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.
538 Tolerate sloppy mount options rather than failing. This will ignore
539 mount options not supported by a filesystem type. Not all filesystems
540 support this option. This option exists for support of the Linux
541 autofs\-based automounter.
542 .IP "\fB\-r, \-\-read\-only\fP"
543 Mount the filesystem read-only. A synonym is
546 Note that, depending on the filesystem type, state and kernel behavior, the
547 system may still write to the device. For example, Ext3 or ext4 will replay its
548 journal if the filesystem is dirty. To prevent this kind of write access, you
549 may want to mount ext3 or ext4 filesystem with "ro,noload" mount options or
550 set the block device to read-only mode, see command
552 .IP "\fB\-w, \-\-rw\fP"
553 Mount the filesystem read/write. This is the default. A synonym is
555 .IP "\fB\-L \fIlabel\fP"
556 Mount the partition that has the specified
558 .IP "\fB\-U \fIuuid\fP"
559 Mount the partition that has the specified
561 These two options require the file
563 (present since Linux 2.1.116) to exist.
564 .IP "\fB\-t, \-\-types \fIvfstype\fP"
565 The argument following the
567 is used to indicate the filesystem type. The filesystem types which are
568 currently supported include:
612 Note that coherent, sysv and xenix are equivalent and that
616 will be removed at some point in the future \(em use
618 instead. Since kernel version 2.1.21 the types
622 do not exist anymore. Earlier,
626 Note, the real list of all supported filesystems depends on your
633 support filesystem subtypes. The subtype is defined by '.subtype' suffix. For
634 example 'fuse.sshfs'. It's recommended to use subtype notation rather than add
635 any prefix to the mount source (for example 'sshfs#example.com' is
638 For most types all the
640 program has to do is issue a simple
642 system call, and no detailed knowledge of the filesystem type is required.
643 For a few types however (like nfs, nfs4, cifs, smbfs, ncpfs) ad hoc code is
644 necessary. The nfs, nfs4, cifs, smbfs, and ncpfs filesystems
645 have a separate mount program. In order to make it possible to
646 treat all types in a uniform way, mount will execute the program
647 .BI /sbin/mount. TYPE
648 (if that exists) when called with type
650 Since various versions of the
652 program have different calling conventions,
654 may have to be a shell script that sets up the desired call.
658 option is given, or if the
660 type is specified, mount will try to guess the desired type.
661 Mount uses the blkid library for guessing the filesystem
662 type; if that does not turn up anything that looks familiar,
663 mount will try to read the file
664 .IR /etc/filesystems ,
665 or, if that does not exist,
666 .IR /proc/filesystems .
667 All of the filesystem types listed there will be tried,
668 except for those that are labeled "nodev" (e.g.,
675 ends in a line with a single * only, mount will read
681 type may be useful for user-mounted floppies.
684 can be useful to change the probe order (e.g., to try vfat before msdos
685 or ext3 before ext2) or if you use a kernel module autoloader.
687 More than one type may be specified in a comma separated
688 list. The list of filesystem types can be prefixed with
690 to specify the filesystem types on which no action should be taken.
691 (This can be meaningful with the
693 option.) For example, the command:
697 .B "mount \-a \-t nomsdos,ext"
700 mounts all filesystems except those of type
705 .IP "\fB\-O, \-\-test-opts \fIopts\fP"
706 Used in conjunction with
708 to limit the set of filesystems to which the
712 in this regard except that it is useless except in the context of
714 For example, the command:
718 .B "mount \-a \-O no_netdev"
721 mounts all filesystems except those which have the option
723 specified in the options field in the
729 in that each option is matched exactly; a leading
731 at the beginning of one option does not negate the rest.
737 options are cumulative in effect; that is, the command
740 .B "mount \-a \-t ext2 \-O _netdev"
743 mounts all ext2 filesystems with the _netdev option, not all filesystems
744 that are either ext2 or have the _netdev option specified.
746 .IP "\fB\-o, \-\-options \fIopts\fP"
747 Options are specified with a
749 flag followed by a comma separated string of options. For example:
753 .B "mount LABEL=mydisk \-o noatime,nouser"
757 For more details, see
758 .B FILESYSTEM INDEPENDENT MOUNT OPTIONS
760 .B FILESYSTEM SPECIFIC MOUNT OPTIONS
763 .IP "\fB\-B, \-\-bind\fP"
764 Remount a subtree somewhere else (so that its contents are available
765 in both places). See above.
766 .IP "\fB\-R, \-\-rbind\fP"
767 Remount a subtree and all possible submounts somewhere else (so that its
768 contents are available in both places). See above.
769 .IP "\fB\-M, \-\-move\fP"
770 Move a subtree to some other place. See above.
772 .SH FILESYSTEM INDEPENDENT MOUNT OPTIONS
773 Some of these options are only useful when they appear in the
777 Some of these options could be enabled or disabled by default
778 in the system kernel. To check the current setting see the options
781 The following options apply to any filesystem that is being
782 mounted (but not every filesystem actually honors them - e.g., the
784 option today has effect only for ext2, ext3, fat, vfat and ufs):
788 All I/O to the filesystem should be done asynchronously. (See also the
793 Do not use noatime feature, then the inode access time is controlled by kernel
794 defaults. See also the description for
801 Do not update inode access times on this filesystem (e.g., for faster
802 access on the news spool to speed up news servers).
805 Can be mounted with the
810 Can only be mounted explicitly (i.e., the
812 option will not cause the filesystem to be mounted).
814 \fBcontext=\fP\fIcontext\fP, \fBfscontext=\fP\fIcontext\fP, \fBdefcontext=\fP\fIcontext\fP and \fBrootcontext=\fP\fIcontext\fP
817 option is useful when mounting filesystems that do not support
818 extended attributes, such as a floppy or hard disk formatted with VFAT, or
819 systems that are not normally running under SELinux, such as an ext3 formatted
820 disk from a non-SELinux workstation. You can also use
822 on filesystems you do not trust, such as a floppy. It also helps in compatibility with
823 xattr-supporting filesystems on earlier 2.4.<x> kernel versions. Even where
824 xattrs are supported, you can save time not having to label every file by
825 assigning the entire disk one security context.
827 A commonly used option for removable media is
828 .BR context="system_u:object_r:removable_t" .
830 Two other options are
834 both of which are mutually exclusive of the context option. This means you
835 can use fscontext and defcontext with each other, but neither can be used with
840 option works for all filesystems, regardless of their xattr
841 support. The fscontext option sets the overarching filesystem label to a
842 specific security context. This filesystem label is separate from the
843 individual labels on the files. It represents the entire filesystem for
844 certain kinds of permission checks, such as during mount or file creation.
845 Individual file labels are still obtained from the xattrs on the files
846 themselves. The context option actually sets the aggregate context that
847 fscontext provides, in addition to supplying the same label for individual
850 You can set the default security context for unlabeled files using
852 option. This overrides the value set for unlabeled files in the policy and requires a
853 filesystem that supports xattr labeling.
857 option allows you to explicitly label the root inode of a FS being mounted
858 before that FS or inode because visible to userspace. This was found to be
859 useful for things like stateless linux.
861 Note that kernel rejects any remount request that includes the context
862 option even if unchanged from the current context.
864 .B Warning that \fIcontext\fP value might contains comma
865 and in this case the value has to be properly quoted otherwise
867 will interpret the comma as separator between mount options. Don't forget that
868 shell strips off quotes and
869 .BR "double quoting is required" ,
874 mount -t tmpfs none /mnt \-o 'context="system_u:object_r:tmp_t:s0:c127,c456",noexec'
878 For more details, see
885 .BR rw ", " suid ", " dev ", " exec ", " auto ", " nouser ", and " async.
888 Interpret character or block special devices on the filesystem.
891 Do not interpret character or block special devices on the file
895 Update directory inode access times on this filesystem. This is the default.
898 Do not update directory inode access times on this filesystem.
901 All directory updates within the filesystem should be done synchronously.
902 This affects the following system calls: creat, link, unlink, symlink,
903 mkdir, rmdir, mknod and rename.
906 Permit execution of binaries.
909 Do not allow direct execution of any binaries on the mounted filesystem.
910 (Until recently it was possible to run binaries anyway using a command like
911 /lib/ld*.so /mnt/binary. This trick fails since Linux 2.4.25 / 2.6.0.)
914 Allow an ordinary (i.e., non-root) user to mount the filesystem if one
915 of his groups matches the group of the device.
916 This option implies the options
917 .BR nosuid " and " nodev
918 (unless overridden by subsequent options, as in the option line
919 .BR group,dev,suid ).
922 Every time the inode is modified, the i_version field will be incremented.
925 Do not increment the i_version inode field.
928 Allow mandatory locks on this filesystem. See
932 Do not allow mandatory locks on this filesystem.
935 The filesystem resides on a device that requires network access
936 (used to prevent the system from attempting to mount these filesystems
937 until the network has been enabled on the system).
940 Do not report errors for this device if it does not exist.
943 Update inode access times relative to modify or change time. Access
944 time is only updated if the previous access time was earlier than the
945 current modify or change time. (Similar to noatime, but doesn't break
946 mutt or other applications that need to know if a file has been read
947 since the last time it was modified.)
949 Since Linux 2.6.30, the kernel defaults to the behavior provided by this
952 was specified), and the
954 option is required to obtain traditional semantics. In addition, since Linux
955 2.6.30, the file's last access time is always updated if it is more than 1
961 feature. See also the
966 Allows to explicitly requesting full atime updates. This makes it
967 possible for kernel to defaults to
971 but still allow userspace to override it. For more details about the default
972 system mount options see /proc/mounts.
975 Use the kernel's default behaviour for inode access time updates.
978 Allow set-user-identifier or set-group-identifier bits to take
982 Do not allow set-user-identifier or set-group-identifier bits to take
983 effect. (This seems safe, but is in fact rather unsafe if you have
984 suidperl(1) installed.)
987 Turn on the silent flag.
990 Turn off the silent flag.
993 Allow an ordinary (i.e., non-root) user to mount the filesystem if he
994 is the owner of the device.
995 This option implies the options
996 .BR nosuid " and " nodev
997 (unless overridden by subsequent options, as in the option line
998 .BR owner,dev,suid ).
1001 Attempt to remount an already-mounted filesystem. This is commonly
1002 used to change the mount flags for a filesystem, especially to make a
1003 readonly filesystem writable. It does not change device or mount point.
1005 The remount functionality follows the standard way how the mount command works
1006 with options from fstab. It means the mount command doesn't read fstab (or
1011 are fully specified.
1013 .BR "mount -o remount,rw /dev/foo /dir"
1015 After this call all old mount options are replaced and arbitrary stuff from
1016 fstab is ignored, except the loop= option which is internally generated and
1017 maintained by the mount command.
1019 .BR "mount -o remount,rw /dir"
1021 After this call mount reads fstab (or mtab) and merges these options with
1022 options from command line (
1027 Mount the filesystem read-only.
1030 Mount the filesystem read-write.
1033 All I/O to the filesystem should be done synchronously. In case of media with limited number of write cycles
1034 (e.g. some flash drives) "sync" may cause life-cycle shortening.
1037 Allow an ordinary user to mount the filesystem.
1038 The name of the mounting user is written to mtab so that he can unmount
1039 the filesystem again.
1040 This option implies the options
1041 .BR noexec ", " nosuid ", and " nodev
1042 (unless overridden by subsequent options, as in the option line
1043 .BR user,exec,dev,suid ).
1046 Forbid an ordinary (i.e., non-root) user to mount the filesystem.
1047 This is the default.
1050 Allow every user to mount and unmount the filesystem.
1051 This option implies the options
1052 .BR noexec ", " nosuid ", and " nodev
1053 (unless overridden by subsequent options, as in the option line
1054 .BR users,exec,dev,suid ).
1056 .SH "FILESYSTEM SPECIFIC MOUNT OPTIONS"
1057 The following options apply only to certain filesystems.
1058 We sort them by filesystem. They all follow the
1062 What options are supported depends a bit on the running kernel.
1063 More info may be found in the kernel source subdirectory
1064 .IR Documentation/filesystems .
1066 .SH "Mount options for adfs"
1068 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1069 Set the owner and group of the files in the filesystem (default: uid=gid=0).
1071 \fBownmask=\fP\fIvalue\fP and \fBothmask=\fP\fIvalue\fP
1072 Set the permission mask for ADFS 'owner' permissions and 'other' permissions,
1073 respectively (default: 0700 and 0077, respectively).
1075 .IR /usr/src/linux/Documentation/filesystems/adfs.txt .
1076 .SH "Mount options for affs"
1078 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1079 Set the owner and group of the root of the filesystem (default: uid=gid=0,
1084 without specified value, the uid and gid of the current process are taken).
1086 \fBsetuid=\fP\fIvalue\fP and \fBsetgid=\fP\fIvalue\fP
1087 Set the owner and group of all files.
1090 Set the mode of all files to
1092 disregarding the original permissions.
1093 Add search permission to directories that have read permission.
1094 The value is given in octal.
1097 Do not allow any changes to the protection bits on the filesystem.
1100 Set uid and gid of the root of the filesystem to the uid and gid
1101 of the mount point upon the first sync or umount, and then
1102 clear this option. Strange...
1105 Print an informational message for each successful mount.
1108 Prefix used before volume name, when following a link.
1111 Prefix (of length at most 30) used before '/' when following a symbolic link.
1114 (Default: 2.) Number of unused blocks at the start of the device.
1117 Give explicitly the location of the root block.
1120 Give blocksize. Allowed values are 512, 1024, 2048, 4096.
1122 .BR grpquota | noquota | quota | usrquota
1123 These options are accepted but ignored.
1124 (However, quota utilities may react to such strings in
1127 .SH "Mount options for cifs"
1128 See the options section of the
1130 man page (cifs-utils package must be installed).
1132 .SH "Mount options for coherent"
1135 .SH "Mount options for debugfs"
1136 The debugfs filesystem is a pseudo filesystem, traditionally mounted on
1137 .IR /sys/kernel/debug .
1139 .\" present since 2.6.11
1140 There are no mount options.
1142 .SH "Mount options for devpts"
1143 The devpts filesystem is a pseudo filesystem, traditionally mounted on
1145 In order to acquire a pseudo terminal, a process opens
1147 the number of the pseudo terminal is then made available to the process
1148 and the pseudo terminal slave can be accessed as
1149 .IR /dev/pts/ <number>.
1151 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1152 This sets the owner or the group of newly created PTYs to
1153 the specified values. When nothing is specified, they will
1154 be set to the UID and GID of the creating process.
1155 For example, if there is a tty group with GID 5, then
1157 will cause newly created PTYs to belong to the tty group.
1160 Set the mode of newly created PTYs to the specified value.
1161 The default is 0600.
1166 makes "mesg y" the default on newly created PTYs.
1169 Create a private instance of devpts filesystem, such that
1170 indices of ptys allocated in this new instance are
1171 independent of indices created in other instances of devpts.
1173 All mounts of devpts without this
1175 option share the same set of pty indices (i.e legacy mode).
1176 Each mount of devpts with the
1178 option has a private set of pty indices.
1180 This option is mainly used to support containers in the
1181 linux kernel. It is implemented in linux kernel versions
1182 starting with 2.6.29. Further, this mount option is valid
1183 only if CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the
1184 kernel configuration.
1186 To use this option effectively,
1188 must be a symbolic link to
1191 .IR Documentation/filesystems/devpts.txt
1192 in the linux kernel source tree for details.
1196 Set the mode for the new
1198 device node in the devpts filesystem.
1200 With the support for multiple instances of devpts (see
1202 option above), each instance has a private
1204 node in the root of the devpts filesystem (typically
1207 For compatibility with older versions of the kernel, the
1208 default mode of the new
1212 specifies a more useful mode for the
1214 node and is highly recommended when the
1216 option is specified.
1218 This option is only implemented in linux kernel versions
1219 starting with 2.6.29. Further this option is valid only if
1220 CONFIG_DEVPTS_MULTIPLE_INSTANCES is enabled in the kernel
1223 .SH "Mount options for ext"
1225 Note that the `ext' filesystem is obsolete. Don't use it.
1226 Since Linux version 2.1.21 extfs is no longer part of the kernel source.
1228 .SH "Mount options for ext2"
1229 The `ext2' filesystem is the standard Linux filesystem.
1230 .\" Due to a kernel bug, it may be mounted with random mount options
1231 .\" (fixed in Linux 2.0.4).
1232 Since Linux 2.5.46, for most mount options the default
1233 is determined by the filesystem superblock. Set them with
1237 Support POSIX Access Control Lists (or not).
1238 .\" requires CONFIG_EXT2_FS_POSIX_ACL
1241 Set the behaviour for the
1245 behaviour is to return in the
1247 field the total number of blocks of the filesystem, while the
1249 behaviour (which is the default) is to subtract the overhead blocks
1250 used by the ext2 filesystem and not available for file storage. Thus
1253 % mount /k -o minixdf; df /k; umount /k
1254 Filesystem 1024-blocks Used Available Capacity Mounted on
1255 /dev/sda6 2630655 86954 2412169 3% /k
1256 % mount /k -o bsddf; df /k; umount /k
1257 Filesystem 1024-blocks Used Available Capacity Mounted on
1258 /dev/sda6 2543714 13 2412169 0% /k
1261 (Note that this example shows that one can add command line options
1262 to the options given in
1266 .BR check=none " or " nocheck
1267 No checking is done at mount time. This is the default. This is fast.
1268 It is wise to invoke
1270 every now and then, e.g. at boot time. The non-default behavior is unssuported
1271 (check=normal and check=strict options have been removed). Note that these mount options
1272 don't have to be supported if ext4 kernel driver is used for ext2 and ext3 filesystems.
1275 Print debugging info upon each (re)mount.
1277 .BR errors= { continue | remount-ro | panic }
1278 Define the behaviour when an error is encountered.
1279 (Either ignore errors and just mark the filesystem erroneous and continue,
1280 or remount the filesystem read-only, or panic and halt the system.)
1281 The default is set in the filesystem superblock, and can be
1285 .BR grpid | bsdgroups " and " nogrpid | sysvgroups
1286 These options define what group id a newly created file gets.
1289 is set, it takes the group id of the directory in which it is created;
1290 otherwise (the default) it takes the fsgid of the current process, unless
1291 the directory has the setgid bit set, in which case it takes the gid
1292 from the parent directory, and also gets the setgid bit set
1293 if it is a directory itself.
1295 .BR grpquota | noquota | quota | usrquota
1296 These options are accepted but ignored.
1299 Disables 32-bit UIDs and GIDs. This is for interoperability with older
1300 kernels which only store and expect 16-bit values.
1302 .BR oldalloc " or " orlov
1303 Use old allocator or Orlov allocator for new inodes. Orlov is default.
1305 \fBresgid=\fP\fIn\fP and \fBresuid=\fP\fIn\fP
1306 The ext2 filesystem reserves a certain percentage of the available
1307 space (by default 5%, see
1311 These options determine who can use the reserved blocks.
1312 (Roughly: whoever has the specified uid, or belongs to the specified group.)
1315 Instead of block 1, use block
1317 as superblock. This could be useful when the filesystem has been damaged.
1318 (Earlier, copies of the superblock would be made every 8192 blocks: in
1319 block 1, 8193, 16385, ... (and one got thousands of copies on
1320 a big filesystem). Since version 1.08,
1322 has a \-s (sparse superblock) option to reduce the number of backup
1323 superblocks, and since version 1.15 this is the default. Note
1324 that this may mean that ext2 filesystems created by a recent
1326 cannot be mounted r/w under Linux 2.0.*.)
1327 The block number here uses 1k units. Thus, if you want to use logical
1328 block 32768 on a filesystem with 4k blocks, use "sb=131072".
1330 .BR user_xattr | nouser_xattr
1331 Support "user." extended attributes (or not).
1332 .\" requires CONFIG_EXT2_FS_XATTR
1335 .SH "Mount options for ext3"
1336 The ext3 filesystem is a version of the ext2 filesystem which has been
1337 enhanced with journalling. It supports the same options as ext2 as
1338 well as the following additions:
1341 .\" Mount the filesystem in abort mode, as if a fatal error has occurred.
1344 Update the ext3 filesystem's journal to the current format.
1347 When a journal already exists, this option is ignored. Otherwise, it
1348 specifies the number of the inode which will represent the ext3 filesystem's
1349 journal file; ext3 will create a new journal, overwriting the old contents
1350 of the file whose inode number is
1353 .BR journal_dev=devnum
1354 When the external journal device's major/minor numbers
1355 have changed, this option allows the user to specify
1356 the new journal location. The journal device is
1357 identified through its new major/minor numbers encoded
1360 .BR norecovery / noload
1361 Don't load the journal on mounting. Note that
1362 if the filesystem was not unmounted cleanly,
1363 skipping the journal replay will lead to the
1364 filesystem containing inconsistencies that can
1365 lead to any number of problems.
1367 .BR data= { journal | ordered | writeback }
1368 Specifies the journalling mode for file data. Metadata is always journaled.
1369 To use modes other than
1371 on the root filesystem, pass the mode to the kernel as boot parameter, e.g.
1372 .IR rootflags=data=journal .
1376 All data is committed into the journal prior to being written into the
1380 This is the default mode. All data is forced directly out to the main file
1381 system prior to its metadata being committed to the journal.
1384 Data ordering is not preserved - data may be written into the main
1385 filesystem after its metadata has been committed to the journal.
1386 This is rumoured to be the highest-throughput option. It guarantees
1387 internal filesystem integrity, however it can allow old data to appear
1388 in files after a crash and journal recovery.
1391 .BR barrier=0 " / " barrier=1 "
1392 This enables/disables barriers. barrier=0 disables it, barrier=1 enables it.
1393 Write barriers enforce proper on-disk ordering of journal commits, making
1394 volatile disk write caches safe to use, at some performance penalty. The ext3
1395 filesystem does not enable write barriers by default. Be sure to enable
1396 barriers unless your disks are battery-backed one way or another. Otherwise
1397 you risk filesystem corruption in case of power failure.
1400 Sync all data and metadata every
1402 seconds. The default value is 5 seconds. Zero means default.
1405 Enable Extended User Attributes. See the
1410 Enable POSIX Access Control Lists. See the
1414 .SH "Mount options for ext4"
1415 The ext4 filesystem is an advanced level of the ext3 filesystem which
1416 incorporates scalability and reliability enhancements for supporting large
1420 .B journal_dev, noload, data, commit, orlov, oldalloc, [no]user_xattr
1421 .B [no]acl, bsddf, minixdf, debug, errors, data_err, grpid, bsdgroups, nogrpid
1422 .B sysvgroups, resgid, resuid, sb, quota, noquota, grpquota and usrquota
1423 are backwardly compatible with ext3 or ext2.
1425 .BR journal_checksum
1426 Enable checksumming of the journal transactions. This will allow the recovery
1427 code in e2fsck and the kernel to detect corruption in the kernel. It is a
1428 compatible change and will be ignored by older kernels.
1430 .BR journal_async_commit
1431 Commit block can be written to disk without waiting for descriptor blocks. If
1432 enabled older kernels cannot mount the device.
1433 This will enable 'journal_checksum' internally.
1436 Update the ext4 filesystem's journal to the current format.
1438 .BR barrier=0 " / " barrier=1 " / " barrier " / " nobarrier
1439 This enables/disables the use of write barriers in the jbd code. barrier=0
1440 disables, barrier=1 enables. This also requires an IO stack which can support
1441 barriers, and if jbd gets an error on a barrier write, it will disable again
1442 with a warning. Write barriers enforce proper on-disk ordering of journal
1443 commits, making volatile disk write caches safe to use, at some performance
1444 penalty. If your disks are battery-backed in one way or another, disabling
1445 barriers may safely improve performance. The mount options "barrier" and
1446 "nobarrier" can also be used to enable or disable barriers, for consistency
1447 with other ext4 mount options.
1449 The ext4 filesystem enables write barriers by default.
1451 .BI inode_readahead= n
1452 This tuning parameter controls the maximum number of inode table blocks that
1453 ext4's inode table readahead algorithm will pre-read into the buffer cache.
1454 The default value is 32 blocks.
1457 Number of filesystem blocks that mballoc will try to use for allocation size
1458 and alignment. For RAID5/6 systems this should be the number of data disks *
1459 RAID chunk size in filesystem blocks.
1462 Deferring block allocation until write-out time.
1465 Disable delayed allocation. Blocks are allocated when data is copied from user
1468 .BI max_batch_time= usec
1469 Maximum amount of time ext4 should wait for additional filesystem operations to
1470 be batch together with a synchronous write operation. Since a synchronous
1471 write operation is going to force a commit and then a wait for the I/O
1472 complete, it doesn't cost much, and can be a huge throughput win, we wait for a
1473 small amount of time to see if any other transactions can piggyback on the
1474 synchronous write. The algorithm used is designed to automatically tune for
1475 the speed of the disk, by measuring the amount of time (on average) that it
1476 takes to finish committing a transaction. Call this time the "commit time".
1477 If the time that the transaction has been running is less than the commit time,
1478 ext4 will try sleeping for the commit time to see if other operations will join
1479 the transaction. The commit time is capped by the max_batch_time, which
1480 defaults to 15000us (15ms). This optimization can be turned off entirely by
1481 setting max_batch_time to 0.
1483 .BI min_batch_time= usec
1484 This parameter sets the commit time (as described above) to be at least
1485 min_batch_time. It defaults to zero microseconds. Increasing this parameter
1486 may improve the throughput of multi-threaded, synchronous workloads on very
1487 fast disks, at the cost of increasing latency.
1489 .BI journal_ioprio= prio
1490 The I/O priority (from 0 to 7, where 0 is the highest priorty) which should be
1491 used for I/O operations submitted by kjournald2 during a commit operation.
1492 This defaults to 3, which is a slightly higher priority than the default I/O
1496 Simulate the effects of calling ext4_abort() for
1497 debugging purposes. This is normally used while
1498 remounting a filesystem which is already mounted.
1500 .BR auto_da_alloc | noauto_da_alloc
1501 Many broken applications don't use fsync() when
1502 replacing existing files via patterns such as
1504 fd = open("foo.new")/write(fd,..)/close(fd)/ rename("foo.new", "foo")
1508 fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).
1510 If auto_da_alloc is enabled, ext4 will detect the replace-via-rename and
1511 replace-via-truncate patterns and force that any delayed allocation blocks are
1512 allocated such that at the next journal commit, in the default data=ordered
1513 mode, the data blocks of the new file are forced to disk before the rename()
1514 operation is committed. This provides roughly the same level of guarantees as
1515 ext3, and avoids the "zero-length" problem that can happen when a system
1516 crashes before the delayed allocation blocks are forced to disk.
1518 .BR discard / nodiscard
1519 Controls whether ext4 should issue discard/TRIM commands to the underlying
1520 block device when blocks are freed. This is useful for SSD devices and
1521 sparse/thinly-provisioned LUNs, but it is off by default until sufficient
1522 testing has been done.
1525 Disables 32-bit UIDs and GIDs. This is for
1526 interoperability with older kernels which only
1527 store and expect 16-bit values.
1530 Allows to resize filesystem to the end of the last
1531 existing block group, further resize has to be done
1532 with resize2fs either online, or offline. It can be
1533 used only with conjunction with remount.
1535 .BR block_validity / noblock_validity
1536 This options allows to enables/disables the in-kernel facility for tracking
1537 filesystem metadata blocks within internal data structures. This allows multi-
1538 block allocator and other routines to quickly locate extents which might
1539 overlap with filesystem metadata blocks. This option is intended for debugging
1540 purposes and since it negatively affects the performance, it is off by default.
1542 .BR dioread_lock / dioread_nolock
1543 Controls whether or not ext4 should use the DIO read locking. If the
1544 dioread_nolock option is specified ext4 will allocate uninitialized extent
1545 before buffer write and convert the extent to initialized after IO completes.
1546 This approach allows ext4 code to avoid using inode mutex, which improves
1547 scalability on high speed storages. However this does not work with data
1548 journaling and dioread_nolock option will be ignored with kernel warning.
1549 Note that dioread_nolock code path is only used for extent-based files.
1550 Because of the restrictions this options comprises it is off by default
1551 (e.g. dioread_lock).
1554 Enable 64-bit inode version support. This option is off by default.
1556 .SH "Mount options for fat"
1559 is not a separate filesystem, but a common part of the
1566 .BR blocksize= { 512 | 1024 | 2048 }
1567 Set blocksize (default 512). This option is obsolete.
1569 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1570 Set the owner and group of all files.
1571 (Default: the uid and gid of the current process.)
1574 Set the umask (the bitmask of the permissions that are
1576 present). The default is the umask of the current process.
1577 The value is given in octal.
1580 Set the umask applied to directories only.
1581 The default is the umask of the current process.
1582 The value is given in octal.
1583 .\" Present since Linux 2.5.43.
1586 Set the umask applied to regular files only.
1587 The default is the umask of the current process.
1588 The value is given in octal.
1589 .\" Present since Linux 2.5.43.
1591 .BI allow_utime= value
1592 This option controls the permission check of mtime/atime.
1596 If current process is in group of file's group ID, you can change timestamp.
1599 Other users can change timestamp.
1601 The default is set from `dmask' option. (If the directory is writable,
1603 is also allowed. I.e. ~dmask & 022)
1607 checks current process is owner of the file, or it has
1608 CAP_FOWNER capability. But FAT filesystem doesn't have uid/gid on disk, so
1609 normal check is too unflexible. With this option you can relax it.
1613 Three different levels of pickyness can be chosen:
1617 Upper and lower case are accepted and equivalent, long name parts are
1619 .I verylongname.foobar
1622 leading and embedded spaces are accepted in each name part (name and extension).
1625 Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are
1626 rejected. This is the default.
1629 Like "normal", but names may not contain long parts and special characters
1630 that are sometimes used on Linux, but are not accepted by MS-DOS are
1631 rejected. (+, =, spaces, etc.)
1635 Sets the codepage for converting to shortname characters on FAT
1636 and VFAT filesystems. By default, codepage 437 is used.
1638 .BR conv= {b [ inary ]| t [ ext ]| a [ uto ]}
1641 filesystem can perform CRLF<-->NL (MS-DOS text format to UNIX text
1642 format) conversion in the kernel. The following conversion modes are
1647 no translation is performed. This is the default.
1650 CRLF<-->NL translation is performed on all files.
1653 CRLF<-->NL translation is performed on all files that don't have a
1654 "well-known binary" extension. The list of known extensions can be found at
1657 (as of 2.0, the list is: exe, com, bin, app, sys, drv, ovl, ovr, obj,
1658 lib, dll, pif, arc, zip, lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz,
1659 gz, tgz, deb, gif, bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl, dvi).
1661 Programs that do computed lseeks won't like in-kernel text conversion.
1662 Several people have had their data ruined by this translation. Beware!
1664 For filesystems mounted in binary mode, a conversion tool
1665 (fromdos/todos) is available. This option is obsolete.
1668 .BI cvf_format= module
1669 Forces the driver to use the CVF (Compressed Volume File) module
1671 instead of auto-detection. If the kernel supports kmod, the
1672 cvf_format=xxx option also controls on-demand CVF module loading.
1673 This option is obsolete.
1675 .BI cvf_option= option
1676 Option passed to the CVF module. This option is obsolete.
1681 flag. A version string and a list of filesystem parameters will be
1682 printed (these data are also printed if the parameters appear to be
1685 .BR fat= {12 | 16 | 32 }
1686 Specify a 12, 16 or 32 bit fat. This overrides
1687 the automatic FAT type detection routine. Use with caution!
1689 .BI iocharset= value
1690 Character set to use for converting between 8 bit characters
1691 and 16 bit Unicode characters. The default is iso8859-1.
1692 Long filenames are stored on disk in Unicode format.
1695 This option disables the conversion of timestamps
1696 between local time (as used by Windows on FAT) and UTC
1697 (which Linux uses internally). This is particularly
1698 useful when mounting devices (like digital cameras)
1699 that are set to UTC in order to avoid the pitfalls of
1705 flag. Attempts to chown or chmod files do not return errors,
1706 although they fail. Use with caution!
1709 If set, the execute permission bits of the file will be allowed only if
1710 the extension part of the name is .EXE, .COM, or .BAT. Not set by default.
1713 If set, ATTR_SYS attribute on FAT is handled as IMMUTABLE flag on Linux.
1717 If set, the filesystem will try to flush to disk more early than normal.
1721 Use the "free clusters" value stored on FSINFO. It'll
1722 be used to determine number of free clusters without
1723 scanning disk. But it's not used by default, because
1724 recent Windows don't update it correctly in some
1725 case. If you are sure the "free clusters" on FSINFO is
1726 correct, by this option you can avoid scanning disk.
1728 .BR dots ", " nodots ", " dotsOK= [ yes | no ]
1729 Various misguided attempts to force Unix or DOS conventions
1730 onto a FAT filesystem.
1732 .SH "Mount options for hfs"
1734 .BI creator= cccc ", type=" cccc
1735 Set the creator/type values as shown by the MacOS finder
1736 used for creating new files. Default values: '????'.
1738 .BI uid= n ", gid=" n
1739 Set the owner and group of all files.
1740 (Default: the uid and gid of the current process.)
1742 .BI dir_umask= n ", file_umask=" n ", umask=" n
1743 Set the umask used for all directories, all regular files, or all
1744 files and directories. Defaults to the umask of the current process.
1747 Select the CDROM session to mount.
1748 Defaults to leaving that decision to the CDROM driver.
1749 This option will fail with anything but a CDROM as underlying device.
1752 Select partition number n from the device.
1753 Only makes sense for CDROMs.
1754 Defaults to not parsing the partition table at all.
1757 Don't complain about invalid mount options.
1759 .SH "Mount options for hpfs"
1761 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1762 Set the owner and group of all files. (Default: the uid and gid
1763 of the current process.)
1766 Set the umask (the bitmask of the permissions that are
1768 present). The default is the umask of the current process.
1769 The value is given in octal.
1771 .BR case= { lower | asis }
1772 Convert all files names to lower case, or leave them.
1776 .BR conv= { binary | text | auto }
1779 delete some random CRs (in particular, all followed by NL)
1780 when reading a file.
1783 choose more or less at random between
1784 .BR conv=binary " and " conv=text .
1787 just read what is in the file. This is the default.
1790 Do not abort mounting when certain consistency checks fail.
1792 .SH "Mount options for iso9660"
1793 ISO 9660 is a standard describing a filesystem structure to be used
1794 on CD-ROMs. (This filesystem type is also seen on some DVDs. See also the
1800 filenames appear in a 8.3 format (i.e., DOS-like restrictions on filename
1801 length), and in addition all characters are in upper case. Also there is
1802 no field for file ownership, protection, number of links, provision for
1803 block/character devices, etc.
1805 Rock Ridge is an extension to iso9660 that provides all of these UNIX-like
1806 features. Basically there are extensions to each directory record that
1807 supply all of the additional information, and when Rock Ridge is in use,
1808 the filesystem is indistinguishable from a normal UNIX filesystem (except
1809 that it is read-only, of course).
1812 Disable the use of Rock Ridge extensions, even if available. Cf.\&
1816 Disable the use of Microsoft Joliet extensions, even if available. Cf.\&
1819 .BR check= { r [ elaxed ]| s [ trict ]}
1822 a filename is first converted to lower case before doing the lookup.
1823 This is probably only meaningful together with
1830 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
1831 Give all files in the filesystem the indicated user or group id,
1832 possibly overriding the information found in the Rock Ridge extensions.
1836 .BR map= { n [ ormal ]| o [ ff ]| a [ corn ]}
1837 For non-Rock Ridge volumes, normal name translation maps upper
1838 to lower case ASCII, drops a trailing `;1', and converts `;' to `.'.
1841 no name translation is done. See
1848 but also apply Acorn extensions if present.
1851 For non-Rock Ridge volumes, give all files the indicated mode.
1852 (Default: read permission for everybody.)
1853 Since Linux 2.1.37 one no longer needs to specify the mode in
1854 decimal. (Octal is indicated by a leading 0.)
1857 Also show hidden and associated files.
1858 (If the ordinary files and the associated or hidden files have
1859 the same filenames, this may make the ordinary files inaccessible.)
1861 .BR block= { 512 | 1024 | 2048 }
1862 Set the block size to the indicated value.
1866 .BR conv= { a [ uto ]| b [ inary ]| m [ text ]| t [ ext ]}
1869 Since Linux 1.3.54 this option has no effect anymore.
1870 (And non-binary settings used to be very dangerous,
1871 possibly leading to silent data corruption.)
1874 If the high byte of the file length contains other garbage,
1875 set this mount option to ignore the high order bits of the file length.
1876 This implies that a file cannot be larger than 16MB.
1879 Select number of session on multisession CD. (Since 2.3.4.)
1882 Session begins from sector xxx. (Since 2.3.4.)
1884 The following options are the same as for vfat and specifying them only makes
1885 sense when using discs encoded using Microsoft's Joliet extensions.
1887 .BI iocharset= value
1888 Character set to use for converting 16 bit Unicode characters on CD
1889 to 8 bit characters. The default is iso8859-1.
1892 Convert 16 bit Unicode characters on CD to UTF-8.
1894 .SH "Mount options for jfs"
1897 Character set to use for converting from Unicode to ASCII. The default is
1898 to do no conversion. Use
1900 for UTF8 translations. This requires CONFIG_NLS_UTF8 to be set in
1906 Resize the volume to
1908 blocks. JFS only supports growing a volume, not shrinking it. This option
1909 is only valid during a remount, when the volume is mounted read-write. The
1911 keyword with no value will grow the volume to the full size of the partition.
1914 Do not write to the journal. The primary use of this option is to allow
1915 for higher performance when restoring a volume from backup media. The
1916 integrity of the volume is not guaranteed if the system abnormally abends.
1919 Default. Commit metadata changes to the journal. Use this option to remount
1922 option was previously specified in order to restore normal behavior.
1924 .BR errors= { continue | remount-ro | panic }
1925 Define the behaviour when an error is encountered.
1926 (Either ignore errors and just mark the filesystem erroneous and continue,
1927 or remount the filesystem read-only, or panic and halt the system.)
1929 .BR noquota | quota | usrquota | grpquota
1930 These options are accepted but ignored.
1932 .SH "Mount options for minix"
1935 .SH "Mount options for msdos"
1936 See mount options for fat.
1939 filesystem detects an inconsistency, it reports an error and sets the file
1940 system read-only. The filesystem can be made writable again by remounting
1943 .SH "Mount options for ncpfs"
1945 .IR nfs ", the " ncpfs
1946 implementation expects a binary argument (a
1947 .IR "struct ncp_mount_data" )
1948 to the mount system call. This argument is constructed by
1950 and the current version of
1952 (2.12) does not know anything about ncpfs.
1954 .SH "Mount options for nfs and nfs4"
1955 See the options section of the
1957 man page (nfs-utils package must be installed).
1960 .IR nfs " and " nfs4
1961 implementation expects a binary argument (a
1962 .IR "struct nfs_mount_data" )
1963 to the mount system call. This argument is constructed by
1965 and the current version of
1967 (2.13) does not know anything about nfs and nfs4.
1969 .SH "Mount options for ntfs"
1972 Character set to use when returning file names.
1973 Unlike VFAT, NTFS suppresses names that contain
1974 nonconvertible characters. Deprecated.
1978 New name for the option earlier called
1983 Use UTF-8 for converting file names.
1985 .BR uni_xlate= { 0 | 1 | 2 }
1986 For 0 (or `no' or `false'), do not use escape sequences
1987 for unknown Unicode characters.
1988 For 1 (or `yes' or `true') or 2, use vfat-style 4-byte escape sequences
1989 starting with ":". Here 2 give a little-endian encoding
1990 and 1 a byteswapped bigendian encoding.
1993 If enabled (posix=1), the filesystem distinguishes between
1994 upper and lower case. The 8.3 alias names are presented as
1995 hard links instead of being suppressed. This option is obsolete.
1997 \fBuid=\fP\fIvalue\fP, \fBgid=\fP\fIvalue\fP and \fBumask=\fP\fIvalue\fP
1998 Set the file permission on the filesystem.
1999 The umask value is given in octal.
2000 By default, the files are owned by root and not readable by somebody else.
2002 .SH "Mount options for proc"
2004 \fBuid=\fP\fIvalue\fP and \fBgid=\fP\fIvalue\fP
2005 These options are recognized, but have no effect as far as I can see.
2007 .SH "Mount options for ramfs"
2008 Ramfs is a memory based filesystem. Mount it and you have it. Unmount it
2009 and it is gone. Present since Linux 2.3.99pre4.
2010 There are no mount options.
2012 .SH "Mount options for reiserfs"
2013 Reiserfs is a journaling filesystem.
2016 Instructs version 3.6 reiserfs software to mount a version 3.5 filesystem,
2017 using the 3.6 format for newly created objects. This filesystem will no
2018 longer be compatible with reiserfs 3.5 tools.
2020 .BR hash= { rupasov | tea | r5 | detect }
2021 Choose which hash function reiserfs will use to find files within directories.
2025 A hash invented by Yury Yu. Rupasov. It is fast and preserves locality,
2026 mapping lexicographically close file names to close hash values.
2027 This option should not be used, as it causes a high probability of hash
2031 A Davis-Meyer function implemented by Jeremy Fitzhardinge.
2032 It uses hash permuting bits in the name. It gets high randomness
2033 and, therefore, low probability of hash collisions at some CPU cost.
2034 This may be used if EHASHCOLLISION errors are experienced with the r5 hash.
2037 A modified version of the rupasov hash. It is used by default and is
2038 the best choice unless the filesystem has huge directories and
2039 unusual file-name patterns.
2044 to detect which hash function is in use by examining
2045 the filesystem being mounted, and to write this information into
2046 the reiserfs superblock. This is only useful on the first mount of
2047 an old format filesystem.
2050 .BR hashed_relocation
2051 Tunes the block allocator. This may provide performance improvements
2054 .BR no_unhashed_relocation
2055 Tunes the block allocator. This may provide performance improvements
2059 Disable the border allocator algorithm invented by Yury Yu. Rupasov.
2060 This may provide performance improvements in some situations.
2063 Disable journalling. This will provide slight performance improvements in
2064 some situations at the cost of losing reiserfs's fast recovery from crashes.
2065 Even with this option turned on, reiserfs still performs all journalling
2066 operations, save for actual writes into its journalling area. Implementation
2069 is a work in progress.
2072 By default, reiserfs stores small files and `file tails' directly into its
2073 tree. This confuses some utilities such as
2075 This option is used to disable packing of files into the tree.
2078 Replay the transactions which are in the journal, but do not actually
2079 mount the filesystem. Mainly used by
2083 A remount option which permits online expansion of reiserfs partitions.
2084 Instructs reiserfs to assume that the device has
2087 This option is designed for use with devices which are under logical
2088 volume management (LVM).
2091 utility which can be obtained from
2092 .IR ftp://ftp.namesys.com/pub/reiserfsprogs .
2095 Enable Extended User Attributes. See the
2100 Enable POSIX Access Control Lists. See the
2104 .BR barrier=none " / " barrier=flush "
2105 This enables/disables the use of write barriers in the journaling code.
2106 barrier=none disables it, barrier=flush enables it. Write barriers enforce
2107 proper on-disk ordering of journal commits, making volatile disk write caches
2108 safe to use, at some performance penalty. The reiserfs filesystem does not
2109 enable write barriers by default. Be sure to enable barriers unless your disks
2110 are battery-backed one way or another. Otherwise you risk filesystem
2111 corruption in case of power failure.
2113 .SH "Mount options for romfs"
2116 .SH "Mount options for squashfs"
2119 .SH "Mount options for smbfs"
2121 .IR nfs ", the " smbfs
2122 implementation expects a binary argument (a
2123 .IR "struct smb_mount_data" )
2124 to the mount system call. This argument is constructed by
2126 and the current version of
2128 (2.12) does not know anything about smbfs.
2130 .SH "Mount options for sysv"
2133 .SH "Mount options for tmpfs"
2136 Override default maximum size of the filesystem.
2137 The size is given in bytes, and rounded up to entire pages.
2138 The default is half of the memory. The size parameter also accepts a suffix %
2139 to limit this tmpfs instance to that percentage of your physical RAM:
2140 the default, when neither size nor nr_blocks is specified, is size=50%
2143 The same as size, but in blocks of PAGE_CACHE_SIZE
2146 The maximum number of inodes for this instance. The default
2147 is half of the number of your physical RAM pages, or (on a
2148 machine with highmem) the number of lowmem RAM pages,
2149 whichever is the lower.
2151 The tmpfs mount options for sizing (
2161 for Ki, Mi, Gi (binary kilo, mega and giga) and can be changed on remount.
2165 Set initial permissions of the root directory.
2173 .B mpol=[default|prefer:Node|bind:NodeList|interleave|interleave:NodeList]
2174 Set the NUMA memory allocation policy for all files in that
2175 instance (if the kernel CONFIG_NUMA is enabled) - which can be adjusted on the
2176 fly via 'mount -o remount ...'
2180 prefers to allocate memory from the local node
2183 prefers to allocate memory from the given Node
2186 allocates memory only from nodes in NodeList
2189 prefers to allocate from each node in turn
2191 .B interleave:NodeList
2192 allocates from each node of NodeList in turn.
2194 The NodeList format is a comma-separated list of decimal numbers and ranges, a
2195 range being two hyphen-separated decimal numbers, the smallest and largest node
2196 numbers in the range. For example, mpol=bind:0-3,5,7,9-15
2198 Note that trying to mount a tmpfs with an mpol option will fail if the
2199 running kernel does not support NUMA; and will fail if its nodelist
2200 specifies a node which is not online. If your system relies on that
2201 tmpfs being mounted, but from time to time runs a kernel built without
2202 NUMA capability (perhaps a safe recovery kernel), or with fewer nodes
2203 online, then it is advisable to omit the mpol option from automatic
2204 mount options. It can be added later, when the tmpfs is already mounted
2205 on MountPoint, by 'mount -o remount,mpol=Policy:NodeList MountPoint'.
2207 .SH "Mount options for ubifs"
2208 UBIFS is a flash file system which works on top of UBI volumes. Note that
2211 is not supported and is always turned off.
2213 The device name may be specified as
2241 separator may be used instead of
2244 The following mount options are available:
2247 Enable bulk-read. VFS read-ahead is disabled because it slows down the file
2248 system. Bulk-Read is an internal optimization. Some flashes may read faster if
2249 the data are read at one go, rather than at several read requests. For
2250 example, OneNAND can do "read-while-load" if it reads more than one NAND page.
2253 Do not bulk-read. This is the default.
2256 Check data CRC-32 checksums. This is the default.
2258 .BR no_chk_data_crc.
2259 Do not check data CRC-32 checksums. With this option, the filesystem does not
2260 check CRC-32 checksum for data, but it does check it for the internal indexing
2261 information. This option only affects reading, not writing. CRC-32 is always
2262 calculated when writing the data.
2264 .BR compr= { none | lzo | zlib }
2265 Select the default compressor which is used when new files are written. It is
2266 still possible to read compressed files if mounted with the
2270 .SH "Mount options for udf"
2271 udf is the "Universal Disk Format" filesystem defined by the Optical
2272 Storage Technology Association, and is often used for DVD-ROM.
2277 Set the default group.
2280 Set the default umask.
2281 The value is given in octal.
2284 Set the default user.
2287 Show otherwise hidden files.
2290 Show deleted files in lists.
2293 Unset strict conformance.
2299 Set the NLS character set.
2302 Set the block size. (May not work unless 2048.)
2305 Skip volume sequence recognition.
2308 Set the CDROM session counting from 0. Default: last session.
2311 Override standard anchor location. Default: 256.
2314 Override the VolumeDesc location. (unused)
2317 Override the PartitionDesc location. (unused)
2320 Set the last block of the filesystem.
2323 Override the fileset block location. (unused)
2326 Override the root directory location. (unused)
2328 .SH "Mount options for ufs"
2331 UFS is a filesystem widely used in different operating systems.
2332 The problem are differences among implementations. Features of some
2333 implementations are undocumented, so its hard to recognize the
2334 type of ufs automatically.
2335 That's why the user must specify the type of ufs by mount option.
2336 Possible values are:
2340 Old format of ufs, this is the default, read only.
2341 (Don't forget to give the \-r option.)
2344 For filesystems created by a BSD-like system (NetBSD,FreeBSD,OpenBSD).
2347 Used in FreeBSD 5.x supported as read-write.
2353 For filesystems created by SunOS or Solaris on Sparc.
2356 For filesystems created by Solaris on x86.
2359 For filesystems created by HP-UX, read-only.
2362 For filesystems created by NeXTStep (on NeXT station) (currently read only).
2365 For NextStep CDROMs (block_size == 2048), read-only.
2368 For filesystems created by OpenStep (currently read only).
2369 The same filesystem type is also used by Mac OS X.
2374 Set behaviour on error:
2378 If an error is encountered, cause a kernel panic.
2380 .RB [ lock | umount | repair ]
2381 These mount options don't do anything at present;
2382 when an error is encountered only a console message is printed.
2385 .SH "Mount options for umsdos"
2386 See mount options for msdos.
2389 option is explicitly killed by
2392 .SH "Mount options for vfat"
2393 First of all, the mount options for
2398 option is explicitly killed by
2400 Furthermore, there are
2403 Translate unhandled Unicode characters to special escaped sequences.
2404 This lets you backup and restore filenames that are created with any
2405 Unicode characters. Without this option, a '?' is used when no
2406 translation is possible. The escape character is ':' because it is
2407 otherwise illegal on the vfat filesystem. The escape sequence
2408 that gets used, where u is the unicode character,
2409 is: ':', (u & 0x3f), ((u>>6) & 0x3f), (u>>12).
2412 Allow two files with names that only differ in case.
2413 This option is obsolete.
2416 First try to make a short name without sequence number,
2421 UTF8 is the filesystem safe 8-bit encoding of Unicode that is used by the
2422 console. It can be enabled for the filesystem with this option or disabled
2423 with utf8=0, utf8=no or utf8=false. If `uni_xlate' gets set, UTF8 gets
2426 .BR shortname= { lower | win95 | winnt | mixed }
2428 Defines the behaviour for creation and display of filenames which fit into
2429 8.3 characters. If a long name for a file exists, it will always be
2430 preferred display. There are four modes:
2435 Force the short name to lower case upon display; store a long name when
2436 the short name is not all upper case.
2439 Force the short name to upper case upon display; store a long name when
2440 the short name is not all upper case.
2443 Display the shortname as is; store a long name when the short name is
2444 not all lower case or all upper case.
2447 Display the short name as is; store a long name when the short name is not
2448 all upper case. This mode is the default since Linux 2.6.32.
2452 .SH "Mount options for usbfs"
2454 \fBdevuid=\fP\fIuid\fP and \fBdevgid=\fP\fIgid\fP and \fBdevmode=\fP\fImode\fP
2455 Set the owner and group and mode of the device files in the usbfs filesystem
2456 (default: uid=gid=0, mode=0644). The mode is given in octal.
2458 \fBbusuid=\fP\fIuid\fP and \fBbusgid=\fP\fIgid\fP and \fBbusmode=\fP\fImode\fP
2459 Set the owner and group and mode of the bus directories in the usbfs
2460 filesystem (default: uid=gid=0, mode=0555). The mode is given in octal.
2462 \fBlistuid=\fP\fIuid\fP and \fBlistgid=\fP\fIgid\fP and \fBlistmode=\fP\fImode\fP
2463 Set the owner and group and mode of the file
2465 (default: uid=gid=0, mode=0444). The mode is given in octal.
2467 .SH "Mount options for xenix"
2470 .SH "Mount options for xfs"
2473 Sets the buffered I/O end-of-file preallocation size when
2474 doing delayed allocation writeout (default size is 64KiB).
2475 Valid values for this option are page size (typically 4KiB)
2476 through to 1GiB, inclusive, in power-of-2 increments.
2479 The options enable/disable (default is enabled) an "opportunistic"
2480 improvement to be made in the way inline extended attributes are
2482 When the new form is used for the first time (by setting or
2483 removing extended attributes) the on-disk superblock feature
2484 bit field will be updated to reflect this format being in use.
2487 Enables the use of block layer write barriers for writes into
2488 the journal and unwritten extent conversion. This allows for
2489 drive level write caching to be enabled, for devices that
2490 support write barriers.
2493 Enable the DMAPI (Data Management API) event callouts.
2498 .BR grpid | bsdgroups " and " nogrpid | sysvgroups
2499 These options define what group ID a newly created file gets.
2500 When grpid is set, it takes the group ID of the directory in
2501 which it is created; otherwise (the default) it takes the fsgid
2502 of the current process, unless the directory has the setgid bit
2503 set, in which case it takes the gid from the parent directory,
2504 and also gets the setgid bit set if it is a directory itself.
2506 .BI ihashsize= value
2507 Sets the number of hash buckets available for hashing the
2508 in-memory inodes of the specified mount point. If a value
2509 of zero is used, the value selected by the default algorithm
2510 will be displayed in
2514 When inode clusters are emptied of inodes, keep them around
2515 on the disk (ikeep) - this is the traditional XFS behaviour
2516 and is still the default for now. Using the noikeep option,
2517 inode clusters are returned to the free space pool.
2520 Indicates that XFS is allowed to create inodes at any location
2521 in the filesystem, including those which will result in inode
2522 numbers occupying more than 32 bits of significance. This is
2523 provided for backwards compatibility, but causes problems for
2524 backup applications that cannot handle large inode numbers.
2526 .BR largeio | nolargeio
2529 is specified, the optimal I/O reported in
2532 will be as small as possible to allow user
2533 applications to avoid inefficient read/modify/write I/O.
2536 is specified, a filesystem that has a
2541 value (in bytes) in st_blksize. If the
2542 filesystem does not have a
2544 specified but does specify
2549 (in bytes) will be returned
2551 If neither of these two options are specified, then filesystem
2557 Set the number of in-memory log buffers. Valid numbers range
2559 The default value is 8 buffers for any recent kernel.
2562 Set the size of each in-memory log buffer.
2563 Size may be specified in bytes, or in kilobytes with a "k" suffix.
2564 Valid sizes for version 1 and version 2 logs are 16384 (16k) and
2565 32768 (32k). Valid sizes for version 2 logs also include
2566 65536 (64k), 131072 (128k) and 262144 (256k).
2567 The default value for any recent kernel is 32768.
2569 \fBlogdev=\fP\fIdevice\fP and \fBrtdev=\fP\fIdevice\fP
2570 Use an external log (metadata journal) and/or real-time device.
2571 An XFS filesystem has up to three parts: a data section, a log section,
2572 and a real-time section.
2573 The real-time section is optional, and the log section can be separate
2574 from the data section or contained within it.
2578 .BI mtpt= mountpoint
2581 option. The value specified here will be
2582 included in the DMAPI mount event, and should be the path of
2583 the actual mountpoint that is used.
2586 Data allocations will not be aligned at stripe unit boundaries.
2589 Access timestamps are not updated when a file is read.
2592 The filesystem will be mounted without running log recovery.
2593 If the filesystem was not cleanly unmounted, it is likely to
2594 be inconsistent when mounted in
2597 Some files or directories may not be accessible because of this.
2600 must be mounted read-only or the mount will fail.
2603 Don't check for double mounted filesystems using the filesystem uuid.
2604 This is useful to mount LVM snapshot volumes.
2607 Make O_SYNC writes implement true O_SYNC. WITHOUT this option,
2608 Linux XFS behaves as if an
2611 which will make writes to files opened with the O_SYNC flag set
2612 behave as if the O_DSYNC flag had been used instead.
2613 This can result in better performance without compromising
2615 However if this option is not in effect, timestamp updates from
2616 O_SYNC writes can be lost if the system crashes.
2617 If timestamp updates are critical, use the
2621 .BR uquota | usrquota | uqnoenforce | quota
2622 User disk quota accounting enabled, and limits (optionally)
2625 for further details.
2627 .BR gquota | grpquota | gqnoenforce
2628 Group disk quota accounting enabled and limits (optionally)
2631 for further details.
2633 .BR pquota | prjquota | pqnoenforce
2634 Project disk quota accounting enabled and limits (optionally)
2637 for further details.
2639 \fBsunit=\fP\fIvalue\fP and \fBswidth=\fP\fIvalue\fP
2640 Used to specify the stripe unit and width for a RAID device or a stripe
2643 must be specified in 512-byte block units.
2644 If this option is not specified and the filesystem was made on a stripe
2645 volume or the stripe width or unit were specified for the RAID device at
2646 mkfs time, then the mount system call will restore the value from the
2648 For filesystems that are made directly on RAID devices, these options can be
2649 used to override the information in the superblock if the underlying disk
2650 layout changes after the filesystem has been created.
2653 option is required if the
2655 option has been specified,
2656 and must be a multiple of the
2661 Data allocations will be rounded up to stripe width boundaries
2662 when the current end of file is being extended and the file
2663 size is larger than the stripe width size.
2665 .SH "Mount options for xiafs"
2666 None. Although nothing is wrong with xiafs, it is not used much,
2667 and is not maintained. Probably one shouldn't use it.
2668 Since Linux version 2.1.21 xiafs is no longer part of the kernel source.
2670 .SH "THE LOOP DEVICE"
2671 One further possible type is a mount via the loop device. For example,
2675 .B "mount /tmp/disk.img /mnt -t vfat -o loop=/dev/loop"
2678 will set up the loop device
2680 to correspond to the file
2682 and then mount this device on
2685 If no explicit loop device is mentioned
2686 (but just an option `\fB\-o loop\fP' is given), then
2688 will try to find some unused loop device and use that, for example
2691 .B "mount /tmp/disk.img /mnt -o loop"
2696 creates a loop device from a regular file if a filesystem type is
2697 not specified or the filesystem is known for libblkid, for example:
2700 .B "mount /tmp/disk.img /mnt"
2702 .B "mount -t ext3 /tmp/disk.img /mnt"
2705 This type of mount knows about three options, namely
2706 .BR loop ", " offset ", " sizelimit " ,
2707 that are really options to
2709 (These options can be used in addition to those specific
2710 to the filesystem type.)
2712 Since Linux 2.6.25 is supported auto-destruction of loop devices and
2713 then any loop device allocated by
2720 You can also free a loop device by hand, using `losetup -d' or `umount -d`.
2724 has the following return codes (the bits can be ORed):
2730 incorrect invocation or permissions
2733 system error (out of memory, cannot fork, no more loop devices)
2744 problems writing or locking /etc/mtab
2750 some mount succeeded
2753 The syntax of external mount helpers is:
2756 .BI /sbin/mount. <suffix>
2765 where the <type> is filesystem type and \-sfnvo options have same meaning like
2766 standard mount options. The \-t option is used for filesystems with subtypes
2767 support (for example /sbin/mount.fuse -t fuse.sshfs).
2775 table of mounted filesystems
2784 a list of filesystem types to try
2802 It is possible for a corrupted filesystem to cause a crash.
2804 Some Linux filesystems don't support
2805 .B "\-o sync and \-o dirsync"
2806 (the ext2, ext3, fat and vfat filesystems
2808 support synchronous updates (a la BSD) when mounted with the
2814 may not be able to change mount parameters (all
2815 .IR ext2fs -specific
2818 are changeable with a remount, for example, but you can't change
2825 Mount by label or uuid will work only if your devices have the names listed in
2826 .IR /proc/partitions .
2827 In particular, it may well fail if the kernel was compiled with devfs
2828 but devfs is not mounted.
2830 It is possible that files
2834 don't match. The first file is based only on the mount command options, but the
2835 content of the second file also depends on the kernel and others settings (e.g.
2836 remote NFS server. In particular case the mount command may reports unreliable
2837 information about a NFS mount point and the /proc/mounts file usually contains
2838 more reliable information.)
2840 Checking files on NFS filesystem referenced by file descriptors (i.e. the
2844 families of functions) may lead to inconsistent result due to the lack of
2845 consistency check in kernel even if noac is used.
2849 command existed in Version 5 AT&T UNIX.
2851 The mount command is part of the util-linux package and is available from
2852 ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
projects / thirdparty / util-linux.git / blob