fstab - 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. 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), 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 (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.
The second field, (fs_file), 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
The third field, (fs_vfstype), describes the type of the filesystem.
The system currently supports these types of filesystems (and possibly
others - consult /proc/filesystems):
minix a local filesystem, supporting filenames of length 14 or 30
ext a local filesystem with longer filenames and larger inodes.
This filesystem has been replaced by the ext2 file system, and
should no longer be used.
ext2 a local filesystem with longer filenames, larger inodes, and
lots of other features.
xiafs a local filesystem with longer filenames, larger inodes, and
lots of other features.
xfs a local filesystem with journaling, scalability and lots of
msdos a local filesystem for MS-DOS partitions.
hpfs a local filesystem for HPFS partitions.
a local filesystem used for CD-ROM drives.
nfs a filesystem for mounting partitions from remote systems.
swap a disk partition to be used for swapping.
If fs_vfstype is specified as ``ignore'' the entry is ignored. This is
useful to show disk partitions which are currently unused.
The fourth field, (fs_mntops), 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 additional options appropriate to the
filesystem type. For documentation on the available options for nonnfs
file systems, see mount(8). For documentation on all nfs-specific
options have a look at nfs(5). Common for all types of file system are
the options ``noauto'' (do not mount when "mount -a" is given, e.g., at
boot time), ``user'' (allow a user to mount), and ``owner'' (allow
device owner to mount). For more details, see mount(8).
The fifth field, (fs_freq), 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), 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
The proper way to read records from fstab is to use the routines getmn-
/etc/fstab The file fstab resides in /etc.
The documentation in mount(8) is often more up-to-date.
getmntent(3), mount(8), swapon(8), fs(5) nfs(5)
The fstab file format appeared in 4.0BSD.
Linux 2.2 15 June 1999 FSTAB(5)
[ Back ]