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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 .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 This default behaviour is possible to change by command line
263 option \fB\-\-options\-mode\fR.
264 The usual behavior is that the last option wins if there are conflicting
269 program does not read the
273 (or LABEL, UUID, PARTUUID or PARTLABEL) and
275 are specified. For example, to mount device
276 .BR foo " at " /dir :
279 .B "mount /dev/foo /dir"
282 This default behaviour is possible to change by command line option
283 \fB\-\-options\-source\-force\fR to always read configuration from fstab. For
286 always read fstab configuration.
288 .SS Non-superuser mounts
289 Normally, only the superuser can mount filesystems.
294 option on a line, anybody can mount the corresponding filesystem.
299 .B "/dev/cdrom /cd iso9660 ro,user,noauto,unhide"
302 any user can mount the iso9660 filesystem found on an inserted CDROM
308 Note that \fBmount\fR is very strict about non-root users and all paths
309 specified on command line are verified before fstab is parsed or a helper
310 program is executed. It's strongly recommended to use a valid mountpoint to
311 specify filesystem, otherwise \fBmount\fR may fail. For example it's bad idea
312 to use NFS or CIFS source on command line.
314 For more details, see
316 Only the user that mounted a filesystem can unmount it again.
317 If any user should be able to unmount it, then use
326 option is similar to the
328 option, with the restriction that the user must be the owner
329 of the special file. This may be useful e.g.\& for
331 if a login script makes the console user owner of this device.
334 option is similar, with the restriction that the user must be
335 member of the group of the special file.
337 .SS Bind mount operation
338 Remount part of the file hierarchy somewhere else. The call is:
346 or by using this fstab entry:
355 After this call the same contents are accessible in two places.
357 It is important to understand that "bind" does not to create any second-class
358 or special node in the kernel VFS. The "bind" is just another operation to
359 attach a filesystem. There is nowhere stored information that the filesystem
360 has been attached by "bind" operation. The \fIolddir\fR and \fInewdir\fR are
361 independent and the \fIolddir\fR maybe be umounted.
363 One can also remount a single file (on a single file). It's also
364 possible to use the bind mount to create a mountpoint from a regular
365 directory, for example:
369 .B mount \-\-bind foo foo
372 The bind mount call attaches only (part of) a single filesystem, not possible
373 submounts. The entire file hierarchy including submounts is attached
374 a second place by using:
382 Note that the filesystem mount options will remain the same as those
383 on the original mount point.
386 since v2.27 allows to change the mount options by passing the
387 relevant options along with
393 .B mount -o bind,ro foo foo
396 This feature is not supported by the Linux kernel; it is implemented in userspace
397 by an additional \fBmount\fR(2) remounting system call.
398 This solution is not atomic.
400 The alternative (classic) way to create a read-only bind mount is to use the remount
401 operation, for example:
408 .B mount \-o remount,bind,ro
412 Note that a read-only bind will create a read-only mountpoint (VFS entry),
413 but the original filesystem superblock will still be writable, meaning that the
415 will be writable, but the
419 It's also possible to change nosuid, nodev, noexec, noatime, nodiratime and
420 relatime VFS entry flags by "remount,bind" operation. It's impossible to change
421 mount options recursively (for example with \fB-o rbind,ro\fR).
424 since v2.31 ignores the \fBbind\fR flag from
428 (if "-o remount" specified on command line). This is necessary to fully control
429 mount options on remount by command line. In the previous versions the bind
430 flag has been always applied and it was impossible to re-define mount options
431 without interaction with the bind semantic. This
433 behavior does not affect situations when "remount,bind" is specified in the
438 .SS The move operation
441 to another place (atomically). The call is:
449 This will cause the contents which previously appeared under
451 to now be accessible under
453 The physical location of the files is not changed.
456 has to be a mountpoint.
458 Note also that moving a mount residing under a shared mount is invalid and
460 .B findmnt \-o TARGET,PROPAGATION
461 to see the current propagation flags.
463 .SS Shared subtree operations
464 Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared,
465 private, slave or unbindable. A shared mount provides the ability to create mirrors
466 of that mount such that mounts and unmounts within any of the mirrors propagate
467 to the other mirror. A slave mount receives propagation from its master, but
468 not vice versa. A private mount carries no propagation abilities. An
469 unbindable mount is a private mount which cannot be cloned through a bind
470 operation. The detailed semantics are documented in
471 .I Documentation/filesystems/sharedsubtree.txt
472 file in the kernel source tree.
474 Supported operations are:
478 .BI "mount \-\-make\-shared " mountpoint
479 .BI "mount \-\-make\-slave " mountpoint
480 .BI "mount \-\-make\-private " mountpoint
481 .BI "mount \-\-make\-unbindable " mountpoint
485 The following commands allow one to recursively change the type of all the
486 mounts under a given mountpoint.
490 .BI "mount \-\-make\-rshared " mountpoint
491 .BI "mount \-\-make\-rslave " mountpoint
492 .BI "mount \-\-make\-rprivate " mountpoint
493 .BI "mount \-\-make\-runbindable " mountpoint
500 when a \fB\-\-make-\fR* operation is requested. All necessary information has to be
501 specified on the command line.
503 Note that the Linux kernel does not allow to change multiple propagation flags
506 system call, and the flags cannot be mixed with other mount options and operations.
508 Since util-linux 2.23 the \fBmount\fR command allows to do more propagation
509 (topology) changes by one mount(8) call and do it also together with other
510 mount operations. This feature is EXPERIMENTAL. The propagation flags are applied
511 by additional \fBmount\fR(2) system calls when the preceding mount operations
512 were successful. Note that this use case is not atomic. It is possible to
513 specify the propagation flags in
529 .BI "mount \-\-make\-private \-\-make\-unbindable /dev/sda1 /foo"
537 .BI "mount /dev/sda1 /foo"
538 .BI "mount \-\-make\-private /foo"
539 .BI "mount \-\-make\-unbindable /foo"
543 .SH COMMAND-LINE OPTIONS
544 The full set of mount options used by an invocation of
546 is determined by first extracting the
547 mount options for the filesystem from the
549 table, then applying any options specified by the
551 argument, and finally applying a
553 option, when present.
555 The command \fBmount\fR does not pass all command-line options to the
556 \fB/sbin/mount.\fIsuffix\fR mount helpers. The interface between \fBmount\fR
557 and the mount helpers is described below in the section \fBEXTERNAL HELPERS\fR.
559 Command-line options available for the
564 Mount all filesystems (of the given types) mentioned in
566 (except for those whose line contains the
568 keyword). The filesystems are mounted following their order in
570 The mount command compares filesystem source, target (and fs root for bind
571 mount or btrfs) to detect already mounted filesystems. The kernel table with
572 already mounted filesystems is cached during \fBmount \-\-all\fR. It means
573 that all duplicated fstab entries will be mounted.
575 Note that it is a bad practice to use \fBmount \-a\fR for
577 checking. The recommended solution is \fBfindmnt \-\-verify\fR.
579 .BR \-B , " \-\-bind"
580 Remount a subtree somewhere else (so that its contents are available
581 in both places). See above, under \fBBind mounts\fR.
583 .BR \-c , " \-\-no\-canonicalize"
584 Don't canonicalize paths. The mount command canonicalizes all paths
585 (from command line or fstab) by default. This option can be used
588 flag for already canonicalized absolute paths. The option is designed for mount
589 helpers which call \fBmount -i\fR. It is strongly recommended to not use this
590 command-line option for normal mount operations.
592 Note that \fBmount\fR(8) does not pass this option to the
593 \fB/sbin/mount.\fItype\fR helpers.
595 .BR \-F , " \-\-fork"
596 (Used in conjunction with
598 Fork off a new incarnation of \fBmount\fR for each device.
599 This will do the mounts on different devices or different NFS servers
601 This has the advantage that it is faster; also NFS timeouts go in
602 parallel. A disadvantage is that the mounts are done in undefined order.
603 Thus, you cannot use this option if you want to mount both
607 .IP "\fB\-f, \-\-fake\fP"
608 Causes everything to be done except for the actual system call; if it's not
609 obvious, this ``fakes'' mounting the filesystem. This option is useful in
612 flag to determine what the
614 command is trying to do. It can also be used to add entries for devices
615 that were mounted earlier with the \fB\-n\fR option. The \fB\-f\fR option
616 checks for an existing record in /etc/mtab and fails when the record already
617 exists (with a regular non-fake mount, this check is done by the kernel).
618 .IP "\fB\-i, \-\-internal\-only\fP"
619 Don't call the \fB/sbin/mount.\fIfilesystem\fR helper even if it exists.
621 .BR \-L , " \-\-label " \fIlabel
622 Mount the partition that has the specified
625 .BR \-l , " \-\-show\-labels"
626 Add the labels in the mount output. \fBmount\fR must have
627 permission to read the disk device (e.g.\& be set-user-ID root) for this to work.
628 One can set such a label for ext2, ext3 or ext4 using the
630 utility, or for XFS using
632 or for reiserfs using
633 .BR reiserfstune (8).
635 .BR \-M , " \-\-move"
636 Move a subtree to some other place. See above, the subsection
637 \fBThe move operation\fR.
639 .BR \-n , " \-\-no\-mtab"
640 Mount without writing in
642 This is necessary for example when
644 is on a read-only filesystem.
646 .BR \-O , " \-\-test\-opts " \fIopts
647 Limit the set of filesystems to which the
649 option applies. In this regard it is like the
655 For example, the command:
659 .B "mount \-a \-O no_netdev"
662 mounts all filesystems except those which have the option
664 specified in the options field in the
670 in that each option is matched exactly; a leading
672 at the beginning of one option does not negate the rest.
678 options are cumulative in effect; that is, the command
681 .B "mount \-a \-t ext2 \-O _netdev"
684 mounts all ext2 filesystems with the _netdev option, not all filesystems
685 that are either ext2 or have the _netdev option specified.
688 .BR \-o , " \-\-options " \fIopts
689 Use the specified mount options. The \fIopts\fR argument is
690 a comma-separated list. For example:
694 .B "mount LABEL=mydisk \-o noatime,nodev,nosuid"
698 For more details, see the
699 .B FILESYSTEM-INDEPENDENT MOUNT OPTIONS
701 .B FILESYSTEM-SPECIFIC MOUNT OPTIONS
706 .BR "\-\-options\-mode " \fImode
707 Controls how to combine options from fstab/mtab with options from command line.
708 \fImode\fR can be one of
709 .BR ignore ", " append ", " prepend " or " replace .
710 For example \fBappend\fR means that options from fstab are appended to options from command line.
711 Default value is \fBprepend\fR -- it means command line options are evaluated after fstab options.
712 Note that the last option wins if there are conflicting ones.
715 .BR "\-\-options\-source " \fIsource
716 Source of default options.
717 \fIsource\fR is comma separated list of
718 .BR fstab ", " mtab " and " disable .
719 \fBdisable\fR disables
720 .BR fstab " and " mtab
721 and disables \fB\-\-options\-source\-force\fR.
722 Default value is \fBfstab,mtab\fR.
725 .BR \-\-options\-source\-force
726 Use options from fstab/mtab even if both \fIdevice\fR and \fIdir\fR are specified.
729 .BR \-R , " \-\-rbind"
730 Remount a subtree and all possible submounts somewhere else (so that its
731 contents are available in both places). See above, the subsection
734 .BR \-r , " \-\-read\-only"
735 Mount the filesystem read-only. A synonym is
738 Note that, depending on the filesystem type, state and kernel behavior, the
739 system may still write to the device. For example, ext3 and ext4 will replay the
740 journal if the filesystem is dirty. To prevent this kind of write access, you
741 may want to mount an ext3 or ext4 filesystem with the \fBro,noload\fR mount
742 options or set the block device itself to read-only mode, see the
747 Tolerate sloppy mount options rather than failing. This will ignore mount
748 options not supported by a filesystem type. Not all filesystems support this
749 option. Currently it's supported by the \fBmount.nfs\fR mount helper only.
751 .BI \-\-source " device"
752 If only one argument for the mount command is given then the argument might be
753 interpreted as target (mountpoint) or source (device). This option allows to
754 explicitly define that the argument is the mount source.
756 .BI \-\-target " directory"
757 If only one argument for the mount command is given then the argument might be
758 interpreted as target (mountpoint) or source (device). This option allows to
759 explicitly define that the argument is the mount target.
761 .BR \-T , " \-\-fstab " \fIpath
762 Specifies an alternative fstab file. If \fIpath\fP is a directory then the files
763 in the directory are sorted by
765 files that start with "."\& or without an \&.fstab extension are ignored. The option
766 can be specified more than once. This option is mostly designed for initramfs
767 or chroot scripts where additional configuration is specified beyond standard
768 system configuration.
770 Note that \fBmount\fR(8) does not pass the option \fB\-\-fstab\fP to the
771 \fB/sbin/mount.\fItype\fR helpers, meaning that the alternative fstab files will be
772 invisible for the helpers. This is no problem for normal mounts, but user
773 (non-root) mounts always require fstab to verify the user's rights.
775 .BR \-t , " \-\-types " \fIfstype
776 The argument following the
778 is used to indicate the filesystem type. The filesystem types which are
779 currently supported depend on the running kernel. See
782 .I /lib/modules/$(uname -r)/kernel/fs
783 for a complete list of the filesystems. The most common are ext2, ext3, ext4,
784 xfs, btrfs, vfat, sysfs, proc, nfs and cifs.
790 support filesystem subtypes. The subtype is defined by a '.subtype' suffix. For
791 example 'fuse.sshfs'. It's recommended to use subtype notation rather than add
792 any prefix to the mount source (for example 'sshfs#example.com' is
797 option is given, or if the
799 type is specified, mount will try to guess the desired type.
800 Mount uses the blkid library for guessing the filesystem
801 type; if that does not turn up anything that looks familiar,
802 mount will try to read the file
803 .IR /etc/filesystems ,
804 or, if that does not exist,
805 .IR /proc/filesystems .
806 All of the filesystem types listed there will be tried,
807 except for those that are labeled "nodev" (e.g.\&
814 ends in a line with a single *, mount will read
816 afterwards. While trying, all filesystem types will be
817 mounted with the mount option \fBsilent\fR.
821 type may be useful for user-mounted floppies.
824 can be useful to change the probe order (e.g., to try vfat before msdos
825 or ext3 before ext2) or if you use a kernel module autoloader.
827 More than one type may be specified in a comma-separated
832 entry. The list of filesystem types for option
836 to specify the filesystem types on which no action should be taken.
839 has no effect when specified in an
845 can be meaningful with the
847 option. For example, the command
851 .B "mount \-a \-t nomsdos,smbfs"
854 mounts all filesystems except those of type
859 For most types all the
861 program has to do is issue a simple
863 system call, and no detailed knowledge of the filesystem type is required.
864 For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) an ad hoc code is
865 necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems
866 have a separate mount program. In order to make it possible to
867 treat all types in a uniform way, \fBmount\fR will execute the program
868 .BI /sbin/mount. type
869 (if that exists) when called with type
871 Since different versions of the
873 program have different calling conventions,
875 may have to be a shell script that sets up the desired call.
878 .BR \-U , " \-\-uuid " \fIuuid
879 Mount the partition that has the specified
882 .BR \-v , " \-\-verbose"
885 .BR \-w , " \-\-rw" , " \-\-read\-write"
886 Mount the filesystem read/write. The read-write is kernel default. A synonym is
889 Note that specify \fB\-w\fR on command line forces \fBmount\fR command
890 to never try read-only mount on write-protected devices. The default is
891 try read-only if the previous mount syscall with read-write flags failed.
893 .BR \-V , " \-\-version"
894 Display version information and exit.
896 .BR \-h , " \-\-help"
897 Display help text and exit.
899 .SH FILESYSTEM-INDEPENDENT MOUNT OPTIONS
900 Some of these options are only useful when they appear in the
904 Some of these options could be enabled or disabled by default
905 in the system kernel. To check the current setting see the options
906 in /proc/mounts. Note that filesystems also have per-filesystem
907 specific default mount options (see for example \fBtune2fs \-l\fP
908 output for extN filesystems).
910 The following options apply to any filesystem that is being
911 mounted (but not every filesystem actually honors them \(en e.g.\&, the
913 option today has an effect only for ext2, ext3, fat, vfat and ufs):
917 All I/O to the filesystem should be done asynchronously. (See also the
922 Do not use the \fBnoatime\fR feature, so the inode access time is controlled
923 by kernel defaults. See also the descriptions of the \fB\%relatime\fR and
928 Do not update inode access times on this filesystem (e.g.\& for faster
929 access on the news spool to speed up news servers). This works for all
930 inode types (directories too), so it implies \fB\%nodiratime\fR.
933 Can be mounted with the
938 Can only be mounted explicitly (i.e., the
940 option will not cause the filesystem to be mounted).
943 .BR context=\fIcontext ", " fscontext=\fIcontext ", " defcontext=\fIcontext ", and " \%rootcontext=\fIcontext
947 option is useful when mounting filesystems that do not support
948 extended attributes, such as a floppy or hard disk formatted with VFAT, or
949 systems that are not normally running under SELinux, such as an ext3 formatted
950 disk from a non-SELinux workstation. You can also use
952 on filesystems you do not trust, such as a floppy. It also helps in compatibility with
953 xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where
954 xattrs are supported, you can save time not having to label every file by
955 assigning the entire disk one security context.
957 A commonly used option for removable media is
958 .BR \%context="system_u:object_r:removable_t" .
960 Two other options are
964 both of which are mutually exclusive of the context option. This means you
965 can use fscontext and defcontext with each other, but neither can be used with
970 option works for all filesystems, regardless of their xattr
971 support. The fscontext option sets the overarching filesystem label to a
972 specific security context. This filesystem label is separate from the
973 individual labels on the files. It represents the entire filesystem for
974 certain kinds of permission checks, such as during mount or file creation.
975 Individual file labels are still obtained from the xattrs on the files
976 themselves. The context option actually sets the aggregate context that
977 fscontext provides, in addition to supplying the same label for individual
980 You can set the default security context for unlabeled files using
982 option. This overrides the value set for unlabeled files in the policy and requires a
983 filesystem that supports xattr labeling.
987 option allows you to explicitly label the root inode of a FS being mounted
988 before that FS or inode becomes visible to userspace. This was found to be
989 useful for things like stateless linux.
991 Note that the kernel rejects any remount request that includes the context
992 option, \fBeven\fP when unchanged from the current context.
994 .BR "Warning: the \fIcontext\fP value might contain commas" ,
995 in which case the value has to be properly quoted, otherwise
997 will interpret the comma as a separator between mount options. Don't forget that
998 the shell strips off quotes and thus
999 .BR "double quoting is required" .
1005 .B mount \-t tmpfs none /mnt \-o \e
1006 .B \ \ 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
1010 For more details, see
1016 Use the default options:
1017 .BR rw ", " suid ", " dev ", " exec ", " auto ", " nouser ", and " async .
1019 Note that the real set of all default mount options depends on kernel
1020 and filesystem type. See the beginning of this section for more details.
1023 Interpret character or block special devices on the filesystem.
1026 Do not interpret character or block special devices on the file
1030 Update directory inode access times on this filesystem. This is the default.
1031 (This option is ignored when \fBnoatime\fR is set.)
1034 Do not update directory inode access times on this filesystem.
1035 (This option is implied when \fBnoatime\fR is set.)
1038 All directory updates within the filesystem should be done synchronously.
1039 This affects the following system calls: creat, link, unlink, symlink,
1040 mkdir, rmdir, mknod and rename.
1043 Permit execution of binaries.
1046 Do not permit direct execution of any binaries on the mounted filesystem.
1049 Allow an ordinary user to mount the filesystem if one
1050 of that user's groups matches the group of the device.
1051 This option implies the options
1052 .BR nosuid " and " nodev
1053 (unless overridden by subsequent options, as in the option line
1054 .BR group,dev,suid ).
1057 Every time the inode is modified, the i_version field will be incremented.
1060 Do not increment the i_version inode field.
1063 Allow mandatory locks on this filesystem. See
1067 Do not allow mandatory locks on this filesystem.
1070 The filesystem resides on a device that requires network access
1071 (used to prevent the system from attempting to mount these filesystems
1072 until the network has been enabled on the system).
1075 Do not report errors for this device if it does not exist.
1078 Update inode access times relative to modify or change time. Access
1079 time is only updated if the previous access time was earlier than the
1080 current modify or change time. (Similar to \fB\%noatime\fR, but it doesn't
1081 break \fBmutt\fR or other applications that need to know if a file has been
1082 read since the last time it was modified.)
1084 Since Linux 2.6.30, the kernel defaults to the behavior provided by this
1087 was specified), and the
1089 option is required to obtain traditional semantics. In addition, since Linux
1090 2.6.30, the file's last access time is always updated if it is more than 1
1096 feature. See also the
1101 Allows to explicitly request full atime updates. This makes it
1102 possible for the kernel to default to
1106 but still allow userspace to override it. For more details about the default
1107 system mount options see /proc/mounts.
1110 Use the kernel's default behavior for inode access time updates.
1113 Only update times (atime, mtime, ctime) on the in-memory version of the file inode.
1115 This mount option significantly reduces writes to the inode table for
1116 workloads that perform frequent random writes to preallocated files.
1118 The on-disk timestamps are updated only when:
1121 - the inode needs to be updated for some change unrelated to file timestamps
1123 - the application employs
1129 - an undeleted inode is evicted from memory
1131 - more than 24 hours have passed since the i-node was written to disk.
1136 Do not use the lazytime feature.
1139 Allow set-user-ID or set-group-ID bits to take
1143 Do not allow set-user-ID or set-group-ID bits to take
1147 Turn on the silent flag.
1150 Turn off the silent flag.
1153 Allow an ordinary user to mount the filesystem if that
1154 user is the owner of the device.
1155 This option implies the options
1156 .BR nosuid " and " nodev
1157 (unless overridden by subsequent options, as in the option line
1158 .BR owner,dev,suid ).
1161 Attempt to remount an already-mounted filesystem. This is commonly
1162 used to change the mount flags for a filesystem, especially to make a
1163 readonly filesystem writable. It does not change device or mount point.
1165 The remount operation together with the
1167 flag has special semantic. See above, the subsection \fBBind mounts\fR.
1169 The remount functionality follows the standard way the mount command works
1170 with options from fstab. This means that \fBmount\fR does not
1171 read fstab (or mtab) only when both
1178 .B "mount \-o remount,rw /dev/foo /dir"
1181 After this call all old mount options are replaced and arbitrary stuff from
1182 fstab (or mtab) is ignored, except the loop= option which is internally
1183 generated and maintained by the mount command.
1186 .B "mount \-o remount,rw /dir"
1189 After this call, mount reads fstab and merges these options with
1190 the options from the command line (\fB\-o\fR).
1191 If no mountpoint is found in fstab, then a remount with unspecified source is
1195 Mount the filesystem read-only.
1198 Mount the filesystem read-write.
1201 All I/O to the filesystem should be done synchronously. In the case of
1202 media with a limited number of write cycles
1203 (e.g.\& some flash drives), \fBsync\fR may cause life-cycle shortening.
1206 Allow an ordinary user to mount the filesystem.
1207 The name of the mounting user is written to the mtab file (or to the private
1208 libmount file in /run/mount on systems without a regular mtab) so that this
1209 same user can unmount the filesystem again.
1210 This option implies the options
1211 .BR noexec ", " nosuid ", and " nodev
1212 (unless overridden by subsequent options, as in the option line
1213 .BR user,exec,dev,suid ).
1216 Forbid an ordinary user to mount the filesystem.
1217 This is the default; it does not imply any other options.
1220 Allow any user to mount and to unmount the filesystem, even
1221 when some other ordinary user mounted it.
1222 This option implies the options
1223 .BR noexec ", " nosuid ", and " nodev
1224 (unless overridden by subsequent options, as in the option line
1225 .BR users,exec,dev,suid ).
1228 All options prefixed with "X-" are interpreted as comments or as userspace
1229 application-specific options. These options are not stored in the user space (e.g. mtab file),
1230 nor sent to the mount.\fItype\fR helpers nor to the
1232 system call. The suggested format is \fBX-\fIappname\fR.\fIoption\fR.
1235 The same as \fBX-*\fR options, but stored permanently in the user space. It
1236 means the options are also available for umount or another operations. Note
1237 that maintain mount options in user space is tricky, because it's necessary use
1238 libmount based tools and there is no guarantee that the options will be always
1239 available (for example after a move mount operation or in unshared namespace).
1241 Note that before util-linux v2.30 the x-* options have not been maintained by
1242 libmount and stored in user space (functionality was the same as have X-* now),
1243 but due to growing number of use-cases (in initrd, systemd etc.) the
1244 functionality have been extended to keep existing fstab configurations usable
1247 .BR X-mount.mkdir [ = \fImode\fR ]
1248 Allow to make a target directory (mountpoint). The optional argument
1250 specifies the filesystem access mode used for
1252 in octal notation. The default mode is 0755. This functionality is supported
1253 only for root users. The option is also supported as x-mount.mkdir, this notation
1254 is deprecated for mount.mkdir since v2.30.
1256 .SH "FILESYSTEM-SPECIFIC MOUNT OPTIONS"
1257 You should consult the respective man page for the filesystem first.
1258 If you want to know what options the ext4 filesystem supports, then check the
1261 If that doesn't exist, you can also check the corresponding mount page like
1263 Note that you might have to install the respective userland tools.
1265 The following options apply only to certain filesystems.
1266 We sort them by filesystem. They all follow the
1270 What options are supported depends a bit on the running kernel.
1271 More info may be found in the kernel source subdirectory
1272 .IR Documentation/filesystems .
1274 .SS "Mount options for adfs"
1276 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1277 Set the owner and group of the files in the filesystem (default: uid=gid=0).
1279 \fBownmask=\fP\,\fIvalue\fP and \fBothmask=\fP\,\fIvalue\fP
1280 Set the permission mask for ADFS 'owner' permissions and 'other' permissions,
1281 respectively (default: 0700 and 0077, respectively).
1283 .IR /usr/src/linux/Documentation/filesystems/adfs.txt .
1285 .SS "Mount options for affs"
1287 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1288 Set the owner and group of the root of the filesystem (default: uid=gid=0,
1293 without specified value, the UID and GID of the current process are taken).
1295 \fBsetuid=\fP\,\fIvalue\fP and \fBsetgid=\fP\,\fIvalue\fP
1296 Set the owner and group of all files.
1299 Set the mode of all files to
1301 disregarding the original permissions.
1302 Add search permission to directories that have read permission.
1303 The value is given in octal.
1306 Do not allow any changes to the protection bits on the filesystem.
1309 Set UID and GID of the root of the filesystem to the UID and GID
1310 of the mount point upon the first sync or umount, and then
1311 clear this option. Strange...
1314 Print an informational message for each successful mount.
1317 Prefix used before volume name, when following a link.
1320 Prefix (of length at most 30) used before '/' when following a symbolic link.
1323 (Default: 2.) Number of unused blocks at the start of the device.
1326 Give explicitly the location of the root block.
1329 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
1331 .BR grpquota | noquota | quota | usrquota
1332 These options are accepted but ignored.
1333 (However, quota utilities may react to such strings in
1336 .SS "Mount options for debugfs"
1337 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1338 .IR /sys/kernel/debug .
1340 .\" present since 2.6.11
1341 As of kernel version 3.4, debugfs has the following options:
1343 .BI uid= n ", gid=" n
1344 Set the owner and group of the mountpoint.
1347 Sets the mode of the mountpoint.
1349 .SS "Mount options for devpts"
1350 The devpts filesystem is a pseudo filesystem, traditionally mounted on
1352 In order to acquire a pseudo terminal, a process opens
1354 the number of the pseudo terminal is then made available to the process
1355 and the pseudo terminal slave can be accessed as
1356 .IR /dev/pts/ <number>.
1358 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1359 This sets the owner or the group of newly created PTYs to
1360 the specified values. When nothing is specified, they will
1361 be set to the UID and GID of the creating process.
1362 For example, if there is a tty group with GID 5, then
1364 will cause newly created PTYs to belong to the tty group.
1367 Set the mode of newly created PTYs to the specified value.
1368 The default is 0600.
1373 makes "mesg y" the default on newly created PTYs.
1376 Create a private instance of devpts filesystem, such that
1377 indices of ptys allocated in this new instance are
1378 independent of indices created in other instances of devpts.
1380 All mounts of devpts without this
1382 option share the same set of pty indices (i.e legacy mode).
1383 Each mount of devpts with the
1385 option has a private set of pty indices.
1387 This option is mainly used to support containers in the
1388 linux kernel. It is implemented in linux kernel versions
1389 starting with 2.6.29. Further, this mount option is valid
1390 only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the
1391 kernel configuration.
1393 To use this option effectively,
1395 must be a symbolic link to
1398 .I Documentation/filesystems/devpts.txt
1399 in the linux kernel source tree for details.
1403 Set the mode for the new
1405 device node in the devpts filesystem.
1407 With the support for multiple instances of devpts (see
1409 option above), each instance has a private
1411 node in the root of the devpts filesystem (typically
1412 .IR /dev/pts/ptmx ).
1414 For compatibility with older versions of the kernel, the
1415 default mode of the new
1419 specifies a more useful mode for the
1421 node and is highly recommended when the
1423 option is specified.
1425 This option is only implemented in linux kernel versions
1426 starting with 2.6.29. Further, this option is valid only if
1427 CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1430 .SS "Mount options for fat"
1433 is not a separate filesystem, but a common part of the
1440 .BR blocksize= { 512 | 1024 | 2048 }
1441 Set blocksize (default 512). This option is obsolete.
1443 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1444 Set the owner and group of all files.
1445 (Default: the UID and GID of the current process.)
1448 Set the umask (the bitmask of the permissions that are
1450 present). The default is the umask of the current process.
1451 The value is given in octal.
1454 Set the umask applied to directories only.
1455 The default is the umask of the current process.
1456 The value is given in octal.
1459 Set the umask applied to regular files only.
1460 The default is the umask of the current process.
1461 The value is given in octal.
1463 .BI allow_utime= value
1464 This option controls the permission check of mtime/atime.
1468 If current process is in group of file's group ID, you can change timestamp.
1471 Other users can change timestamp.
1473 The default is set from `dmask' option. (If the directory is writable,
1475 is also allowed. I.e.\& \s+3~\s0dmask & 022)
1479 checks current process is owner of the file, or it has
1480 CAP_FOWNER capability. But FAT filesystem doesn't have UID/GID on disk, so
1481 normal check is too inflexible. With this option you can relax it.
1485 Three different levels of pickyness can be chosen:
1489 Upper and lower case are accepted and equivalent, long name parts are
1491 .I verylongname.foobar
1494 leading and embedded spaces are accepted in each name part (name and extension).
1497 Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are
1498 rejected. This is the default.
1501 Like "normal", but names that contain long parts or special characters
1502 that are sometimes used on Linux but are not accepted by MS-DOS
1503 (+, =, etc.) are rejected.
1507 Sets the codepage for converting to shortname characters on FAT
1508 and VFAT filesystems. By default, codepage 437 is used.
1511 This option is obsolete and may fail or being ignored.
1513 .BI cvf_format= module
1514 Forces the driver to use the CVF (Compressed Volume File) module
1516 instead of auto-detection. If the kernel supports kmod, the
1517 cvf_format=xxx option also controls on-demand CVF module loading.
1518 This option is obsolete.
1520 .BI cvf_option= option
1521 Option passed to the CVF module. This option is obsolete.
1526 flag. A version string and a list of filesystem parameters will be
1527 printed (these data are also printed if the parameters appear to be
1531 If set, causes discard/TRIM commands to be issued to the block device
1532 when blocks are freed. This is useful for SSD devices and
1533 sparse/thinly-provisioned LUNs.
1536 If set, use a fallback default BIOS Parameter Block configuration, determined
1537 by backing device size. These static parameters match defaults assumed by DOS
1538 1.x for 160 kiB, 180 kiB, 320 kiB, and 360 kiB floppies and floppy images.
1540 .BR errors= { panic | continue | remount-ro }
1541 Specify FAT behavior on critical errors: panic, continue without doing
1542 anything, or remount the partition in read-only mode (default behavior).
1544 .BR fat= { 12 | 16 | 32 }
1545 Specify a 12, 16 or 32 bit fat. This overrides
1546 the automatic FAT type detection routine. Use with caution!
1548 .BI iocharset= value
1549 Character set to use for converting between 8 bit characters
1550 and 16 bit Unicode characters. The default is iso8859-1.
1551 Long filenames are stored on disk in Unicode format.
1553 .BR nfs= { stale_rw | nostale_ro }
1554 Enable this only if you want to export the FAT filesystem over NFS.
1557 This option maintains an index (cache) of directory inodes which is used by the
1558 nfs-related code to improve look-ups. Full file operations (read/write) over
1559 NFS are supported but with cache eviction at NFS server, this could result in
1565 This option bases the inode number and file handle
1566 on the on-disk location of a file in the FAT directory entry.
1569 will not be returned after a file is
1570 evicted from the inode cache. However, it means that operations
1571 such as rename, create and unlink could cause file handles that
1572 previously pointed at one file to point at a different file,
1573 potentially causing data corruption. For this reason, this
1574 option also mounts the filesystem readonly.
1576 To maintain backward compatibility, '-o nfs' is also accepted,
1581 This option disables the conversion of timestamps
1582 between local time (as used by Windows on FAT) and UTC
1583 (which Linux uses internally). This is particularly
1584 useful when mounting devices (like digital cameras)
1585 that are set to UTC in order to avoid the pitfalls of
1588 .BI time_offset= minutes
1589 Set offset for conversion of timestamps from local time used by FAT to UTC.
1592 will be subtracted from each timestamp to convert it to UTC used
1593 internally by Linux. This is useful when the time zone set in the kernel via
1594 .BR settimeofday (2)
1595 is not the time zone used by the filesystem. Note
1596 that this option still does not provide correct time stamps in all cases in
1597 presence of DST - time stamps in a different DST setting will be off by one
1603 flag. Attempts to chown or chmod files do not return errors,
1604 although they fail. Use with caution!
1607 FAT has the ATTR_RO (read-only) attribute. On Windows, the ATTR_RO of the
1608 directory will just be ignored, and is used only by applications as a flag
1609 (e.g.\& it's set for the customized folder).
1611 If you want to use ATTR_RO as read-only flag even for the directory, set this
1615 If set, the execute permission bits of the file will be allowed only if
1616 the extension part of the name is \&.EXE, \&.COM, or \&.BAT. Not set by default.
1619 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux.
1623 If set, the filesystem will try to flush to disk more early than normal.
1627 Use the "free clusters" value stored on FSINFO. It'll
1628 be used to determine number of free clusters without
1629 scanning disk. But it's not used by default, because
1630 recent Windows don't update it correctly in some
1631 case. If you are sure the "free clusters" on FSINFO is
1632 correct, by this option you can avoid scanning disk.
1634 .BR dots ", " nodots ", " dotsOK= [ yes | no ]
1635 Various misguided attempts to force Unix or DOS conventions
1636 onto a FAT filesystem.
1638 .SS "Mount options for hfs"
1640 .BI creator= cccc ", type=" cccc
1641 Set the creator/type values as shown by the MacOS finder
1642 used for creating new files. Default values: '????'.
1644 .BI uid= n ", gid=" n
1645 Set the owner and group of all files.
1646 (Default: the UID and GID of the current process.)
1648 .BI dir_umask= n ", file_umask=" n ", umask=" n
1649 Set the umask used for all directories, all regular files, or all
1650 files and directories. Defaults to the umask of the current process.
1653 Select the CDROM session to mount.
1654 Defaults to leaving that decision to the CDROM driver.
1655 This option will fail with anything but a CDROM as underlying device.
1658 Select partition number n from the device.
1659 Only makes sense for CDROMs.
1660 Defaults to not parsing the partition table at all.
1663 Don't complain about invalid mount options.
1665 .SS "Mount options for hpfs"
1667 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1668 Set the owner and group of all files. (Default: the UID and GID
1669 of the current process.)
1672 Set the umask (the bitmask of the permissions that are
1674 present). The default is the umask of the current process.
1675 The value is given in octal.
1677 .BR case= { lower | asis }
1678 Convert all files names to lower case, or leave them.
1683 This option is obsolete and may fail or being ignored.
1686 Do not abort mounting when certain consistency checks fail.
1688 .SS "Mount options for iso9660"
1689 ISO 9660 is a standard describing a filesystem structure to be used
1690 on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1696 filenames appear in a 8.3 format (i.e., DOS-like restrictions on filename
1697 length), and in addition all characters are in upper case. Also there is
1698 no field for file ownership, protection, number of links, provision for
1699 block/character devices, etc.
1701 Rock Ridge is an extension to iso9660 that provides all of these UNIX-like
1702 features. Basically there are extensions to each directory record that
1703 supply all of the additional information, and when Rock Ridge is in use,
1704 the filesystem is indistinguishable from a normal UNIX filesystem (except
1705 that it is read-only, of course).
1708 Disable the use of Rock Ridge extensions, even if available. Cf.\&
1712 Disable the use of Microsoft Joliet extensions, even if available. Cf.\&
1715 .BR check= { r [ elaxed ]| s [ trict ]}
1718 a filename is first converted to lower case before doing the lookup.
1719 This is probably only meaningful together with
1726 \fBuid=\fP\,\fIvalue\fP and \fBgid=\fP\,\fIvalue\fP
1727 Give all files in the filesystem the indicated user or group id,
1728 possibly overriding the information found in the Rock Ridge extensions.
1732 .BR map= { n [ ormal ]| o [ ff ]| a [ corn ]}
1733 For non-Rock Ridge volumes, normal name translation maps upper
1734 to lower case ASCII, drops a trailing `;1', and converts `;' to `.'.
1737 no name translation is done. See
1744 but also apply Acorn extensions if present.
1747 For non-Rock Ridge volumes, give all files the indicated mode.
1748 (Default: read and execute permission for everybody.)
1749 Octal mode values require a leading 0.
1752 Also show hidden and associated files.
1753 (If the ordinary files and the associated or hidden files have
1754 the same filenames, this may make the ordinary files inaccessible.)
1756 .BR block= { 512 | 1024 | 2048 }
1757 Set the block size to the indicated value.
1762 This option is obsolete and may fail or being ignored.
1765 If the high byte of the file length contains other garbage,
1766 set this mount option to ignore the high order bits of the file length.
1767 This implies that a file cannot be larger than 16\ MB.
1770 Select number of session on multisession CD.
1773 Session begins from sector xxx.
1775 The following options are the same as for vfat and specifying them only makes
1776 sense when using discs encoded using Microsoft's Joliet extensions.
1778 .BI iocharset= value
1779 Character set to use for converting 16 bit Unicode characters on CD
1780 to 8 bit characters. The default is iso8859-1.
1783 Convert 16 bit Unicode characters on CD to UTF-8.
1785 .SS "Mount options for jfs"
1788 Character set to use for converting from Unicode to ASCII. The default is
1789 to do no conversion. Use
1791 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in
1797 Resize the volume to
1799 blocks. JFS only supports growing a volume, not shrinking it. This option
1800 is only valid during a remount, when the volume is mounted read-write. The
1802 keyword with no value will grow the volume to the full size of the partition.
1805 Do not write to the journal. The primary use of this option is to allow
1806 for higher performance when restoring a volume from backup media. The
1807 integrity of the volume is not guaranteed if the system abnormally ends.
1810 Default. Commit metadata changes to the journal. Use this option to remount
1813 option was previously specified in order to restore normal behavior.
1815 .BR errors= { continue | remount-ro | panic }
1816 Define the behavior when an error is encountered.
1817 (Either ignore errors and just mark the filesystem erroneous and continue,
1818 or remount the filesystem read-only, or panic and halt the system.)
1820 .BR noquota | quota | usrquota | grpquota
1821 These options are accepted but ignored.
1823 .SS "Mount options for msdos"
1824 See mount options for fat.
1827 filesystem detects an inconsistency, it reports an error and sets the file
1828 system read-only. The filesystem can be made writable again by remounting
1831 .SS "Mount options for ncpfs"
1833 .IR nfs ", the " ncpfs
1834 implementation expects a binary argument (a
1835 .IR "struct ncp_mount_data" )
1836 to the mount system call. This argument is constructed by
1838 and the current version of
1840 (2.12) does not know anything about ncpfs.
1842 .SS "Mount options for ntfs"
1845 Character set to use when returning file names.
1846 Unlike VFAT, NTFS suppresses names that contain
1847 nonconvertible characters. Deprecated.
1850 New name for the option earlier called
1854 Use UTF-8 for converting file names.
1856 .BR uni_xlate= { 0 | 1 | 2 }
1857 For 0 (or `no' or `false'), do not use escape sequences
1858 for unknown Unicode characters.
1859 For 1 (or `yes' or `true') or 2, use vfat-style 4-byte escape sequences
1860 starting with ":". Here 2 give a little-endian encoding
1861 and 1 a byteswapped bigendian encoding.
1864 If enabled (posix=1), the filesystem distinguishes between
1865 upper and lower case. The 8.3 alias names are presented as
1866 hard links instead of being suppressed. This option is obsolete.
1868 \fBuid=\fP\,\fIvalue\fP, \fBgid=\fP\,\fIvalue\fP and \fBumask=\fP\,\fIvalue\fP
1869 Set the file permission on the filesystem.
1870 The umask value is given in octal.
1871 By default, the files are owned by root and not readable by somebody else.
1873 .SS "Mount options for overlay"
1874 Since Linux 3.18 the overlay pseudo filesystem implements a union mount for
1877 An overlay filesystem combines two filesystems - an \fBupper\fR filesystem and
1878 a \fBlower\fR filesystem. When a name exists in both filesystems, the object
1879 in the upper filesystem is visible while the object in the lower filesystem is
1880 either hidden or, in the case of directories, merged with the upper object.
1882 The lower filesystem can be any filesystem supported by Linux and does not need
1883 to be writable. The lower filesystem can even be another overlayfs. The upper
1884 filesystem will normally be writable and if it is it must support the creation
1885 of trusted.* extended attributes, and must provide a valid d_type in readdir
1886 responses, so NFS is not suitable.
1888 A read-only overlay of two read-only filesystems may use any filesystem type.
1889 The options \fBlowerdir\fR and \fBupperdir\fR are combined into a merged
1895 .B "mount \-t overlay overlay \e"
1896 .B " \-olowerdir=/lower,upperdir=/upper,workdir=/work /merged"
1902 .BI lowerdir= directory
1903 Any filesystem, does not need to be on a writable filesystem.
1905 .BI upperdir= directory
1906 The upperdir is normally on a writable filesystem.
1908 .BI workdir= directory
1909 The workdir needs to be an empty directory on the same filesystem as upperdir.
1911 .SS "Mount options for reiserfs"
1912 Reiserfs is a journaling filesystem.
1915 Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem,
1916 using the 3.6 format for newly created objects. This filesystem will no
1917 longer be compatible with reiserfs 3.5 tools.
1919 .BR hash= { rupasov | tea | r5 | detect }
1920 Choose which hash function reiserfs will use to find files within directories.
1924 A hash invented by Yury Yu.\& Rupasov. It is fast and preserves locality,
1925 mapping lexicographically close file names to close hash values.
1926 This option should not be used, as it causes a high probability of hash
1930 A Davis-Meyer function implemented by Jeremy Fitzhardinge.
1931 It uses hash permuting bits in the name. It gets high randomness
1932 and, therefore, low probability of hash collisions at some CPU cost.
1933 This may be used if EHASHCOLLISION errors are experienced with the r5 hash.
1936 A modified version of the rupasov hash. It is used by default and is
1937 the best choice unless the filesystem has huge directories and
1938 unusual file-name patterns.
1943 to detect which hash function is in use by examining
1944 the filesystem being mounted, and to write this information into
1945 the reiserfs superblock. This is only useful on the first mount of
1946 an old format filesystem.
1949 .B hashed_relocation
1950 Tunes the block allocator. This may provide performance improvements
1953 .B no_unhashed_relocation
1954 Tunes the block allocator. This may provide performance improvements
1958 Disable the border allocator algorithm invented by Yury Yu.\& Rupasov.
1959 This may provide performance improvements in some situations.
1962 Disable journaling. This will provide slight performance improvements in
1963 some situations at the cost of losing reiserfs's fast recovery from crashes.
1964 Even with this option turned on, reiserfs still performs all journaling
1965 operations, save for actual writes into its journaling area. Implementation
1968 is a work in progress.
1971 By default, reiserfs stores small files and `file tails' directly into its
1972 tree. This confuses some utilities such as
1974 This option is used to disable packing of files into the tree.
1977 Replay the transactions which are in the journal, but do not actually
1978 mount the filesystem. Mainly used by
1982 A remount option which permits online expansion of reiserfs partitions.
1983 Instructs reiserfs to assume that the device has
1986 This option is designed for use with devices which are under logical
1987 volume management (LVM).
1990 utility which can be obtained from
1991 .IR ftp://ftp.namesys.com/pub/reiserfsprogs .
1994 Enable Extended User Attributes. See the
1999 Enable POSIX Access Control Lists. See the
2003 .BR barrier=none " / " barrier=flush "
2004 This disables / enables the use of write barriers in the journaling code.
2005 barrier=none disables, barrier=flush enables (default). This also requires an
2006 IO stack which can support barriers, and if reiserfs gets an error on a barrier
2007 write, it will disable barriers again with a warning. Write barriers enforce
2008 proper on-disk ordering of journal commits, making volatile disk write caches
2009 safe to use, at some performance penalty. If your disks are battery-backed in
2010 one way or another, disabling barriers may safely improve performance.
2012 .SS "Mount options for ubifs"
2013 UBIFS is a flash filesystem which works on top of UBI volumes. Note that
2014 \fBatime\fR is not supported and is always turned off.
2016 The device name may be specified as
2044 separator may be used instead of
2047 The following mount options are available:
2050 Enable bulk-read. VFS read-ahead is disabled because it slows down the file
2051 system. Bulk-Read is an internal optimization. Some flashes may read faster if
2052 the data are read at one go, rather than at several read requests. For
2053 example, OneNAND can do "read-while-load" if it reads more than one NAND page.
2056 Do not bulk-read. This is the default.
2059 Check data CRC-32 checksums. This is the default.
2061 .BR no_chk_data_crc .
2062 Do not check data CRC-32 checksums. With this option, the filesystem does not
2063 check CRC-32 checksum for data, but it does check it for the internal indexing
2064 information. This option only affects reading, not writing. CRC-32 is always
2065 calculated when writing the data.
2067 .BR compr= { none | lzo | zlib }
2068 Select the default compressor which is used when new files are written. It is
2069 still possible to read compressed files if mounted with the
2073 .SS "Mount options for udf"
2074 UDF is the "Universal Disk Format" filesystem defined by OSTA, the Optical
2075 Storage Technology Association, and is often used for DVD-ROM, frequently
2076 in the form of a hybrid UDF/ISO-9660 filesystem. It is, however,
2077 perfectly usable by itself on disk drives, flash drives and other block devices.
2082 Make all files in the filesystem belong to the given user.
2083 uid=forget can be specified independently of (or usually in
2084 addition to) uid=<user> and results in UDF
2085 not storing uids to the media. In fact the recorded uid
2086 is the 32-bit overflow uid -1 as defined by the UDF standard.
2087 The value is given as either <user> which is a valid user name or the corresponding
2088 decimal user id, or the special string "forget".
2091 Make all files in the filesystem belong to the given group.
2092 gid=forget can be specified independently of (or usually in
2093 addition to) gid=<group> and results in UDF
2094 not storing gids to the media. In fact the recorded gid
2095 is the 32-bit overflow gid -1 as defined by the UDF standard.
2096 The value is given as either <group> which is a valid group name or the corresponding
2097 decimal group id, or the special string "forget".
2100 Mask out the given permissions from all inodes read from the filesystem.
2101 The value is given in octal.
2104 If mode= is set the permissions of all non-directory inodes read from the
2105 filesystem will be set to the given mode. The value is given in octal.
2108 If dmode= is set the permissions of all directory inodes read from the
2109 filesystem will be set to the given dmode. The value is given in octal.
2112 Set the block size. Default value prior to kernel version 2.6.30 was
2113 2048. Since 2.6.30 and prior to 4.11 it was logical device block size with
2114 fallback to 2048. Since 4.11 it is logical block size with fallback to
2115 any valid block size between logical device block size and 4096.
2117 For other details see the updated mkudffs.8 manpage, section
2118 COMPATIBILITY and BLOCK SIZE.
2121 Show otherwise hidden files.
2124 Show deleted files in lists.
2127 Embed data in the inode. (default)
2130 Don't embed data in the inode.
2133 Use short UDF address descriptors.
2136 Use long UDF address descriptors. (default)
2139 Unset strict conformance.
2142 Set the NLS character set.
2143 .SS Mount options for debugging and disaster recovery
2146 Ignore the Volume Recognition Sequence and attempt to mount anyway.
2149 Select the session number for multi-session recorded optical media. (default= last session)
2152 Override standard anchor location. (default= 256)
2155 Set the last block of the filesystem.
2156 .SS Unused historical mount options that may be encountered and should be removed
2159 use uid=<user> instead.
2162 use gid=<group> instead.
2165 Override the VolumeDesc location.
2168 Override the PartitionDesc location.
2171 Override the fileset block location.
2174 Override the root directory location.
2176 .SS "Mount options for ufs"
2179 UFS is a filesystem widely used in different operating systems.
2180 The problem are differences among implementations. Features of some
2181 implementations are undocumented, so its hard to recognize the
2182 type of ufs automatically.
2183 That's why the user must specify the type of ufs by mount option.
2184 Possible values are:
2188 Old format of ufs, this is the default, read only.
2189 (Don't forget to give the \-r option.)
2192 For filesystems created by a BSD-like system (NetBSD, FreeBSD, OpenBSD).
2195 Used in FreeBSD 5.x supported as read-write.
2201 For filesystems created by SunOS or Solaris on Sparc.
2204 For filesystems created by Solaris on x86.
2207 For filesystems created by HP-UX, read-only.
2210 For filesystems created by NeXTStep (on NeXT station) (currently read only).
2213 For NextStep CDROMs (block_size == 2048), read-only.
2216 For filesystems created by OpenStep (currently read only).
2217 The same filesystem type is also used by Mac OS X.
2222 Set behavior on error:
2226 If an error is encountered, cause a kernel panic.
2228 .RB [ lock | umount | repair ]
2229 These mount options don't do anything at present;
2230 when an error is encountered only a console message is printed.
2233 .SS "Mount options for umsdos"
2234 See mount options for msdos.
2237 option is explicitly killed by
2240 .SS "Mount options for vfat"
2241 First of all, the mount options for
2246 option is explicitly killed by
2248 Furthermore, there are
2251 Translate unhandled Unicode characters to special escaped sequences.
2252 This lets you backup and restore filenames that are created with any
2253 Unicode characters. Without this option, a '?' is used when no
2254 translation is possible. The escape character is ':' because it is
2255 otherwise invalid on the vfat filesystem. The escape sequence
2256 that gets used, where u is the Unicode character,
2257 is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
2260 Allow two files with names that only differ in case.
2261 This option is obsolete.
2264 First try to make a short name without sequence number,
2266 .IR name\s+3~\s0num.ext .
2269 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the
2270 console. It can be enabled for the filesystem with this option or disabled
2271 with utf8=0, utf8=no or utf8=false. If `uni_xlate' gets set, UTF8 gets
2275 Defines the behavior for creation and display of filenames which fit into
2276 8.3 characters. If a long name for a file exists, it will always be the
2277 preferred one for display. There are four \fImode\fRs:
2281 Force the short name to lower case upon display; store a long name when
2282 the short name is not all upper case.
2285 Force the short name to upper case upon display; store a long name when
2286 the short name is not all upper case.
2289 Display the short name as is; store a long name when the short name is
2290 not all lower case or all upper case.
2293 Display the short name as is; store a long name when the short name is not
2294 all upper case. This mode is the default since Linux 2.6.32.
2297 .SS "Mount options for usbfs"
2299 \fBdevuid=\fP\,\fIuid\fP and \fBdevgid=\fP\,\fIgid\fP and \fBdevmode=\fP\,\fImode\fP
2300 Set the owner and group and mode of the device files in the usbfs filesystem
2301 (default: uid=gid=0, mode=0644). The mode is given in octal.
2303 \fBbusuid=\fP\,\fIuid\fP and \fBbusgid=\fP\,\fIgid\fP and \fBbusmode=\fP\,\fImode\fP
2304 Set the owner and group and mode of the bus directories in the usbfs
2305 filesystem (default: uid=gid=0, mode=0555). The mode is given in octal.
2307 \fBlistuid=\fP\,\fIuid\fP and \fBlistgid=\fP\,\fIgid\fP and \fBlistmode=\fP\,\fImode\fP
2308 Set the owner and group and mode of the file
2310 (default: uid=gid=0, mode=0444). The mode is given in octal.
2312 .SH "THE LOOP DEVICE"
2313 One further possible type is a mount via the loop device. For example,
2317 .B "mount /tmp/disk.img /mnt \-t vfat \-o loop=/dev/loop3"
2320 will set up the loop device
2322 to correspond to the file
2324 and then mount this device on
2327 If no explicit loop device is mentioned
2328 (but just an option `\fB\-o loop\fP' is given), then
2330 will try to find some unused loop device and use that, for example
2333 .B "mount /tmp/disk.img /mnt \-o loop"
2338 creates a loop device from a regular file if a filesystem type is
2339 not specified or the filesystem is known for libblkid, for example:
2342 .B "mount /tmp/disk.img /mnt"
2344 .B "mount \-t ext3 /tmp/disk.img /mnt"
2347 This type of mount knows about three options, namely
2348 .BR loop ", " offset " and " sizelimit ,
2349 that are really options to
2351 (These options can be used in addition to those specific
2352 to the filesystem type.)
2354 Since Linux 2.6.25 auto-destruction of loop devices is supported,
2355 meaning that any loop device allocated by
2362 You can also free a loop device by hand, using
2363 .BR "losetup \-d " or " umount \-d" .
2365 Since util-linux v2.29 mount command re-uses the loop device rather than
2366 initialize a new device if the same backing file is already used for some loop
2367 device with the same offset and sizelimit. This is necessary to avoid
2368 a filesystem corruption.
2372 has the following return codes (the bits can be ORed):
2378 incorrect invocation or permissions
2381 system error (out of memory, cannot fork, no more loop devices)
2392 problems writing or locking /etc/mtab
2398 some mount succeeded
2401 The command \fBmount \-a\fR returns 0 (all succeeded), 32 (all failed), or 64 (some
2402 failed, some succeeded).
2404 .SH "EXTERNAL HELPERS"
2405 The syntax of external mount helpers is:
2408 .BI /sbin/mount. suffix
2414 .IR type \fB. subtype ]
2417 where the \fIsuffix\fR is the filesystem type and the \fB\-sfnvo\fR options have
2418 the same meaning as the normal mount options. The \fB\-t\fR option is used for
2419 filesystems with subtypes support (for example
2420 .BR "/sbin/mount.fuse \-t fuse.sshfs" ).
2422 The command \fBmount\fR does not pass the mount options
2439 to the mount.<suffix> helpers. All other options are used in a
2440 comma-separated list as argument to the \fB\-o\fR option.
2448 table of mounted filesystems
2450 .I /etc/mtab\s+3~\s0
2457 a list of filesystem types to try
2459 .IP LIBMOUNT_FSTAB=<path>
2460 overrides the default location of the fstab file (ignored for suid)
2461 .IP LIBMOUNT_MTAB=<path>
2462 overrides the default location of the mtab file (ignored for suid)
2463 .IP LIBMOUNT_DEBUG=all
2464 enables libmount debug output
2465 .IP LIBBLKID_DEBUG=all
2466 enables libblkid debug output
2467 .IP LOOPDEV_DEBUG=all
2468 enables loop device setup debug output
2488 It is possible for a corrupted filesystem to cause a crash.
2490 Some Linux filesystems don't support
2491 .BR "\-o sync " nor " \-o dirsync"
2492 (the ext2, ext3, fat and vfat filesystems
2494 support synchronous updates (a la BSD) when mounted with the
2500 may not be able to change mount parameters (all
2501 .IR ext2fs -specific
2504 are changeable with a remount, for example, but you can't change
2511 It is possible that the files
2515 don't match on systems with a regular mtab file. The first file is based only on
2516 the mount command options, but the content of the second file also depends on
2517 the kernel and others settings (e.g.\& on a remote NFS server -- in certain cases
2518 the mount command may report unreliable information about an NFS mount point
2519 and the /proc/mounts file usually contains more reliable information.) This is
2520 another reason to replace the mtab file with a symlink to the
2524 Checking files on NFS filesystems referenced by file descriptors (i.e.\& the
2528 families of functions) may lead to inconsistent results due to the lack of
2529 a consistency check in the kernel even if noac is used.
2537 options used may fail when using older kernels if the
2539 command can't confirm that the size of the block device has been configured
2540 as requested. This situation can be worked around by using
2543 command manually before calling
2545 with the configured loop device.
2549 command existed in Version 5 AT&T UNIX.
2552 Karel Zak <kzak@redhat.com>
2555 The mount command is part of the util-linux package and is available from
2556 https://www.kernel.org/pub/linux/utils/util-linux/.