1 .\" Copyright (c) 1996-2004 Andries Brouwer
2 .\" Copyright (C) 2006-2012 Karel Zak <kzak@redhat.com>
4 .\" This page is somewhat derived from a page that was
5 .\" (c) 1980, 1989, 1991 The Regents of the University of California
6 .\" and had been heavily modified by Rik Faith and myself.
7 .\" (Probably no BSD text remains.)
8 .\" Fragments of text were written by Werner Almesberger, Remy Card,
9 .\" Stephen Tweedie and Eric Youngdale.
11 .\" This is free documentation; you can redistribute it and/or
12 .\" modify it under the terms of the GNU General Public License as
13 .\" published by the Free Software Foundation; either version 2 of
14 .\" the License, or (at your option) any later version.
16 .\" The GNU General Public License's references to "object code"
17 .\" and "executables" are to be interpreted as the output of any
18 .\" document formatting or typesetting system, including
19 .\" intermediate and printed output.
21 .\" This manual is distributed in the hope that it will be useful,
22 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of
23 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
24 .\" GNU General Public License for more details.
26 .\" You should have received a copy of the GNU General Public License along
27 .\" with this program; if not, write to the Free Software Foundation, Inc.,
28 .\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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 .BI "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 maybe 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 kernel and it is usually
120 specific to 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 name of disk partitions are unstable; hardware reconfiguration,
153 adding or removing a device can cause change in names. This is reason why it's
154 strongly recommended to use filesystem or partition identificators like UUID or
157 The command \fBlsblk --fs\fR provides 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 This real mtab file is still supported, but on current Linux systems it is
242 better to make it a symlink to
244 instead, because a regular mtab file maintained in userspace cannot reliably
245 work with namespaces, containers and other advanced Linux features.
247 If no arguments are given to
249 the list of mounted filesystems is printed.
251 If you want to override mount options from
253 you have to use the \fB\-o\fR option:
256 .BI mount " device" \fR| "dir " \-o " options"
259 and then the mount options from the command line will be appended to
260 the list of options from
262 The usual behavior is that the last option wins if there are conflicting
267 program does not read the
271 (or LABEL, UUID, PARTUUID or PARTLABEL) and
273 are specified. For example, to mount device
274 .BR foo " at " /dir :
277 .B "mount /dev/foo /dir"
281 .SS Non-superuser mounts
282 Normally, only the superuser can mount filesystems.
287 option on a line, anybody can mount the corresponding filesystem.
292 .B "/dev/cdrom /cd iso9660 ro,user,noauto,unhide"
295 any user can mount the iso9660 filesystem found on an inserted CDROM
301 Note that \fBmount\fR is very strict about non-root users and all paths
302 specified on command line are verified before fstab is parsed or a helper
303 program is executed. It's strongly recommended to use a valid mountpoint to
304 specify filesystem, otherwise \fBmount\fR may fail. For example it's bad idea
305 to use NFS or CIFS source on command line.
307 For more details, see
309 Only the user that mounted a filesystem can unmount it again.
310 If any user should be able to unmount it, then use
319 option is similar to the
321 option, with the restriction that the user must be the owner
322 of the special file. This may be useful e.g.\& for
324 if a login script makes the console user owner of this device.
327 option is similar, with the restriction that the user must be
328 member of the group of the special file.
331 Remount part of the file hierarchy somewhere else. The call is:
339 or by using this fstab entry:
348 After this call the same contents are accessible in two places.
349 One can also remount a single file (on a single file). It's also
350 possible to use the bind mount to create a mountpoint from a regular
351 directory, for example:
355 .B mount \-\-bind foo foo
358 The bind mount call attaches only (part of) a single filesystem, not possible
359 submounts. The entire file hierarchy including submounts is attached
360 a second place by using:
368 Note that the filesystem mount options will remain the same as those
369 on the original mount point.
372 since v2.27 allows to change the mount options by passing the
373 relevant options along with
379 .B mount -o bind,ro foo foo
382 This feature is not supported by the Linux kernel; it is implemented in userspace
383 by an additional \fBmount\fR(2) remounting system call.
384 This solution is not atomic.
386 The alternative (classic) way to create a read-only bind mount is to use the remount
387 operation, for example:
394 .B mount \-o remount,bind,ro
398 Note that a read-only bind will create a read-only mountpoint (VFS entry),
399 but the original filesystem superblock will still be writable, meaning that the
401 will be writable, but the
405 It's also possible to change nosuid, nodev, noexec, noatime, nodiratime and
406 relatime VFS entry flags by "remount,bind" operation. It's impossible to change
407 mount options recursively (for example with \fB-o rbind,ro\fR).
410 since v2.31 ignores the \fBbind\fR flag from
414 (if "-o remount" specified on command line). This is necessary to fully control
415 mount options on remount by command line. In the previous versions the bind
416 flag has been always applied and it was impossible to re-define mount options
417 without interaction with the bind semantic. This
419 behavior does not affect situations when "remount,bind" is specified in the
424 .SS The move operation
427 to another place (atomically). The call is:
435 This will cause the contents which previously appeared under
437 to now be accessible under
439 The physical location of the files is not changed.
442 has to be a mountpoint.
444 Note also that moving a mount residing under a shared mount is invalid and
446 .B findmnt \-o TARGET,PROPAGATION
447 to see the current propagation flags.
449 .SS Shared subtree operations
450 Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared,
451 private, slave or unbindable. A shared mount provides the ability to create mirrors
452 of that mount such that mounts and unmounts within any of the mirrors propagate
453 to the other mirror. A slave mount receives propagation from its master, but
454 not vice versa. A private mount carries no propagation abilities. An
455 unbindable mount is a private mount which cannot be cloned through a bind
456 operation. The detailed semantics are documented in
457 .I Documentation/filesystems/sharedsubtree.txt
458 file in the kernel source tree.
460 Supported operations are:
464 .BI "mount \-\-make\-shared " mountpoint
465 .BI "mount \-\-make\-slave " mountpoint
466 .BI "mount \-\-make\-private " mountpoint
467 .BI "mount \-\-make\-unbindable " mountpoint
471 The following commands allow one to recursively change the type of all the
472 mounts under a given mountpoint.
476 .BI "mount \-\-make\-rshared " mountpoint
477 .BI "mount \-\-make\-rslave " mountpoint
478 .BI "mount \-\-make\-rprivate " mountpoint
479 .BI "mount \-\-make\-runbindable " mountpoint
486 when a \fB\-\-make-\fR* operation is requested. All necessary information has to be
487 specified on the command line.
489 Note that the Linux kernel does not allow to change multiple propagation flags
492 system call, and the flags cannot be mixed with other mount options and operations.
494 Since util-linux 2.23 the \fBmount\fR command allows to do more propagation
495 (topology) changes by one mount(8) call and do it also together with other
496 mount operations. This feature is EXPERIMENTAL. The propagation flags are applied
497 by additional \fBmount\fR(2) system calls when the preceding mount operations
498 were successful. Note that this use case is not atomic. It is possible to
499 specify the propagation flags in
515 .BI "mount \-\-make\-private \-\-make\-unbindable /dev/sda1 /foo"
523 .BI "mount /dev/sda1 /foo"
524 .BI "mount \-\-make\-private /foo"
525 .BI "mount \-\-make\-unbindable /foo"
529 .SH COMMAND-LINE OPTIONS
530 The full set of mount options used by an invocation of
532 is determined by first extracting the
533 mount options for the filesystem from the
535 table, then applying any options specified by the
537 argument, and finally applying a
539 option, when present.
541 The command \fBmount\fR does not pass all command-line options to the
542 \fB/sbin/mount.\fIsuffix\fR mount helpers. The interface between \fBmount\fR
543 and the mount helpers is described below in the section \fBEXTERNAL HELPERS\fR.
545 Command-line options available for the
550 Mount all filesystems (of the given types) mentioned in
552 (except for those whose line contains the
554 keyword). The filesystems are mounted following their order in
556 The mount command compares filesystem source, target (and fs root for bind
557 mount or btrfs) to detect already mounted filesystems. The kernel table with
558 already mounted filesystems is cached during \fBmount \-\-all\fR. It means
559 that all duplicated fstab entries will be mounted.
561 Note that it is a bad practice to use \fBmount \-a\fR for
563 checking. The recommended solution is \fBfindmnt \-\-verify\fR.
565 .BR \-B , " \-\-bind"
566 Remount a subtree somewhere else (so that its contents are available
567 in both places). See above, under \fBBind mounts\fR.
569 .BR \-c , " \-\-no\-canonicalize"
570 Don't canonicalize paths. The mount command canonicalizes all paths
571 (from command line or fstab) by default. This option can be used
574 flag for already canonicalized absolute paths. The option is designed for mount
575 helpers which call \fBmount -i\fR. It is strongly recommended to not use this
576 command-line option for normal mount operations.
578 Note that \fBmount\fR(8) does not pass this option to the
579 \fB/sbin/mount.\fItype\fR helpers.
581 .BR \-F , " \-\-fork"
582 (Used in conjunction with
584 Fork off a new incarnation of \fBmount\fR for each device.
585 This will do the mounts on different devices or different NFS servers
587 This has the advantage that it is faster; also NFS timeouts go in
588 parallel. A disadvantage is that the mounts are done in undefined order.
589 Thus, you cannot use this option if you want to mount both
593 .IP "\fB\-f, \-\-fake\fP"
594 Causes everything to be done except for the actual system call; if it's not
595 obvious, this ``fakes'' mounting the filesystem. This option is useful in
598 flag to determine what the
600 command is trying to do. It can also be used to add entries for devices
601 that were mounted earlier with the \fB\-n\fR option. The \fB\-f\fR option
602 checks for an existing record in /etc/mtab and fails when the record already
603 exists (with a regular non-fake mount, this check is done by the kernel).
604 .IP "\fB\-i, \-\-internal\-only\fP"
605 Don't call the \fB/sbin/mount.\fIfilesystem\fR helper even if it exists.
607 .BR \-L , " \-\-label " \fIlabel
608 Mount the partition that has the specified
611 .BR \-l , " \-\-show\-labels"
612 Add the labels in the mount output. \fBmount\fR must have
613 permission to read the disk device (e.g.\& be set-user-ID root) for this to work.
614 One can set such a label for ext2, ext3 or ext4 using the
616 utility, or for XFS using
618 or for reiserfs using
619 .BR reiserfstune (8).
621 .BR \-M , " \-\-move"
622 Move a subtree to some other place. See above, the subsection
623 \fBThe move operation\fR.
625 .BR \-n , " \-\-no\-mtab"
626 Mount without writing in
628 This is necessary for example when
630 is on a read-only filesystem.
632 .BR \-O , " \-\-test\-opts " \fIopts
633 Limit the set of filesystems to which the
635 option applies. In this regard it is like the
641 For example, the command:
645 .B "mount \-a \-O no_netdev"
648 mounts all filesystems except those which have the option
650 specified in the options field in the
656 in that each option is matched exactly; a leading
658 at the beginning of one option does not negate the rest.
664 options are cumulative in effect; that is, the command
667 .B "mount \-a \-t ext2 \-O _netdev"
670 mounts all ext2 filesystems with the _netdev option, not all filesystems
671 that are either ext2 or have the _netdev option specified.
674 .BR \-o , " \-\-options " \fIopts
675 Use the specified mount options. The \fIopts\fR argument is
676 a comma-separated list. For example:
680 .B "mount LABEL=mydisk \-o noatime,nodev,nosuid"
684 For more details, see the
685 .B FILESYSTEM-INDEPENDENT MOUNT OPTIONS
687 .B FILESYSTEM-SPECIFIC MOUNT OPTIONS
692 .BR \-R , " \-\-rbind"
693 Remount a subtree and all possible submounts somewhere else (so that its
694 contents are available in both places). See above, the subsection
697 .BR \-r , " \-\-read\-only"
698 Mount the filesystem read-only. A synonym is
701 Note that, depending on the filesystem type, state and kernel behavior, the
702 system may still write to the device. For example, ext3 and ext4 will replay the
703 journal if the filesystem is dirty. To prevent this kind of write access, you
704 may want to mount an ext3 or ext4 filesystem with the \fBro,noload\fR mount
705 options or set the block device itself to read-only mode, see the
710 Tolerate sloppy mount options rather than failing. This will ignore mount
711 options not supported by a filesystem type. Not all filesystems support this
712 option. Currently it's supported by the \fBmount.nfs\fR mount helper only.
714 .BI \-\-source " device"
715 If only one argument for the mount command is given then the argument might be
716 interpreted as target (mountpoint) or source (device). This option allows to
717 explicitly define that the argument is the mount source.
719 .BI \-\-target " directory"
720 If only one argument for the mount command is given then the argument might be
721 interpreted as target (mountpoint) or source (device). This option allows to
722 explicitly define that the argument is the mount target.
724 .BR \-T , " \-\-fstab " \fIpath
725 Specifies an alternative fstab file. If \fIpath\fP is a directory then the files
726 in the directory are sorted by
728 files that start with "."\& or without an \&.fstab extension are ignored. The option
729 can be specified more than once. This option is mostly designed for initramfs
730 or chroot scripts where additional configuration is specified beyond standard
731 system configuration.
733 Note that \fBmount\fR(8) does not pass the option \fB\-\-fstab\fP to the
734 \fB/sbin/mount.\fItype\fR helpers, meaning that the alternative fstab files will be
735 invisible for the helpers. This is no problem for normal mounts, but user
736 (non-root) mounts always require fstab to verify the user's rights.
738 .BR \-t , " \-\-types " \fIfstype
739 The argument following the
741 is used to indicate the filesystem type. The filesystem types which are
742 currently supported depend on the running kernel. See
745 .I /lib/modules/$(uname -r)/kernel/fs
746 for a complete list of the filesystems. The most common are ext2, ext3, ext4,
747 xfs, btrfs, vfat, sysfs, proc, nfs and cifs.
753 support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For
754 example 'fuse.sshfs'. It's recommended to use subtype notation rather than add
755 any prefix to the mount source (for example 'sshfs#example.com' is
760 option is given, or if the
762 type is specified, mount will try to guess the desired type.
763 Mount uses the blkid library for guessing the filesystem
764 type; if that does not turn up anything that looks familiar,
765 mount will try to read the file
766 .IR /etc/filesystems ,
767 or, if that does not exist,
768 .IR /proc/filesystems .
769 All of the filesystem types listed there will be tried,
770 except for those that are labeled "nodev" (e.g.\&
777 ends in a line with a single *, mount will read
779 afterwards. While trying, all filesystem types will be
780 mounted with the mount option \fBsilent\fR.
784 type may be useful for user-mounted floppies.
787 can be useful to change the probe order (e.g., to try vfat before msdos
788 or ext3 before ext2) or if you use a kernel module autoloader.
790 More than one type may be specified in a comma-separated
795 entry. The list of filesystem types for option
799 to specify the filesystem types on which no action should be taken.
802 has no effect when specified in an
808 can be meaningful with the
810 option. For example, the command
814 .B "mount \-a \-t nomsdos,smbfs"
817 mounts all filesystems except those of type
822 For most types all the
824 program has to do is issue a simple
826 system call, and no detailed knowledge of the filesystem type is required.
827 For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is
828 necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems
829 have a separate mount program. In order to make it possible to
830 treat all types in a uniform way, \fBmount\fR will execute the program
831 .BI /sbin/mount. type
832 (if that exists) when called with type
834 Since different versions of the
836 program have different calling conventions,
838 may have to be a shell script that sets up the desired call.
841 .BR \-U , " \-\-uuid " \fIuuid
842 Mount the partition that has the specified
845 .BR \-v , " \-\-verbose"
848 .BR \-w , " \-\-rw" , " \-\-read\-write"
849 Mount the filesystem read/write. The read-write is kernel default. A synonym is
852 Note that specify \fB\-w\fR on command line forces \fBmount\fR command
853 to never try read-only mount on write-protected devices. The default is
854 try read-only if the previous mount syscall with read-write flags failed.
856 .BR \-V , " \-\-version"
857 Display version information and exit.
859 .BR \-h , " \-\-help"
860 Display help text and exit.
862 .SH FILESYSTEM-INDEPENDENT MOUNT OPTIONS
863 Some of these options are only useful when they appear in the
867 Some of these options could be enabled or disabled by default
868 in the system kernel. To check the current setting see the options
869 in /proc/mounts. Note that filesystems also have per-filesystem
870 specific default mount options (see for example \fBtune2fs \-l\fP
871 output for extN filesystems).
873 The following options apply to any filesystem that is being
874 mounted (but not every filesystem actually honors them \(en e.g.\&, the
876 option today has an effect only for ext2, ext3, fat, vfat and ufs):
880 All I/O to the filesystem should be done asynchronously. (See also the
885 Do not use the \fBnoatime\fR feature, so the inode access time is controlled
886 by kernel defaults. See also the descriptions of the \fB\%relatime\fR and
891 Do not update inode access times on this filesystem (e.g.\& for faster
892 access on the news spool to speed up news servers). This works for all
893 inode types (directories too), so it implies \fB\%nodiratime\fR.
896 Can be mounted with the
901 Can only be mounted explicitly (i.e., the
903 option will not cause the filesystem to be mounted).
906 .BR context=\fIcontext ", " fscontext=\fIcontext ", " defcontext=\fIcontext ", and " \%rootcontext=\fIcontext
910 option is useful when mounting filesystems that do not support
911 extended attributes, such as a floppy or hard disk formatted with VFAT, or
912 systems that are not normally running under SELinux, such as an ext3 formatted
913 disk from a non-SELinux workstation. You can also use
915 on filesystems you do not trust, such as a floppy. It also helps in compatibility with
916 xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where
917 xattrs are supported, you can save time not having to label every file by
918 assigning the entire disk one security context.
920 A commonly used option for removable media is
921 .BR \%context="system_u:object_r:removable_t" .
923 Two other options are
927 both of which are mutually exclusive of the context option. This means you
928 can use fscontext and defcontext with each other, but neither can be used with
933 option works for all filesystems, regardless of their xattr
934 support. The fscontext option sets the overarching filesystem label to a
935 specific security context. This filesystem label is separate from the
936 individual labels on the files. It represents the entire filesystem for
937 certain kinds of permission checks, such as during mount or file creation.
938 Individual file labels are still obtained from the xattrs on the files
939 themselves. The context option actually sets the aggregate context that
940 fscontext provides, in addition to supplying the same label for individual
943 You can set the default security context for unlabeled files using
945 option. This overrides the value set for unlabeled files in the policy and requires a
946 filesystem that supports xattr labeling.
950 option allows you to explicitly label the root inode of a FS being mounted
951 before that FS or inode becomes visible to userspace. This was found to be
952 useful for things like stateless linux.
954 Note that the kernel rejects any remount request that includes the context
955 option, \fBeven\fP when unchanged from the current context.
957 .BR "Warning: the \fIcontext\fP value might contain commas" ,
958 in which case the value has to be properly quoted, otherwise
960 will interpret the comma as a separator between mount options. Don't forget that
961 the shell strips off quotes and thus
962 .BR "double quoting is required" .
968 .B mount \-t tmpfs none /mnt \-o \e
969 .B \ \ 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
973 For more details, see
979 Use the default options:
980 .BR rw ", " suid ", " dev ", " exec ", " auto ", " nouser ", and " async .
982 Note that the real set of all default mount options depends on kernel
983 and filesystem type. See the beginning of this section for more details.
986 Interpret character or block special devices on the filesystem.
989 Do not interpret character or block special devices on the file
993 Update directory inode access times on this filesystem. This is the default.
994 (This option is ignored when \fBnoatime\fR is set.)
997 Do not update directory inode access times on this filesystem.
998 (This option is implied when \fBnoatime\fR is set.)
1001 All directory updates within the filesystem should be done synchronously.
1002 This affects the following system calls: creat, link, unlink, symlink,
1003 mkdir, rmdir, mknod and rename.
1006 Permit execution of binaries.
1009 Do not permit direct execution of any binaries on the mounted filesystem.
1012 Allow an ordinary user to mount the filesystem if one
1013 of that user's groups matches the group of the device.
1014 This option implies the options
1015 .BR nosuid " and " nodev
1016 (unless overridden by subsequent options, as in the option line
1017 .BR group,dev,suid ).
1020 Every time the inode is modified, the i_version field will be incremented.
1023 Do not increment the i_version inode field.
1026 Allow mandatory locks on this filesystem. See
1030 Do not allow mandatory locks on this filesystem.
1033 The filesystem resides on a device that requires network access
1034 (used to prevent the system from attempting to mount these filesystems
1035 until the network has been enabled on the system).
1038 Do not report errors for this device if it does not exist.
1041 Update inode access times relative to modify or change time. Access
1042 time is only updated if the previous access time was earlier than the
1043 current modify or change time. (Similar to \fB\%noatime\fR, but it doesn't
1044 break \fBmutt\fR or other applications that need to know if a file has been
1045 read since the last time it was modified.)
1047 Since Linux 2.6.30, the kernel defaults to the behavior provided by this
1050 was specified), and the
1052 option is required to obtain traditional semantics. In addition, since Linux
1053 2.6.30, the file's last access time is always updated if it is more than 1
1059 feature. See also the
1064 Allows to explicitly request full atime updates. This makes it
1065 possible for the kernel to default to
1069 but still allow userspace to override it. For more details about the default
1070 system mount options see /proc/mounts.
1073 Use the kernel's default behavior for inode access time updates.
1076 Only update times (atime, mtime, ctime) on the in-memory version of the file inode.
1078 This mount option significantly reduces writes to the inode table for
1079 workloads that perform frequent random writes to preallocated files.
1081 The on-disk timestamps are updated only when:
1084 - the inode needs to be updated for some change unrelated to file timestamps
1086 - the application employs
1092 - an undeleted inode is evicted from memory
1094 - more than 24 hours have passed since the i-node was written to disk.
1099 Do not use the lazytime feature.
1102 Allow set-user-ID or set-group-ID bits to take
1106 Do not allow set-user-ID or set-group-ID bits to take
1110 Turn on the silent flag.
1113 Turn off the silent flag.
1116 Allow an ordinary user to mount the filesystem if that
1117 user is the owner of the device.
1118 This option implies the options
1119 .BR nosuid " and " nodev
1120 (unless overridden by subsequent options, as in the option line
1121 .BR owner,dev,suid ).
1124 Attempt to remount an already-mounted filesystem. This is commonly
1125 used to change the mount flags for a filesystem, especially to make a
1126 readonly filesystem writable. It does not change device or mount point.
1128 The remount operation together with the
1130 flag has special semantic. See above, the subsection \fBBind mounts\fR.
1132 The remount functionality follows the standard way the mount command works
1133 with options from fstab. This means that \fBmount\fR does not
1134 read fstab (or mtab) only when both
1141 .B "mount \-o remount,rw /dev/foo /dir"
1144 After this call all old mount options are replaced and arbitrary stuff from
1145 fstab (or mtab) is ignored, except the loop= option which is internally
1146 generated and maintained by the mount command.
1149 .B "mount \-o remount,rw /dir"
1152 After this call, mount reads fstab and merges these options with
1153 the options from the command line (\fB\-o\fR).
1154 If no mountpoint is found in fstab, then a remount with unspecified source is
1158 Mount the filesystem read-only.
1161 Mount the filesystem read-write.
1164 All I/O to the filesystem should be done synchronously. In the case of
1165 media with a limited number of write cycles
1166 (e.g.\& some flash drives), \fBsync\fR may cause life-cycle shortening.
1169 Allow an ordinary user to mount the filesystem.
1170 The name of the mounting user is written to the mtab file (or to the private
1171 libmount file in /run/mount on systems without a regular mtab) so that this
1172 same user can unmount the filesystem again.
1173 This option implies the options
1174 .BR noexec ", " nosuid ", and " nodev
1175 (unless overridden by subsequent options, as in the option line
1176 .BR user,exec,dev,suid ).
1179 Forbid an ordinary user to mount the filesystem.
1180 This is the default; it does not imply any other options.
1183 Allow any user to mount and to unmount the filesystem, even
1184 when some other ordinary user mounted it.
1185 This option implies the options
1186 .BR noexec ", " nosuid ", and " nodev
1187 (unless overridden by subsequent options, as in the option line
1188 .BR users,exec,dev,suid ).
1191 All options prefixed with "X-" are interpreted as comments or as userspace
1192 application-specific options. These options are not stored in the user space (e.g. mtab file),
1193 nor sent to the mount.\fItype\fR helpers nor to the
1195 system call. The suggested format is \fBX-\fIappname\fR.\fIoption\fR.
1198 The same as \fBX-*\fR options, but stored permanently in the user space. It
1199 means the options are also available for umount or another operations. Note
1200 that maintain mount options in user space is tricky, because it's necessary use
1201 libmount based tools and there is no guarantee that the options will be always
1202 available (for example after a move mount operation or in unshared namespace).
1204 Note that before util-linux v2.30 the x-* options have not been maintained by
1205 libmount and stored in user space (functionality was the same as have X-* now),
1206 but due to growing number of use-cases (in initrd, systemd etc.) the
1207 functionality have been extended to keep existing fstab configurations usable
1210 .BR X-mount.mkdir [ = \fImode\fR ]
1211 Allow to make a target directory (mountpoint). The optional argument
1213 specifies the filesystem access mode used for
1215 in octal notation. The default mode is 0755. This functionality is supported
1216 only for root users. The option is also supported as x-mount.mkdir, this notation
1217 is deprecated for mount.mkdir since v2.30.
1219 .SH "FILESYSTEM-SPECIFIC MOUNT OPTIONS"
1220 You should consult the respective man page for the filesystem first.
1221 If you want to know what options the ext4 filesystem supports, then check the
1224 If that doesn't exist, you can also check the corresponding mount page like
1226 Note that you might have to install the respective userland tools.
1228 The following options apply only to certain filesystems.
1229 We sort them by filesystem. They all follow the
1233 What options are supported depends a bit on the running kernel.
1234 More info may be found in the kernel source subdirectory
1235 .IR Documentation/filesystems .
1237 .SS "Mount options for adfs"
1239 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1240 Set the owner and group of the files in the filesystem (default: uid=gid=0).
1242 \fBownmask=\fP\,\fIvalue\fP and \fBothmask=\fP\,\fIvalue\fP
1243 Set the permission mask for ADFS 'owner' permissions and 'other' permissions,
1244 respectively (default: 0700 and 0077, respectively).
1246 .IR /usr/src/linux/Documentation/filesystems/adfs.txt .
1248 .SS "Mount options for affs"
1250 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1251 Set the owner and group of the root of the filesystem (default: uid=gid=0,
1256 without specified value, the UID and GID of the current process are taken).
1258 \fBsetuid=\fP\,\fIvalue\fP and \fBsetgid=\fP\,\fIvalue\fP
1259 Set the owner and group of all files.
1262 Set the mode of all files to
1264 disregarding the original permissions.
1265 Add search permission to directories that have read permission.
1266 The value is given in octal.
1269 Do not allow any changes to the protection bits on the filesystem.
1272 Set UID and GID of the root of the filesystem to the UID and GID
1273 of the mount point upon the first sync or umount, and then
1274 clear this option. Strange...
1277 Print an informational message for each successful mount.
1280 Prefix used before volume name, when following a link.
1283 Prefix (of length at most 30) used before '/' when following a symbolic link.
1286 (Default: 2.) Number of unused blocks at the start of the device.
1289 Give explicitly the location of the root block.
1292 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
1294 .BR grpquota | noquota | quota | usrquota
1295 These options are accepted but ignored.
1296 (However, quota utilities may react to such strings in
1299 .SS "Mount options for debugfs"
1300 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1301 .IR /sys/kernel/debug .
1303 .\" present since 2.6.11
1304 As of kernel version 3.4, debugfs has the following options:
1306 .BI uid= n ", gid=" n
1307 Set the owner and group of the mountpoint.
1310 Sets the mode of the mountpoint.
1312 .SS "Mount options for devpts"
1313 The devpts filesystem is a pseudo filesystem, traditionally mounted on
1315 In order to acquire a pseudo terminal, a process opens
1317 the number of the pseudo terminal is then made available to the process
1318 and the pseudo terminal slave can be accessed as
1319 .IR /dev/pts/ <number>.
1321 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1322 This sets the owner or the group of newly created PTYs to
1323 the specified values. When nothing is specified, they will
1324 be set to the UID and GID of the creating process.
1325 For example, if there is a tty group with GID 5, then
1327 will cause newly created PTYs to belong to the tty group.
1330 Set the mode of newly created PTYs to the specified value.
1331 The default is 0600.
1336 makes "mesg y" the default on newly created PTYs.
1339 Create a private instance of devpts filesystem, such that
1340 indices of ptys allocated in this new instance are
1341 independent of indices created in other instances of devpts.
1343 All mounts of devpts without this
1345 option share the same set of pty indices (i.e legacy mode).
1346 Each mount of devpts with the
1348 option has a private set of pty indices.
1350 This option is mainly used to support containers in the
1351 linux kernel. It is implemented in linux kernel versions
1352 starting with 2.6.29. Further, this mount option is valid
1353 only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the
1354 kernel configuration.
1356 To use this option effectively,
1358 must be a symbolic link to
1361 .I Documentation/filesystems/devpts.txt
1362 in the linux kernel source tree for details.
1366 Set the mode for the new
1368 device node in the devpts filesystem.
1370 With the support for multiple instances of devpts (see
1372 option above), each instance has a private
1374 node in the root of the devpts filesystem (typically
1375 .IR /dev/pts/ptmx ).
1377 For compatibility with older versions of the kernel, the
1378 default mode of the new
1382 specifies a more useful mode for the
1384 node and is highly recommended when the
1386 option is specified.
1388 This option is only implemented in linux kernel versions
1389 starting with 2.6.29. Further, this option is valid only if
1390 CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1393 .SS "Mount options for fat"
1396 is not a separate filesystem, but a common part of the
1403 .BR blocksize= { 512 | 1024 | 2048 }
1404 Set blocksize (default 512). This option is obsolete.
1406 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1407 Set the owner and group of all files.
1408 (Default: the UID and GID of the current process.)
1411 Set the umask (the bitmask of the permissions that are
1413 present). The default is the umask of the current process.
1414 The value is given in octal.
1417 Set the umask applied to directories only.
1418 The default is the umask of the current process.
1419 The value is given in octal.
1422 Set the umask applied to regular files only.
1423 The default is the umask of the current process.
1424 The value is given in octal.
1426 .BI allow_utime= value
1427 This option controls the permission check of mtime/atime.
1431 If current process is in group of file's group ID, you can change timestamp.
1434 Other users can change timestamp.
1436 The default is set from `dmask' option. (If the directory is writable,
1438 is also allowed. I.e.\& \s+3~\s0dmask & 022)
1442 checks current process is owner of the file, or it has
1443 CAP_FOWNER capability. But FAT filesystem doesn't have UID/GID on disk, so
1444 normal check is too inflexible. With this option you can relax it.
1448 Three different levels of pickyness can be chosen:
1452 Upper and lower case are accepted and equivalent, long name parts are
1454 .I verylongname.foobar
1457 leading and embedded spaces are accepted in each name part (name and extension).
1460 Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are
1461 rejected. This is the default.
1464 Like "normal", but names that contain long parts or special characters
1465 that are sometimes used on Linux but are not accepted by MS-DOS
1466 (+, =, etc.) are rejected.
1470 Sets the codepage for converting to shortname characters on FAT
1471 and VFAT filesystems. By default, codepage 437 is used.
1474 This option is obsolete and may fail or being ignored.
1476 .BI cvf_format= module
1477 Forces the driver to use the CVF (Compressed Volume File) module
1479 instead of auto-detection. If the kernel supports kmod, the
1480 cvf_format=xxx option also controls on-demand CVF module loading.
1481 This option is obsolete.
1483 .BI cvf_option= option
1484 Option passed to the CVF module. This option is obsolete.
1489 flag. A version string and a list of filesystem parameters will be
1490 printed (these data are also printed if the parameters appear to be
1494 If set, causes discard/TRIM commands to be issued to the block device
1495 when blocks are freed. This is useful for SSD devices and
1496 sparse/thinly-provisioned LUNs.
1499 If set, use a fallback default BIOS Parameter Block configuration, determined
1500 by backing device size. These static parameters match defaults assumed by DOS
1501 1.x for 160 kiB, 180 kiB, 320 kiB, and 360 kiB floppies and floppy images.
1503 .BR errors= { panic | continue | remount-ro }
1504 Specify FAT behavior on critical errors: panic, continue without doing
1505 anything, or remount the partition in read-only mode (default behavior).
1507 .BR fat= { 12 | 16 | 32 }
1508 Specify a 12, 16 or 32 bit fat. This overrides
1509 the automatic FAT type detection routine. Use with caution!
1511 .BI iocharset= value
1512 Character set to use for converting between 8 bit characters
1513 and 16 bit Unicode characters. The default is iso8859-1.
1514 Long filenames are stored on disk in Unicode format.
1516 .BR nfs= { stale_rw | nostale_ro }
1517 Enable this only if you want to export the FAT filesystem over NFS.
1520 This option maintains an index (cache) of directory inodes which is used by the
1521 nfs-related code to improve look-ups. Full file operations (read/write) over
1522 NFS are supported but with cache eviction at NFS server, this could result in
1528 This option bases the inode number and file handle
1529 on the on-disk location of a file in the FAT directory entry.
1532 will not be returned after a file is
1533 evicted from the inode cache. However, it means that operations
1534 such as rename, create and unlink could cause file handles that
1535 previously pointed at one file to point at a different file,
1536 potentially causing data corruption. For this reason, this
1537 option also mounts the filesystem readonly.
1539 To maintain backward compatibility, '-o nfs' is also accepted,
1544 This option disables the conversion of timestamps
1545 between local time (as used by Windows on FAT) and UTC
1546 (which Linux uses internally). This is particularly
1547 useful when mounting devices (like digital cameras)
1548 that are set to UTC in order to avoid the pitfalls of
1551 .BI time_offset= minutes
1552 Set offset for conversion of timestamps from local time used by FAT to UTC.
1555 will be subtracted from each timestamp to convert it to UTC used
1556 internally by Linux. This is useful when the time zone set in the kernel via
1557 .BR settimeofday (2)
1558 is not the time zone used by the filesystem. Note
1559 that this option still does not provide correct time stamps in all cases in
1560 presence of DST - time stamps in a different DST setting will be off by one
1566 flag. Attempts to chown or chmod files do not return errors,
1567 although they fail. Use with caution!
1570 FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO of the
1571 directory will just be ignored, and is used only by applications as a flag
1572 (e.g.\& it's set for the customized folder).
1574 If you want to use ATTR_RO as read-only flag even for the directory, set this
1578 If set, the execute permission bits of the file will be allowed only if
1579 the extension part of the name is \&.EXE, \&.COM, or \&.BAT. Not set by default.
1582 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux.
1586 If set, the filesystem will try to flush to disk more early than normal.
1590 Use the "free clusters" value stored on FSINFO. It'll
1591 be used to determine number of free clusters without
1592 scanning disk. But it's not used by default, because
1593 recent Windows don't update it correctly in some
1594 case. If you are sure the "free clusters" on FSINFO is
1595 correct, by this option you can avoid scanning disk.
1597 .BR dots ", " nodots ", " dotsOK= [ yes | no ]
1598 Various misguided attempts to force Unix or DOS conventions
1599 onto a FAT filesystem.
1601 .SS "Mount options for hfs"
1603 .BI creator= cccc ", type=" cccc
1604 Set the creator/type values as shown by the MacOS finder
1605 used for creating new files. Default values: '????'.
1607 .BI uid= n ", gid=" n
1608 Set the owner and group of all files.
1609 (Default: the UID and GID of the current process.)
1611 .BI dir_umask= n ", file_umask=" n ", umask=" n
1612 Set the umask used for all directories, all regular files, or all
1613 files and directories. Defaults to the umask of the current process.
1616 Select the CDROM session to mount.
1617 Defaults to leaving that decision to the CDROM driver.
1618 This option will fail with anything but a CDROM as underlying device.
1621 Select partition number n from the device.
1622 Only makes sense for CDROMs.
1623 Defaults to not parsing the partition table at all.
1626 Don't complain about invalid mount options.
1628 .SS "Mount options for hpfs"
1630 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1631 Set the owner and group of all files. (Default: the UID and GID
1632 of the current process.)
1635 Set the umask (the bitmask of the permissions that are
1637 present). The default is the umask of the current process.
1638 The value is given in octal.
1640 .BR case= { lower | asis }
1641 Convert all files names to lower case, or leave them.
1646 This option is obsolete and may fail or being ignored.
1649 Do not abort mounting when certain consistency checks fail.
1651 .SS "Mount options for iso9660"
1652 ISO 9660 is a standard describing a filesystem structure to be used
1653 on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1659 filenames appear in a 8.3 format (i.e., DOS-like restrictions on filename
1660 length), and in addition all characters are in upper case. Also there is
1661 no field for file ownership, protection, number of links, provision for
1662 block/character devices, etc.
1664 Rock Ridge is an extension to iso9660 that provides all of these UNIX-like
1665 features. Basically there are extensions to each directory record that
1666 supply all of the additional information, and when Rock Ridge is in use,
1667 the filesystem is indistinguishable from a normal UNIX filesystem (except
1668 that it is read-only, of course).
1671 Disable the use of Rock Ridge extensions, even if available. Cf.\&
1675 Disable the use of Microsoft Joliet extensions, even if available. Cf.\&
1678 .BR check= { r [ elaxed ]| s [ trict ]}
1681 a filename is first converted to lower case before doing the lookup.
1682 This is probably only meaningful together with
1689 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1690 Give all files in the filesystem the indicated user or group id,
1691 possibly overriding the information found in the Rock Ridge extensions.
1695 .BR map= { n [ ormal ]| o [ ff ]| a [ corn ]}
1696 For non-Rock Ridge volumes, normal name translation maps upper
1697 to lower case ASCII, drops a trailing `;1', and converts `;' to `.'.
1700 no name translation is done. See
1707 but also apply Acorn extensions if present.
1710 For non-Rock Ridge volumes, give all files the indicated mode.
1711 (Default: read and execute permission for everybody.)
1712 Octal mode values require a leading 0.
1715 Also show hidden and associated files.
1716 (If the ordinary files and the associated or hidden files have
1717 the same filenames, this may make the ordinary files inaccessible.)
1719 .BR block= { 512 | 1024 | 2048 }
1720 Set the block size to the indicated value.
1725 This option is obsolete and may fail or being ignored.
1728 If the high byte of the file length contains other garbage,
1729 set this mount option to ignore the high order bits of the file length.
1730 This implies that a file cannot be larger than 16\ MB.
1733 Select number of session on multisession CD.
1736 Session begins from sector xxx.
1738 The following options are the same as for vfat and specifying them only makes
1739 sense when using discs encoded using Microsoft's Joliet extensions.
1741 .BI iocharset= value
1742 Character set to use for converting 16 bit Unicode characters on CD
1743 to 8 bit characters. The default is iso8859-1.
1746 Convert 16 bit Unicode characters on CD to UTF-8.
1748 .SS "Mount options for jfs"
1751 Character set to use for converting from Unicode to ASCII. The default is
1752 to do no conversion. Use
1754 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in
1760 Resize the volume to
1762 blocks. JFS only supports growing a volume, not shrinking it. This option
1763 is only valid during a remount, when the volume is mounted read-write. The
1765 keyword with no value will grow the volume to the full size of the partition.
1768 Do not write to the journal. The primary use of this option is to allow
1769 for higher performance when restoring a volume from backup media. The
1770 integrity of the volume is not guaranteed if the system abnormally ends.
1773 Default. Commit metadata changes to the journal. Use this option to remount
1776 option was previously specified in order to restore normal behavior.
1778 .BR errors= { continue | remount-ro | panic }
1779 Define the behavior when an error is encountered.
1780 (Either ignore errors and just mark the filesystem erroneous and continue,
1781 or remount the filesystem read-only, or panic and halt the system.)
1783 .BR noquota | quota | usrquota | grpquota
1784 These options are accepted but ignored.
1786 .SS "Mount options for msdos"
1787 See mount options for fat.
1790 filesystem detects an inconsistency, it reports an error and sets the file
1791 system read-only. The filesystem can be made writable again by remounting
1794 .SS "Mount options for ncpfs"
1796 .IR nfs ", the " ncpfs
1797 implementation expects a binary argument (a
1798 .IR "struct ncp_mount_data" )
1799 to the mount system call. This argument is constructed by
1801 and the current version of
1803 (2.12) does not know anything about ncpfs.
1805 .SS "Mount options for ntfs"
1808 Character set to use when returning file names.
1809 Unlike VFAT, NTFS suppresses names that contain
1810 nonconvertible characters. Deprecated.
1813 New name for the option earlier called
1817 Use UTF-8 for converting file names.
1819 .BR uni_xlate= { 0 | 1 | 2 }
1820 For 0 (or `no' or `false'), do not use escape sequences
1821 for unknown Unicode characters.
1822 For 1 (or `yes' or `true') or 2, use vfat-style 4-byte escape sequences
1823 starting with ":". Here 2 give a little-endian encoding
1824 and 1 a byteswapped bigendian encoding.
1827 If enabled (posix=1), the filesystem distinguishes between
1828 upper and lower case. The 8.3 alias names are presented as
1829 hard links instead of being suppressed. This option is obsolete.
1831 \fBuid=\fP\,\fIvalue\fP, \fBgid=\fP\,\fIvalue\fP and \fBumask=\fP\,\fIvalue\fP
1832 Set the file permission on the filesystem.
1833 The umask value is given in octal.
1834 By default, the files are owned by root and not readable by somebody else.
1836 .SS "Mount options for overlay"
1837 Since Linux 3.18 the overlay pseudo filesystem implements a union mount for
1840 An overlay filesystem combines two filesystems - an \fBupper\fR filesystem and
1841 a \fBlower\fR filesystem. When a name exists in both filesystems, the object
1842 in the upper filesystem is visible while the object in the lower filesystem is
1843 either hidden or, in the case of directories, merged with the upper object.
1845 The lower filesystem can be any filesystem supported by Linux and does not need
1846 to be writable. The lower filesystem can even be another overlayfs. The upper
1847 filesystem will normally be writable and if it is it must support the creation
1848 of trusted.* extended attributes, and must provide a valid d_type in readdir
1849 responses, so NFS is not suitable.
1851 A read-only overlay of two read-only filesystems may use any filesystem type.
1852 The options \fBlowerdir\fR and \fBupperdir\fR are combined into a merged
1858 .B "mount \-t overlay overlay \e"
1859 .B " \-olowerdir=/lower,upperdir=/upper,workdir=/work /merged"
1865 .BI lowerdir= directory
1866 Any filesystem, does not need to be on a writable filesystem.
1868 .BI upperdir= directory
1869 The upperdir is normally on a writable filesystem.
1871 .BI workdir= directory
1872 The workdir needs to be an empty directory on the same filesystem as upperdir.
1874 .SS "Mount options for reiserfs"
1875 Reiserfs is a journaling filesystem.
1878 Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem,
1879 using the 3.6 format for newly created objects. This filesystem will no
1880 longer be compatible with reiserfs 3.5 tools.
1882 .BR hash= { rupasov | tea | r5 | detect }
1883 Choose which hash function reiserfs will use to find files within directories.
1887 A hash invented by Yury Yu.\& Rupasov. It is fast and preserves locality,
1888 mapping lexicographically close file names to close hash values.
1889 This option should not be used, as it causes a high probability of hash
1893 A Davis-Meyer function implemented by Jeremy Fitzhardinge.
1894 It uses hash permuting bits in the name. It gets high randomness
1895 and, therefore, low probability of hash collisions at some CPU cost.
1896 This may be used if EHASHCOLLISION errors are experienced with the r5 hash.
1899 A modified version of the rupasov hash. It is used by default and is
1900 the best choice unless the filesystem has huge directories and
1901 unusual file-name patterns.
1906 to detect which hash function is in use by examining
1907 the filesystem being mounted, and to write this information into
1908 the reiserfs superblock. This is only useful on the first mount of
1909 an old format filesystem.
1912 .B hashed_relocation
1913 Tunes the block allocator. This may provide performance improvements
1916 .B no_unhashed_relocation
1917 Tunes the block allocator. This may provide performance improvements
1921 Disable the border allocator algorithm invented by Yury Yu.\& Rupasov.
1922 This may provide performance improvements in some situations.
1925 Disable journaling. This will provide slight performance improvements in
1926 some situations at the cost of losing reiserfs's fast recovery from crashes.
1927 Even with this option turned on, reiserfs still performs all journaling
1928 operations, save for actual writes into its journaling area. Implementation
1931 is a work in progress.
1934 By default, reiserfs stores small files and `file tails' directly into its
1935 tree. This confuses some utilities such as
1937 This option is used to disable packing of files into the tree.
1940 Replay the transactions which are in the journal, but do not actually
1941 mount the filesystem. Mainly used by
1945 A remount option which permits online expansion of reiserfs partitions.
1946 Instructs reiserfs to assume that the device has
1949 This option is designed for use with devices which are under logical
1950 volume management (LVM).
1953 utility which can be obtained from
1954 .IR ftp://ftp.namesys.com/pub/reiserfsprogs .
1957 Enable Extended User Attributes. See the
1962 Enable POSIX Access Control Lists. See the
1966 .BR barrier=none " / " barrier=flush "
1967 This disables / enables the use of write barriers in the journaling code.
1968 barrier=none disables, barrier=flush enables (default). This also requires an
1969 IO stack which can support barriers, and if reiserfs gets an error on a barrier
1970 write, it will disable barriers again with a warning. Write barriers enforce
1971 proper on-disk ordering of journal commits, making volatile disk write caches
1972 safe to use, at some performance penalty. If your disks are battery-backed in
1973 one way or another, disabling barriers may safely improve performance.
1975 .SS "Mount options for ubifs"
1976 UBIFS is a flash filesystem which works on top of UBI volumes. Note that
1977 \fBatime\fR is not supported and is always turned off.
1979 The device name may be specified as
2007 separator may be used instead of
2010 The following mount options are available:
2013 Enable bulk-read. VFS read-ahead is disabled because it slows down the file
2014 system. Bulk-Read is an internal optimization. Some flashes may read faster if
2015 the data are read at one go, rather than at several read requests. For
2016 example, OneNAND can do "read-while-load" if it reads more than one NAND page.
2019 Do not bulk-read. This is the default.
2022 Check data CRC-32 checksums. This is the default.
2024 .BR no_chk_data_crc .
2025 Do not check data CRC-32 checksums. With this option, the filesystem does not
2026 check CRC-32 checksum for data, but it does check it for the internal indexing
2027 information. This option only affects reading, not writing. CRC-32 is always
2028 calculated when writing the data.
2030 .BR compr= { none | lzo | zlib }
2031 Select the default compressor which is used when new files are written. It is
2032 still possible to read compressed files if mounted with the
2036 .SS "Mount options for udf"
2037 UDF is the "Universal Disk Format" filesystem defined by OSTA, the Optical
2038 Storage Technology Association, and is often used for DVD-ROM, frequently
2039 in the form of a hybrid UDF/ISO-9660 filesystem. It is, however,
2040 perfectly usable by itself on disk drives, flash drives and other block devices.
2045 Make all files in the filesystem belong to the given user.
2046 uid=forget can be specified independently of (or usually in
2047 addition to) uid=<user> and results in UDF
2048 not storing uids to the media. In fact the recorded uid
2049 is the 32-bit overflow uid -1 as defined by the UDF standard.
2050 The value is given as either <user> which is a valid user name or the corresponding
2051 decimal user id, or the special string "forget".
2054 Make all files in the filesystem belong to the given group.
2055 gid=forget can be specified independently of (or usually in
2056 addition to) gid=<group> and results in UDF
2057 not storing gids to the media. In fact the recorded gid
2058 is the 32-bit overflow gid -1 as defined by the UDF standard.
2059 The value is given as either <group> which is a valid group name or the corresponding
2060 decimal group id, or the special string "forget".
2063 Mask out the given permissions from all inodes read from the filesystem.
2064 The value is given in octal.
2067 If mode= is set the permissions of all non-directory inodes read from the
2068 filesystem will be set to the given mode. The value is given in octal.
2071 If dmode= is set the permissions of all directory inodes read from the
2072 filesystem will be set to the given dmode. The value is given in octal.
2075 Set the block size. Default value prior to kernel version 2.6.30 was
2076 2048. Since 2.6.30 and prior to 4.11 it was logical device block size with
2077 fallback to 2048. Since 4.11 it is logical block size with fallback to
2078 any valid block size between logical device block size and 4096.
2080 For other details see the updated mkudffs.8 manpage, section
2081 COMPATIBILITY and BLOCK SIZE.
2084 Show otherwise hidden files.
2087 Show deleted files in lists.
2090 Embed data in the inode. (default)
2093 Don't embed data in the inode.
2096 Use short UDF address descriptors.
2099 Use long UDF address descriptors. (default)
2102 Unset strict conformance.
2105 Set the NLS character set.
2106 .SS Mount options for debugging and disaster recovery
2109 Ignore the Volume Recognition Sequence and attempt to mount anyway.
2112 Select the session number for multi-session recorded optical media. (default= last session)
2115 Override standard anchor location. (default= 256)
2118 Set the last block of the filesystem.
2119 .SS Unused historical mount options that may be encountered and should be removed
2122 use uid=<user> instead.
2125 use gid=<group> instead.
2128 Override the VolumeDesc location.
2131 Override the PartitionDesc location.
2134 Override the fileset block location.
2137 Override the root directory location.
2139 .SS "Mount options for ufs"
2142 UFS is a filesystem widely used in different operating systems.
2143 The problem are differences among implementations. Features of some
2144 implementations are undocumented, so its hard to recognize the
2145 type of ufs automatically.
2146 That's why the user must specify the type of ufs by mount option.
2147 Possible values are:
2151 Old format of ufs, this is the default, read only.
2152 (Don't forget to give the \-r option.)
2155 For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD).
2158 Used in FreeBSD 5.x supported as read-write.
2164 For filesystems created by SunOS or Solaris on Sparc.
2167 For filesystems created by Solaris on x86.
2170 For filesystems created by HP-UX, read-only.
2173 For filesystems created by NeXTStep (on NeXT station) (currently read only).
2176 For NextStep CDROMs (block_size == 2048), read-only.
2179 For filesystems created by OpenStep (currently read only).
2180 The same filesystem type is also used by Mac OS X.
2185 Set behavior on error:
2189 If an error is encountered, cause a kernel panic.
2191 .RB [ lock | umount | repair ]
2192 These mount options don't do anything at present;
2193 when an error is encountered only a console message is printed.
2196 .SS "Mount options for umsdos"
2197 See mount options for msdos.
2200 option is explicitly killed by
2203 .SS "Mount options for vfat"
2204 First of all, the mount options for
2209 option is explicitly killed by
2211 Furthermore, there are
2214 Translate unhandled Unicode characters to special escaped sequences.
2215 This lets you backup and restore filenames that are created with any
2216 Unicode characters. Without this option, a '?' is used when no
2217 translation is possible. The escape character is ':' because it is
2218 otherwise invalid on the vfat filesystem. The escape sequence
2219 that gets used, where u is the Unicode character,
2220 is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
2223 Allow two files with names that only differ in case.
2224 This option is obsolete.
2227 First try to make a short name without sequence number,
2229 .IR name\s+3~\s0num.ext .
2232 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the
2233 console. It can be enabled for the filesystem with this option or disabled
2234 with utf8=0, utf8=no or utf8=false. If `uni_xlate' gets set, UTF8 gets
2238 Defines the behavior for creation and display of filenames which fit into
2239 8.3 characters. If a long name for a file exists, it will always be the
2240 preferred one for display. There are four \fImode\fRs:
2244 Force the short name to lower case upon display; store a long name when
2245 the short name is not all upper case.
2248 Force the short name to upper case upon display; store a long name when
2249 the short name is not all upper case.
2252 Display the short name as is; store a long name when the short name is
2253 not all lower case or all upper case.
2256 Display the short name as is; store a long name when the short name is not
2257 all upper case. This mode is the default since Linux 2.6.32.
2260 .SS "Mount options for usbfs"
2262 \fBdevuid=\fP\,\fIuid\fP and \fBdevgid=\fP\,\fIgid\fP and \fBdevmode=\fP\,\fImode\fP
2263 Set the owner and group and mode of the device files in the usbfs filesystem
2264 (default: uid=gid=0, mode=0644). The mode is given in octal.
2266 \fBbusuid=\fP\,\fIuid\fP and \fBbusgid=\fP\,\fIgid\fP and \fBbusmode=\fP\,\fImode\fP
2267 Set the owner and group and mode of the bus directories in the usbfs
2268 filesystem (default: uid=gid=0, mode=0555). The mode is given in octal.
2270 \fBlistuid=\fP\,\fIuid\fP and \fBlistgid=\fP\,\fIgid\fP and \fBlistmode=\fP\,\fImode\fP
2271 Set the owner and group and mode of the file
2273 (default: uid=gid=0, mode=0444). The mode is given in octal.
2275 .SH "THE LOOP DEVICE"
2276 One further possible type is a mount via the loop device. For example,
2280 .B "mount /tmp/disk.img /mnt \-t vfat \-o loop=/dev/loop3"
2283 will set up the loop device
2285 to correspond to the file
2287 and then mount this device on
2290 If no explicit loop device is mentioned
2291 (but just an option `\fB\-o loop\fP' is given), then
2293 will try to find some unused loop device and use that, for example
2296 .B "mount /tmp/disk.img /mnt \-o loop"
2301 creates a loop device from a regular file if a filesystem type is
2302 not specified or the filesystem is known for libblkid, for example:
2305 .B "mount /tmp/disk.img /mnt"
2307 .B "mount \-t ext3 /tmp/disk.img /mnt"
2310 This type of mount knows about three options, namely
2311 .BR loop ", " offset " and " sizelimit ,
2312 that are really options to
2314 (These options can be used in addition to those specific
2315 to the filesystem type.)
2317 Since Linux 2.6.25 auto-destruction of loop devices is supported,
2318 meaning that any loop device allocated by
2325 You can also free a loop device by hand, using
2326 .BR "losetup \-d " or " umount \-d" .
2328 Since util-linux v2.29 mount command re-uses the loop device rather than
2329 initialize a new device if the same backing file is already used for some loop
2330 device with the same offset and sizelimit. This is necessary to avoid
2331 a filesystem corruption.
2335 has the following return codes (the bits can be ORed):
2341 incorrect invocation or permissions
2344 system error (out of memory, cannot fork, no more loop devices)
2355 problems writing or locking /etc/mtab
2361 some mount succeeded
2364 The command \fBmount \-a\fR returns 0 (all succeeded), 32 (all failed), or 64 (some
2365 failed, some succeeded).
2367 .SH "EXTERNAL HELPERS"
2368 The syntax of external mount helpers is:
2371 .BI /sbin/mount. suffix
2377 .IR type \fB. subtype ]
2380 where the \fIsuffix\fR is the filesystem type and the \fB\-sfnvo\fR options have
2381 the same meaning as the normal mount options. The \fB\-t\fR option is used for
2382 filesystems with subtypes support (for example
2383 .BR "/sbin/mount.fuse \-t fuse.sshfs" ).
2385 The command \fBmount\fR does not pass the mount options
2402 to the mount.<suffix> helpers. All other options are used in a
2403 comma-separated list as argument to the \fB\-o\fR option.
2411 table of mounted filesystems
2413 .I /etc/mtab\s+3~\s0
2420 a list of filesystem types to try
2422 .IP LIBMOUNT_FSTAB=<path>
2423 overrides the default location of the fstab file (ignored for suid)
2424 .IP LIBMOUNT_MTAB=<path>
2425 overrides the default location of the mtab file (ignored for suid)
2426 .IP LIBMOUNT_DEBUG=all
2427 enables libmount debug output
2428 .IP LIBBLKID_DEBUG=all
2429 enables libblkid debug output
2430 .IP LOOPDEV_DEBUG=all
2431 enables loop device setup debug output
2451 It is possible for a corrupted filesystem to cause a crash.
2453 Some Linux filesystems don't support
2454 .BR "\-o sync " nor " \-o dirsync"
2455 (the ext2, ext3, fat and vfat filesystems
2457 support synchronous updates (a la BSD) when mounted with the
2463 may not be able to change mount parameters (all
2464 .IR ext2fs -specific
2467 are changeable with a remount, for example, but you can't change
2474 It is possible that the files
2478 don't match on systems with a regular mtab file. The first file is based only on
2479 the mount command options, but the content of the second file also depends on
2480 the kernel and others settings (e.g.\& on a remote NFS server -- in certain cases
2481 the mount command may report unreliable information about an NFS mount point
2482 and the /proc/mounts file usually contains more reliable information.) This is
2483 another reason to replace the mtab file with a symlink to the
2487 Checking files on NFS filesystems referenced by file descriptors (i.e.\& the
2491 families of functions) may lead to inconsistent results due to the lack of
2492 a consistency check in the kernel even if noac is used.
2500 options used may fail when using older kernels if the
2502 command can't confirm that the size of the block device has been configured
2503 as requested. This situation can be worked around by using
2506 command manually before calling
2508 with the configured loop device.
2512 command existed in Version 5 AT&T UNIX.
2515 Karel Zak <kzak@redhat.com>
2518 The mount command is part of the util-linux package and is available from
2519 https://www.kernel.org/pub/linux/utils/util-linux/.