Linux man pages : mount (8)
MOUNT(8) Linux Programmer's Manual MOUNT(8)
NAME
mount - mount a file system
SYNOPSIS
mount [-lhV]
mount -a [-fFnrsvw] [-t vfstype] [-O optlist]
mount [-fnrsvw] [-o options [,...]] device | dir
mount [-fnrsvw] [-t vfstype] [-o options] device dir
DESCRIPTION
All files accessible in a Unix system are arranged in one big tree, the
file hierarchy, rooted at /. These files can be spread out over sev-
eral devices. The mount command serves to attach the file system found
on some device to the big file tree. Conversely, the umount(8) command
will detach it again.
The standard form of the mount command, is
mount -t type device dir
This tells the kernel to attach the file system found on device (which
is of type type) at the directory dir. The previous contents (if any)
and owner and mode of dir become invisible, and as long as this file
system remains mounted, the pathname dir refers to the root of the file
system on device.
Three forms of invocation do not actually mount anything:
mount -h
prints a help message;
mount -V
prints a version string; and just
mount [-l] [-t type]
lists all mounted file systems (of type type). The option -l adds the
(ext2, ext3 and XFS) labels in this listing. See below.
Since Linux 2.4.0 it is possible to remount part of the file hierarchy
somewhere else. The call is
mount --bind olddir newdir
After this call the same contents is accessible in two places.
This call attaches only (part of) a single filesystem, not possible
submounts. The entire file hierarchy including submounts is attached a
second place using
mount --rbind olddir newdir
Since Linux 2.5.1 it is possible to atomically move a subtree to
another place. The call is
mount --move olddir newdir
The proc file system is not associated with a special device, and when
mounting it, an arbitrary keyword, such as proc can be used instead of
a device specification. (The customary choice none is less fortunate:
the error message `none busy' from umount can be confusing.)
Most devices are indicated by a file name (of a block special device),
like /dev/sda1, but there are other possibilities. For example, in the
case of an NFS mount, device may look like knuth.cwi.nl:/dir. It is
possible to indicate a block special device using its volume label or
UUID (see the -L and -U options below).
The file /etc/fstab (see fstab(5)), may contain lines describing what
devices are usually mounted where, using which options. This file is
used in three ways:
(i) The command
mount -a [-t type] [-O optlist]
(usually given in a bootscript) causes all file systems mentioned in
fstab (of the proper type and/or having or not having the proper
options) to be mounted as indicated, except for those whose line con-
tains the noauto keyword. Adding the -F option will make mount fork, so
that the filesystems are mounted simultaneously.
(ii) When mounting a file system mentioned in fstab, it suffices to
give only the device, or only the mount point.
(iii) Normally, only the superuser can mount file systems. However,
when fstab contains the user option on a line, then anybody can mount
the corresponding system.
Thus, given a line
/dev/cdrom /cd iso9660 ro,user,noauto,unhide
any user can mount the iso9660 file system found on his CDROM using the
command
mount /dev/cdrom
or
mount /cd
For more details, see fstab(5). Only the user that mounted a filesys-
tem can unmount it again. If any user should be able to unmount, then
use users instead of user in the fstab line. The owner option is simi-
lar to the user option, with the restriction that the user must be the
owner of the special file. This may be useful e.g. for /dev/fd if a
login script makes the console user owner of this device.
The programs mount and umount maintain a list of currently mounted file
systems in the file /etc/mtab. If no arguments are given to mount,
this list is printed. When the proc filesystem is mounted (say at
/proc), the files /etc/mtab and /proc/mounts have very similar con-
tents. The former has somewhat more information, such as the mount
options used, but is not necessarily up-to-date (cf. the -n option
below). It is possible to replace /etc/mtab by a symbolic link to
/proc/mounts, but some information is lost that way, and in particular
working with the loop device will be less convenient.
OPTIONS
The full set of options used by an invocation of mount 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 a -r or -w option, when present.
Options available for the mount command:
-V Output version.
-h Print a help message.
-v Verbose mode.
-a Mount all filesystems (of the given types) mentioned in fstab.
-F (Used in conjunction with -a.) Fork off a new incarnation of
mount for each device. This will do the mounts on different
devices or different NFS servers in parallel. This has the
advantage that it is faster; also NFS timeouts go in parallel. A
disadvantage is that the mounts are done in undefined order.
Thus, you cannot use this option if you want to mount both /usr
and /usr/spool.
-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 deter-
mine what the mount command is trying to do. It can also be used
to add entries for devices that were mounted earlier with the -n
option.
-l Add the ext2, ext3 and XFS labels in the mount output. Mount
must have permission to read the disk device (e.g. be suid root)
for this to work. One can set such a label for ext2 or ext3
using the e2label(8) utility, or for XFS using xfs_admin(8).
-n Mount without writing in /etc/mtab. This is necessary for exam-
ple when /etc is on a read-only file system.
-s Tolerate sloppy mount options rather than failing. This will
ignore mount options not supported by a filesystem type. Not all
filesystems support this option. This option exists for support
of the Linux autofs-based automounter.
-r Mount the file system read-only. A synonym is -o ro.
-w Mount the file system read/write. This is the default. A synonym
is -o rw.
-L label
Mount the partition that has the specified label.
-U uuid
Mount the partition that has the specified uuid. These two
options require the file /proc/partitions (present since Linux
2.1.116) to exist.
-t vfstype
The argument following the -t is used to indicate the file sys-
tem type. The file system types which are currently supported
are: adfs, affs, autofs, coda, coherent, cramfs, devpts, efs,
ext, ext2, ext3, hfs, hpfs, iso9660, jfs, minix, msdos, ncpfs,
nfs, ntfs, proc, qnx4, ramfs, reiserfs, romfs, smbfs, sysv,
tmpfs, udf, ufs, umsdos, vfat, xenix, xfs, xiafs. Note that
coherent, sysv and xenix are equivalent and that xenix and
coherent will be removed at some point in the future
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