MOUNT(8)

NAME
mount, umount - mount and dismount file systems

SYNOPSIS
mount [-afrwuvn] [-t vfstype]
mount [-frwuvn] [-o remount [,...]] special | node
mount [-frwun] [-t vfstype] [-o options] special node
umount [-a] [-t vfstype]
umount special | node

DESCRIPTION
The mount command calls the mount(2) system call to prepare and graft a special device on to the file system tree at the point node. If either special or node are not provided, the appropriate information is taken from the fstab(5) file. The special keyword none can be used instead of a path or node specification. This is useful when mounting the proc file system. The system maintains a list of currently mounted file systems. If no arguments are given to mount, this list is printed. Options available for the mount command:

-f  Causes everything to be done except for the actual system call; if it's not obvious, this ``fakes'' mounting the file system. This option is useful in conjunction with the -v flag to determine what the mount command is trying to do.

-o  Options are specified with a -o flag followed by a comma separated string of options. N.B., many of these options are only useful when they appear in the /etc/fstab file. The following options apply to any file system that is being mounted:

    async
        All I/O to the file system should be done asynchronously.

    auto
        Can be mounted with the -a option.

    defaults
        Use default options: rw, suid, dev, exec, auto, nouser, and async.

    dev Interpret character or block special devices on the file system.

    exec
        Permit execution of binaries.

    noauto
        Can only be mounted explicitly (i.e., the -a option will not cause the file system to be mounted).

    nodev
        Do not interpret character or block special devices on the file system. This options is useful for a server that has file systems containing special devices for architectures other than its own.

    noexec
        Do not allow execution of any binaries on the mounted file system. This options is useful for a server that has file systems containing binaries for architectures other than its own.

    nosuid
        Do not allow set-user-identifier or set-group-identifier bits to take effect.

    nouser
        Forbid an ordinary (i.e., non-root) user to mount the file system.

    remount
        Attempt to remount an already-mounted file system. This is commonly used to change the mount flags for a file system, especially to make a readonly file system writeable.

    ro  Mount the file system read-only.

    rw  Mount the file system read-write.

    suid
        Allow set-user-identifier or set-group-identifier bits to take effect.

    sync
        All I/O to the file system should be done synchronously.

    user
        Allow an ordinary user to mount the file system. Ordinary users always have the following options activated: noexec, nosuid, and nodev (unless overridden by the superuser by using, for example, the following option line: user,exec,dev,suid.

    The following options apply only to certain file systems:

    case=value
        For the hpfs file system, specify case as lower or asis.

    check=value
        Tells the ext2 file sysem kernel code to do some more checks while the file system is mounted. Currently (0.99.15), the following values can be specified with this option:

        none
            no extra check is performed by the kernel code

        normal
            The inodes and blocks bitmaps are checked when the file system is mounted (this is the default)

        strict
            In addition to the normal checks, block deallocation checks that the block to free is in the data zone.

    check=value
        For the msdos file system, three different levels of pickyness can be chosen:

        relaxed
            Upper and lower case are accepted and equivalent, long name parts are truncated (e.g. verlongname.foobar becomes verylong.foo), leading and embedded spaces are accepted in each name part (name and extension).

        normal
            Like "relaxed", but many special characters (*, ?, <, spaces, etc.) are rejected. This is the default.

        strict
            Like "normal", but names may not contain long parts and special characters that are sometimes used on Linux, but are not accepted by MS-DOS are rejected. (+, =, spaces, etc.)

    conv=value
        For the msdos, hpfs, and iso9660 file systems, specify file conversion as binary, text, or auto. The iso9660 file system also allows value to be mtext. The msdos file system can perform CRLF<-->NL (MS-DOS text format to UNIX text format) conversion in the kernel. The following conversion modes are available:

        binary
            no translation is performed. This is the default.

        text
            CRLF<-->NL translation is performed on all files.

        auto
            CRLF<-->NL translation is performed on all files that don't have a "well-known binary" extension. The list of known extensions can be found at the beginning of fs/msdos/misc.c (as of 09913r, the list is: exe, com, bin, app, sys, drv, ovl, ovr, obj, lib, dll, pif, arc, zip, lha, lzh, zoo, tar, z, arj, tz, taz, tzp, tpz, gif, bmp, tif, gl, jpg, pcx, tfm, vf, gf, pk, pxl, dvi).

        Programs that do computed lseeks won't like in-kernel text conversion. For file systems mounted in binary mode, a conversion tool (fromdos/todos) is available.

    block=value
        For the iso9660 file system, set the blocksize.

    bsdgroups
        See grpid

    cruft
        For the iso9660 file system, set the cruft flag to 'y'. This option is available because there are buggy premastering programs out there that leave junk in the top byte of the file size. This option clears the top byte, but restricts files to 16Mb maximum in the process.

    debug
        For the msdos file system, turn on the debug flag. A version string and a list of file system parameters will be printed (these data are also printed if the parameters appear to be inconsistent).

    debug
        For the ext2fs file system, causes the kernel code to display the file system parameters when the file system is mounted.

    errors=value
        For the ext2fs file system, specifies the error behavior:

        continue
            No special action is taken on errors (except marking the file system as erroneous). This is the default.

        remount

        ro  The file system is remounted read only, and subsequent writes are refused.

        panic
            When an error is detected, the system panics.

    fat=value
        For the msdos file system, specify either a 12 bit fat or a 16 bit fat. This overrides the automatic FAT type detection routine. Use with caution!

    gid=value
        For the msdos and hpfs file systems, give every file a gid equal to value.

    B grpid
        Causes the ext2fs to use the BSD behavior when creating files: file are created with the group id of their parent directory.

    map=value
        For the iso9660 file system, specify mapping as off or normal. In general, non-Rock Ridge discs have all of the filenames in upper case, and all of the filenames have a ";1" appended. The map option strips the ";1" and makes the name lower case. C.f. norock.

    nocheck
        For the ext2fs, turns of checking (see check=none).

    nogrpid
        Causes the ext2fs to use the System V behaviour when creating files: files are created with the group id of the creating process, unless the setgid bit is set on the parent directory. This is the default for all Linux file systems.

    norock
        Normal iso9600 filenames appear in a 8.3 format (i.e., DOS-like restrictions on filename length), and in addition all characters are in upper case. Also there is no field for file ownership, protection, number of links, provision for block/character devices, etc. Rock Ridge is an extension to iso9660 that provides all of these unix like features. Basically there are extensions to each directory record that supply all of the additional information, and when Rock Ridge is in use, the filesysetem is indistinguishable from a normal UNIX file system (except that it is read-only, of course). The norock switch disables the use of Rock Ridge extensions, even if available. C.f. map.

    quiet
        For the msdos file system, turn on the quiet flag. Attempts to chown or chmod files do not yield errors, although they fail. Use with caution!

    sb=value
        For the ext2 file system, use an alternate superblock located at block value. value is numbered in 1024 bytes blocks. An ext2 file system usually has backups of the super block at blocks 1, 8193, 16385 and so on.

    sysvgroups
        See nogrpid

    uid=value
        For the msdos and hpfs file systems, give every file a uid equal to value.

    umask=value
        For the msdos and hpfs file systems, give every file a umask of value. The radix defaults to octal.

    The full set of options applied is determined by first extracting the options for the file system from the fstab table, then applying any options specified by the -o argument, and finally applying the -r or -w option. If the msdos file system detects an inconsistency, it reports an error and sets the file system read-only. The file system can be made writeable again by remounting it.

-r  The file system object is to be mounted read-only.

-t vfstype
    The argument following the -t is used to indicate the file system type. The file system types which are currently supported are listed in linux/fs/filesystems.c: minux, ext, ext2, xiafs, msdos, hpfs, proc, nfs, iso9660, sysv, xenix, coherent. Note that that last three are equivalent and that "xenix" and "coherent" will be removed at some point in the future — use "sysv" instead. The type minix is the default. If no -t option is given, and if /proc/filesystems exists, then all of the filesystems listed will be tried, except for those that are labeled "nodev" (e.g., "proc" and "nfs"). For example, the mount command:
        mount -a -t nomsdos,ext
    mounts all file systems except those of type msdos and ext.

-v  Verbose mode.

-w  The file system object is to be read and write.

-n  Mount without writing in /etc/mtab.

Umount removes the special device grafted at point node from file system tree. Options for the umount command:

-a  All of the file systems described in /etc/mtab are unmounted.

-t vfstype
    Is used to indicate the actions should only be taken on file systems of the specified type. More than one type may be specified in a comma separated list. The list of file system types can be prefixed with ``no'' to specify the file system types on which no action should be taken. (See example above for the mount command.)

FILES
/etc/fstab file system table
/etc/mtab~ lock file
/etc/mtab.tmp temporary file

SEE ALSO
mount(2), umount(2), fstab(5), swapon(8)

BUGS
It is possible for a corrupted file system to cause a crash.

Some Linux file systems don't support -o synchronous (the ext2fs does support synchronous updates (a la BSD) when mounted with the sync option).

The -o remount may not be able to change mount parameters (all ext2fs parameters, except sb, are changeable with a remount, for example, but you can't change gid or umask for the dosfs).

HISTORY
A mount command appeared in Version 6 AT&T UNIX.

AUTHORS AND CONTRIBUTORS
The Linux mount command has a long and continuing history. Major releases are noted below, with the name of the primary modifier noted:

0.97.3: Doug Quale (quale@saavik.cs.wisc.edu).
0.98.5: H. J. Lu (hlu@eecs.wsu.edu).
0.99.2: Rick Sladkey (jrs@world.std.com).
0.99.6: Rick Sladkey (jrs@world.std.com).
0.99.10: Stephen Tweedie (sct@dcs.ed.ac.uk).
0.99.14: Rick Sladkey (jrs@world.std.com).

(File-system specific information added to man page on 27 November 1993 by Rik Faith with lots of information and text from the following file system authors: Werner Almesberger, Eric Youngdale, and Remy Card.)