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"
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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
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25 .\" You should have received a copy of the GNU General Public
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27 .\" Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
30 .\" 960705, aeb: version for mount-2.7g
31 .\" 970114, aeb: xiafs and ext are dead; romfs is new
32 .\" 970623, aeb: -F option
33 .\" 970914, reg: -s option
34 .\" 981111, K.Garloff: /etc/filesystems
35 .\" 990111, aeb: documented /sbin/mount.smbfs
36 .\" 990730, Yann Droneaud <lch@multimania.com>: updated page
37 .\" 991214, Elrond <Elrond@Wunder-Nett.org>: added some docs on devpts
38 .\" 010714, Michael K. Johnson <johnsonm@redhat.com> added -O
39 .\" 010725, Nikita Danilov <NikitaDanilov@Yahoo.COM>: reiserfs options
40 .\" 011124, Karl Eichwalder <ke@gnu.franken.de>: tmpfs options
42 .TH MOUNT 8 "December 2004" "util-linux" "System Administration"
44 mount \- mount a filesystem
59 .IR option [ \fB,\fPoption ]...]
70 All files accessible in a Unix system are arranged in one big
71 tree, the file hierarchy, rooted at
73 These files can be spread out over several devices. The
75 command serves to attach the filesystem found on some device
76 to the big file tree. Conversely, the
78 command will detach it again.
80 The standard form of the
86 .BI "mount \-t" " type device dir"
90 This tells the kernel to attach the filesystem found on
96 The previous contents (if any) and owner and mode of
98 become invisible, and as long as this filesystem remains mounted,
101 refers to the root of the filesystem on
104 If only directory or device is given, for example:
112 then mount looks for a mountpoint and if not found then for a device in the
115 .B The listing and help.
117 Three forms of invocation do not actually mount anything:
120 prints a help message
123 prints a version string
125 .BR "mount " [ -l "] [" "-t \fItype\fP" ]
126 lists all mounted filesystems (of type
128 The option \-l adds the labels in this listing.
132 .B The device indication.
134 Most devices are indicated by a file name (of a block special device), like
136 but there are other possibilities. For example, in the case of an NFS mount,
139 .IR knuth.cwi.nl:/dir .
140 It is possible to indicate a block special device using its
145 (see the \-L and \-U options below).
147 The recommended setup is to use LABEL=<label> or UUID=<uuid> tags rather than
148 .B /dev/disk/by-{label,uuid}
149 udev symlinks in the /etc/fstab file. The tags are
150 more readable, robust and portable. The
152 command internally uses udev
153 symlinks, so use the symlinks in /etc/fstab has no advantage over LABEL=/UUID=.
159 uses UUIDs as strings. The UUIDs from command line or
161 are not converted to internal binary representation. The string representation
162 of the UUID should be based on lower case characters.
166 filesystem is not associated with a special device, and when
167 mounting it, an arbitrary keyword, such as
169 can be used instead of a device specification.
170 (The customary choice
172 is less fortunate: the error message `none busy' from
177 .B The /etc/fstab, /etc/mtab and /proc/mounts files.
183 may contain lines describing what devices are usually
184 mounted where, using which options.
196 (usually given in a bootscript) causes all filesystems mentioned in
198 (of the proper type and/or having or not having the proper options)
199 to be mounted as indicated, except for those whose line contains the
203 option will make mount fork, so that the
204 filesystems are mounted simultaneously.
206 When mounting a filesystem mentioned in
210 it suffices to give only the device, or only the mount point.
217 maintain a list of currently mounted filesystems in the file
219 If no arguments are given to
221 this list is printed.
225 program does not read the
231 are specified. For example:
234 .B "mount /dev/foo /dir"
237 If you want to override mount options from
242 .B "mount device|dir -o <options>"
245 and then the mount options from command line will be appended to
246 the list of options from
248 The usual behaviour is that the last option wins if there is more duplicated
253 filesystem is mounted (say at
259 have very similar contents. The former has somewhat
260 more information, such as the mount options used,
261 but is not necessarily up-to-date (cf. the
263 option below). It is possible to replace
265 by a symbolic link to
267 and especially when you have very large numbers of mounts
268 things will be much faster with that symlink,
269 but some information is lost that way, and in particular
270 using the "user" option will fail.
273 .B The non-superuser mounts.
275 Normally, only the superuser can mount filesystems.
280 option on a line, anybody can mount the corresponding system.
285 .B "/dev/cdrom /cd iso9660 ro,user,noauto,unhide"
288 any user can mount the iso9660 filesystem found on his CDROM
292 .B "mount /dev/cdrom"
301 For more details, see
303 Only the user that mounted a filesystem can unmount it again.
304 If any user should be able to unmount, then use
313 option is similar to the
315 option, with the restriction that the user must be the owner
316 of the special file. This may be useful e.g. for
318 if a login script makes the console user owner of this device.
321 option is similar, with the restriction that the user must be
322 member of the group of the special file.
328 .\" In fact since 2.3.99. At first the syntax was mount -t bind.
329 Since Linux 2.4.0 it is possible to remount part of the
330 file hierarchy somewhere else. The call is
350 After this call the same contents is accessible in two places.
351 One can also remount a single file (on a single file). It's also
352 possible to use the bind mount to create a mountpoint from a regular
353 directory, for example:
361 The bind mount call attaches only (part of) a single filesystem, not possible
362 submounts. The entire file hierarchy including submounts is attached
378 .\" available since Linux 2.4.11.
380 Note that the filesystem mount options will remain the same as those
381 on the original mount point, and cannot be changed by passing the -o
382 option along with --bind/--rbind. The mount options can be
383 changed by a separate remount command, for example:
390 .B mount -o remount,ro
394 Note that behavior of the remount operation depends on the /etc/mtab file. The
395 first command stores the 'bind' flag to the /etc/mtab file and the second
396 command reads the flag from the file. If you have a system without the
397 /etc/mtab file or if you explicitly define source and target for the remount
398 command (then mount(8) does not read /etc/mtab), then you have to use bind flag
399 (or option) for the remount command too. For example:
406 .B mount -o remount,ro,bind
411 .B The move operation.
413 Since Linux 2.5.1 it is possible to atomically move a
415 to another place. The call is
427 This will cause the contents which previously appeared under olddir to be
428 accessed under newdir. The physical location of the files is not changed.
431 has to be a mountpoint.
434 .B The shared subtrees operations.
436 Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared,
437 private, slave or unbindable. A shared mount provides ability to create mirrors
438 of that mount such that mounts and umounts within any of the mirrors propagate
439 to the other mirror. A slave mount receives propagation from its master, but
440 any not vice-versa. A private mount carries no propagation abilities. A
441 unbindable mount is a private mount which cannot be cloned through a bind
442 operation. Detailed semantics is documented in Documentation/filesystems/sharedsubtree.txt
443 file in the kernel source tree.
447 .BI "mount --make-shared " mountpoint
448 .BI "mount --make-slave " mountpoint
449 .BI "mount --make-private " mountpoint
450 .BI "mount --make-unbindable " mountpoint
454 The following commands allows one to recursively change the type of all the
455 mounts under a given mountpoint.
459 .BI "mount --make-rshared " mountpoint
460 .BI "mount --make-rslave " mountpoint
461 .BI "mount --make-rprivate " mountpoint
462 .BI "mount --make-runbindable " mountpoint
467 .SH COMMAND LINE OPTIONS
468 The full set of mount options used by an invocation of
470 is determined by first extracting the
471 mount options for the filesystem from the
473 table, then applying any options specified by the
475 argument, and finally applying a
477 option, when present.
479 Command line options available for the
482 .IP "\fB\-V, \-\-version\fP"
484 .IP "\fB\-h, \-\-help\fP"
485 Print a help message.
486 .IP "\fB\-v, \-\-verbose\fP"
488 .IP "\fB\-a, \-\-all\fP"
489 Mount all filesystems (of the given types) mentioned in
491 .IP "\fB\-F, \-\-fork\fP"
492 (Used in conjunction with
494 Fork off a new incarnation of mount for each device.
495 This will do the mounts on different devices or different NFS servers
497 This has the advantage that it is faster; also NFS timeouts go in
498 parallel. A disadvantage is that the mounts are done in undefined order.
499 Thus, you cannot use this option if you want to mount both
503 .IP "\fB\-f, \-\-fake\fP"
504 Causes everything to be done except for the actual system call; if it's not
505 obvious, this ``fakes'' mounting the filesystem. This option is useful in
508 flag to determine what the
510 command is trying to do. It can also be used to add entries for devices
511 that were mounted earlier with the -n option. The -f option checks for
512 existing record in /etc/mtab and fails when the record already
513 exists (with regular non-fake mount, this check is done by kernel).
514 .IP "\fB\-i, \-\-internal\-only\fP"
515 Don't call the /sbin/mount.<filesystem> helper even if it exists.
517 Add the labels in the mount output. Mount must have
518 permission to read the disk device (e.g. be suid root) for this to work.
519 One can set such a label for ext2, ext3 or ext4 using the
521 utility, or for XFS using
523 or for reiserfs using
524 .BR reiserfstune (8).
525 .IP "\fB\-n, \-\-no\-mtab\fP"
526 Mount without writing in
528 This is necessary for example when
530 is on a read-only filesystem.
531 .IP "\fB\-\-no\-canonicalize\fP"
532 Don't canonicalize paths. The mount command canonicalizes all paths
533 (from command line or fstab) and stores canonicalized paths to the
535 file. This option can be used together with the
537 flag for already canonicalized absolut paths.
538 .IP "\fB\-p, \-\-pass\-fd \fInum\fP"
539 In case of a loop mount with encryption, read the passphrase from
542 instead of from the terminal.
544 Tolerate sloppy mount options rather than failing. This will ignore
545 mount options not supported by a filesystem type. Not all filesystems
546 support this option. This option exists for support of the Linux
547 autofs\-based automounter.
548 .IP "\fB\-r, \-\-read\-only\fP"
549 Mount the filesystem read-only. A synonym is
552 Note that, depending on the filesystem type, state and kernel behavior, the
553 system may still write to the device. For example, Ext3 or ext4 will replay its
554 journal if the filesystem is dirty. To prevent this kind of write access, you
555 may want to mount ext3 or ext4 filesystem with "ro,noload" mount options or
556 set the block device to read-only mode, see command
558 .IP "\fB\-w, \-\-rw\fP"
559 Mount the filesystem read/write. This is the default. A synonym is
561 .IP "\fB\-L \fIlabel\fP"
562 Mount the partition that has the specified
564 .IP "\fB\-U \fIuuid\fP"
565 Mount the partition that has the specified
567 These two options require the file
569 (present since Linux 2.1.116) to exist.
570 .IP "\fB\-t, \-\-types \fIvfstype\fP"
571 The argument following the
573 is used to indicate the filesystem type. The filesystem types which are
574 currently supported include:
618 Note that coherent, sysv and xenix are equivalent and that
622 will be removed at some point in the future \(em use
624 instead. Since kernel version 2.1.21 the types
628 do not exist anymore. Earlier,
632 Note, the real list of all supported filesystems depends on your
639 support filesystem subtypes. The subtype is defined by '.subtype' suffix. For
640 example 'fuse.sshfs'. It's recommended to use subtype notation rather than add
641 any prefix to the mount source (for example 'sshfs#example.com' is
644 For most types all the
646 program has to do is issue a simple
648 system call, and no detailed knowledge of the filesystem type is required.
649 For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) ad hoc code is
650 necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems
651 have a separate mount program. In order to make it possible to
652 treat all types in a uniform way, mount will execute the program
653 .BI /sbin/mount. TYPE
654 (if that exists) when called with type
656 Since various versions of the
658 program have different calling conventions,
660 may have to be a shell script that sets up the desired call.
664 option is given, or if the
666 type is specified, mount will try to guess the desired type.
667 Mount uses the blkid library for guessing the filesystem
668 type; if that does not turn up anything that looks familiar,
669 mount will try to read the file
670 .IR /etc/filesystems ,
671 or, if that does not exist,
672 .IR /proc/filesystems .
673 All of the filesystem types listed there will be tried,
674 except for those that are labeled "nodev" (e.g.,
681 ends in a line with a single * only, mount will read
687 type may be useful for user-mounted floppies.
690 can be useful to change the probe order (e.g., to try vfat before msdos
691 or ext3 before ext2) or if you use a kernel module autoloader.
693 More than one type may be specified in a comma separated
694 list. The list of filesystem types can be prefixed with
696 to specify the filesystem types on which no action should be taken.
697 (This can be meaningful with the
699 option.) For example, the command:
703 .B "mount \-a \-t nomsdos,ext"
706 mounts all filesystems except those of type
711 .IP "\fB\-O, \-\-test-opts \fIopts\fP"
712 Used in conjunction with
714 to limit the set of filesystems to which the
718 in this regard except that it is useless except in the context of
720 For example, the command:
724 .B "mount \-a \-O no_netdev"
727 mounts all filesystems except those which have the option
729 specified in the options field in the
735 in that each option is matched exactly; a leading
737 at the beginning of one option does not negate the rest.
743 options are cumulative in effect; that is, the command
746 .B "mount \-a \-t ext2 \-O _netdev"
749 mounts all ext2 filesystems with the _netdev option, not all filesystems
750 that are either ext2 or have the _netdev option specified.
752 .IP "\fB\-o, \-\-options \fIopts\fP"
753 Options are specified with a
755 flag followed by a comma separated string of options. For example:
759 .B "mount LABEL=mydisk \-o noatime,nouser"
763 For more details, see
764 .B FILESYSTEM INDEPENDENT MOUNT OPTIONS
766 .B FILESYSTEM SPECIFIC MOUNT OPTIONS
769 .IP "\fB\-B, \-\-bind\fP"
770 Remount a subtree somewhere else (so that its contents are available
771 in both places). See above.
772 .IP "\fB\-R, \-\-rbind\fP"
773 Remount a subtree and all possible submounts somewhere else (so that its
774 contents are available in both places). See above.
775 .IP "\fB\-M, \-\-move\fP"
776 Move a subtree to some other place. See above.
778 .SH FILESYSTEM INDEPENDENT MOUNT OPTIONS
779 Some of these options are only useful when they appear in the
783 Some of these options could be enabled or disabled by default
784 in the system kernel. To check the current setting see the options
787 The following options apply to any filesystem that is being
788 mounted (but not every filesystem actually honors them - e.g., the
790 option today has effect only for ext2, ext3, fat, vfat and ufs):
794 All I/O to the filesystem should be done asynchronously. (See also the
799 Do not use noatime feature, then the inode access time is controlled by kernel
800 defaults. See also the description for
807 Do not update inode access times on this filesystem (e.g., for faster
808 access on the news spool to speed up news servers).
811 Can be mounted with the
816 Can only be mounted explicitly (i.e., the
818 option will not cause the filesystem to be mounted).
820 \fBcontext=\fP\fIcontext\fP, \fBfscontext=\fP\fIcontext\fP, \fBdefcontext=\fP\fIcontext\fP and \fBrootcontext=\fP\fIcontext\fP
823 option is useful when mounting filesystems that do not support
824 extended attributes, such as a floppy or hard disk formatted with VFAT, or
825 systems that are not normally running under SELinux, such as an ext3 formatted
826 disk from a non-SELinux workstation. You can also use
828 on filesystems you do not trust, such as a floppy. It also helps in compatibility with
829 xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where
830 xattrs are supported, you can save time not having to label every file by
831 assigning the entire disk one security context.
833 A commonly used option for removable media is
834 .BR context=system_u:object_r:removable_t .
836 Two other options are
840 both of which are mutually exclusive of the context option. This means you
841 can use fscontext and defcontext with each other, but neither can be used with
846 option works for all filesystems, regardless of their xattr
847 support. The fscontext option sets the overarching filesystem label to a
848 specific security context. This filesystem label is separate from the
849 individual labels on the files. It represents the entire filesystem for
850 certain kinds of permission checks, such as during mount or file creation.
851 Individual file labels are still obtained from the xattrs on the files
852 themselves. The context option actually sets the aggregate context that
853 fscontext provides, in addition to supplying the same label for individual
856 You can set the default security context for unlabeled files using
858 option. This overrides the value set for unlabeled files in the policy and requires a
859 filesystem that supports xattr labeling.
863 option allows you to explicitly label the root inode of a FS being mounted
864 before that FS or inode because visable to userspace. This was found to be
865 useful for things like stateless linux.
867 Note that kernel rejects any remount request that includes the context
868 option even if unchanged from the current context.
870 For more details, see
876 .BR rw ", " suid ", " dev ", " exec ", " auto ", " nouser ", and " async.
879 Interpret character or block special devices on the filesystem.
882 Do not interpret character or block special devices on the file
886 Update directory inode access times on this filesystem. This is the default.
889 Do not update directory inode access times on this filesystem.
892 All directory updates within the filesystem should be done synchronously.
893 This affects the following system calls: creat, link, unlink, symlink,
894 mkdir, rmdir, mknod and rename.
897 Permit execution of binaries.
900 Do not allow direct execution of any binaries on the mounted filesystem.
901 (Until recently it was possible to run binaries anyway using a command like
902 /lib/ld*.so /mnt/binary. This trick fails since Linux 2.4.25 / 2.6.0.)
905 Allow an ordinary (i.e., non-root) user to mount the filesystem if one
906 of his groups matches the group of the device.
907 This option implies the options
908 .BR nosuid " and " nodev
909 (unless overridden by subsequent options, as in the option line
910 .BR group,dev,suid ).
913 Every time the inode is modified, the i_version field will be incremented.
916 Do not increment the i_version inode field.
919 Allow mandatory locks on this filesystem. See
923 Do not allow mandatory locks on this filesystem.
926 The filesystem resides on a device that requires network access
927 (used to prevent the system from attempting to mount these filesystems
928 until the network has been enabled on the system).
931 Do not report errors for this device if it does not exist.
934 Update inode access times relative to modify or change time. Access
935 time is only updated if the previous access time was earlier than the
936 current modify or change time. (Similar to noatime, but doesn't break
937 mutt or other applications that need to know if a file has been read
938 since the last time it was modified.)
940 Since Linux 2.6.30, the kernel defaults to the behavior provided by this
943 was specified), and the
945 option is required to obtain traditional semantics. In addition, since Linux
946 2.6.30, the file's last access time is always updated if it is more than 1
952 feature. See also the
957 Allows to explicitly requesting full atime updates. This makes it
958 possible for kernel to defaults to
962 but still allow userspace to override it. For more details about the default
963 system mount options see /proc/mounts.
966 Use the kernel's default behaviour for inode access time updates.
969 Allow set-user-identifier or set-group-identifier bits to take
973 Do not allow set-user-identifier or set-group-identifier bits to take
974 effect. (This seems safe, but is in fact rather unsafe if you have
975 suidperl(1) installed.)
978 Turn on the silent flag.
981 Turn off the silent flag.
984 Allow an ordinary (i.e., non-root) user to mount the filesystem if he
985 is the owner of the device.
986 This option implies the options
987 .BR nosuid " and " nodev
988 (unless overridden by subsequent options, as in the option line
989 .BR owner,dev,suid ).
992 Attempt to remount an already-mounted filesystem. This is commonly
993 used to change the mount flags for a filesystem, especially to make a
994 readonly filesystem writable. It does not change device or mount point.
996 The remount functionality follows the standard way how the mount command works
997 with options from fstab. It means the mount command doesn't read fstab (or
1002 are fully specified.
1004 .BR "mount -o remount,rw /dev/foo /dir"
1006 After this call all old mount options are replaced and arbitrary stuff from
1007 fstab is ignored, except the loop= option which is internally generated and
1008 maintained by the mount command.
1010 .BR "mount -o remount,rw /dir"
1012 After this call mount reads fstab (or mtab) and merges these options with
1013 options from command line (
1018 Mount the filesystem read-only.
1021 Mount the filesystem read-write.
1024 All I/O to the filesystem should be done synchronously. In case of media with limited number of write cycles
1025 (e.g. some flash drives) "sync" may cause life-cycle shortening.
1028 Allow an ordinary user to mount the filesystem.
1029 The name of the mounting user is written to mtab so that he can unmount
1030 the filesystem again.
1031 This option implies the options
1032 .BR noexec ", " nosuid ", and " nodev
1033 (unless overridden by subsequent options, as in the option line
1034 .BR user,exec,dev,suid ).
1037 Forbid an ordinary (i.e., non-root) user to mount the filesystem.
1038 This is the default.
1041 Allow every user to mount and unmount the filesystem.
1042 This option implies the options
1043 .BR noexec ", " nosuid ", and " nodev
1044 (unless overridden by subsequent options, as in the option line
1045 .BR users,exec,dev,suid ).
1047 .SH "FILESYSTEM SPECIFIC MOUNT OPTIONS"
1048 The following options apply only to certain filesystems.
1049 We sort them by filesystem. They all follow the
1053 What options are supported depends a bit on the running kernel.
1054 More info may be found in the kernel source subdirectory
1055 .IR Documentation/filesystems .
1057 .SH "Mount options for adfs"
1059 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1060 Set the owner and group of the files in the filesystem (default: uid=gid=0).
1062 \fBownmask=\fP\fIvalue\fP and \fBothmask=\fP\fIvalue\fP
1063 Set the permission mask for ADFS 'owner' permissions and 'other' permissions,
1064 respectively (default: 0700 and 0077, respectively).
1066 .IR /usr/src/linux/Documentation/filesystems/adfs.txt .
1067 .SH "Mount options for affs"
1069 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1070 Set the owner and group of the root of the filesystem (default: uid=gid=0,
1075 without specified value, the uid and gid of the current process are taken).
1077 \fBsetuid=\fP\fIvalue\fP and \fBsetgid=\fP\fIvalue\fP
1078 Set the owner and group of all files.
1081 Set the mode of all files to
1083 disregarding the original permissions.
1084 Add search permission to directories that have read permission.
1085 The value is given in octal.
1088 Do not allow any changes to the protection bits on the filesystem.
1091 Set uid and gid of the root of the filesystem to the uid and gid
1092 of the mount point upon the first sync or umount, and then
1093 clear this option. Strange...
1096 Print an informational message for each successful mount.
1099 Prefix used before volume name, when following a link.
1102 Prefix (of length at most 30) used before '/' when following a symbolic link.
1105 (Default: 2.) Number of unused blocks at the start of the device.
1108 Give explicitly the location of the root block.
1111 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
1113 .BR grpquota | noquota | quota | usrquota
1114 These options are accepted but ignored.
1115 (However, quota utilities may react to such strings in
1118 .SH "Mount options for cifs"
1119 See the options section of the
1121 man page (cifs-utils package must be installed).
1123 .SH "Mount options for coherent"
1126 .SH "Mount options for debugfs"
1127 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1128 .IR /sys/kernel/debug .
1130 .\" present since 2.6.11
1131 There are no mount options.
1133 .SH "Mount options for devpts"
1134 The devpts filesystem is a pseudo filesystem, traditionally mounted on
1136 In order to acquire a pseudo terminal, a process opens
1138 the number of the pseudo terminal is then made available to the process
1139 and the pseudo terminal slave can be accessed as
1140 .IR /dev/pts/ <number>.
1142 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1143 This sets the owner or the group of newly created PTYs to
1144 the specified values. When nothing is specified, they will
1145 be set to the UID and GID of the creating process.
1146 For example, if there is a tty group with GID 5, then
1148 will cause newly created PTYs to belong to the tty group.
1151 Set the mode of newly created PTYs to the specified value.
1152 The default is 0600.
1157 makes "mesg y" the default on newly created PTYs.
1160 Create a private instance of devpts filesystem, such that
1161 indices of ptys allocated in this new instance are
1162 independent of indices created in other instances of devpts.
1164 All mounts of devpts without this
1166 option share the same set of pty indices (i.e legacy mode).
1167 Each mount of devpts with the
1169 option has a private set of pty indices.
1171 This option is mainly used to support containers in the
1172 linux kernel. It is implemented in linux kernel versions
1173 starting with 2.6.29. Further, this mount option is valid
1174 only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the
1175 kernel configuration.
1177 To use this option effectively,
1179 must be a symbolic link to
1182 .IR Documentation/filesystems/devpts.txt
1183 in the linux kernel source tree for details.
1187 Set the mode for the new
1189 device node in the devpts filesystem.
1191 With the support for multiple instances of devpts (see
1193 option above), each instance has a private
1195 node in the root of the devpts filesystem (typically
1198 For compatibility with older versions of the kernel, the
1199 default mode of the new
1203 specifies a more useful mode for the
1205 node and is highly recommended when the
1207 option is specified.
1209 This option is only implemented in linux kernel versions
1210 starting with 2.6.29. Further this option is valid only if
1211 CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1214 .SH "Mount options for ext"
1216 Note that the `ext' filesystem is obsolete. Don't use it.
1217 Since Linux version 2.1.21 extfs is no longer part of the kernel source.
1219 .SH "Mount options for ext2"
1220 The `ext2' filesystem is the standard Linux filesystem.
1221 .\" Due to a kernel bug, it may be mounted with random mount options
1222 .\" (fixed in Linux 2.0.4).
1223 Since Linux 2.5.46, for most mount options the default
1224 is determined by the filesystem superblock. Set them with
1228 Support POSIX Access Control Lists (or not).
1229 .\" requires CONFIG_EXT2_FS_POSIX_ACL
1232 Set the behaviour for the
1236 behaviour is to return in the
1238 field the total number of blocks of the filesystem, while the
1240 behaviour (which is the default) is to subtract the overhead blocks
1241 used by the ext2 filesystem and not available for file storage. Thus
1244 % mount /k -o minixdf; df /k; umount /k
1245 Filesystem 1024-blocks Used Available Capacity Mounted on
1246 /dev/sda6 2630655 86954 2412169 3% /k
1247 % mount /k -o bsddf; df /k; umount /k
1248 Filesystem 1024-blocks Used Available Capacity Mounted on
1249 /dev/sda6 2543714 13 2412169 0% /k
1252 (Note that this example shows that one can add command line options
1253 to the options given in
1257 .BR check= { none | nocheck }
1258 No checking is done at mount time. This is the default. This is fast.
1259 It is wise to invoke
1261 every now and then, e.g. at boot time.
1264 Print debugging info upon each (re)mount.
1266 .BR errors= { continue | remount-ro | panic }
1267 Define the behaviour when an error is encountered.
1268 (Either ignore errors and just mark the filesystem erroneous and continue,
1269 or remount the filesystem read-only, or panic and halt the system.)
1270 The default is set in the filesystem superblock, and can be
1274 .BR grpid | bsdgroups " and " nogrpid | sysvgroups
1275 These options define what group id a newly created file gets.
1278 is set, it takes the group id of the directory in which it is created;
1279 otherwise (the default) it takes the fsgid of the current process, unless
1280 the directory has the setgid bit set, in which case it takes the gid
1281 from the parent directory, and also gets the setgid bit set
1282 if it is a directory itself.
1284 .BR grpquota | noquota | quota | usrquota
1285 These options are accepted but ignored.
1288 Disables 32-bit UIDs and GIDs. This is for interoperability with older
1289 kernels which only store and expect 16-bit values.
1291 .BR oldalloc " or " orlov
1292 Use old allocator or Orlov allocator for new inodes. Orlov is default.
1294 \fBresgid=\fP\fIn\fP and \fBresuid=\fP\fIn\fP
1295 The ext2 filesystem reserves a certain percentage of the available
1296 space (by default 5%, see
1300 These options determine who can use the reserved blocks.
1301 (Roughly: whoever has the specified uid, or belongs to the specified group.)
1304 Instead of block 1, use block
1306 as superblock. This could be useful when the filesystem has been damaged.
1307 (Earlier, copies of the superblock would be made every 8192 blocks: in
1308 block 1, 8193, 16385, ... (and one got thousands of copies on
1309 a big filesystem). Since version 1.08,
1311 has a \-s (sparse superblock) option to reduce the number of backup
1312 superblocks, and since version 1.15 this is the default. Note
1313 that this may mean that ext2 filesystems created by a recent
1315 cannot be mounted r/w under Linux 2.0.*.)
1316 The block number here uses 1k units. Thus, if you want to use logical
1317 block 32768 on a filesystem with 4k blocks, use "sb=131072".
1319 .BR user_xattr | nouser_xattr
1320 Support "user." extended attributes (or not).
1321 .\" requires CONFIG_EXT2_FS_XATTR
1324 .SH "Mount options for ext3"
1325 The ext3 filesystem is a version of the ext2 filesystem which has been
1326 enhanced with journalling. It supports the same options as ext2 as
1327 well as the following additions:
1330 .\" Mount the filesystem in abort mode, as if a fatal error has occurred.
1333 Update the ext3 filesystem's journal to the current format.
1336 When a journal already exists, this option is ignored. Otherwise, it
1337 specifies the number of the inode which will represent the ext3 filesystem's
1338 journal file; ext3 will create a new journal, overwriting the old contents
1339 of the file whose inode number is
1342 .BR journal_dev=devnum
1343 When the external journal device's major/minor numbers
1344 have changed, this option allows the user to specify
1345 the new journal location. The journal device is
1346 identified through its new major/minor numbers encoded
1349 .BR norecovery / noload
1350 Don't load the journal on mounting. Note that
1351 if the filesystem was not unmounted cleanly,
1352 skipping the journal replay will lead to the
1353 filesystem containing inconsistencies that can
1354 lead to any number of problems.
1356 .BR data= { journal | ordered | writeback }
1357 Specifies the journalling mode for file data. Metadata is always journaled.
1358 To use modes other than
1360 on the root filesystem, pass the mode to the kernel as boot parameter, e.g.
1361 .IR rootflags=data=journal .
1365 All data is committed into the journal prior to being written into the
1369 This is the default mode. All data is forced directly out to the main file
1370 system prior to its metadata being committed to the journal.
1373 Data ordering is not preserved - data may be written into the main
1374 filesystem after its metadata has been committed to the journal.
1375 This is rumoured to be the highest-throughput option. It guarantees
1376 internal filesystem integrity, however it can allow old data to appear
1377 in files after a crash and journal recovery.
1380 .BR barrier=0 " / " barrier=1 "
1381 This enables/disables barriers. barrier=0 disables it, barrier=1 enables it.
1382 Write barriers enforce proper on-disk ordering of journal commits, making
1383 volatile disk write caches safe to use, at some performance penalty. The ext3
1384 filesystem does not enable write barriers by default. Be sure to enable
1385 barriers unless your disks are battery-backed one way or another. Otherwise
1386 you risk filesystem corruption in case of power failure.
1389 Sync all data and metadata every
1391 seconds. The default value is 5 seconds. Zero means default.
1394 Enable Extended User Attributes. See the
1399 Enable POSIX Access Control Lists. See the
1403 .SH "Mount options for ext4"
1404 The ext4 filesystem is an advanced level of the ext3 filesystem which
1405 incorporates scalability and reliability enhancements for supporting large
1409 .B journal_dev, noload, data, commit, orlov, oldalloc, [no]user_xattr
1410 .B [no]acl, bsddf, minixdf, debug, errors, data_err, grpid, bsdgroups, nogrpid
1411 .B sysvgroups, resgid, resuid, sb, quota, noquota, grpquota and usrquota
1412 are backwardly compatible with ext3 or ext2.
1414 .BR journal_checksum
1415 Enable checksumming of the journal transactions. This will allow the recovery
1416 code in e2fsck and the kernel to detect corruption in the kernel. It is a
1417 compatible change and will be ignored by older kernels.
1419 .BR journal_async_commit
1420 Commit block can be written to disk without waiting for descriptor blocks. If
1421 enabled older kernels cannot mount the device.
1422 This will enable 'journal_checksum' internally.
1425 Update the ext4 filesystem's journal to the current format.
1427 .BR barrier=0 " / " barrier=1 " / " barrier " / " nobarrier
1428 This enables/disables the use of write barriers in the jbd code. barrier=0
1429 disables, barrier=1 enables. This also requires an IO stack which can support
1430 barriers, and if jbd gets an error on a barrier write, it will disable again
1431 with a warning. Write barriers enforce proper on-disk ordering of journal
1432 commits, making volatile disk write caches safe to use, at some performance
1433 penalty. If your disks are battery-backed in one way or another, disabling
1434 barriers may safely improve performance. The mount options "barrier" and
1435 "nobarrier" can also be used to enable or disable barriers, for consistency
1436 with other ext4 mount options.
1438 The ext4 filesystem enables write barriers by default.
1440 .BI inode_readahead= n
1441 This tuning parameter controls the maximum number of inode table blocks that
1442 ext4's inode table readahead algorithm will pre-read into the buffer cache.
1443 The default value is 32 blocks.
1446 Number of filesystem blocks that mballoc will try to use for allocation size
1447 and alignment. For RAID5/6 systems this should be the number of data disks *
1448 RAID chunk size in filesystem blocks.
1451 Deferring block allocation until write-out time.
1454 Disable delayed allocation. Blocks are allocated when data is copied from user
1457 .BI max_batch_time= usec
1458 Maximum amount of time ext4 should wait for additional filesystem operations to
1459 be batch together with a synchronous write operation. Since a synchronous
1460 write operation is going to force a commit and then a wait for the I/O
1461 complete, it doesn't cost much, and can be a huge throughput win, we wait for a
1462 small amount of time to see if any other transactions can piggyback on the
1463 synchronous write. The algorithm used is designed to automatically tune for
1464 the speed of the disk, by measuring the amount of time (on average) that it
1465 takes to finish committing a transaction. Call this time the "commit time".
1466 If the time that the transaction has been running is less than the commit time,
1467 ext4 will try sleeping for the commit time to see if other operations will join
1468 the transaction. The commit time is capped by the max_batch_time, which
1469 defaults to 15000us (15ms). This optimization can be turned off entirely by
1470 setting max_batch_time to 0.
1472 .BI min_batch_time= usec
1473 This parameter sets the commit time (as described above) to be at least
1474 min_batch_time. It defaults to zero microseconds. Increasing this parameter
1475 may improve the throughput of multi-threaded, synchronous workloads on very
1476 fast disks, at the cost of increasing latency.
1478 .BI journal_ioprio= prio
1479 The I/O priority (from 0 to 7, where 0 is the highest priorty) which should be
1480 used for I/O operations submitted by kjournald2 during a commit operation.
1481 This defaults to 3, which is a slightly higher priority than the default I/O
1485 Simulate the effects of calling ext4_abort() for
1486 debugging purposes. This is normally used while
1487 remounting a filesystem which is already mounted.
1489 .BR auto_da_alloc | noauto_da_alloc
1490 Many broken applications don't use fsync() when
1491 replacing existing files via patterns such as
1493 fd = open("foo.new")/write(fd,..)/close(fd)/ rename("foo.new", "foo")
1497 fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).
1499 If auto_da_alloc is enabled, ext4 will detect the replace-via-rename and
1500 replace-via-truncate patterns and force that any delayed allocation blocks are
1501 allocated such that at the next journal commit, in the default data=ordered
1502 mode, the data blocks of the new file are forced to disk before the rename()
1503 operation is committed. This provides roughly the same level of guarantees as
1504 ext3, and avoids the "zero-length" problem that can happen when a system
1505 crashes before the delayed allocation blocks are forced to disk.
1507 .BR discard / nodiscard
1508 Controls whether ext4 should issue discard/TRIM commands to the underlying
1509 block device when blocks are freed. This is useful for SSD devices and
1510 sparse/thinly-provisioned LUNs, but it is off by default until sufficient
1511 testing has been done.
1514 Disables 32-bit UIDs and GIDs. This is for
1515 interoperability with older kernels which only
1516 store and expect 16-bit values.
1519 Allows to resize filesystem to the end of the last
1520 existing block group, further resize has to be done
1521 with resize2fs either online, or offline. It can be
1522 used only with conjunction with remount.
1524 .BR block_validity / noblock_validity
1525 This options allows to enables/disables the in-kernel facility for tracking
1526 filesystem metadata blocks within internal data structures. This allows multi-
1527 block allocator and other routines to quickly locate extents which might
1528 overlap with filesystem metadata blocks. This option is intended for debugging
1529 purposes and since it negatively affects the performance, it is off by default.
1531 .BR dioread_lock / dioread_nolock
1532 Controls whether or not ext4 should use the DIO read locking. If the
1533 dioread_nolock option is specified ext4 will allocate uninitialized extent
1534 before buffer write and convert the extent to initialized after IO completes.
1535 This approach allows ext4 code to avoid using inode mutex, which improves
1536 scalability on high speed storages. However this does not work with data
1537 journaling and dioread_nolock option will be ignored with kernel warning.
1538 Note that dioread_nolock code path is only used for extent-based files.
1539 Because of the restrictions this options comprises it is off by default
1540 (e.g. dioread_lock).
1543 Enable 64-bit inode version support. This option is off by default.
1545 .SH "Mount options for fat"
1548 is not a separate filesystem, but a common part of the
1555 .BR blocksize= { 512 | 1024 | 2048 }
1556 Set blocksize (default 512). This option is obsolete.
1558 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1559 Set the owner and group of all files.
1560 (Default: the uid and gid of the current process.)
1563 Set the umask (the bitmask of the permissions that are
1565 present). The default is the umask of the current process.
1566 The value is given in octal.
1569 Set the umask applied to directories only.
1570 The default is the umask of the current process.
1571 The value is given in octal.
1572 .\" Present since Linux 2.5.43.
1575 Set the umask applied to regular files only.
1576 The default is the umask of the current process.
1577 The value is given in octal.
1578 .\" Present since Linux 2.5.43.
1580 .BI allow_utime= value
1581 This option controls the permission check of mtime/atime.
1585 If current process is in group of file's group ID, you can change timestamp.
1588 Other users can change timestamp.
1590 The default is set from `dmask' option. (If the directory is writable,
1592 is also allowed. I.e. ~dmask & 022)
1596 checks current process is owner of the file, or it has
1597 CAP_FOWNER capability. But FAT filesystem doesn't have uid/gid on disk, so
1598 normal check is too unflexible. With this option you can relax it.
1602 Three different levels of pickyness can be chosen:
1606 Upper and lower case are accepted and equivalent, long name parts are
1608 .I verylongname.foobar
1611 leading and embedded spaces are accepted in each name part (name and extension).
1614 Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are
1615 rejected. This is the default.
1618 Like "normal", but names may not contain long parts and special characters
1619 that are sometimes used on Linux, but are not accepted by MS-DOS are
1620 rejected. (+, =, spaces, etc.)
1624 Sets the codepage for converting to shortname characters on FAT
1625 and VFAT filesystems. By default, codepage 437 is used.
1627 .BR conv= {b [ inary ]| t [ ext ]| a [ uto ]}
1630 filesystem can perform CRLF<-->NL (MS-DOS text format to UNIX text
1631 format) conversion in the kernel. The following conversion modes are
1636 no translation is performed. This is the default.
1639 CRLF<-->NL translation is performed on all files.
1642 CRLF<-->NL translation is performed on all files that don't have a
1643 "well-known binary" extension. The list of known extensions can be found at
1646 (as of 2.0, the list is: exe, com, bin, app, sys, drv, ovl, ovr, obj,
1647 lib, dll, pif, arc, zip, lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz,
1648 gz, tgz, deb, gif, bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl, dvi).
1650 Programs that do computed lseeks won't like in-kernel text conversion.
1651 Several people have had their data ruined by this translation. Beware!
1653 For filesystems mounted in binary mode, a conversion tool
1654 (fromdos/todos) is available. This option is obsolete.
1657 .BI cvf_format= module
1658 Forces the driver to use the CVF (Compressed Volume File) module
1660 instead of auto-detection. If the kernel supports kmod, the
1661 cvf_format=xxx option also controls on-demand CVF module loading.
1662 This option is obsolete.
1664 .BI cvf_option= option
1665 Option passed to the CVF module. This option is obsolete.
1670 flag. A version string and a list of filesystem parameters will be
1671 printed (these data are also printed if the parameters appear to be
1674 .BR fat= {12 | 16 | 32 }
1675 Specify a 12, 16 or 32 bit fat. This overrides
1676 the automatic FAT type detection routine. Use with caution!
1678 .BI iocharset= value
1679 Character set to use for converting between 8 bit characters
1680 and 16 bit Unicode characters. The default is iso8859-1.
1681 Long filenames are stored on disk in Unicode format.
1684 This option disables the conversion of timestamps
1685 between local time (as used by Windows on FAT) and UTC
1686 (which Linux uses internally). This is particularly
1687 useful when mounting devices (like digital cameras)
1688 that are set to UTC in order to avoid the pitfalls of
1694 flag. Attempts to chown or chmod files do not return errors,
1695 although they fail. Use with caution!
1698 If set, the execute permission bits of the file will be allowed only if
1699 the extension part of the name is .EXE, .COM, or .BAT. Not set by default.
1702 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux.
1706 If set, the filesystem will try to flush to disk more early than normal.
1710 Use the "free clusters" value stored on FSINFO. It'll
1711 be used to determine number of free clusters without
1712 scanning disk. But it's not used by default, because
1713 recent Windows don't update it correctly in some
1714 case. If you are sure the "free clusters" on FSINFO is
1715 correct, by this option you can avoid scanning disk.
1717 .BR dots ", " nodots ", " dotsOK= [ yes | no ]
1718 Various misguided attempts to force Unix or DOS conventions
1719 onto a FAT filesystem.
1721 .SH "Mount options for hfs"
1723 .BI creator= cccc ", type=" cccc
1724 Set the creator/type values as shown by the MacOS finder
1725 used for creating new files. Default values: '????'.
1727 .BI uid= n ", gid=" n
1728 Set the owner and group of all files.
1729 (Default: the uid and gid of the current process.)
1731 .BI dir_umask= n ", file_umask=" n ", umask=" n
1732 Set the umask used for all directories, all regular files, or all
1733 files and directories. Defaults to the umask of the current process.
1736 Select the CDROM session to mount.
1737 Defaults to leaving that decision to the CDROM driver.
1738 This option will fail with anything but a CDROM as underlying device.
1741 Select partition number n from the device.
1742 Only makes sense for CDROMs.
1743 Defaults to not parsing the partition table at all.
1746 Don't complain about invalid mount options.
1748 .SH "Mount options for hpfs"
1750 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1751 Set the owner and group of all files. (Default: the uid and gid
1752 of the current process.)
1755 Set the umask (the bitmask of the permissions that are
1757 present). The default is the umask of the current process.
1758 The value is given in octal.
1760 .BR case= { lower | asis }
1761 Convert all files names to lower case, or leave them.
1765 .BR conv= { binary | text | auto }
1768 delete some random CRs (in particular, all followed by NL)
1769 when reading a file.
1772 choose more or less at random between
1773 .BR conv=binary " and " conv=text .
1776 just read what is in the file. This is the default.
1779 Do not abort mounting when certain consistency checks fail.
1781 .SH "Mount options for iso9660"
1782 ISO 9660 is a standard describing a filesystem structure to be used
1783 on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1789 filenames appear in a 8.3 format (i.e., DOS-like restrictions on filename
1790 length), and in addition all characters are in upper case. Also there is
1791 no field for file ownership, protection, number of links, provision for
1792 block/character devices, etc.
1794 Rock Ridge is an extension to iso9660 that provides all of these UNIX-like
1795 features. Basically there are extensions to each directory record that
1796 supply all of the additional information, and when Rock Ridge is in use,
1797 the filesystem is indistinguishable from a normal UNIX filesystem (except
1798 that it is read-only, of course).
1801 Disable the use of Rock Ridge extensions, even if available. Cf.\&
1805 Disable the use of Microsoft Joliet extensions, even if available. Cf.\&
1808 .BR check= { r [ elaxed ]| s [ trict ]}
1811 a filename is first converted to lower case before doing the lookup.
1812 This is probably only meaningful together with
1819 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1820 Give all files in the filesystem the indicated user or group id,
1821 possibly overriding the information found in the Rock Ridge extensions.
1825 .BR map= { n [ ormal ]| o [ ff ]| a [ corn ]}
1826 For non-Rock Ridge volumes, normal name translation maps upper
1827 to lower case ASCII, drops a trailing `;1', and converts `;' to `.'.
1830 no name translation is done. See
1837 but also apply Acorn extensions if present.
1840 For non-Rock Ridge volumes, give all files the indicated mode.
1841 (Default: read permission for everybody.)
1842 Since Linux 2.1.37 one no longer needs to specify the mode in
1843 decimal. (Octal is indicated by a leading 0.)
1846 Also show hidden and associated files.
1847 (If the ordinary files and the associated or hidden files have
1848 the same filenames, this may make the ordinary files inaccessible.)
1850 .BR block= { 512 | 1024 | 2048 }
1851 Set the block size to the indicated value.
1855 .BR conv= { a [ uto ]| b [ inary ]| m [ text ]| t [ ext ]}
1858 Since Linux 1.3.54 this option has no effect anymore.
1859 (And non-binary settings used to be very dangerous,
1860 possibly leading to silent data corruption.)
1863 If the high byte of the file length contains other garbage,
1864 set this mount option to ignore the high order bits of the file length.
1865 This implies that a file cannot be larger than 16MB.
1868 Select number of session on multisession CD. (Since 2.3.4.)
1871 Session begins from sector xxx. (Since 2.3.4.)
1873 The following options are the same as for vfat and specifying them only makes
1874 sense when using discs encoded using Microsoft's Joliet extensions.
1876 .BI iocharset= value
1877 Character set to use for converting 16 bit Unicode characters on CD
1878 to 8 bit characters. The default is iso8859-1.
1881 Convert 16 bit Unicode characters on CD to UTF-8.
1883 .SH "Mount options for jfs"
1886 Character set to use for converting from Unicode to ASCII. The default is
1887 to do no conversion. Use
1889 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in
1895 Resize the volume to
1897 blocks. JFS only supports growing a volume, not shrinking it. This option
1898 is only valid during a remount, when the volume is mounted read-write. The
1900 keyword with no value will grow the volume to the full size of the partition.
1903 Do not write to the journal. The primary use of this option is to allow
1904 for higher performance when restoring a volume from backup media. The
1905 integrity of the volume is not guaranteed if the system abnormally abends.
1908 Default. Commit metadata changes to the journal. Use this option to remount
1911 option was previously specified in order to restore normal behavior.
1913 .BR errors= { continue | remount-ro | panic }
1914 Define the behaviour when an error is encountered.
1915 (Either ignore errors and just mark the filesystem erroneous and continue,
1916 or remount the filesystem read-only, or panic and halt the system.)
1918 .BR noquota | quota | usrquota | grpquota
1919 These options are accepted but ignored.
1921 .SH "Mount options for minix"
1924 .SH "Mount options for msdos"
1925 See mount options for fat.
1928 filesystem detects an inconsistency, it reports an error and sets the file
1929 system read-only. The filesystem can be made writable again by remounting
1932 .SH "Mount options for ncpfs"
1934 .IR nfs ", the " ncpfs
1935 implementation expects a binary argument (a
1936 .IR "struct ncp_mount_data" )
1937 to the mount system call. This argument is constructed by
1939 and the current version of
1941 (2.12) does not know anything about ncpfs.
1943 .SH "Mount options for nfs and nfs4"
1944 See the options section of the
1946 man page (nfs-utils package must be installed).
1949 .IR nfs " and " nfs4
1950 implementation expects a binary argument (a
1951 .IR "struct nfs_mount_data" )
1952 to the mount system call. This argument is constructed by
1954 and the current version of
1956 (2.13) does not know anything about nfs and nfs4.
1958 .SH "Mount options for ntfs"
1961 Character set to use when returning file names.
1962 Unlike VFAT, NTFS suppresses names that contain
1963 nonconvertible characters. Deprecated.
1967 New name for the option earlier called
1972 Use UTF-8 for converting file names.
1974 .BR uni_xlate= { 0 | 1 | 2 }
1975 For 0 (or `no' or `false'), do not use escape sequences
1976 for unknown Unicode characters.
1977 For 1 (or `yes' or `true') or 2, use vfat-style 4-byte escape sequences
1978 starting with ":". Here 2 give a little-endian encoding
1979 and 1 a byteswapped bigendian encoding.
1982 If enabled (posix=1), the filesystem distinguishes between
1983 upper and lower case. The 8.3 alias names are presented as
1984 hard links instead of being suppressed. This option is obsolete.
1986 \fBuid=\fP\fIvalue\fP, \fBgid=\fP\fIvalue\fP and \fBumask=\fP\fIvalue\fP
1987 Set the file permission on the filesystem.
1988 The umask value is given in octal.
1989 By default, the files are owned by root and not readable by somebody else.
1991 .SH "Mount options for proc"
1993 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1994 These options are recognized, but have no effect as far as I can see.
1996 .SH "Mount options for ramfs"
1997 Ramfs is a memory based filesystem. Mount it and you have it. Unmount it
1998 and it is gone. Present since Linux 2.3.99pre4.
1999 There are no mount options.
2001 .SH "Mount options for reiserfs"
2002 Reiserfs is a journaling filesystem.
2005 Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem,
2006 using the 3.6 format for newly created objects. This filesystem will no
2007 longer be compatible with reiserfs 3.5 tools.
2009 .BR hash= { rupasov | tea | r5 | detect }
2010 Choose which hash function reiserfs will use to find files within directories.
2014 A hash invented by Yury Yu. Rupasov. It is fast and preserves locality,
2015 mapping lexicographically close file names to close hash values.
2016 This option should not be used, as it causes a high probability of hash
2020 A Davis-Meyer function implemented by Jeremy Fitzhardinge.
2021 It uses hash permuting bits in the name. It gets high randomness
2022 and, therefore, low probability of hash collisions at some CPU cost.
2023 This may be used if EHASHCOLLISION errors are experienced with the r5 hash.
2026 A modified version of the rupasov hash. It is used by default and is
2027 the best choice unless the filesystem has huge directories and
2028 unusual file-name patterns.
2033 to detect which hash function is in use by examining
2034 the filesystem being mounted, and to write this information into
2035 the reiserfs superblock. This is only useful on the first mount of
2036 an old format filesystem.
2039 .BR hashed_relocation
2040 Tunes the block allocator. This may provide performance improvements
2043 .BR no_unhashed_relocation
2044 Tunes the block allocator. This may provide performance improvements
2048 Disable the border allocator algorithm invented by Yury Yu. Rupasov.
2049 This may provide performance improvements in some situations.
2052 Disable journalling. This will provide slight performance improvements in
2053 some situations at the cost of losing reiserfs's fast recovery from crashes.
2054 Even with this option turned on, reiserfs still performs all journalling
2055 operations, save for actual writes into its journalling area. Implementation
2058 is a work in progress.
2061 By default, reiserfs stores small files and `file tails' directly into its
2062 tree. This confuses some utilities such as
2064 This option is used to disable packing of files into the tree.
2067 Replay the transactions which are in the journal, but do not actually
2068 mount the filesystem. Mainly used by
2072 A remount option which permits online expansion of reiserfs partitions.
2073 Instructs reiserfs to assume that the device has
2076 This option is designed for use with devices which are under logical
2077 volume management (LVM).
2080 utility which can be obtained from
2081 .IR ftp://ftp.namesys.com/pub/reiserfsprogs .
2084 Enable Extended User Attributes. See the
2089 Enable POSIX Access Control Lists. See the
2093 .BR barrier=none " / " barrier=flush "
2094 This enables/disables the use of write barriers in the journaling code.
2095 barrier=none disables it, barrier=flush enables it. Write barriers enforce
2096 proper on-disk ordering of journal commits, making volatile disk write caches
2097 safe to use, at some performance penalty. The reiserfs filesystem does not
2098 enable write barriers by default. Be sure to enable barriers unless your disks
2099 are battery-backed one way or another. Otherwise you risk filesystem
2100 corruption in case of power failure.
2102 .SH "Mount options for romfs"
2105 .SH "Mount options for squashfs"
2108 .SH "Mount options for smbfs"
2110 .IR nfs ", the " smbfs
2111 implementation expects a binary argument (a
2112 .IR "struct smb_mount_data" )
2113 to the mount system call. This argument is constructed by
2115 and the current version of
2117 (2.12) does not know anything about smbfs.
2119 .SH "Mount options for sysv"
2122 .SH "Mount options for tmpfs"
2125 Override default maximum size of the filesystem.
2126 The size is given in bytes, and rounded up to entire pages.
2127 The default is half of the memory. The size parameter also accepts a suffix %
2128 to limit this tmpfs instance to that percentage of your physical RAM:
2129 the default, when neither size nor nr_blocks is specified, is size=50%
2132 The same as size, but in blocks of PAGE_CACHE_SIZE
2135 The maximum number of inodes for this instance. The default
2136 is half of the number of your physical RAM pages, or (on a
2137 machine with highmem) the number of lowmem RAM pages,
2138 whichever is the lower.
2140 The tmpfs mount options for sizing (
2150 for Ki, Mi, Gi (binary kilo, mega and giga) and can be changed on remount.
2154 Set initial permissions of the root directory.
2162 .B mpol=[default|prefer:Node|bind:NodeList|interleave|interleave:NodeList]
2163 Set the NUMA memory allocation policy for all files in that
2164 instance (if the kernel CONFIG_NUMA is enabled) - which can be adjusted on the
2165 fly via 'mount -o remount ...'
2169 prefers to allocate memory from the local node
2172 prefers to allocate memory from the given Node
2175 allocates memory only from nodes in NodeList
2178 prefers to allocate from each node in turn
2180 .B interleave:NodeList
2181 allocates from each node of NodeList in turn.
2183 The NodeList format is a comma-separated list of decimal numbers and ranges, a
2184 range being two hyphen-separated decimal numbers, the smallest and largest node
2185 numbers in the range. For example, mpol=bind:0-3,5,7,9-15
2187 Note that trying to mount a tmpfs with an mpol option will fail if the
2188 running kernel does not support NUMA; and will fail if its nodelist
2189 specifies a node which is not online. If your system relies on that
2190 tmpfs being mounted, but from time to time runs a kernel built without
2191 NUMA capability (perhaps a safe recovery kernel), or with fewer nodes
2192 online, then it is advisable to omit the mpol option from automatic
2193 mount options. It can be added later, when the tmpfs is already mounted
2194 on MountPoint, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.
2196 .SH "Mount options for ubifs"
2197 UBIFS is a flash file system which works on top of UBI volumes. Note that
2200 is not supported and is always turned off.
2202 The device name may be specified as
2230 separator may be used instead of
2233 The following mount options are available:
2236 Enable bulk-read. VFS read-ahead is disabled because it slows down the file
2237 system. Bulk-Read is an internal optimization. Some flashes may read faster if
2238 the data are read at one go, rather than at several read requests. For
2239 example, OneNAND can do "read-while-load" if it reads more than one NAND page.
2242 Do not bulk-read. This is the default.
2245 Check data CRC-32 checksums. This is the default.
2247 .BR no_chk_data_crc.
2248 Do not check data CRC-32 checksums. With this option, the filesystem does not
2249 check CRC-32 checksum for data, but it does check it for the internal indexing
2250 information. This option only affects reading, not writing. CRC-32 is always
2251 calculated when writing the data.
2253 .BR compr= { none | lzo | zlib }
2254 Select the default compressor which is used when new files are written. It is
2255 still possible to read compressed files if mounted with the
2259 .SH "Mount options for udf"
2260 udf is the "Universal Disk Format" filesystem defined by the Optical
2261 Storage Technology Association, and is often used for DVD-ROM.
2266 Set the default group.
2269 Set the default umask.
2270 The value is given in octal.
2273 Set the default user.
2276 Show otherwise hidden files.
2279 Show deleted files in lists.
2282 Unset strict conformance.
2288 Set the NLS character set.
2291 Set the block size. (May not work unless 2048.)
2294 Skip volume sequence recognition.
2297 Set the CDROM session counting from 0. Default: last session.
2300 Override standard anchor location. Default: 256.
2303 Override the VolumeDesc location. (unused)
2306 Override the PartitionDesc location. (unused)
2309 Set the last block of the filesystem.
2312 Override the fileset block location. (unused)
2315 Override the root directory location. (unused)
2317 .SH "Mount options for ufs"
2320 UFS is a filesystem widely used in different operating systems.
2321 The problem are differences among implementations. Features of some
2322 implementations are undocumented, so its hard to recognize the
2323 type of ufs automatically.
2324 That's why the user must specify the type of ufs by mount option.
2325 Possible values are:
2329 Old format of ufs, this is the default, read only.
2330 (Don't forget to give the \-r option.)
2333 For filesystems created by a BSD-like system (NetBSD,FreeBSD,OpenBSD).
2336 Used in FreeBSD 5.x supported as read-write.
2342 For filesystems created by SunOS or Solaris on Sparc.
2345 For filesystems created by Solaris on x86.
2348 For filesystems created by HP-UX, read-only.
2351 For filesystems created by NeXTStep (on NeXT station) (currently read only).
2354 For NextStep CDROMs (block_size == 2048), read-only.
2357 For filesystems created by OpenStep (currently read only).
2358 The same filesystem type is also used by Mac OS X.
2363 Set behaviour on error:
2367 If an error is encountered, cause a kernel panic.
2369 .RB [ lock | umount | repair ]
2370 These mount options don't do anything at present;
2371 when an error is encountered only a console message is printed.
2374 .SH "Mount options for umsdos"
2375 See mount options for msdos.
2378 option is explicitly killed by
2381 .SH "Mount options for vfat"
2382 First of all, the mount options for
2387 option is explicitly killed by
2389 Furthermore, there are
2392 Translate unhandled Unicode characters to special escaped sequences.
2393 This lets you backup and restore filenames that are created with any
2394 Unicode characters. Without this option, a '?' is used when no
2395 translation is possible. The escape character is ':' because it is
2396 otherwise illegal on the vfat filesystem. The escape sequence
2397 that gets used, where u is the unicode character,
2398 is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
2401 Allow two files with names that only differ in case.
2402 This option is obsolete.
2405 First try to make a short name without sequence number,
2410 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the
2411 console. It can be enabled for the filesystem with this option or disabled
2412 with utf8=0, utf8=no or utf8=false. If `uni_xlate' gets set, UTF8 gets
2415 .BR shortname= { lower | win95 | winnt | mixed }
2417 Defines the behaviour for creation and display of filenames which fit into
2418 8.3 characters. If a long name for a file exists, it will always be
2419 preferred display. There are four modes:
2424 Force the short name to lower case upon display; store a long name when
2425 the short name is not all upper case.
2428 Force the short name to upper case upon display; store a long name when
2429 the short name is not all upper case.
2432 Display the shortname as is; store a long name when the short name is
2433 not all lower case or all upper case.
2436 Display the short name as is; store a long name when the short name is not
2437 all upper case. This mode is the default since Linux 2.6.32.
2441 .SH "Mount options for usbfs"
2443 \fBdevuid=\fP\fIuid\fP and \fBdevgid=\fP\fIgid\fP and \fBdevmode=\fP\fImode\fP
2444 Set the owner and group and mode of the device files in the usbfs filesystem
2445 (default: uid=gid=0, mode=0644). The mode is given in octal.
2447 \fBbusuid=\fP\fIuid\fP and \fBbusgid=\fP\fIgid\fP and \fBbusmode=\fP\fImode\fP
2448 Set the owner and group and mode of the bus directories in the usbfs
2449 filesystem (default: uid=gid=0, mode=0555). The mode is given in octal.
2451 \fBlistuid=\fP\fIuid\fP and \fBlistgid=\fP\fIgid\fP and \fBlistmode=\fP\fImode\fP
2452 Set the owner and group and mode of the file
2454 (default: uid=gid=0, mode=0444). The mode is given in octal.
2456 .SH "Mount options for xenix"
2459 .SH "Mount options for xfs"
2462 Sets the buffered I/O end-of-file preallocation size when
2463 doing delayed allocation writeout (default size is 64KiB).
2464 Valid values for this option are page size (typically 4KiB)
2465 through to 1GiB, inclusive, in power-of-2 increments.
2468 The options enable/disable (default is enabled) an "opportunistic"
2469 improvement to be made in the way inline extended attributes are
2471 When the new form is used for the first time (by setting or
2472 removing extended attributes) the on-disk superblock feature
2473 bit field will be updated to reflect this format being in use.
2476 Enables the use of block layer write barriers for writes into
2477 the journal and unwritten extent conversion. This allows for
2478 drive level write caching to be enabled, for devices that
2479 support write barriers.
2482 Enable the DMAPI (Data Management API) event callouts.
2487 .BR grpid | bsdgroups " and " nogrpid | sysvgroups
2488 These options define what group ID a newly created file gets.
2489 When grpid is set, it takes the group ID of the directory in
2490 which it is created; otherwise (the default) it takes the fsgid
2491 of the current process, unless the directory has the setgid bit
2492 set, in which case it takes the gid from the parent directory,
2493 and also gets the setgid bit set if it is a directory itself.
2495 .BI ihashsize= value
2496 Sets the number of hash buckets available for hashing the
2497 in-memory inodes of the specified mount point. If a value
2498 of zero is used, the value selected by the default algorithm
2499 will be displayed in
2503 When inode clusters are emptied of inodes, keep them around
2504 on the disk (ikeep) - this is the traditional XFS behaviour
2505 and is still the default for now. Using the noikeep option,
2506 inode clusters are returned to the free space pool.
2509 Indicates that XFS is allowed to create inodes at any location
2510 in the filesystem, including those which will result in inode
2511 numbers occupying more than 32 bits of significance. This is
2512 provided for backwards compatibility, but causes problems for
2513 backup applications that cannot handle large inode numbers.
2515 .BR largeio | nolargeio
2518 is specified, the optimal I/O reported in
2521 will be as small as possible to allow user
2522 applications to avoid inefficient read/modify/write I/O.
2525 is specified, a filesystem that has a
2530 value (in bytes) in st_blksize. If the
2531 filesystem does not have a
2533 specified but does specify
2538 (in bytes) will be returned
2540 If neither of these two options are specified, then filesystem
2546 Set the number of in-memory log buffers. Valid numbers range
2548 The default value is 8 buffers for any recent kernel.
2551 Set the size of each in-memory log buffer.
2552 Size may be specified in bytes, or in kilobytes with a "k" suffix.
2553 Valid sizes for version 1 and version 2 logs are 16384 (16k) and
2554 32768 (32k). Valid sizes for version 2 logs also include
2555 65536 (64k), 131072 (128k) and 262144 (256k).
2556 The default value for any recent kernel is 32768.
2558 \fBlogdev=\fP\fIdevice\fP and \fBrtdev=\fP\fIdevice\fP
2559 Use an external log (metadata journal) and/or real-time device.
2560 An XFS filesystem has up to three parts: a data section, a log section,
2561 and a real-time section.
2562 The real-time section is optional, and the log section can be separate
2563 from the data section or contained within it.
2567 .BI mtpt= mountpoint
2570 option. The value specified here will be
2571 included in the DMAPI mount event, and should be the path of
2572 the actual mountpoint that is used.
2575 Data allocations will not be aligned at stripe unit boundaries.
2578 Access timestamps are not updated when a file is read.
2581 The filesystem will be mounted without running log recovery.
2582 If the filesystem was not cleanly unmounted, it is likely to
2583 be inconsistent when mounted in
2586 Some files or directories may not be accessible because of this.
2589 must be mounted read-only or the mount will fail.
2592 Don't check for double mounted filesystems using the filesystem uuid.
2593 This is useful to mount LVM snapshot volumes.
2596 Make O_SYNC writes implement true O_SYNC. WITHOUT this option,
2597 Linux XFS behaves as if an
2600 which will make writes to files opened with the O_SYNC flag set
2601 behave as if the O_DSYNC flag had been used instead.
2602 This can result in better performance without compromising
2604 However if this option is not in effect, timestamp updates from
2605 O_SYNC writes can be lost if the system crashes.
2606 If timestamp updates are critical, use the
2610 .BR uquota | usrquota | uqnoenforce | quota
2611 User disk quota accounting enabled, and limits (optionally)
2614 for further details.
2616 .BR gquota | grpquota | gqnoenforce
2617 Group disk quota accounting enabled and limits (optionally)
2620 for further details.
2622 .BR pquota | prjquota | pqnoenforce
2623 Project disk quota accounting enabled and limits (optionally)
2626 for further details.
2628 \fBsunit=\fP\fIvalue\fP and \fBswidth=\fP\fIvalue\fP
2629 Used to specify the stripe unit and width for a RAID device or a stripe
2632 must be specified in 512-byte block units.
2633 If this option is not specified and the filesystem was made on a stripe
2634 volume or the stripe width or unit were specified for the RAID device at
2635 mkfs time, then the mount system call will restore the value from the
2637 For filesystems that are made directly on RAID devices, these options can be
2638 used to override the information in the superblock if the underlying disk
2639 layout changes after the filesystem has been created.
2642 option is required if the
2644 option has been specified,
2645 and must be a multiple of the
2650 Data allocations will be rounded up to stripe width boundaries
2651 when the current end of file is being extended and the file
2652 size is larger than the stripe width size.
2654 .SH "Mount options for xiafs"
2655 None. Although nothing is wrong with xiafs, it is not used much,
2656 and is not maintained. Probably one shouldn't use it.
2657 Since Linux version 2.1.21 xiafs is no longer part of the kernel source.
2659 .SH "THE LOOP DEVICE"
2660 One further possible type is a mount via the loop device. For example,
2664 .B "mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop"
2667 will set up the loop device
2669 to correspond to the file
2671 and then mount this device on
2674 If no explicit loop device is mentioned
2675 (but just an option `\fB\-o loop\fP' is given), then
2677 will try to find some unused loop device and use that, for example
2680 .B "mount /tmp/disk.img /mnt -o loop"
2685 creates a loop device from a regular file if a filesystem type is
2686 not specified or the filesystem is known for libblkid, for example:
2689 .B "mount /tmp/disk.img /mnt"
2691 .B "mount -t ext3 /tmp/disk.img /mnt"
2694 This type of mount knows about four options, namely
2695 .BR loop ", " offset ", " sizelimit " and " encryption ,
2696 that are really options to
2698 (These options can be used in addition to those specific
2699 to the filesystem type.)
2701 Since Linux 2.6.25 is supported auto-destruction of loop devices and
2702 then any loop device allocated by
2709 You can also free a loop device by hand, using `losetup -d' or `umount -d`.
2713 has the following return codes (the bits can be ORed):
2719 incorrect invocation or permissions
2722 system error (out of memory, cannot fork, no more loop devices)
2733 problems writing or locking /etc/mtab
2739 some mount succeeded
2742 The syntax of external mount helpers is:
2745 .BI /sbin/mount. <suffix>
2754 where the <type> is filesystem type and \-sfnvo options have same meaning like
2755 standard mount options. The \-t option is used for filesystems with subtypes
2756 support (for example /sbin/mount.fuse -t fuse.sshfs).
2764 table of mounted filesystems
2773 a list of filesystem types to try
2791 It is possible for a corrupted filesystem to cause a crash.
2793 Some Linux filesystems don't support
2794 .B "\-o sync and \-o dirsync"
2795 (the ext2, ext3, fat and vfat filesystems
2797 support synchronous updates (a la BSD) when mounted with the
2803 may not be able to change mount parameters (all
2804 .IR ext2fs -specific
2807 are changeable with a remount, for example, but you can't change
2814 Mount by label or uuid will work only if your devices have the names listed in
2815 .IR /proc/partitions .
2816 In particular, it may well fail if the kernel was compiled with devfs
2817 but devfs is not mounted.
2819 It is possible that files
2823 don't match. The first file is based only on the mount command options, but the
2824 content of the second file also depends on the kernel and others settings (e.g.
2825 remote NFS server. In particular case the mount command may reports unreliable
2826 information about a NFS mount point and the /proc/mounts file usually contains
2827 more reliable information.)
2829 Checking files on NFS filesystem referenced by file descriptors (i.e. the
2833 families of functions) may lead to inconsistent result due to the lack of
2834 consistency check in kernel even if noac is used.
2838 command existed in Version 5 AT&T UNIX.
2840 The mount command is part of the util-linux package and is available from
2841 ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
projects / framework / base / util-linux-ng.git / blob