC
1644 (which Linux uses internally). This is particularly
1645 useful when mounting devices (like digital cameras)
1646 that are set to UTC in order to avoid the pitfalls of
1649 .BI time_offset= minutes
1650 Set offset for conversion of timestamps from local time used by FAT to UTC.
1653 will be subtracted from each timestamp to convert it to UTC used
1654 internally by Linux. This is useful when the time zone set in the kernel via
1655 .BR settimeofday (2)
1656 is not the time zone used by the filesystem. Note
1657 that this option still does not provide correct time stamps in all cases in
1658 presence of DST - time stamps in a different DST setting will be off by one
1664 flag. Attempts to chown or chmod files do not return errors,
1665 although they fail. Use with caution!
1668 FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO of the
1669 directory will just be ignored, and is used only by applications as a flag
1670 (e.g.\& it's set for the customized folder).
1672 If you want to use ATTR_RO as read-only flag even for the directory, set this
1676 If set, the execute permission bits of the file will be allowed only if
1677 the extension part of the name is \&.EXE, \&.COM, or \&.BAT. Not set by default.
1680 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux.
1684 If set, the filesystem will try to flush to disk more early than normal.
1688 Use the "free clusters" value stored on FSINFO. It'll
1689 be used to determine number of free clusters without
1690 scanning disk. But it's not used by default, because
1691 recent Windows don't update it correctly in some
1692 case. If you are sure the "free clusters" on FSINFO is
1693 correct, by this option you can avoid scanning disk.
1695 .BR dots ", " nodots ", " dotsOK= [ yes | no ]
1696 Various misguided attempts to force Unix or DOS conventions
1697 onto a FAT filesystem.
1699 .SS "Mount options for hfs"
1701 .BI creator= cccc ", type=" cccc
1702 Set the creator/type values as shown by the MacOS finder
1703 used for creating new files. Default values: '????'.
1705 .BI uid= n ", gid=" n
1706 Set the owner and group of all files.
1707 (Default: the UID and GID of the current process.)
1709 .BI dir_umask= n ", file_umask=" n ", umask=" n
1710 Set the umask used for all directories, all regular files, or all
1711 files and directories. Defaults to the umask of the current process.
1714 Select the CDROM session to mount.
1715 Defaults to leaving that decision to the CDROM driver.
1716 This option will fail with anything but a CDROM as underlying device.
1719 Select partition number n from the device.
1720 Only makes sense for CDROMs.
1721 Defaults to not parsing the partition table at all.
1724 Don't complain about invalid mount options.
1726 .SS "Mount options for hpfs"
1728 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1729 Set the owner and group of all files. (Default: the UID and GID
1730 of the current process.)
1733 Set the umask (the bitmask of the permissions that are
1735 present). The default is the umask of the current process.
1736 The value is given in octal.
1738 .BR case= { lower | asis }
1739 Convert all files names to lower case, or leave them.
1744 This option is obsolete and may fail or being ignored.
1747 Do not abort mounting when certain consistency checks fail.
1749 .SS "Mount options for iso9660"
1750 ISO 9660 is a standard describing a filesystem structure to be used
1751 on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1757 filenames appear in an 8.3 format (i.e., DOS-like restrictions on filename
1758 length), and in addition all characters are in upper case. Also there is
1759 no field for file ownership, protection, number of links, provision for
1760 block/character devices, etc.
1762 Rock Ridge is an extension to iso9660 that provides all of these UNIX-like
1763 features. Basically there are extensions to each directory record that
1764 supply all of the additional information, and when Rock Ridge is in use,
1765 the filesystem is indistinguishable from a normal UNIX filesystem (except
1766 that it is read-only, of course).
1769 Disable the use of Rock Ridge extensions, even if available. Cf.\&
1773 Disable the use of Microsoft Joliet extensions, even if available. Cf.\&
1776 .BR check= { r [ elaxed ]| s [ trict ]}
1779 a filename is first converted to lower case before doing the lookup.
1780 This is probably only meaningful together with
1787 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1788 Give all files in the filesystem the indicated user or group id,
1789 possibly overriding the information found in the Rock Ridge extensions.
1793 .BR map= { n [ ormal ]| o [ ff ]| a [ corn ]}
1794 For non-Rock Ridge volumes, normal name translation maps upper
1795 to lower case ASCII, drops a trailing `;1', and converts `;' to `.'.
1798 no name translation is done. See
1805 but also apply Acorn extensions if present.
1808 For non-Rock Ridge volumes, give all files the indicated mode.
1809 (Default: read and execute permission for everybody.)
1810 Octal mode values require a leading 0.
1813 Also show hidden and associated files.
1814 (If the ordinary files and the associated or hidden files have
1815 the same filenames, this may make the ordinary files inaccessible.)
1817 .BR block= { 512 | 1024 | 2048 }
1818 Set the block size to the indicated value.
1823 This option is obsolete and may fail or being ignored.
1826 If the high byte of the file length contains other garbage,
1827 set this mount option to ignore the high order bits of the file length.
1828 This implies that a file cannot be larger than 16\ MB.
1831 Select number of session on multisession CD.
1834 Session begins from sector xxx.
1836 The following options are the same as for vfat and specifying them only makes
1837 sense when using discs encoded using Microsoft's Joliet extensions.
1839 .BI iocharset= value
1840 Character set to use for converting 16 bit Unicode characters on CD
1841 to 8 bit characters. The default is iso8859-1.
1844 Convert 16 bit Unicode characters on CD to UTF-8.
1846 .SS "Mount options for jfs"
1849 Character set to use for converting from Unicode to ASCII. The default is
1850 to do no conversion. Use
1852 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in
1858 Resize the volume to
1860 blocks. JFS only supports growing a volume, not shrinking it. This option
1861 is only valid during a remount, when the volume is mounted read-write. The
1863 keyword with no value will grow the volume to the full size of the partition.
1866 Do not write to the journal. The primary use of this option is to allow
1867 for higher performance when restoring a volume from backup media. The
1868 integrity of the volume is not guaranteed if the system abnormally ends.
1871 Default. Commit metadata changes to the journal. Use this option to remount
1874 option was previously specified in order to restore normal behavior.
1876 .BR errors= { continue | remount-ro | panic }
1877 Define the behavior when an error is encountered.
1878 (Either ignore errors and just mark the filesystem erroneous and continue,
1879 or remount the filesystem read-only, or panic and halt the system.)
1881 .BR noquota | quota | usrquota | grpquota
1882 These options are accepted but ignored.
1884 .SS "Mount options for msdos"
1885 See mount options for fat.
1888 filesystem detects an inconsistency, it reports an error and sets the file
1889 system read-only. The filesystem can be made writable again by remounting
1892 .SS "Mount options for ncpfs"
1894 .IR nfs ", the " ncpfs
1895 implementation expects a binary argument (a
1896 .IR "struct ncp_mount_data" )
1897 to the mount system call. This argument is constructed by
1899 and the current version of
1901 (2.12) does not know anything about ncpfs.
1903 .SS "Mount options for ntfs"
1906 Character set to use when returning file names.
1907 Unlike VFAT, NTFS suppresses names that contain
1908 nonconvertible characters. Deprecated.
1911 New name for the option earlier called
1915 Use UTF-8 for converting file names.
1917 .BR uni_xlate= { 0 | 1 | 2 }
1918 For 0 (or `no' or `false'), do not use escape sequences
1919 for unknown Unicode characters.
1920 For 1 (or `yes' or `true') or 2, use vfat-style 4-byte escape sequences
1921 starting with ":". Here 2 give a little-endian encoding
1922 and 1 a byteswapped bigendian encoding.
1925 If enabled (posix=1), the filesystem distinguishes between
1926 upper and lower case. The 8.3 alias names are presented as
1927 hard links instead of being suppressed. This option is obsolete.
1929 \fBuid=\fP\,\fIvalue\fP, \fBgid=\fP\,\fIvalue\fP and \fBumask=\fP\,\fIvalue\fP
1930 Set the file permission on the filesystem.
1931 The umask value is given in octal.
1932 By default, the files are owned by root and not readable by somebody else.
1934 .SS "Mount options for overlay"
1935 Since Linux 3.18 the overlay pseudo filesystem implements a union mount for
1938 An overlay filesystem combines two filesystems - an \fBupper\fR filesystem and
1939 a \fBlower\fR filesystem. When a name exists in both filesystems, the object
1940 in the upper filesystem is visible while the object in the lower filesystem is
1941 either hidden or, in the case of directories, merged with the upper object.
1943 The lower filesystem can be any filesystem supported by Linux and does not need
1944 to be writable. The lower filesystem can even be another overlayfs. The upper
1945 filesystem will normally be writable and if it is it must support the creation
1946 of trusted.* extended attributes, and must provide a valid d_type in readdir
1947 responses, so NFS is not suitable.
1949 A read-only overlay of two read-only filesystems may use any filesystem type.
1950 The options \fBlowerdir\fR and \fBupperdir\fR are combined into a merged
1956 .B "mount \-t overlay overlay \e"
1957 .B " \-olowerdir=/lower,upperdir=/upper,workdir=/work /merged"
1963 .BI lowerdir= directory
1964 Any filesystem, does not need to be on a writable filesystem.
1966 .BI upperdir= directory
1967 The upperdir is normally on a writable filesystem.
1969 .BI workdir= directory
1970 The workdir needs to be an empty directory on the same filesystem as upperdir.
1972 .SS "Mount options for reiserfs"
1973 Reiserfs is a journaling filesystem.
1976 Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem,
1977 using the 3.6 format for newly created objects. This filesystem will no
1978 longer be compatible with reiserfs 3.5 tools.
1980 .BR hash= { rupasov | tea | r5 | detect }
1981 Choose which hash function reiserfs will use to find files within directories.
1985 A hash invented by Yury Yu.\& Rupasov. It is fast and preserves locality,
1986 mapping lexicographically close file names to close hash values.
1987 This option should not be used, as it causes a high probability of hash
1991 A Davis-Meyer function implemented by Jeremy Fitzhardinge.
1992 It uses hash permuting bits in the name. It gets high randomness
1993 and, therefore, low probability of hash collisions at some CPU cost.
1994 This may be used if EHASHCOLLISION errors are experienced with the r5 hash.
1997 A modified version of the rupasov hash. It is used by default and is
1998 the best choice unless the filesystem has huge directories and
1999 unusual file-name patterns.
2004 to detect which hash function is in use by examining
2005 the filesystem being mounted, and to write this information into
2006 the reiserfs superblock. This is only useful on the first mount of
2007 an old format filesystem.
2010 .B hashed_relocation
2011 Tunes the block allocator. This may provide performance improvements
2014 .B no_unhashed_relocation
2015 Tunes the block allocator. This may provide performance improvements
2019 Disable the border allocator algorithm invented by Yury Yu.\& Rupasov.
2020 This may provide performance improvements in some situations.
2023 Disable journaling. This will provide slight performance improvements in
2024 some situations at the cost of losing reiserfs's fast recovery from crashes.
2025 Even with this option turned on, reiserfs still performs all journaling
2026 operations, save for actual writes into its journaling area. Implementation
2029 is a work in progress.
2032 By default, reiserfs stores small files and `file tails' directly into its
2033 tree. This confuses some utilities such as
2035 This option is used to disable packing of files into the tree.
2038 Replay the transactions which are in the journal, but do not actually
2039 mount the filesystem. Mainly used by
2043 A remount option which permits online expansion of reiserfs partitions.
2044 Instructs reiserfs to assume that the device has
2047 This option is designed for use with devices which are under logical
2048 volume management (LVM).
2051 utility which can be obtained from
2052 .IR ftp://ftp.namesys.com/pub/reiserfsprogs .
2055 Enable Extended User Attributes. See the
2060 Enable POSIX Access Control Lists. See the
2064 .BR barrier=none " / " barrier=flush "
2065 This disables / enables the use of write barriers in the journaling code.
2066 barrier=none disables, barrier=flush enables (default). This also requires an
2067 IO stack which can support barriers, and if reiserfs gets an error on a barrier
2068 write, it will disable barriers again with a warning. Write barriers enforce
2069 proper on-disk ordering of journal commits, making volatile disk write caches
2070 safe to use, at some performance penalty. If your disks are battery-backed in
2071 one way or another, disabling barriers may safely improve performance.
2073 .SS "Mount options for ubifs"
2074 UBIFS is a flash filesystem which works on top of UBI volumes. Note that
2075 \fBatime\fR is not supported and is always turned off.
2077 The device name may be specified as
2105 separator may be used instead of
2108 The following mount options are available:
2111 Enable bulk-read. VFS read-ahead is disabled because it slows down the file
2112 system. Bulk-Read is an internal optimization. Some flashes may read faster if
2113 the data are read at one go, rather than at several read requests. For
2114 example, OneNAND can do "read-while-load" if it reads more than one NAND page.
2117 Do not bulk-read. This is the default.
2120 Check data CRC-32 checksums. This is the default.
2122 .BR no_chk_data_crc .
2123 Do not check data CRC-32 checksums. With this option, the filesystem does not
2124 check CRC-32 checksum for data, but it does check it for the internal indexing
2125 information. This option only affects reading, not writing. CRC-32 is always
2126 calculated when writing the data.
2128 .BR compr= { none | lzo | zlib }
2129 Select the default compressor which is used when new files are written. It is
2130 still possible to read compressed files if mounted with the
2134 .SS "Mount options for udf"
2135 UDF is the "Universal Disk Format" filesystem defined by OSTA, the Optical
2136 Storage Technology Association, and is often used for DVD-ROM, frequently
2137 in the form of a hybrid UDF/ISO-9660 filesystem. It is, however,
2138 perfectly usable by itself on disk drives, flash drives and other block devices.
2143 Make all files in the filesystem belong to the given user.
2144 uid=forget can be specified independently of (or usually in
2145 addition to) uid=<user> and results in UDF
2146 not storing uids to the media. In fact the recorded uid
2147 is the 32-bit overflow uid -1 as defined by the UDF standard.
2148 The value is given as either <user> which is a valid user name or the corresponding
2149 decimal user id, or the special string "forget".
2152 Make all files in the filesystem belong to the given group.
2153 gid=forget can be specified independently of (or usually in
2154 addition to) gid=<group> and results in UDF
2155 not storing gids to the media. In fact the recorded gid
2156 is the 32-bit overflow gid -1 as defined by the UDF standard.
2157 The value is given as either <group> which is a valid group name or the corresponding
2158 decimal group id, or the special string "forget".
2161 Mask out the given permissions from all inodes read from the filesystem.
2162 The value is given in octal.
2165 If mode= is set the permissions of all non-directory inodes read from the
2166 filesystem will be set to the given mode. The value is given in octal.
2169 If dmode= is set the permissions of all directory inodes read from the
2170 filesystem will be set to the given dmode. The value is given in octal.
2173 Set the block size. Default value prior to kernel version 2.6.30 was
2174 2048. Since 2.6.30 and prior to 4.11 it was logical device block size with
2175 fallback to 2048. Since 4.11 it is logical block size with fallback to
2176 any valid block size between logical device block size and 4096.
2178 For other details see the \fBmkudffs\fP(8) 2.0+ manpage, sections
2179 \fBCOMPATIBILITY\fP and \fBBLOCK SIZE\fP.
2182 Show otherwise hidden files.
2185 Show deleted files in lists.
2188 Embed data in the inode. (default)
2191 Don't embed data in the inode.
2194 Use short UDF address descriptors.
2197 Use long UDF address descriptors. (default)
2200 Unset strict conformance.
2203 Set the NLS character set. This requires kernel compiled with CONFIG_UDF_NLS option.
2206 Set the UTF-8 character set.
2207 .SS Mount options for debugging and disaster recovery
2210 Ignore the Volume Recognition Sequence and attempt to mount anyway.
2213 Select the session number for multi-session recorded optical media. (default= last session)
2216 Override standard anchor location. (default= 256)
2219 Set the last block of the filesystem.
2220 .SS Unused historical mount options that may be encountered and should be removed
2223 Ignored, use uid=<user> instead.
2226 Ignored, use gid=<group> instead.
2229 Unimplemented and ignored.
2232 Unimplemented and ignored.
2235 Unimplemented and ignored.
2238 Unimplemented and ignored.
2240 .SS "Mount options for ufs"
2243 UFS is a filesystem widely used in different operating systems.
2244 The problem are differences among implementations. Features of some
2245 implementations are undocumented, so its hard to recognize the
2246 type of ufs automatically.
2247 That's why the user must specify the type of ufs by mount option.
2248 Possible values are:
2252 Old format of ufs, this is the default, read only.
2253 (Don't forget to give the \-r option.)
2256 For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD).
2259 Used in FreeBSD 5.x supported as read-write.
2265 For filesystems created by SunOS or Solaris on Sparc.
2268 For filesystems created by Solaris on x86.
2271 For filesystems created by HP-UX, read-only.
2274 For filesystems created by NeXTStep (on NeXT station) (currently read only).
2277 For NextStep CDROMs (block_size == 2048), read-only.
2280 For filesystems created by OpenStep (currently read only).
2281 The same filesystem type is also used by Mac OS X.
2286 Set behavior on error:
2290 If an error is encountered, cause a kernel panic.
2292 .RB [ lock | umount | repair ]
2293 These mount options don't do anything at present;
2294 when an error is encountered only a console message is printed.
2297 .SS "Mount options for umsdos"
2298 See mount options for msdos.
2301 option is explicitly killed by
2304 .SS "Mount options for vfat"
2305 First of all, the mount options for
2310 option is explicitly killed by
2312 Furthermore, there are
2315 Translate unhandled Unicode characters to special escaped sequences.
2316 This lets you backup and restore filenames that are created with any
2317 Unicode characters. Without this option, a '?' is used when no
2318 translation is possible. The escape character is ':' because it is
2319 otherwise invalid on the vfat filesystem. The escape sequence
2320 that gets used, where u is the Unicode character,
2321 is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
2324 Allow two files with names that only differ in case.
2325 This option is obsolete.
2328 First try to make a short name without sequence number,
2330 .IR name\s+3~\s0num.ext .
2333 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the
2334 console. It can be enabled for the filesystem with this option or disabled
2335 with utf8=0, utf8=no or utf8=false. If `uni_xlate' gets set, UTF8 gets
2339 Defines the behavior for creation and display of filenames which fit into
2340 8.3 characters. If a long name for a file exists, it will always be the
2341 preferred one for display. There are four \fImode\fRs:
2345 Force the short name to lower case upon display; store a long name when
2346 the short name is not all upper case.
2349 Force the short name to upper case upon display; store a long name when
2350 the short name is not all upper case.
2353 Display the short name as is; store a long name when the short name is
2354 not all lower case or all upper case.
2357 Display the short name as is; store a long name when the short name is not
2358 all upper case. This mode is the default since Linux 2.6.32.
2361 .SS "Mount options for usbfs"
2363 \fBdevuid=\fP\,\fIuid\fP and \fBdevgid=\fP\,\fIgid\fP and \fBdevmode=\fP\,\fImode\fP
2364 Set the owner and group and mode of the device files in the usbfs filesystem
2365 (default: uid=gid=0, mode=0644). The mode is given in octal.
2367 \fBbusuid=\fP\,\fIuid\fP and \fBbusgid=\fP\,\fIgid\fP and \fBbusmode=\fP\,\fImode\fP
2368 Set the owner and group and mode of the bus directories in the usbfs
2369 filesystem (default: uid=gid=0, mode=0555). The mode is given in octal.
2371 \fBlistuid=\fP\,\fIuid\fP and \fBlistgid=\fP\,\fIgid\fP and \fBlistmode=\fP\,\fImode\fP
2372 Set the owner and group and mode of the file
2374 (default: uid=gid=0, mode=0444). The mode is given in octal.
2376 .SS "Mount options for dm-verity""
2377 Mounting volumes using dm-verity for integrity verification is supported where appropriate
2378 using the following options. Requires libcryptsetup.
2379 If libcryptsetup supports extracting the root hash of an already mounted device, existing
2380 devices will be automatically reused in case of a match.
2382 \fBverity.hashdevice=\fP\,\fIpath\fP
2383 Path to the hash tree device associated with the source volume to pass to dm-verity.
2385 \fBverity.roothash=\fP\,\fIhex\fP
2386 Hex-encoded hash of the root of
2387 .I verity.hashdevice
2389 \fBverity.hashoffset=\fP\,\fIoffset\fP
2390 If the hash tree device is embedded in the source volume,
2392 (default: 0) is used by dm-verity to get to the tree.
2394 .SH "THE LOOP DEVICE"
2395 One further possible type is a mount via the loop device. For example,
2399 .B "mount /tmp/disk.img /mnt \-t vfat \-o loop=/dev/loop3"
2402 will set up the loop device
2404 to correspond to the file
2406 and then mount this device on
2409 If no explicit loop device is mentioned
2410 (but just an option `\fB\-o loop\fP' is given), then
2412 will try to find some unused loop device and use that, for example
2415 .B "mount /tmp/disk.img /mnt \-o loop"
2420 creates a loop device from a regular file if a filesystem type is
2421 not specified or the filesystem is known for libblkid, for example:
2424 .B "mount /tmp/disk.img /mnt"
2426 .B "mount \-t ext4 /tmp/disk.img /mnt"
2429 This type of mount knows about three options, namely
2430 .BR loop ", " offset " and " sizelimit ,
2431 that are really options to
2433 (These options can be used in addition to those specific
2434 to the filesystem type.)
2436 Since Linux 2.6.25 auto-destruction of loop devices is supported,
2437 meaning that any loop device allocated by
2444 You can also free a loop device by hand, using
2445 .BR "losetup \-d " or " umount \-d" .
2447 Since util-linux v2.29 mount command re-uses the loop device rather than
2448 initialize a new device if the same backing file is already used for some loop
2449 device with the same offset and sizelimit. This is necessary to avoid
2450 a filesystem corruption.
2454 has the following return codes (the bits can be ORed):
2460 incorrect invocation or permissions
2463 system error (out of memory, cannot fork, no more loop devices)
2474 problems writing or locking /etc/mtab
2480 some mount succeeded
2482 The command \fBmount \-a\fR returns 0 (all succeeded), 32 (all failed), or 64 (some
2483 failed, some succeeded).
2485 .SH "EXTERNAL HELPERS"
2486 The syntax of external mount helpers is:
2489 .BI /sbin/mount. suffix
2497 .IR type \fB. subtype ]
2500 where the \fIsuffix\fR is the filesystem type and the \fB\-sfnvoN\fR options have
2501 the same meaning as the normal mount options. The \fB\-t\fR option is used for
2502 filesystems with subtypes support (for example
2503 .BR "/sbin/mount.fuse \-t fuse.sshfs" ).
2505 The command \fBmount\fR does not pass the mount options
2522 to the mount.<suffix> helpers. All other options are used in a
2523 comma-separated list as argument to the \fB\-o\fR option.
2526 See also "\fBThe files /etc/fstab, /etc/mtab and /proc/mounts\fR" section above.
2532 libmount private runtime directory
2535 table of mounted filesystems or symlink to /proc/mounts
2537 .I /etc/mtab\s+3~\s0
2538 lock file (unused on systems with mtab symlink)
2541 temporary file (unused on systems with mtab symlink)
2544 a list of filesystem types to try
2546 .IP LIBMOUNT_FSTAB=<path>
2547 overrides the default location of the fstab file (ignored for suid)
2548 .IP LIBMOUNT_MTAB=<path>
2549 overrides the default location of the mtab file (ignored for suid)
2550 .IP LIBMOUNT_DEBUG=all
2551 enables libmount debug output
2552 .IP LIBBLKID_DEBUG=all
2553 enables libblkid debug output
2554 .IP LOOPDEV_DEBUG=all
2555 enables loop device setup debug output
2575 It is possible for a corrupted filesystem to cause a crash.
2577 Some Linux filesystems don't support
2578 .BR "\-o sync " nor " \-o dirsync"
2579 (the ext2, ext3, ext4, fat and vfat filesystems
2581 support synchronous updates (a la BSD) when mounted with the
2587 may not be able to change mount parameters (all
2588 .IR ext2fs -specific
2591 are changeable with a remount, for example, but you can't change
2598 It is possible that the files
2602 don't match on systems with a regular mtab file. The first file is based only on
2603 the mount command options, but the content of the second file also depends on
2604 the kernel and others settings (e.g.\& on a remote NFS server -- in certain cases
2605 the mount command may report unreliable information about an NFS mount point
2606 and the /proc/mounts file usually contains more reliable information.) This is
2607 another reason to replace the mtab file with a symlink to the
2611 Checking files on NFS filesystems referenced by file descriptors (i.e.\& the
2615 families of functions) may lead to inconsistent results due to the lack of
2616 a consistency check in the kernel even if noac is used.
2624 options used may fail when using older kernels if the
2626 command can't confirm that the size of the block device has been configured
2627 as requested. This situation can be worked around by using
2630 command manually before calling
2632 with the configured loop device.
2636 command existed in Version 5 AT&T UNIX.
2639 Karel Zak <kzak@redhat.com>
2642 The mount command is part of the util-linux package and is available from
2643 https://www.kernel.org/pub/linux/utils/util-linux/.