FSTAB
Section: File Formats (5)
Updated: August 2010
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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 comments, 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 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.
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/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.
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
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:
- 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
-
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 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)
or
libmount.
FILES
/etc/fstab,
<fstab.h>
SEE ALSO
mount(8),
mountall(8),
swapon(8),
fs(5),
nfs(5),
xfs(5),
proc(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/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- FILES
-
- SEE ALSO
-
- HISTORY
-
- AVAILABILITY
-
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