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 several 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. One can also remount a single file (on a single file).

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

Note that the filesystem mount options will remain the same as those on the original mount point, and cannot be changed by passing the -o option along with --bind/--rbind.

Since Linux 2.5.1 it is possible to atomically move a mounted tree to another place. The call is

    mount --move olddir newdir

Since Linux 2.6.15 it is possible to mark a mount and its submounts as shared, private, slave or unbindable. A shared mount provides ability to create mirrors of that mount such that mounts and umounts within any of the mirrors propagate to the other mirror. A slave mount receives propagation from its master, but any not vice-versa. A private mount carries no propagation abilities. A unbindable mount is a private mount which cannot cloned through a bind operation. Detailed semantics is documented in Documentation/sharedsubtree.txt file in the kernel source tree.

    mount --make-shared mountpoint mount --make-slave mountpoint mount --make-private mountpoint mount --make-unbindable mountpoint

The following commands allows one to recursively change the type of all the mounts under a given mountpoint.

    mount --make-rshared mountpoint mount --make-rslave mountpoint mount --make-rprivate mountpoint "mount --make-runbindable mountpoint"

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 contains 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, 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 filesystem 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 similar 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 group option is similar, with the restriction that the user must be member of the group of the special file.

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 contents. 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, and especially when you have very large numbers of mounts things will be much faster with that symlink, but some information is lost that way, and in particular working with the loop device will be less convenient, and using the "user" option will fail.