Mount

Resources

Wikipedia

Man page

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 sys-apps/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:

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

Usage

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 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

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

root #umount <DEVICE>

root #umount <DIRECTORY>

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 man 5 ext4 or man 5 xfs).

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.
users	Allow every user to mount the filesystem.
nouser	Allow only "root" to mount the filesystem.

Changing mount options

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

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