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, 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,
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 filesystem to be mounted.
For ordinary mounts it will hold (a link to) a block special device node (as cre-
ated 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 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/filesys-
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 parti-
tions which are currently 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 nota-
tion rather than add any prefix to the first fstab field (for example 'sshfs#exam-
ple.com' is depreacated).
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 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, and async.
noauto do not mount when "mount -a" is given (e.g., at boot time)
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 exist.
The mountall(8) program that mounts filesystem during boot also recognises 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 filesys-
tem 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) or libmount.
mount(8), mountall(8), swapon(8), fs(5), nfs(5), xfs(5), proc(5), getmntent(3)
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 ftp://ftp.ker-
Linux 2.6 August 2010 FSTAB(5)