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
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
Note that mount(8) uses UUIDs as strings. The string
representation of the UUID should be based on lower case
The second field (fs_file).
This field describes the mount point for the filesystem. For
swap partitions, this field should be specified as `none'. If
the name of the mount point contains spaces these can be
escaped as `\040'.
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
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
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:
use default options: rw, suid, dev, exec, auto, nouser,
noauto do not mount when "mount -a" is given (e.g., at boot
user allow a user to mount
owner allow device owner to mount
or x-<name> for use by fstab-maintaining programs
nofail do not report errors for this device if it does not
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
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
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
This page is part of the util-linux (a random collection of Linux
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⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
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util-linux February 2015 FSTAB(5)