FSTAB(5) File Formats FSTAB(5)NAMEfstab - static information about the filesystems
The file fstab contains descriptive information about the various file
systems. fstab is only read by programs, 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 com‐
ments, blank lines are ignored. The order of records in fstab is impor‐
tant because fsck(8), mount(8), and umount(8) sequentially iterate
through fstab doing their thing, though at boot time mountall(8) may
process the file out-of-order when it believes it is safe to do so.
The first field (fs_spec).
This field describes the block special device or remote filesys‐
tem 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
Instead of giving the device explicitly, one may indicate the
(ext2 or xfs) filesystem that is to be mounted by its UUID or
volume 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'. This will make the
system more robust: adding or removing a SCSI disk changes the
disk device name but not the filesystem volume label.
Note that mount(8) uses UUIDs as strings. The string representa‐
tion 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
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,
An entry swap denotes a file or partition to be used for swap‐
ping, cf. swapon(8). An entry ignore causes the line to be
ignored. This is useful to show disk partitions which are cur‐
rently unused. 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
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 con‐
tains at least the type of mount plus any additional options
appropriate to the filesystem type. For documentation on the
available mount options, see mount(8). For documentation on the
available swap options, see swapon(8).
Basic file system 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
for use by fstab-maintaining programs
nofail do not report errors for this device if it does not
The mountall(8) program that mounts filesystem during boot also recog‐
nises additional options that the ordinary mount(8) tool does not.
These are: ``bootwait'' which can be applied to remote filesystems
mounted outside of /usr or /var, without which mountall(8) would not
hold up the boot for these; ``nobootwait'' which can be applied to non-
remote filesystems to explicitly instruct mountall(8) not to hold up
the boot for them; ``optional'' which causes the entry to be ignored if
the filesystem type is not known at boot time; and ``showthrough''
which permits a mountpoint to be mounted before its parent mountpoint
(this latter should be used carefully, as it can cause boot hangs).
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.
The proper way to read records from fstab is to use the routines getmn‐
tent(3) or libmount.
SEE ALSOmount(8), mountall(8), swapon(8), fs(5), nfs(5), xfs(5), proc(5), getm‐
The ancestor of this fstab file format appeared in 4.0BSD.
This man page is part of the util-linux package and is available from
util-linux August 2010 FSTAB(5)