Mount

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Mounting typically involves the attaching of an additional filesystem to the currently accessible filesystem of a computer.

Installation

The mount command is part of the util-linux package. In Gentoo Linux, sys-apps/util-linux is part of the system set and is installed on all Gentoo systems by default.

If for some strange and unordinary reason it is missing it can be re-installed by running a simple emerge command (always use the --oneshot option). This can also be used after changing USE flags:

root #emerge --ask --oneshot sys-apps/util-linux

Usage

root #mount --help

Usage:
 mount [-lhV]
 mount -a [options]
 mount [options] [--source] <source> | [--target] <directory>
 mount [options] <source> <directory>
 mount <operation> <mountpoint> [<target>]
 
Mount a filesystem.
 
Options:
 -a, --all               mount all filesystems mentioned in fstab
 -c, --no-canonicalize   don't canonicalize paths
 -f, --fake              dry run; skip the mount(2) syscall
 -F, --fork              fork off for each device (use with -a)
 -T, --fstab <path>      alternative file to /etc/fstab
 -i, --internal-only     don't call the mount.<type> helpers
 -l, --show-labels       show also filesystem labels
 -m, --mkdir[=<mode>]    alias to '-o X-mount.mkdir[=<mode>]'
 -n, --no-mtab           don't write to /etc/mtab
     --options-mode <mode>
                         what to do with options loaded from fstab
     --options-source <source>
                         mount options source
     --options-source-force
                         force use of options from fstab/mtab
 -o, --options <list>    comma-separated list of mount options
 -O, --test-opts <list>  limit the set of filesystems (use with -a)
 -r, --read-only         mount the filesystem read-only (same as -o ro)
 -t, --types <list>      limit the set of filesystem types
     --source <src>      explicitly specifies source (path, label, uuid)
     --target <target>   explicitly specifies mountpoint
     --target-prefix <path>
                         specifies path used for all mountpoints
 -v, --verbose           say what is being done
 -w, --rw, --read-write  mount the filesystem read-write (default)
 -N, --namespace <ns>    perform mount in another namespace
 
 -h, --help              display this help
 -V, --version           display version
 
Source:
 -L, --label <label>     synonym for LABEL=<label>
 -U, --uuid <uuid>       synonym for UUID=<uuid>
 LABEL=<label>           specifies device by filesystem label
 UUID=<uuid>             specifies device by filesystem UUID
 PARTLABEL=<label>       specifies device by partition label
 PARTUUID=<uuid>         specifies device by partition UUID
 ID=<id>                 specifies device by udev hardware ID
 <device>                specifies device by path
 <directory>             mountpoint for bind mounts (see --bind/rbind)
 <file>                  regular file for loopdev setup
 
Operations:
 -B, --bind              mount a subtree somewhere else (same as -o bind)
 -M, --move              move a subtree to some other place
 -R, --rbind             mount a subtree and all submounts somewhere else
 --make-shared           mark a subtree as shared
 --make-slave            mark a subtree as slave
 --make-private          mark a subtree as private
 --make-unbindable       mark a subtree as unbindable
 --make-rshared          recursively mark a whole subtree as shared
 --make-rslave           recursively mark a whole subtree as slave
 --make-rprivate         recursively mark a whole subtree as private
 --make-runbindable      recursively mark a whole subtree as unbindable
 
For more details see mount(8).

List mounts

Show mounted filesystems by running the mount command with no arguments or options:

root #mount

Tip
There is also a more visual way of showing mounted filesystems using the findmnt tool also provided by sys-apps/util-linux. For more details see man 8 findmnt.

Mount filesystem

To mount a filesystem, a device file, UUID or label or other means of locating the partition or data source and a mount point are required. Non-system relevant filesystems are normally mounted in the /mnt directory. The proper syntax for mounting a file system is as follows:

root #mount <DEVICE> <DIRECTORY>

For further details, see man 8 mount.

The /media directory is generally used to mount removable devices such as USB drives or SD cards. After determining which device the USB drive shows up as, a command like the following could be used to mount its contents to a newly created usb folder in /media:

root #mkdir /media/usb

root #mount /dev/sdb1 /media/usb

Tip
A mount from fstab may by mounted by providing just the mountpoint, or device name, for example:

root #mount /dev/sdb1

Unmount a filesystem

To unmount a filesystem, the device file or the mount point can be specified:

root #umount <DEVICE>

root #umount <DIRECTORY>

Invocation information:

user $umount --help

Usage:
 umount [-hV]
 umount -a [options]
 umount [options] <source> | <directory>
 
Unmount filesystems.
 
Options:
 -a, --all               unmount all filesystems
 -A, --all-targets       unmount all mountpoints for the given device in the
                           current namespace
 -c, --no-canonicalize   don't canonicalize paths
 -d, --detach-loop       if mounted loop device, also free this loop device
     --fake              dry run; skip the umount(2) syscall
 -f, --force             force unmount (in case of an unreachable NFS system)
 -i, --internal-only     don't call the umount.<type> helpers
 -n, --no-mtab           don't write to /etc/mtab
 -l, --lazy              detach the filesystem now, clean up things later
 -O, --test-opts <list>  limit the set of filesystems (use with -a)
 -R, --recursive         recursively unmount a target with all its children
 -r, --read-only         in case unmounting fails, try to remount read-only
 -t, --types <list>      limit the set of filesystem types
 -v, --verbose           say what is being done
 -q, --quiet             suppress 'not mounted' error messages
 -N, --namespace <ns>    perform umount in another namespace
 
 -h, --help              display this help
 -V, --version           display version
 
For more details see umount(8).

Mount options

Sometimes, mounting a filesystem requires special options:

root #mount [OPTIONS] <DEVICE> <DIRECTORY>

Program options:

Option	Description
-f	Simulate the mount
-t	Specify the filesystem, e.g ext4
-o OPTION1,OPTION2,...	Specify the mount options (see below)
-a	Mount all filesystems in /etc/fstab

The filesystem being used must support the mount option being passed. Many options are common, but some are filesystem specific.

Note
It is advised to always consult man pages of both mount and the particular filesystem (for example ext4(5) or xfs(5)).

Mount options:

Option	Description
defaults	Use the default mount options: rw, suid, dev, exec, auto, nouser, async.
auto	Mount the filesystem automatically on boot.
noauto	Do not mount the filesystem automatically on boot.
ro	Mount the filesystem read-only.
rw	Mount the filesystem read-write.
sw	Mount a swap partition.
atime	Update inode access times on every read.
relatime	Update inode access times only on writes to improve I/O performance.
noatime	Never update inode access times for best I/O performance.
sync	Sync drive after each write. Can shorten lifespan for e.g. some flash drives.
async	Sync drive asynchronously.
discard	The equivalent of trim support on Linux.
exec	Allow execution of binaries.
noexec	Do not allow execution of binaries.
suid	Follow SUID and SGID bits.
nosuid	Do not follow SUID and SGID bits.
user	Allow a user to mount the filesystem. Implies nodev, noexec, and nosuid options unless explicitly setting dev, exec, or suid respectively.
users	Allow every user to mount the filesystem.
nouser	Allow only "root" to mount the filesystem.

Mount options of already-mounted filesystems can be changed using remount option. For example, setting a filesystem on /dev/foo to be mounted as read-write can be achieved using:

root #mount -o remount,rw /dev/foo /dir

Tips

Mounting as non-superuser

According to man mount, only the superuser can mount filesystems. However, when /etc/fstab contains the user option on a line, any user will be capable of mounting the corresponding partition, device, drive, etc.

Mounting removable media

See the relevant section in the Removable media article.

Mounting Windows shares (CIFS)

Despite /etc/fstab entries, non-superuser mounts of Windows shares will fail (for security reasons). In the following example is found a fstab entry for Windows share; pay close attention to the cifs option:

FILE /etc/fstab

[...]
//server/folder /home/larry/winmount cifs noauto,user 0 0
[...]

user $mount /home/larry/winmount

This program is not installed setuid root -  "user" CIFS mounts not supported.

The solution is to use sudo mount /home/larry/winmount in combination with a corresponding entry in /etc/sudoers to allow passwordless mounting.

Warning
Be sure to understand the sudo configuration before editing the /etc/sudoers file!

FILE /etc/sudoers

[...]
larry    ALL = NOPASSWD: /bin/mount  /home/larry/winmount/, /bin/mount  /home/larry/winmount
larry    ALL = NOPASSWD: /bin/umount /home/larry/winmount/, /bin/umount /home/larry/winmount
[...]

See also

• Mounting partitions in the Security Handbook
• /etc/fstab — a configuration file that defines how and where the main filesystems are to be mounted, especially at boot time.
• Removable media — any media that is easily removed from a system.
• AutoFS — a program that uses the Linux kernel automounter to automatically mount filesystems on demand.
• Udevil — a small auto-mount utility created to be a "a hassle-free replacement for udisks."
• CurlFtpFS — allows for mounting an FTP folder as a regular directory to the local directory tree.
• USB/Guide - Mounting a USB Mass Storage device
• UUIDs and labels