1 .\" Copyright (c) 1996-2004 Andries Brouwer
3 .\" This page is somewhat derived from a page that was
4 .\" (c) 1980, 1989, 1991 The Regents of the University of California
5 .\" and had been heavily modified by Rik Faith and myself.
6 .\" (Probably no BSD text remains.)
7 .\" Fragments of text were written by Werner Almesberger, Remy Card,
8 .\" Stephen Tweedie and Eric Youngdale.
10 .\" This is free documentation; you can redistribute it and/or
11 .\" modify it under the terms of the GNU General Public License as
12 .\" published by the Free Software Foundation; either version 2 of
13 .\" the License, or (at your option) any later version.
15 .\" The GNU General Public License's references to "object code"
16 .\" and "executables" are to be interpreted as the output of any
17 .\" document formatting or typesetting system, including
18 .\" intermediate and printed output.
20 .\" This manual is distributed in the hope that it will be useful,
21 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of
22 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23 .\" GNU General Public License for more details.
25 .\" You should have received a copy of the GNU General Public License along
26 .\" with this program; if not, write to the Free Software Foundation, Inc.,
27 .\" 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
29 .\" 960705, aeb: version for mount-2.7g
30 .\" 970114, aeb: xiafs and ext are dead; romfs is new
31 .\" 970623, aeb: -F option
32 .\" 970914, reg: -s option
33 .\" 981111, K.Garloff: /etc/filesystems
34 .\" 990111, aeb: documented /sbin/mount.smbfs
35 .\" 990730, Yann Droneaud <lch@multimania.com>: updated page
36 .\" 991214, Elrond <Elrond@Wunder-Nett.org>: added some docs on devpts
37 .\" 010714, Michael K. Johnson <johnsonm@redhat.com> added -O
38 .\" 010725, Nikita Danilov <NikitaDanilov@Yahoo.COM>: reiserfs options
39 .\" 011124, Karl Eichwalder <ke@gnu.franken.de>: tmpfs options
41 .TH MOUNT 8 "December 2004" "util-linux" "System Administration"
43 mount \- mount a filesystem
58 .IR option [ \fB,\fPoption ]...]
69 All files accessible in a Unix system are arranged in one big
70 tree, the file hierarchy, rooted at
72 These files can be spread out over several devices. The
74 command serves to attach the filesystem found on some device
75 to the big file tree. Conversely, the
77 command will detach it again.
79 The standard form of the
85 .BI "mount \-t" " type device dir"
89 This tells the kernel to attach the filesystem found on
95 The previous contents (if any) and owner and mode of
97 become invisible, and as long as this filesystem remains mounted,
100 refers to the root of the filesystem on
103 If only directory or device is given, for example:
111 then mount looks for a mountpoint and if not found then for a device in the
114 .B The listing and help.
116 Three forms of invocation do not actually mount anything:
119 prints a help message
122 prints a version string
124 .BR "mount " [ -l "] [" "-t \fItype\fP" ]
125 lists all mounted filesystems (of type
127 The option \-l adds the labels in this listing.
131 .B The device indication.
133 Most devices are indicated by a file name (of a block special device), like
135 but there are other possibilities. For example, in the case of an NFS mount,
138 .IR knuth.cwi.nl:/dir .
139 It is possible to indicate a block special device using its
144 (see the \-L and \-U options below).
146 The recommended setup is to use LABEL=<label> or UUID=<uuid> tags rather than
147 .B /dev/disk/by-{label,uuid}
148 udev symlinks in the /etc/fstab file. The tags are
149 more readable, robust and portable. The
151 command internally uses udev
152 symlinks, so use the symlinks in /etc/fstab has no advantage over LABEL=/UUID=.
158 uses UUIDs as strings. The UUIDs from command line or
160 are not converted to internal binary representation. The string representation
161 of the UUID should be based on lower case characters.
165 filesystem is not associated with a special device, and when
166 mounting it, an arbitrary keyword, such as
168 can be used instead of a device specification.
169 (The customary choice
171 is less fortunate: the error message `none busy' from
176 .B The /etc/fstab, /etc/mtab and /proc/mounts files.
182 may contain lines describing what devices are usually
183 mounted where, using which options.
195 (usually given in a bootscript) causes all filesystems mentioned in
197 (of the proper type and/or having or not having the proper options)
198 to be mounted as indicated, except for those whose line contains the
202 option will make mount fork, so that the
203 filesystems are mounted simultaneously.
205 When mounting a filesystem mentioned in
209 it suffices to give only the device, or only the mount point.
216 maintain a list of currently mounted filesystems in the file
218 If no arguments are given to
220 this list is printed.
224 program does not read the
230 are specified. For example:
233 .B "mount /dev/foo /dir"
236 If you want to override mount options from
241 .B "mount device|dir -o <options>"
244 and then the mount options from command line will be appended to
245 the list of options from
247 The usual behaviour is that the last option wins if there is more duplicated
252 filesystem is mounted (say at
258 have very similar contents. The former has somewhat
259 more information, such as the mount options used,
260 but is not necessarily up-to-date (cf. the
262 option below). It is possible to replace
264 by a symbolic link to
266 and especially when you have very large numbers of mounts
267 things will be much faster with that symlink,
268 but some information is lost that way, and in particular
269 using the "user" option will fail.
272 .B The non-superuser mounts.
274 Normally, only the superuser can mount filesystems.
279 option on a line, anybody can mount the corresponding system.
284 .B "/dev/cdrom /cd iso9660 ro,user,noauto,unhide"
287 any user can mount the iso9660 filesystem found on his CDROM
291 .B "mount /dev/cdrom"
300 For more details, see
302 Only the user that mounted a filesystem can unmount it again.
303 If any user should be able to unmount, then use
312 option is similar to the
314 option, with the restriction that the user must be the owner
315 of the special file. This may be useful e.g. for
317 if a login script makes the console user owner of this device.
320 option is similar, with the restriction that the user must be
321 member of the group of the special file.
327 .\" In fact since 2.3.99. At first the syntax was mount -t bind.
328 Since Linux 2.4.0 it is possible to remount part of the
329 file hierarchy somewhere else. The call is
349 After this call the same contents is accessible in two places.
350 One can also remount a single file (on a single file). It's also
351 possible to use the bind mount to create a mountpoint from a regular
352 directory, for example:
360 The bind mount call attaches only (part of) a single filesystem, not possible
361 submounts. The entire file hierarchy including submounts is attached
377 .\" available since Linux 2.4.11.
379 Note that the filesystem mount options will remain the same as those
380 on the original mount point, and cannot be changed by passing the -o
381 option along with --bind/--rbind. The mount options can be
382 changed by a separate remount command, for example:
389 .B mount -o remount,ro
393 Note that behavior of the remount operation depends on the /etc/mtab file. The
394 first command stores the 'bind' flag to the /etc/mtab file and the second
395 command reads the flag from the file. If you have a system without the
396 /etc/mtab file or if you explicitly define source and target for the remount
397 command (then mount(8) does not read /etc/mtab), then you have to use bind flag
398 (or option) for the remount command too. For example:
405 .B mount -o remount,ro,bind
410 .B The move operation.
412 Since Linux 2.5.1 it is possible to atomically move a
414 to another place. The call is
426 This will cause the contents which previously appeared under olddir to be
427 accessed under newdir. The physical location of the files is not changed.
430 has to be a mountpoint.
433 .B The shared subtrees operations.
435 Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared,
436 private, slave or unbindable. A shared mount provides ability to create mirrors
437 of that mount such that mounts and umounts within any of the mirrors propagate
438 to the other mirror. A slave mount receives propagation from its master, but
439 any not vice-versa. A private mount carries no propagation abilities. A
440 unbindable mount is a private mount which cannot be cloned through a bind
441 operation. Detailed semantics is documented in Documentation/filesystems/sharedsubtree.txt
442 file in the kernel source tree.
446 .BI "mount --make-shared " mountpoint
447 .BI "mount --make-slave " mountpoint
448 .BI "mount --make-private " mountpoint
449 .BI "mount --make-unbindable " mountpoint
453 The following commands allows one to recursively change the type of all the
454 mounts under a given mountpoint.
458 .BI "mount --make-rshared " mountpoint
459 .BI "mount --make-rslave " mountpoint
460 .BI "mount --make-rprivate " mountpoint
461 .BI "mount --make-runbindable " mountpoint
466 .SH COMMAND LINE OPTIONS
467 The full set of mount options used by an invocation of
469 is determined by first extracting the
470 mount options for the filesystem from the
472 table, then applying any options specified by the
474 argument, and finally applying a
476 option, when present.
478 Command line options available for the
481 .IP "\fB\-V, \-\-version\fP"
483 .IP "\fB\-h, \-\-help\fP"
484 Print a help message.
485 .IP "\fB\-v, \-\-verbose\fP"
487 .IP "\fB\-a, \-\-all\fP"
488 Mount all filesystems (of the given types) mentioned in
490 .IP "\fB\-F, \-\-fork\fP"
491 (Used in conjunction with
493 Fork off a new incarnation of mount for each device.
494 This will do the mounts on different devices or different NFS servers
496 This has the advantage that it is faster; also NFS timeouts go in
497 parallel. A disadvantage is that the mounts are done in undefined order.
498 Thus, you cannot use this option if you want to mount both
502 .IP "\fB\-f, \-\-fake\fP"
503 Causes everything to be done except for the actual system call; if it's not
504 obvious, this ``fakes'' mounting the filesystem. This option is useful in
507 flag to determine what the
509 command is trying to do. It can also be used to add entries for devices
510 that were mounted earlier with the -n option. The -f option checks for
511 existing record in /etc/mtab and fails when the record already
512 exists (with regular non-fake mount, this check is done by kernel).
513 .IP "\fB\-i, \-\-internal\-only\fP"
514 Don't call the /sbin/mount.<filesystem> helper even if it exists.
516 Add the labels in the mount output. Mount must have
517 permission to read the disk device (e.g. be suid root) for this to work.
518 One can set such a label for ext2, ext3 or ext4 using the
520 utility, or for XFS using
522 or for reiserfs using
523 .BR reiserfstune (8).
524 .IP "\fB\-n, \-\-no\-mtab\fP"
525 Mount without writing in
527 This is necessary for example when
529 is on a read-only filesystem.
530 .IP "\fB\-\-no\-canonicalize\fP"
531 Don't canonicalize paths. The mount command canonicalizes all paths
532 (from command line or fstab) and stores canonicalized paths to the
534 file. This option can be used together with the
536 flag for already canonicalized absolut paths.
537 .IP "\fB\-p, \-\-pass\-fd \fInum\fP"
538 In case of a loop mount with encryption, read the passphrase from
541 instead of from the terminal.
543 Tolerate sloppy mount options rather than failing. This will ignore
544 mount options not supported by a filesystem type. Not all filesystems
545 support this option. This option exists for support of the Linux
546 autofs\-based automounter.
547 .IP "\fB\-r, \-\-read\-only\fP"
548 Mount the filesystem read-only. A synonym is
551 Note that, depending on the filesystem type, state and kernel behavior, the
552 system may still write to the device. For example, Ext3 or ext4 will replay its
553 journal if the filesystem is dirty. To prevent this kind of write access, you
554 may want to mount ext3 or ext4 filesystem with "ro,noload" mount options or
555 set the block device to read-only mode, see command
557 .IP "\fB\-w, \-\-rw\fP"
558 Mount the filesystem read/write. This is the default. A synonym is
560 .IP "\fB\-L \fIlabel\fP"
561 Mount the partition that has the specified
563 .IP "\fB\-U \fIuuid\fP"
564 Mount the partition that has the specified
566 These two options require the file
568 (present since Linux 2.1.116) to exist.
569 .IP "\fB\-t, \-\-types \fIvfstype\fP"
570 The argument following the
572 is used to indicate the filesystem type. The filesystem types which are
573 currently supported include:
617 Note that coherent, sysv and xenix are equivalent and that
621 will be removed at some point in the future \(em use
623 instead. Since kernel version 2.1.21 the types
627 do not exist anymore. Earlier,
631 Note, the real list of all supported filesystems depends on your
638 support filesystem subtypes. The subtype is defined by '.subtype' suffix. For
639 example 'fuse.sshfs'. It's recommended to use subtype notation rather than add
640 any prefix to the mount source (for example 'sshfs#example.com' is
643 For most types all the
645 program has to do is issue a simple
647 system call, and no detailed knowledge of the filesystem type is required.
648 For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) ad hoc code is
649 necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems
650 have a separate mount program. In order to make it possible to
651 treat all types in a uniform way, mount will execute the program
652 .BI /sbin/mount. TYPE
653 (if that exists) when called with type
655 Since various versions of the
657 program have different calling conventions,
659 may have to be a shell script that sets up the desired call.
663 option is given, or if the
665 type is specified, mount will try to guess the desired type.
666 Mount uses the blkid library for guessing the filesystem
667 type; if that does not turn up anything that looks familiar,
668 mount will try to read the file
669 .IR /etc/filesystems ,
670 or, if that does not exist,
671 .IR /proc/filesystems .
672 All of the filesystem types listed there will be tried,
673 except for those that are labeled "nodev" (e.g.,
680 ends in a line with a single * only, mount will read
686 type may be useful for user-mounted floppies.
689 can be useful to change the probe order (e.g., to try vfat before msdos
690 or ext3 before ext2) or if you use a kernel module autoloader.
692 More than one type may be specified in a comma separated
693 list. The list of filesystem types can be prefixed with
695 to specify the filesystem types on which no action should be taken.
696 (This can be meaningful with the
698 option.) For example, the command:
702 .B "mount \-a \-t nomsdos,ext"
705 mounts all filesystems except those of type
710 .IP "\fB\-O, \-\-test-opts \fIopts\fP"
711 Used in conjunction with
713 to limit the set of filesystems to which the
717 in this regard except that it is useless except in the context of
719 For example, the command:
723 .B "mount \-a \-O no_netdev"
726 mounts all filesystems except those which have the option
728 specified in the options field in the
734 in that each option is matched exactly; a leading
736 at the beginning of one option does not negate the rest.
742 options are cumulative in effect; that is, the command
745 .B "mount \-a \-t ext2 \-O _netdev"
748 mounts all ext2 filesystems with the _netdev option, not all filesystems
749 that are either ext2 or have the _netdev option specified.
751 .IP "\fB\-o, \-\-options \fIopts\fP"
752 Options are specified with a
754 flag followed by a comma separated string of options. For example:
758 .B "mount LABEL=mydisk \-o noatime,nouser"
762 For more details, see
763 .B FILESYSTEM INDEPENDENT MOUNT OPTIONS
765 .B FILESYSTEM SPECIFIC MOUNT OPTIONS
768 .IP "\fB\-B, \-\-bind\fP"
769 Remount a subtree somewhere else (so that its contents are available
770 in both places). See above.
771 .IP "\fB\-R, \-\-rbind\fP"
772 Remount a subtree and all possible submounts somewhere else (so that its
773 contents are available in both places). See above.
774 .IP "\fB\-M, \-\-move\fP"
775 Move a subtree to some other place. See above.
777 .SH FILESYSTEM INDEPENDENT MOUNT OPTIONS
778 Some of these options are only useful when they appear in the
782 Some of these options could be enabled or disabled by default
783 in the system kernel. To check the current setting see the options
786 The following options apply to any filesystem that is being
787 mounted (but not every filesystem actually honors them - e.g., the
789 option today has effect only for ext2, ext3, fat, vfat and ufs):
793 All I/O to the filesystem should be done asynchronously. (See also the
798 Do not use noatime feature, then the inode access time is controlled by kernel
799 defaults. See also the description for
806 Do not update inode access times on this filesystem (e.g., for faster
807 access on the news spool to speed up news servers).
810 Can be mounted with the
815 Can only be mounted explicitly (i.e., the
817 option will not cause the filesystem to be mounted).
819 \fBcontext=\fP\fIcontext\fP, \fBfscontext=\fP\fIcontext\fP, \fBdefcontext=\fP\fIcontext\fP and \fBrootcontext=\fP\fIcontext\fP
822 option is useful when mounting filesystems that do not support
823 extended attributes, such as a floppy or hard disk formatted with VFAT, or
824 systems that are not normally running under SELinux, such as an ext3 formatted
825 disk from a non-SELinux workstation. You can also use
827 on filesystems you do not trust, such as a floppy. It also helps in compatibility with
828 xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where
829 xattrs are supported, you can save time not having to label every file by
830 assigning the entire disk one security context.
832 A commonly used option for removable media is
833 .BR context="system_u:object_r:removable_t" .
835 Two other options are
839 both of which are mutually exclusive of the context option. This means you
840 can use fscontext and defcontext with each other, but neither can be used with
845 option works for all filesystems, regardless of their xattr
846 support. The fscontext option sets the overarching filesystem label to a
847 specific security context. This filesystem label is separate from the
848 individual labels on the files. It represents the entire filesystem for
849 certain kinds of permission checks, such as during mount or file creation.
850 Individual file labels are still obtained from the xattrs on the files
851 themselves. The context option actually sets the aggregate context that
852 fscontext provides, in addition to supplying the same label for individual
855 You can set the default security context for unlabeled files using
857 option. This overrides the value set for unlabeled files in the policy and requires a
858 filesystem that supports xattr labeling.
862 option allows you to explicitly label the root inode of a FS being mounted
863 before that FS or inode because visible to userspace. This was found to be
864 useful for things like stateless linux.
866 Note that kernel rejects any remount request that includes the context
867 option even if unchanged from the current context.
869 .B Warning that \fIcontext\fP value might contains comma
870 and in this case the value has to be properly quoted otherwise
872 will interpret the comma as separator between mount options. Don't forget that
873 shell strips off quotes and
874 .BR "double quoting is required" ,
879 mount -t tmpfs none /mnt \-o 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
883 For more details, see
890 .BR rw ", " suid ", " dev ", " exec ", " auto ", " nouser ", and " async.
893 Interpret character or block special devices on the filesystem.
896 Do not interpret character or block special devices on the file
900 Update directory inode access times on this filesystem. This is the default.
903 Do not update directory inode access times on this filesystem.
906 All directory updates within the filesystem should be done synchronously.
907 This affects the following system calls: creat, link, unlink, symlink,
908 mkdir, rmdir, mknod and rename.
911 Permit execution of binaries.
914 Do not allow direct execution of any binaries on the mounted filesystem.
915 (Until recently it was possible to run binaries anyway using a command like
916 /lib/ld*.so /mnt/binary. This trick fails since Linux 2.4.25 / 2.6.0.)
919 Allow an ordinary (i.e., non-root) user to mount the filesystem if one
920 of his groups matches the group of the device.
921 This option implies the options
922 .BR nosuid " and " nodev
923 (unless overridden by subsequent options, as in the option line
924 .BR group,dev,suid ).
927 Every time the inode is modified, the i_version field will be incremented.
930 Do not increment the i_version inode field.
933 Allow mandatory locks on this filesystem. See
937 Do not allow mandatory locks on this filesystem.
940 The filesystem resides on a device that requires network access
941 (used to prevent the system from attempting to mount these filesystems
942 until the network has been enabled on the system).
945 Do not report errors for this device if it does not exist.
948 Update inode access times relative to modify or change time. Access
949 time is only updated if the previous access time was earlier than the
950 current modify or change time. (Similar to noatime, but doesn't break
951 mutt or other applications that need to know if a file has been read
952 since the last time it was modified.)
954 Since Linux 2.6.30, the kernel defaults to the behavior provided by this
957 was specified), and the
959 option is required to obtain traditional semantics. In addition, since Linux
960 2.6.30, the file's last access time is always updated if it is more than 1
966 feature. See also the
971 Allows to explicitly requesting full atime updates. This makes it
972 possible for kernel to defaults to
976 but still allow userspace to override it. For more details about the default
977 system mount options see /proc/mounts.
980 Use the kernel's default behaviour for inode access time updates.
983 Allow set-user-identifier or set-group-identifier bits to take
987 Do not allow set-user-identifier or set-group-identifier bits to take
988 effect. (This seems safe, but is in fact rather unsafe if you have
989 suidperl(1) installed.)
992 Turn on the silent flag.
995 Turn off the silent flag.
998 Allow an ordinary (i.e., non-root) user to mount the filesystem if he
999 is the owner of the device.
1000 This option implies the options
1001 .BR nosuid " and " nodev
1002 (unless overridden by subsequent options, as in the option line
1003 .BR owner,dev,suid ).
1006 Attempt to remount an already-mounted filesystem. This is commonly
1007 used to change the mount flags for a filesystem, especially to make a
1008 readonly filesystem writable. It does not change device or mount point.
1010 The remount functionality follows the standard way how the mount command works
1011 with options from fstab. It means the mount command doesn't read fstab (or
1016 are fully specified.
1018 .BR "mount -o remount,rw /dev/foo /dir"
1020 After this call all old mount options are replaced and arbitrary stuff from
1021 fstab is ignored, except the loop= option which is internally generated and
1022 maintained by the mount command.
1024 .BR "mount -o remount,rw /dir"
1026 After this call mount reads fstab (or mtab) and merges these options with
1027 options from command line (
1032 Mount the filesystem read-only.
1035 Mount the filesystem read-write.
1038 All I/O to the filesystem should be done synchronously. In case of media with limited number of write cycles
1039 (e.g. some flash drives) "sync" may cause life-cycle shortening.
1042 Allow an ordinary user to mount the filesystem.
1043 The name of the mounting user is written to mtab so that he can unmount
1044 the filesystem again.
1045 This option implies the options
1046 .BR noexec ", " nosuid ", and " nodev
1047 (unless overridden by subsequent options, as in the option line
1048 .BR user,exec,dev,suid ).
1051 Forbid an ordinary (i.e., non-root) user to mount the filesystem.
1052 This is the default.
1055 Allow every user to mount and unmount the filesystem.
1056 This option implies the options
1057 .BR noexec ", " nosuid ", and " nodev
1058 (unless overridden by subsequent options, as in the option line
1059 .BR users,exec,dev,suid ).
1061 .SH "FILESYSTEM SPECIFIC MOUNT OPTIONS"
1062 The following options apply only to certain filesystems.
1063 We sort them by filesystem. They all follow the
1067 What options are supported depends a bit on the running kernel.
1068 More info may be found in the kernel source subdirectory
1069 .IR Documentation/filesystems .
1071 .SH "Mount options for adfs"
1073 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1074 Set the owner and group of the files in the filesystem (default: uid=gid=0).
1076 \fBownmask=\fP\fIvalue\fP and \fBothmask=\fP\fIvalue\fP
1077 Set the permission mask for ADFS 'owner' permissions and 'other' permissions,
1078 respectively (default: 0700 and 0077, respectively).
1080 .IR /usr/src/linux/Documentation/filesystems/adfs.txt .
1081 .SH "Mount options for affs"
1083 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1084 Set the owner and group of the root of the filesystem (default: uid=gid=0,
1089 without specified value, the uid and gid of the current process are taken).
1091 \fBsetuid=\fP\fIvalue\fP and \fBsetgid=\fP\fIvalue\fP
1092 Set the owner and group of all files.
1095 Set the mode of all files to
1097 disregarding the original permissions.
1098 Add search permission to directories that have read permission.
1099 The value is given in octal.
1102 Do not allow any changes to the protection bits on the filesystem.
1105 Set uid and gid of the root of the filesystem to the uid and gid
1106 of the mount point upon the first sync or umount, and then
1107 clear this option. Strange...
1110 Print an informational message for each successful mount.
1113 Prefix used before volume name, when following a link.
1116 Prefix (of length at most 30) used before '/' when following a symbolic link.
1119 (Default: 2.) Number of unused blocks at the start of the device.
1122 Give explicitly the location of the root block.
1125 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
1127 .BR grpquota | noquota | quota | usrquota
1128 These options are accepted but ignored.
1129 (However, quota utilities may react to such strings in
1132 .SH "Mount options for cifs"
1133 See the options section of the
1135 man page (cifs-utils package must be installed).
1137 .SH "Mount options for coherent"
1140 .SH "Mount options for debugfs"
1141 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1142 .IR /sys/kernel/debug .
1144 .\" present since 2.6.11
1145 There are no mount options.
1147 .SH "Mount options for devpts"
1148 The devpts filesystem is a pseudo filesystem, traditionally mounted on
1150 In order to acquire a pseudo terminal, a process opens
1152 the number of the pseudo terminal is then made available to the process
1153 and the pseudo terminal slave can be accessed as
1154 .IR /dev/pts/ <number>.
1156 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1157 This sets the owner or the group of newly created PTYs to
1158 the specified values. When nothing is specified, they will
1159 be set to the UID and GID of the creating process.
1160 For example, if there is a tty group with GID 5, then
1162 will cause newly created PTYs to belong to the tty group.
1165 Set the mode of newly created PTYs to the specified value.
1166 The default is 0600.
1171 makes "mesg y" the default on newly created PTYs.
1174 Create a private instance of devpts filesystem, such that
1175 indices of ptys allocated in this new instance are
1176 independent of indices created in other instances of devpts.
1178 All mounts of devpts without this
1180 option share the same set of pty indices (i.e legacy mode).
1181 Each mount of devpts with the
1183 option has a private set of pty indices.
1185 This option is mainly used to support containers in the
1186 linux kernel. It is implemented in linux kernel versions
1187 starting with 2.6.29. Further, this mount option is valid
1188 only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the
1189 kernel configuration.
1191 To use this option effectively,
1193 must be a symbolic link to
1196 .IR Documentation/filesystems/devpts.txt
1197 in the linux kernel source tree for details.
1201 Set the mode for the new
1203 device node in the devpts filesystem.
1205 With the support for multiple instances of devpts (see
1207 option above), each instance has a private
1209 node in the root of the devpts filesystem (typically
1212 For compatibility with older versions of the kernel, the
1213 default mode of the new
1217 specifies a more useful mode for the
1219 node and is highly recommended when the
1221 option is specified.
1223 This option is only implemented in linux kernel versions
1224 starting with 2.6.29. Further this option is valid only if
1225 CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1228 .SH "Mount options for ext"
1230 Note that the `ext' filesystem is obsolete. Don't use it.
1231 Since Linux version 2.1.21 extfs is no longer part of the kernel source.
1233 .SH "Mount options for ext2"
1234 The `ext2' filesystem is the standard Linux filesystem.
1235 .\" Due to a kernel bug, it may be mounted with random mount options
1236 .\" (fixed in Linux 2.0.4).
1237 Since Linux 2.5.46, for most mount options the default
1238 is determined by the filesystem superblock. Set them with
1242 Support POSIX Access Control Lists (or not).
1243 .\" requires CONFIG_EXT2_FS_POSIX_ACL
1246 Set the behaviour for the
1250 behaviour is to return in the
1252 field the total number of blocks of the filesystem, while the
1254 behaviour (which is the default) is to subtract the overhead blocks
1255 used by the ext2 filesystem and not available for file storage. Thus
1258 % mount /k -o minixdf; df /k; umount /k
1259 Filesystem 1024-blocks Used Available Capacity Mounted on
1260 /dev/sda6 2630655 86954 2412169 3% /k
1261 % mount /k -o bsddf; df /k; umount /k
1262 Filesystem 1024-blocks Used Available Capacity Mounted on
1263 /dev/sda6 2543714 13 2412169 0% /k
1266 (Note that this example shows that one can add command line options
1267 to the options given in
1271 .BR check=none " or " nocheck
1272 No checking is done at mount time. This is the default. This is fast.
1273 It is wise to invoke
1275 every now and then, e.g. at boot time. The non-default behavior is unssuported
1276 (check=normal and check=strict options have been removed). Note that these mount options
1277 don't have to be supported if ext4 kernel driver is used for ext2 and ext3 filesystems.
1280 Print debugging info upon each (re)mount.
1282 .BR errors= { continue | remount-ro | panic }
1283 Define the behaviour when an error is encountered.
1284 (Either ignore errors and just mark the filesystem erroneous and continue,
1285 or remount the filesystem read-only, or panic and halt the system.)
1286 The default is set in the filesystem superblock, and can be
1290 .BR grpid | bsdgroups " and " nogrpid | sysvgroups
1291 These options define what group id a newly created file gets.
1294 is set, it takes the group id of the directory in which it is created;
1295 otherwise (the default) it takes the fsgid of the current process, unless
1296 the directory has the setgid bit set, in which case it takes the gid
1297 from the parent directory, and also gets the setgid bit set
1298 if it is a directory itself.
1300 .BR grpquota | noquota | quota | usrquota
1301 These options are accepted but ignored.
1304 Disables 32-bit UIDs and GIDs. This is for interoperability with older
1305 kernels which only store and expect 16-bit values.
1307 .BR oldalloc " or " orlov
1308 Use old allocator or Orlov allocator for new inodes. Orlov is default.
1310 \fBresgid=\fP\fIn\fP and \fBresuid=\fP\fIn\fP
1311 The ext2 filesystem reserves a certain percentage of the available
1312 space (by default 5%, see
1316 These options determine who can use the reserved blocks.
1317 (Roughly: whoever has the specified uid, or belongs to the specified group.)
1320 Instead of block 1, use block
1322 as superblock. This could be useful when the filesystem has been damaged.
1323 (Earlier, copies of the superblock would be made every 8192 blocks: in
1324 block 1, 8193, 16385, ... (and one got thousands of copies on
1325 a big filesystem). Since version 1.08,
1327 has a \-s (sparse superblock) option to reduce the number of backup
1328 superblocks, and since version 1.15 this is the default. Note
1329 that this may mean that ext2 filesystems created by a recent
1331 cannot be mounted r/w under Linux 2.0.*.)
1332 The block number here uses 1k units. Thus, if you want to use logical
1333 block 32768 on a filesystem with 4k blocks, use "sb=131072".
1335 .BR user_xattr | nouser_xattr
1336 Support "user." extended attributes (or not).
1337 .\" requires CONFIG_EXT2_FS_XATTR
1340 .SH "Mount options for ext3"
1341 The ext3 filesystem is a version of the ext2 filesystem which has been
1342 enhanced with journalling. It supports the same options as ext2 as
1343 well as the following additions:
1346 .\" Mount the filesystem in abort mode, as if a fatal error has occurred.
1349 Update the ext3 filesystem's journal to the current format.
1352 When a journal already exists, this option is ignored. Otherwise, it
1353 specifies the number of the inode which will represent the ext3 filesystem's
1354 journal file; ext3 will create a new journal, overwriting the old contents
1355 of the file whose inode number is
1358 .BR journal_dev=devnum
1359 When the external journal device's major/minor numbers
1360 have changed, this option allows the user to specify
1361 the new journal location. The journal device is
1362 identified through its new major/minor numbers encoded
1365 .BR norecovery / noload
1366 Don't load the journal on mounting. Note that
1367 if the filesystem was not unmounted cleanly,
1368 skipping the journal replay will lead to the
1369 filesystem containing inconsistencies that can
1370 lead to any number of problems.
1372 .BR data= { journal | ordered | writeback }
1373 Specifies the journalling mode for file data. Metadata is always journaled.
1374 To use modes other than
1376 on the root filesystem, pass the mode to the kernel as boot parameter, e.g.
1377 .IR rootflags=data=journal .
1381 All data is committed into the journal prior to being written into the
1385 This is the default mode. All data is forced directly out to the main file
1386 system prior to its metadata being committed to the journal.
1389 Data ordering is not preserved - data may be written into the main
1390 filesystem after its metadata has been committed to the journal.
1391 This is rumoured to be the highest-throughput option. It guarantees
1392 internal filesystem integrity, however it can allow old data to appear
1393 in files after a crash and journal recovery.
1396 .BR barrier=0 " / " barrier=1 "
1397 This enables/disables barriers. barrier=0 disables it, barrier=1 enables it.
1398 Write barriers enforce proper on-disk ordering of journal commits, making
1399 volatile disk write caches safe to use, at some performance penalty. The ext3
1400 filesystem does not enable write barriers by default. Be sure to enable
1401 barriers unless your disks are battery-backed one way or another. Otherwise
1402 you risk filesystem corruption in case of power failure.
1405 Sync all data and metadata every
1407 seconds. The default value is 5 seconds. Zero means default.
1410 Enable Extended User Attributes. See the
1415 Enable POSIX Access Control Lists. See the
1419 .SH "Mount options for ext4"
1420 The ext4 filesystem is an advanced level of the ext3 filesystem which
1421 incorporates scalability and reliability enhancements for supporting large
1425 .B journal_dev, noload, data, commit, orlov, oldalloc, [no]user_xattr
1426 .B [no]acl, bsddf, minixdf, debug, errors, data_err, grpid, bsdgroups, nogrpid
1427 .B sysvgroups, resgid, resuid, sb, quota, noquota, grpquota and usrquota
1428 are backwardly compatible with ext3 or ext2.
1430 .BR journal_checksum
1431 Enable checksumming of the journal transactions. This will allow the recovery
1432 code in e2fsck and the kernel to detect corruption in the kernel. It is a
1433 compatible change and will be ignored by older kernels.
1435 .BR journal_async_commit
1436 Commit block can be written to disk without waiting for descriptor blocks. If
1437 enabled older kernels cannot mount the device.
1438 This will enable 'journal_checksum' internally.
1441 Update the ext4 filesystem's journal to the current format.
1443 .BR barrier=0 " / " barrier=1 " / " barrier " / " nobarrier
1444 This enables/disables the use of write barriers in the jbd code. barrier=0
1445 disables, barrier=1 enables. This also requires an IO stack which can support
1446 barriers, and if jbd gets an error on a barrier write, it will disable again
1447 with a warning. Write barriers enforce proper on-disk ordering of journal
1448 commits, making volatile disk write caches safe to use, at some performance
1449 penalty. If your disks are battery-backed in one way or another, disabling
1450 barriers may safely improve performance. The mount options "barrier" and
1451 "nobarrier" can also be used to enable or disable barriers, for consistency
1452 with other ext4 mount options.
1454 The ext4 filesystem enables write barriers by default.
1456 .BI inode_readahead= n
1457 This tuning parameter controls the maximum number of inode table blocks that
1458 ext4's inode table readahead algorithm will pre-read into the buffer cache.
1459 The default value is 32 blocks.
1462 Number of filesystem blocks that mballoc will try to use for allocation size
1463 and alignment. For RAID5/6 systems this should be the number of data disks *
1464 RAID chunk size in filesystem blocks.
1467 Deferring block allocation until write-out time.
1470 Disable delayed allocation. Blocks are allocated when data is copied from user
1473 .BI max_batch_time= usec
1474 Maximum amount of time ext4 should wait for additional filesystem operations to
1475 be batch together with a synchronous write operation. Since a synchronous
1476 write operation is going to force a commit and then a wait for the I/O
1477 complete, it doesn't cost much, and can be a huge throughput win, we wait for a
1478 small amount of time to see if any other transactions can piggyback on the
1479 synchronous write. The algorithm used is designed to automatically tune for
1480 the speed of the disk, by measuring the amount of time (on average) that it
1481 takes to finish committing a transaction. Call this time the "commit time".
1482 If the time that the transaction has been running is less than the commit time,
1483 ext4 will try sleeping for the commit time to see if other operations will join
1484 the transaction. The commit time is capped by the max_batch_time, which
1485 defaults to 15000us (15ms). This optimization can be turned off entirely by
1486 setting max_batch_time to 0.
1488 .BI min_batch_time= usec
1489 This parameter sets the commit time (as described above) to be at least
1490 min_batch_time. It defaults to zero microseconds. Increasing this parameter
1491 may improve the throughput of multi-threaded, synchronous workloads on very
1492 fast disks, at the cost of increasing latency.
1494 .BI journal_ioprio= prio
1495 The I/O priority (from 0 to 7, where 0 is the highest priorty) which should be
1496 used for I/O operations submitted by kjournald2 during a commit operation.
1497 This defaults to 3, which is a slightly higher priority than the default I/O
1501 Simulate the effects of calling ext4_abort() for
1502 debugging purposes. This is normally used while
1503 remounting a filesystem which is already mounted.
1505 .BR auto_da_alloc | noauto_da_alloc
1506 Many broken applications don't use fsync() when
1507 replacing existing files via patterns such as
1509 fd = open("foo.new")/write(fd,..)/close(fd)/ rename("foo.new", "foo")
1513 fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).
1515 If auto_da_alloc is enabled, ext4 will detect the replace-via-rename and
1516 replace-via-truncate patterns and force that any delayed allocation blocks are
1517 allocated such that at the next journal commit, in the default data=ordered
1518 mode, the data blocks of the new file are forced to disk before the rename()
1519 operation is committed. This provides roughly the same level of guarantees as
1520 ext3, and avoids the "zero-length" problem that can happen when a system
1521 crashes before the delayed allocation blocks are forced to disk.
1523 .BR discard / nodiscard
1524 Controls whether ext4 should issue discard/TRIM commands to the underlying
1525 block device when blocks are freed. This is useful for SSD devices and
1526 sparse/thinly-provisioned LUNs, but it is off by default until sufficient
1527 testing has been done.
1530 Disables 32-bit UIDs and GIDs. This is for
1531 interoperability with older kernels which only
1532 store and expect 16-bit values.
1535 Allows to resize filesystem to the end of the last
1536 existing block group, further resize has to be done
1537 with resize2fs either online, or offline. It can be
1538 used only with conjunction with remount.
1540 .BR block_validity / noblock_validity
1541 This options allows to enables/disables the in-kernel facility for tracking
1542 filesystem metadata blocks within internal data structures. This allows multi-
1543 block allocator and other routines to quickly locate extents which might
1544 overlap with filesystem metadata blocks. This option is intended for debugging
1545 purposes and since it negatively affects the performance, it is off by default.
1547 .BR dioread_lock / dioread_nolock
1548 Controls whether or not ext4 should use the DIO read locking. If the
1549 dioread_nolock option is specified ext4 will allocate uninitialized extent
1550 before buffer write and convert the extent to initialized after IO completes.
1551 This approach allows ext4 code to avoid using inode mutex, which improves
1552 scalability on high speed storages. However this does not work with data
1553 journaling and dioread_nolock option will be ignored with kernel warning.
1554 Note that dioread_nolock code path is only used for extent-based files.
1555 Because of the restrictions this options comprises it is off by default
1556 (e.g. dioread_lock).
1559 Enable 64-bit inode version support. This option is off by default.
1561 .SH "Mount options for fat"
1564 is not a separate filesystem, but a common part of the
1571 .BR blocksize= { 512 | 1024 | 2048 }
1572 Set blocksize (default 512). This option is obsolete.
1574 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1575 Set the owner and group of all files.
1576 (Default: the uid and gid of the current process.)
1579 Set the umask (the bitmask of the permissions that are
1581 present). The default is the umask of the current process.
1582 The value is given in octal.
1585 Set the umask applied to directories only.
1586 The default is the umask of the current process.
1587 The value is given in octal.
1588 .\" Present since Linux 2.5.43.
1591 Set the umask applied to regular files only.
1592 The default is the umask of the current process.
1593 The value is given in octal.
1594 .\" Present since Linux 2.5.43.
1596 .BI allow_utime= value
1597 This option controls the permission check of mtime/atime.
1601 If current process is in group of file's group ID, you can change timestamp.
1604 Other users can change timestamp.
1606 The default is set from `dmask' option. (If the directory is writable,
1608 is also allowed. I.e. ~dmask & 022)
1612 checks current process is owner of the file, or it has
1613 CAP_FOWNER capability. But FAT filesystem doesn't have uid/gid on disk, so
1614 normal check is too unflexible. With this option you can relax it.
1618 Three different levels of pickyness can be chosen:
1622 Upper and lower case are accepted and equivalent, long name parts are
1624 .I verylongname.foobar
1627 leading and embedded spaces are accepted in each name part (name and extension).
1630 Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are
1631 rejected. This is the default.
1634 Like "normal", but names may not contain long parts and special characters
1635 that are sometimes used on Linux, but are not accepted by MS-DOS are
1636 rejected. (+, =, spaces, etc.)
1640 Sets the codepage for converting to shortname characters on FAT
1641 and VFAT filesystems. By default, codepage 437 is used.
1643 .BR conv= {b [ inary ]| t [ ext ]| a [ uto ]}
1646 filesystem can perform CRLF<-->NL (MS-DOS text format to UNIX text
1647 format) conversion in the kernel. The following conversion modes are
1652 no translation is performed. This is the default.
1655 CRLF<-->NL translation is performed on all files.
1658 CRLF<-->NL translation is performed on all files that don't have a
1659 "well-known binary" extension. The list of known extensions can be found at
1662 (as of 2.0, the list is: exe, com, bin, app, sys, drv, ovl, ovr, obj,
1663 lib, dll, pif, arc, zip, lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz,
1664 gz, tgz, deb, gif, bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl, dvi).
1666 Programs that do computed lseeks won't like in-kernel text conversion.
1667 Several people have had their data ruined by this translation. Beware!
1669 For filesystems mounted in binary mode, a conversion tool
1670 (fromdos/todos) is available. This option is obsolete.
1673 .BI cvf_format= module
1674 Forces the driver to use the CVF (Compressed Volume File) module
1676 instead of auto-detection. If the kernel supports kmod, the
1677 cvf_format=xxx option also controls on-demand CVF module loading.
1678 This option is obsolete.
1680 .BI cvf_option= option
1681 Option passed to the CVF module. This option is obsolete.
1686 flag. A version string and a list of filesystem parameters will be
1687 printed (these data are also printed if the parameters appear to be
1690 .BR fat= {12 | 16 | 32 }
1691 Specify a 12, 16 or 32 bit fat. This overrides
1692 the automatic FAT type detection routine. Use with caution!
1694 .BI iocharset= value
1695 Character set to use for converting between 8 bit characters
1696 and 16 bit Unicode characters. The default is iso8859-1.
1697 Long filenames are stored on disk in Unicode format.
1700 This option disables the conversion of timestamps
1701 between local time (as used by Windows on FAT) and UTC
1702 (which Linux uses internally). This is particularly
1703 useful when mounting devices (like digital cameras)
1704 that are set to UTC in order to avoid the pitfalls of
1710 flag. Attempts to chown or chmod files do not return errors,
1711 although they fail. Use with caution!
1714 If set, the execute permission bits of the file will be allowed only if
1715 the extension part of the name is .EXE, .COM, or .BAT. Not set by default.
1718 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux.
1722 If set, the filesystem will try to flush to disk more early than normal.
1726 Use the "free clusters" value stored on FSINFO. It'll
1727 be used to determine number of free clusters without
1728 scanning disk. But it's not used by default, because
1729 recent Windows don't update it correctly in some
1730 case. If you are sure the "free clusters" on FSINFO is
1731 correct, by this option you can avoid scanning disk.
1733 .BR dots ", " nodots ", " dotsOK= [ yes | no ]
1734 Various misguided attempts to force Unix or DOS conventions
1735 onto a FAT filesystem.
1737 .SH "Mount options for hfs"
1739 .BI creator= cccc ", type=" cccc
1740 Set the creator/type values as shown by the MacOS finder
1741 used for creating new files. Default values: '????'.
1743 .BI uid= n ", gid=" n
1744 Set the owner and group of all files.
1745 (Default: the uid and gid of the current process.)
1747 .BI dir_umask= n ", file_umask=" n ", umask=" n
1748 Set the umask used for all directories, all regular files, or all
1749 files and directories. Defaults to the umask of the current process.
1752 Select the CDROM session to mount.
1753 Defaults to leaving that decision to the CDROM driver.
1754 This option will fail with anything but a CDROM as underlying device.
1757 Select partition number n from the device.
1758 Only makes sense for CDROMs.
1759 Defaults to not parsing the partition table at all.
1762 Don't complain about invalid mount options.
1764 .SH "Mount options for hpfs"
1766 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1767 Set the owner and group of all files. (Default: the uid and gid
1768 of the current process.)
1771 Set the umask (the bitmask of the permissions that are
1773 present). The default is the umask of the current process.
1774 The value is given in octal.
1776 .BR case= { lower | asis }
1777 Convert all files names to lower case, or leave them.
1781 .BR conv= { binary | text | auto }
1784 delete some random CRs (in particular, all followed by NL)
1785 when reading a file.
1788 choose more or less at random between
1789 .BR conv=binary " and " conv=text .
1792 just read what is in the file. This is the default.
1795 Do not abort mounting when certain consistency checks fail.
1797 .SH "Mount options for iso9660"
1798 ISO 9660 is a standard describing a filesystem structure to be used
1799 on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1805 filenames appear in a 8.3 format (i.e., DOS-like restrictions on filename
1806 length), and in addition all characters are in upper case. Also there is
1807 no field for file ownership, protection, number of links, provision for
1808 block/character devices, etc.
1810 Rock Ridge is an extension to iso9660 that provides all of these UNIX-like
1811 features. Basically there are extensions to each directory record that
1812 supply all of the additional information, and when Rock Ridge is in use,
1813 the filesystem is indistinguishable from a normal UNIX filesystem (except
1814 that it is read-only, of course).
1817 Disable the use of Rock Ridge extensions, even if available. Cf.\&
1821 Disable the use of Microsoft Joliet extensions, even if available. Cf.\&
1824 .BR check= { r [ elaxed ]| s [ trict ]}
1827 a filename is first converted to lower case before doing the lookup.
1828 This is probably only meaningful together with
1835 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1836 Give all files in the filesystem the indicated user or group id,
1837 possibly overriding the information found in the Rock Ridge extensions.
1841 .BR map= { n [ ormal ]| o [ ff ]| a [ corn ]}
1842 For non-Rock Ridge volumes, normal name translation maps upper
1843 to lower case ASCII, drops a trailing `;1', and converts `;' to `.'.
1846 no name translation is done. See
1853 but also apply Acorn extensions if present.
1856 For non-Rock Ridge volumes, give all files the indicated mode.
1857 (Default: read permission for everybody.)
1858 Since Linux 2.1.37 one no longer needs to specify the mode in
1859 decimal. (Octal is indicated by a leading 0.)
1862 Also show hidden and associated files.
1863 (If the ordinary files and the associated or hidden files have
1864 the same filenames, this may make the ordinary files inaccessible.)
1866 .BR block= { 512 | 1024 | 2048 }
1867 Set the block size to the indicated value.
1871 .BR conv= { a [ uto ]| b [ inary ]| m [ text ]| t [ ext ]}
1874 Since Linux 1.3.54 this option has no effect anymore.
1875 (And non-binary settings used to be very dangerous,
1876 possibly leading to silent data corruption.)
1879 If the high byte of the file length contains other garbage,
1880 set this mount option to ignore the high order bits of the file length.
1881 This implies that a file cannot be larger than 16MB.
1884 Select number of session on multisession CD. (Since 2.3.4.)
1887 Session begins from sector xxx. (Since 2.3.4.)
1889 The following options are the same as for vfat and specifying them only makes
1890 sense when using discs encoded using Microsoft's Joliet extensions.
1892 .BI iocharset= value
1893 Character set to use for converting 16 bit Unicode characters on CD
1894 to 8 bit characters. The default is iso8859-1.
1897 Convert 16 bit Unicode characters on CD to UTF-8.
1899 .SH "Mount options for jfs"
1902 Character set to use for converting from Unicode to ASCII. The default is
1903 to do no conversion. Use
1905 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in
1911 Resize the volume to
1913 blocks. JFS only supports growing a volume, not shrinking it. This option
1914 is only valid during a remount, when the volume is mounted read-write. The
1916 keyword with no value will grow the volume to the full size of the partition.
1919 Do not write to the journal. The primary use of this option is to allow
1920 for higher performance when restoring a volume from backup media. The
1921 integrity of the volume is not guaranteed if the system abnormally abends.
1924 Default. Commit metadata changes to the journal. Use this option to remount
1927 option was previously specified in order to restore normal behavior.
1929 .BR errors= { continue | remount-ro | panic }
1930 Define the behaviour when an error is encountered.
1931 (Either ignore errors and just mark the filesystem erroneous and continue,
1932 or remount the filesystem read-only, or panic and halt the system.)
1934 .BR noquota | quota | usrquota | grpquota
1935 These options are accepted but ignored.
1937 .SH "Mount options for minix"
1940 .SH "Mount options for msdos"
1941 See mount options for fat.
1944 filesystem detects an inconsistency, it reports an error and sets the file
1945 system read-only. The filesystem can be made writable again by remounting
1948 .SH "Mount options for ncpfs"
1950 .IR nfs ", the " ncpfs
1951 implementation expects a binary argument (a
1952 .IR "struct ncp_mount_data" )
1953 to the mount system call. This argument is constructed by
1955 and the current version of
1957 (2.12) does not know anything about ncpfs.
1959 .SH "Mount options for nfs and nfs4"
1960 See the options section of the
1962 man page (nfs-utils package must be installed).
1965 .IR nfs " and " nfs4
1966 implementation expects a binary argument (a
1967 .IR "struct nfs_mount_data" )
1968 to the mount system call. This argument is constructed by
1970 and the current version of
1972 (2.13) does not know anything about nfs and nfs4.
1974 .SH "Mount options for ntfs"
1977 Character set to use when returning file names.
1978 Unlike VFAT, NTFS suppresses names that contain
1979 nonconvertible characters. Deprecated.
1983 New name for the option earlier called
1988 Use UTF-8 for converting file names.
1990 .BR uni_xlate= { 0 | 1 | 2 }
1991 For 0 (or `no' or `false'), do not use escape sequences
1992 for unknown Unicode characters.
1993 For 1 (or `yes' or `true') or 2, use vfat-style 4-byte escape sequences
1994 starting with ":". Here 2 give a little-endian encoding
1995 and 1 a byteswapped bigendian encoding.
1998 If enabled (posix=1), the filesystem distinguishes between
1999 upper and lower case. The 8.3 alias names are presented as
2000 hard links instead of being suppressed. This option is obsolete.
2002 \fBuid=\fP\fIvalue\fP, \fBgid=\fP\fIvalue\fP and \fBumask=\fP\fIvalue\fP
2003 Set the file permission on the filesystem.
2004 The umask value is given in octal.
2005 By default, the files are owned by root and not readable by somebody else.
2007 .SH "Mount options for proc"
2009 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
2010 These options are recognized, but have no effect as far as I can see.
2012 .SH "Mount options for ramfs"
2013 Ramfs is a memory based filesystem. Mount it and you have it. Unmount it
2014 and it is gone. Present since Linux 2.3.99pre4.
2015 There are no mount options.
2017 .SH "Mount options for reiserfs"
2018 Reiserfs is a journaling filesystem.
2021 Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem,
2022 using the 3.6 format for newly created objects. This filesystem will no
2023 longer be compatible with reiserfs 3.5 tools.
2025 .BR hash= { rupasov | tea | r5 | detect }
2026 Choose which hash function reiserfs will use to find files within directories.
2030 A hash invented by Yury Yu. Rupasov. It is fast and preserves locality,
2031 mapping lexicographically close file names to close hash values.
2032 This option should not be used, as it causes a high probability of hash
2036 A Davis-Meyer function implemented by Jeremy Fitzhardinge.
2037 It uses hash permuting bits in the name. It gets high randomness
2038 and, therefore, low probability of hash collisions at some CPU cost.
2039 This may be used if EHASHCOLLISION errors are experienced with the r5 hash.
2042 A modified version of the rupasov hash. It is used by default and is
2043 the best choice unless the filesystem has huge directories and
2044 unusual file-name patterns.
2049 to detect which hash function is in use by examining
2050 the filesystem being mounted, and to write this information into
2051 the reiserfs superblock. This is only useful on the first mount of
2052 an old format filesystem.
2055 .BR hashed_relocation
2056 Tunes the block allocator. This may provide performance improvements
2059 .BR no_unhashed_relocation
2060 Tunes the block allocator. This may provide performance improvements
2064 Disable the border allocator algorithm invented by Yury Yu. Rupasov.
2065 This may provide performance improvements in some situations.
2068 Disable journalling. This will provide slight performance improvements in
2069 some situations at the cost of losing reiserfs's fast recovery from crashes.
2070 Even with this option turned on, reiserfs still performs all journalling
2071 operations, save for actual writes into its journalling area. Implementation
2074 is a work in progress.
2077 By default, reiserfs stores small files and `file tails' directly into its
2078 tree. This confuses some utilities such as
2080 This option is used to disable packing of files into the tree.
2083 Replay the transactions which are in the journal, but do not actually
2084 mount the filesystem. Mainly used by
2088 A remount option which permits online expansion of reiserfs partitions.
2089 Instructs reiserfs to assume that the device has
2092 This option is designed for use with devices which are under logical
2093 volume management (LVM).
2096 utility which can be obtained from
2097 .IR ftp://ftp.namesys.com/pub/reiserfsprogs .
2100 Enable Extended User Attributes. See the
2105 Enable POSIX Access Control Lists. See the
2109 .BR barrier=none " / " barrier=flush "
2110 This enables/disables the use of write barriers in the journaling code.
2111 barrier=none disables it, barrier=flush enables it. Write barriers enforce
2112 proper on-disk ordering of journal commits, making volatile disk write caches
2113 safe to use, at some performance penalty. The reiserfs filesystem does not
2114 enable write barriers by default. Be sure to enable barriers unless your disks
2115 are battery-backed one way or another. Otherwise you risk filesystem
2116 corruption in case of power failure.
2118 .SH "Mount options for romfs"
2121 .SH "Mount options for squashfs"
2124 .SH "Mount options for smbfs"
2126 .IR nfs ", the " smbfs
2127 implementation expects a binary argument (a
2128 .IR "struct smb_mount_data" )
2129 to the mount system call. This argument is constructed by
2131 and the current version of
2133 (2.12) does not know anything about smbfs.
2135 .SH "Mount options for sysv"
2138 .SH "Mount options for tmpfs"
2141 Override default maximum size of the filesystem.
2142 The size is given in bytes, and rounded up to entire pages.
2143 The default is half of the memory. The size parameter also accepts a suffix %
2144 to limit this tmpfs instance to that percentage of your physical RAM:
2145 the default, when neither size nor nr_blocks is specified, is size=50%
2148 The same as size, but in blocks of PAGE_CACHE_SIZE
2151 The maximum number of inodes for this instance. The default
2152 is half of the number of your physical RAM pages, or (on a
2153 machine with highmem) the number of lowmem RAM pages,
2154 whichever is the lower.
2156 The tmpfs mount options for sizing (
2166 for Ki, Mi, Gi (binary kilo, mega and giga) and can be changed on remount.
2170 Set initial permissions of the root directory.
2178 .B mpol=[default|prefer:Node|bind:NodeList|interleave|interleave:NodeList]
2179 Set the NUMA memory allocation policy for all files in that
2180 instance (if the kernel CONFIG_NUMA is enabled) - which can be adjusted on the
2181 fly via 'mount -o remount ...'
2185 prefers to allocate memory from the local node
2188 prefers to allocate memory from the given Node
2191 allocates memory only from nodes in NodeList
2194 prefers to allocate from each node in turn
2196 .B interleave:NodeList
2197 allocates from each node of NodeList in turn.
2199 The NodeList format is a comma-separated list of decimal numbers and ranges, a
2200 range being two hyphen-separated decimal numbers, the smallest and largest node
2201 numbers in the range. For example, mpol=bind:0-3,5,7,9-15
2203 Note that trying to mount a tmpfs with an mpol option will fail if the
2204 running kernel does not support NUMA; and will fail if its nodelist
2205 specifies a node which is not online. If your system relies on that
2206 tmpfs being mounted, but from time to time runs a kernel built without
2207 NUMA capability (perhaps a safe recovery kernel), or with fewer nodes
2208 online, then it is advisable to omit the mpol option from automatic
2209 mount options. It can be added later, when the tmpfs is already mounted
2210 on MountPoint, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.
2212 .SH "Mount options for ubifs"
2213 UBIFS is a flash file system which works on top of UBI volumes. Note that
2216 is not supported and is always turned off.
2218 The device name may be specified as
2246 separator may be used instead of
2249 The following mount options are available:
2252 Enable bulk-read. VFS read-ahead is disabled because it slows down the file
2253 system. Bulk-Read is an internal optimization. Some flashes may read faster if
2254 the data are read at one go, rather than at several read requests. For
2255 example, OneNAND can do "read-while-load" if it reads more than one NAND page.
2258 Do not bulk-read. This is the default.
2261 Check data CRC-32 checksums. This is the default.
2263 .BR no_chk_data_crc.
2264 Do not check data CRC-32 checksums. With this option, the filesystem does not
2265 check CRC-32 checksum for data, but it does check it for the internal indexing
2266 information. This option only affects reading, not writing. CRC-32 is always
2267 calculated when writing the data.
2269 .BR compr= { none | lzo | zlib }
2270 Select the default compressor which is used when new files are written. It is
2271 still possible to read compressed files if mounted with the
2275 .SH "Mount options for udf"
2276 udf is the "Universal Disk Format" filesystem defined by the Optical
2277 Storage Technology Association, and is often used for DVD-ROM.
2282 Set the default group.
2285 Set the default umask.
2286 The value is given in octal.
2289 Set the default user.
2292 Show otherwise hidden files.
2295 Show deleted files in lists.
2298 Unset strict conformance.
2304 Set the NLS character set.
2307 Set the block size. (May not work unless 2048.)
2310 Skip volume sequence recognition.
2313 Set the CDROM session counting from 0. Default: last session.
2316 Override standard anchor location. Default: 256.
2319 Override the VolumeDesc location. (unused)
2322 Override the PartitionDesc location. (unused)
2325 Set the last block of the filesystem.
2328 Override the fileset block location. (unused)
2331 Override the root directory location. (unused)
2333 .SH "Mount options for ufs"
2336 UFS is a filesystem widely used in different operating systems.
2337 The problem are differences among implementations. Features of some
2338 implementations are undocumented, so its hard to recognize the
2339 type of ufs automatically.
2340 That's why the user must specify the type of ufs by mount option.
2341 Possible values are:
2345 Old format of ufs, this is the default, read only.
2346 (Don't forget to give the \-r option.)
2349 For filesystems created by a BSD-like system (NetBSD,FreeBSD,OpenBSD).
2352 Used in FreeBSD 5.x supported as read-write.
2358 For filesystems created by SunOS or Solaris on Sparc.
2361 For filesystems created by Solaris on x86.
2364 For filesystems created by HP-UX, read-only.
2367 For filesystems created by NeXTStep (on NeXT station) (currently read only).
2370 For NextStep CDROMs (block_size == 2048), read-only.
2373 For filesystems created by OpenStep (currently read only).
2374 The same filesystem type is also used by Mac OS X.
2379 Set behaviour on error:
2383 If an error is encountered, cause a kernel panic.
2385 .RB [ lock | umount | repair ]
2386 These mount options don't do anything at present;
2387 when an error is encountered only a console message is printed.
2390 .SH "Mount options for umsdos"
2391 See mount options for msdos.
2394 option is explicitly killed by
2397 .SH "Mount options for vfat"
2398 First of all, the mount options for
2403 option is explicitly killed by
2405 Furthermore, there are
2408 Translate unhandled Unicode characters to special escaped sequences.
2409 This lets you backup and restore filenames that are created with any
2410 Unicode characters. Without this option, a '?' is used when no
2411 translation is possible. The escape character is ':' because it is
2412 otherwise illegal on the vfat filesystem. The escape sequence
2413 that gets used, where u is the unicode character,
2414 is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
2417 Allow two files with names that only differ in case.
2418 This option is obsolete.
2421 First try to make a short name without sequence number,
2426 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the
2427 console. It can be enabled for the filesystem with this option or disabled
2428 with utf8=0, utf8=no or utf8=false. If `uni_xlate' gets set, UTF8 gets
2431 .BR shortname= { lower | win95 | winnt | mixed }
2433 Defines the behaviour for creation and display of filenames which fit into
2434 8.3 characters. If a long name for a file exists, it will always be
2435 preferred display. There are four modes:
2440 Force the short name to lower case upon display; store a long name when
2441 the short name is not all upper case.
2444 Force the short name to upper case upon display; store a long name when
2445 the short name is not all upper case.
2448 Display the shortname as is; store a long name when the short name is
2449 not all lower case or all upper case.
2452 Display the short name as is; store a long name when the short name is not
2453 all upper case. This mode is the default since Linux 2.6.32.
2457 .SH "Mount options for usbfs"
2459 \fBdevuid=\fP\fIuid\fP and \fBdevgid=\fP\fIgid\fP and \fBdevmode=\fP\fImode\fP
2460 Set the owner and group and mode of the device files in the usbfs filesystem
2461 (default: uid=gid=0, mode=0644). The mode is given in octal.
2463 \fBbusuid=\fP\fIuid\fP and \fBbusgid=\fP\fIgid\fP and \fBbusmode=\fP\fImode\fP
2464 Set the owner and group and mode of the bus directories in the usbfs
2465 filesystem (default: uid=gid=0, mode=0555). The mode is given in octal.
2467 \fBlistuid=\fP\fIuid\fP and \fBlistgid=\fP\fIgid\fP and \fBlistmode=\fP\fImode\fP
2468 Set the owner and group and mode of the file
2470 (default: uid=gid=0, mode=0444). The mode is given in octal.
2472 .SH "Mount options for xenix"
2475 .SH "Mount options for xfs"
2478 Sets the buffered I/O end-of-file preallocation size when
2479 doing delayed allocation writeout (default size is 64KiB).
2480 Valid values for this option are page size (typically 4KiB)
2481 through to 1GiB, inclusive, in power-of-2 increments.
2484 The options enable/disable (default is enabled) an "opportunistic"
2485 improvement to be made in the way inline extended attributes are
2487 When the new form is used for the first time (by setting or
2488 removing extended attributes) the on-disk superblock feature
2489 bit field will be updated to reflect this format being in use.
2492 Enables the use of block layer write barriers for writes into
2493 the journal and unwritten extent conversion. This allows for
2494 drive level write caching to be enabled, for devices that
2495 support write barriers.
2498 Enable the DMAPI (Data Management API) event callouts.
2503 .BR grpid | bsdgroups " and " nogrpid | sysvgroups
2504 These options define what group ID a newly created file gets.
2505 When grpid is set, it takes the group ID of the directory in
2506 which it is created; otherwise (the default) it takes the fsgid
2507 of the current process, unless the directory has the setgid bit
2508 set, in which case it takes the gid from the parent directory,
2509 and also gets the setgid bit set if it is a directory itself.
2511 .BI ihashsize= value
2512 Sets the number of hash buckets available for hashing the
2513 in-memory inodes of the specified mount point. If a value
2514 of zero is used, the value selected by the default algorithm
2515 will be displayed in
2519 When inode clusters are emptied of inodes, keep them around
2520 on the disk (ikeep) - this is the traditional XFS behaviour
2521 and is still the default for now. Using the noikeep option,
2522 inode clusters are returned to the free space pool.
2525 Indicates that XFS is allowed to create inodes at any location
2526 in the filesystem, including those which will result in inode
2527 numbers occupying more than 32 bits of significance. This is
2528 provided for backwards compatibility, but causes problems for
2529 backup applications that cannot handle large inode numbers.
2531 .BR largeio | nolargeio
2534 is specified, the optimal I/O reported in
2537 will be as small as possible to allow user
2538 applications to avoid inefficient read/modify/write I/O.
2541 is specified, a filesystem that has a
2546 value (in bytes) in st_blksize. If the
2547 filesystem does not have a
2549 specified but does specify
2554 (in bytes) will be returned
2556 If neither of these two options are specified, then filesystem
2562 Set the number of in-memory log buffers. Valid numbers range
2564 The default value is 8 buffers for any recent kernel.
2567 Set the size of each in-memory log buffer.
2568 Size may be specified in bytes, or in kilobytes with a "k" suffix.
2569 Valid sizes for version 1 and version 2 logs are 16384 (16k) and
2570 32768 (32k). Valid sizes for version 2 logs also include
2571 65536 (64k), 131072 (128k) and 262144 (256k).
2572 The default value for any recent kernel is 32768.
2574 \fBlogdev=\fP\fIdevice\fP and \fBrtdev=\fP\fIdevice\fP
2575 Use an external log (metadata journal) and/or real-time device.
2576 An XFS filesystem has up to three parts: a data section, a log section,
2577 and a real-time section.
2578 The real-time section is optional, and the log section can be separate
2579 from the data section or contained within it.
2583 .BI mtpt= mountpoint
2586 option. The value specified here will be
2587 included in the DMAPI mount event, and should be the path of
2588 the actual mountpoint that is used.
2591 Data allocations will not be aligned at stripe unit boundaries.
2594 Access timestamps are not updated when a file is read.
2597 The filesystem will be mounted without running log recovery.
2598 If the filesystem was not cleanly unmounted, it is likely to
2599 be inconsistent when mounted in
2602 Some files or directories may not be accessible because of this.
2605 must be mounted read-only or the mount will fail.
2608 Don't check for double mounted filesystems using the filesystem uuid.
2609 This is useful to mount LVM snapshot volumes.
2612 Make O_SYNC writes implement true O_SYNC. WITHOUT this option,
2613 Linux XFS behaves as if an
2616 which will make writes to files opened with the O_SYNC flag set
2617 behave as if the O_DSYNC flag had been used instead.
2618 This can result in better performance without compromising
2620 However if this option is not in effect, timestamp updates from
2621 O_SYNC writes can be lost if the system crashes.
2622 If timestamp updates are critical, use the
2626 .BR uquota | usrquota | uqnoenforce | quota
2627 User disk quota accounting enabled, and limits (optionally)
2630 for further details.
2632 .BR gquota | grpquota | gqnoenforce
2633 Group disk quota accounting enabled and limits (optionally)
2636 for further details.
2638 .BR pquota | prjquota | pqnoenforce
2639 Project disk quota accounting enabled and limits (optionally)
2642 for further details.
2644 \fBsunit=\fP\fIvalue\fP and \fBswidth=\fP\fIvalue\fP
2645 Used to specify the stripe unit and width for a RAID device or a stripe
2648 must be specified in 512-byte block units.
2649 If this option is not specified and the filesystem was made on a stripe
2650 volume or the stripe width or unit were specified for the RAID device at
2651 mkfs time, then the mount system call will restore the value from the
2653 For filesystems that are made directly on RAID devices, these options can be
2654 used to override the information in the superblock if the underlying disk
2655 layout changes after the filesystem has been created.
2658 option is required if the
2660 option has been specified,
2661 and must be a multiple of the
2666 Data allocations will be rounded up to stripe width boundaries
2667 when the current end of file is being extended and the file
2668 size is larger than the stripe width size.
2670 .SH "Mount options for xiafs"
2671 None. Although nothing is wrong with xiafs, it is not used much,
2672 and is not maintained. Probably one shouldn't use it.
2673 Since Linux version 2.1.21 xiafs is no longer part of the kernel source.
2675 .SH "THE LOOP DEVICE"
2676 One further possible type is a mount via the loop device. For example,
2680 .B "mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop"
2683 will set up the loop device
2685 to correspond to the file
2687 and then mount this device on
2690 If no explicit loop device is mentioned
2691 (but just an option `\fB\-o loop\fP' is given), then
2693 will try to find some unused loop device and use that, for example
2696 .B "mount /tmp/disk.img /mnt -o loop"
2701 creates a loop device from a regular file if a filesystem type is
2702 not specified or the filesystem is known for libblkid, for example:
2705 .B "mount /tmp/disk.img /mnt"
2707 .B "mount -t ext3 /tmp/disk.img /mnt"
2710 This type of mount knows about four options, namely
2711 .BR loop ", " offset ", " sizelimit " and " encryption ,
2712 that are really options to
2714 (These options can be used in addition to those specific
2715 to the filesystem type.)
2717 Since Linux 2.6.25 is supported auto-destruction of loop devices and
2718 then any loop device allocated by
2725 You can also free a loop device by hand, using `losetup -d' or `umount -d`.
2729 has the following return codes (the bits can be ORed):
2735 incorrect invocation or permissions
2738 system error (out of memory, cannot fork, no more loop devices)
2749 problems writing or locking /etc/mtab
2755 some mount succeeded
2758 The syntax of external mount helpers is:
2761 .BI /sbin/mount. <suffix>
2770 where the <type> is filesystem type and \-sfnvo options have same meaning like
2771 standard mount options. The \-t option is used for filesystems with subtypes
2772 support (for example /sbin/mount.fuse -t fuse.sshfs).
2780 table of mounted filesystems
2789 a list of filesystem types to try
2807 It is possible for a corrupted filesystem to cause a crash.
2809 Some Linux filesystems don't support
2810 .B "\-o sync and \-o dirsync"
2811 (the ext2, ext3, fat and vfat filesystems
2813 support synchronous updates (a la BSD) when mounted with the
2819 may not be able to change mount parameters (all
2820 .IR ext2fs -specific
2823 are changeable with a remount, for example, but you can't change
2830 Mount by label or uuid will work only if your devices have the names listed in
2831 .IR /proc/partitions .
2832 In particular, it may well fail if the kernel was compiled with devfs
2833 but devfs is not mounted.
2835 It is possible that files
2839 don't match. The first file is based only on the mount command options, but the
2840 content of the second file also depends on the kernel and others settings (e.g.
2841 remote NFS server. In particular case the mount command may reports unreliable
2842 information about a NFS mount point and the /proc/mounts file usually contains
2843 more reliable information.)
2845 Checking files on NFS filesystem referenced by file descriptors (i.e. the
2849 families of functions) may lead to inconsistent result due to the lack of
2850 consistency check in kernel even if noac is used.
2854 command existed in Version 5 AT&T UNIX.
2856 The mount command is part of the util-linux package and is available from
2857 ftp://ftp.kernel.org/pub/linux/utils/util-linux/.