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 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.
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
`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 parti-
tions identifiers are supported for GUID Partition Table (GPT)
and MAC partition table only.
See blkid(8) or lsblk(8) for more details about devices identi-
fiers.
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
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 swap-
ping, 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 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:
defaults
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
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 getmn-
tent(3) or libmount.
The keyword ignore as filesystem type (3rd field) is not more supported
by the pure libmount based mount utility (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.kernel.org/pub/linux/utils/util-linux/.
util-linux August 2010 FSTAB(5)
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