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 various file systems. fstab is only read by pro‐
grams, and not written; it is the duty of the system administrator to properly create and maintain this file.
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 order of records in fstab is important because
fsck(8), mount(8), and umount(8) sequentially iterate through fstab doing their thing.
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 one will have <host>:<dir>,
e.g., `knuth.aeb.nl:/'. For procfs, use `proc'.
Instead of giving the device explicitly, one may indicate the filesystem that is to be mounted by its
UUID or LABEL (cf. e2label(8) or xfs_admin(8)), writing LABEL=<label> or UUID=<uuid>, e.g.,
`LABEL=Boot' or `UUID=3e6be9de-8139-11d1-9106-a43f08d823a6'.
It's also possible to use PARTUUID= and PARTLABEL=. These partitions identifiers are supported for GUID
Partition Table (GPT) and MAC partition table only.
See blkid(8) or lsblk(8) for more details about devices 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 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 lots of filesystem types, such as
adfs, affs, autofs, coda, coherent, cramfs, devpts, efs, ext2, ext3, hfs, hpfs, iso9660, jfs, minix,
msdos, ncpfs, nfs, ntfs, proc, qnx4, reiserfs, romfs, smbfs, sysv, tmpfs, udf, ufs, umsdos, vfat,
xenix, xfs, and possibly others. For more details, see mount(8).
For the filesystems currently supported by the running kernel, see /proc/filesystems.
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.
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 plus any
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 for these filesystems by the dump(8) command to determine which filesystems need to
be dumped. If the fifth field is not present, a value of zero is returned and dump will assume that
the filesystem does not need to be dumped.
The sixth field (fs_passno).
This field is used by the fsck(8) program to determine the order in which filesystem checks are done at
reboot time. The root filesystem should be specified with a fs_passno of 1, and 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.
If the sixth field is not present or zero, a value of zero is returned and fsck will assume that the
filesystem does not need to be checked.
NOTES
The proper way to read records from fstab is to use the routines getmntent(3) or libmount.
The keyword ignore as filesystem type (3rd field) is not more supported by the pure libmount based mount util‐
ity (since util-linux v2.22).
FILES
/etc/fstab, <fstab.h>
SEE ALSO
findmnt(8), mount(8), swapon(8), fs(5), getmntent(3)
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 ftp://ftp.ker‐
nel.org/pub/linux/utils/util-linux/.
util-linux August 2010 FSTAB(5)
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