FSTAB(5) Linux Programmer's Manual FSTAB(5)
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. Lines starting with '#' are com-
ments. 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
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)), writ-
ing 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 par-
titions, 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), 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 ker-
nel, see /proc/filesystems. An entry swap denotes a file or partition to be used for
swapping, cf. swapon(8). An entry ignore causes the line to be 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 non-nfs 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), and ``_netdev''
(device requires network to be available). The ``owner'' and ``_netdev'' options are
Linux-specific. For more details, see mount(8).
The fifth field, (fs_freq), is used for these filesystems by the dump(8) command to deter-
mine 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 be checked.
The proper way to read records from fstab is to use the routines getmntent(3).
getmntent(3), mount(8), swapon(8), fs(5) nfs(5)
The ancestor of this fstab file format appeared in 4.0BSD.
Linux 2.2 15 June 1999 FSTAB(5)