Name

fstab — static information about the filesystems

Synopsis

.I /etc/fstab
  

DESCRIPTION

The file fstab contains descriptive information about the filesystems the system can mount. fstab is only read by programs, and not written; it is the duty of the system administrator to properly create and maintain this file. The order of records in fstab is important because fsck(8), mount(8), and umount(8) sequentially iterate through fstab doing their thing.

Each filesystem is described on a separate line. Fields on each line are separated by tabs or spaces. Lines starting with '#' are comments. Blank lines are ignored.

The following is a typical example of an fstab entry:

LABEL=t-home2 /home ext4 defaults,auto_da_alloc 0 2

The first field (fs_spec).

This field describes the block special device or remote filesystem to be mounted.

For ordinary mounts, it will hold (a link to) a block special device node (as created by mknod(8)) for the device to be mounted, like `/dev/cdrom' or `/dev/sdb7'. For NFS mounts, this field is <host>:<dir>, e.g., `knuth.aeb.nl:/'. For filesystems with no storage, any string can be used, and will show up in df(1) output, for example. Typical usage is `proc' for procfs; `mem', `none', or `tmpfs' for tmpfs. Other special filesystems, like udev and sysfs, are typically not listed in fstab.

LABEL=<label> or UUID=<uuid> may be given instead of a device name. This is the recommended method, as device names are often a coincidence of hardware detection order, and can change when other disks are added or removed. For example, `LABEL=Boot' or `UUID=3e6be9de-8139-11d1-9106-a43f08d823a6'. (Use a filesystem-specific tool like e2label(8), xfs_admin(8), or fatlabel(8) to set LABELs on filesystems).

It's also possible to use PARTUUID= and PARTLABEL=. These partitions identifiers are supported for example for GUID Partition Table (GPT).

See mount(8), blkid(8) or lsblk(8) for more details about device identifiers.

Note that mount(8) uses UUIDs as strings. The string representation of the UUID should be based on lower case characters.

The second field (fs_file).

This field describes the mount point (target) for the filesystem. For swap partitions, this field should be specified as `none'. If the name of the mount point contains spaces or tabs these can be escaped as `\040' and '\011' respectively.

The third field (fs_vfstype).

This field describes the type of the filesystem. Linux supports many filesystem types: ext4, xfs, btrfs, f2fs, vfat, ntfs, hfsplus, tmpfs, sysfs, proc, iso9660, udf, squashfs, nfs, cifs, and many more. For more details, see mount(8).

An entry swap denotes a file or partition to be used for swapping, cf. swapon(8). An entry none is useful for bind or move mounts.

More than one type may be specified in a comma-separated list.

mount(8) and umount(8) support filesystem subtypes. The subtype is defined by '.subtype' suffix. For example 'fuse.sshfs'. It's recommended to use subtype notation rather than add any prefix to the first fstab field (for example 'sshfs#example.com' is deprecated).

The fourth field (fs_mntops).

This field describes the mount options associated with the filesystem.

It is formatted as a comma-separated list of options. It contains at least the type of mount (ro or rw), plus any additional options appropriate to the filesystem type (including performance-tuning options). For details, see mount(8) or swapon(8).

Basic filesystem-independent options are:

defaults

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

noauto

do not mount when "mount -a" is given (e.g., at boot time)

user

allow a user to mount

owner

allow device owner to mount

comment

or x-<name> for use by fstab-maintaining programs

nofail

do not report errors for this device if it does not exist.

The fifth field (fs_freq).

This field is used by dump(8) to determine which filesystems need to be dumped. Defaults to zero (don't dump) if not present.

The sixth field (fs_passno).

This field is used by fsck(8) to determine the order in which filesystem checks are done at boot time. The root filesystem should be specified with a fs_passno of 1. Other filesystems should have a fs_passno of 2. Filesystems within a drive will be checked sequentially, but filesystems on different drives will be checked at the same time to utilize parallelism available in the hardware. Defaults to zero (don't fsck) if not present.

NOTES

The proper way to read records from fstab is to use the routines getmntent(3) or libmount.

The keyword ignore as a filesystem type (3rd field) is no longer supported by the pure libmount based mount utility (since util-linux v2.22).

FILES

/etc/fstab, <fstab.h>

SEE ALSO

getmntent(3), fs(5), findmnt(8), mount(8), swapon(8)

HISTORY

The ancestor of this fstab file format appeared in 4.0BSD.

AVAILABILITY

This man page is part of the util-linux package and is available from https://www.kernel.org/pub/linux/utils/util-linux/.


  Copyright (c) 1980, 1989, 1991 The Regents of the University of California.
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software
   must display the following acknowledgement:
This product includes software developed by the University of
California, Berkeley and its contributors.
4. Neither the name of the University nor the names of its contributors
   may be used to endorse or promote products derived from this software
   without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.

    (#)fstab.5 6.5 (Berkeley) 5/10/91