FSTAB(5) File formats FSTAB(5)
NAME
fstab - static information about the filesystems
SYNOPSIS
/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, remote filesystem or
filesystem image for loop device to be mounted or swap file or swap
partition to be enabled.
For ordinary mounts, it will hold (a link to) a block special device
node (as created by mknod(2)) 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. But when specifying
the volume ID of FAT or NTFS file systems upper case characters are
used (e.g UUID="A40D-85E7" or UUID="61DB7756DB7779B3").
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 check the filesystem) if not present.
FILES
/etc/fstab, <fstab.h>
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).
HISTORY
The ancestor of this fstab file format appeared in 4.0BSD.
SEE ALSO
getmntent(3), fs(5), findmnt(8), mount(8), swapon(8)
REPORTING BUGS
For bug reports, use the issue tracker at
https://github.com/util-linux/util-linux/issues.
AVAILABILITY
fstab is part of the util-linux package which can be downloaded from
Linux Kernel Archive
<https://www.kernel.org/pub/linux/utils/util-linux/>.
util-linux 2.38.1 2022-05-11 FSTAB(5)
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