fstab.5

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.\"     @(#)fstab.5	6.5 (Berkeley) 5/10/91
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.\" Modified Sat Mar  6 20:45:03 1993, [e-mail], for Linux
.\" Sat Oct  9 10:07:10 1993: converted to man format by [e-mail]
.\" Sat Nov 20 20:47:38 1993: hpfs documentation added
.\" Sat Nov 27 20:23:32 1993: Updated authorship information
.\" Wed Jul 26 00:00:00 1995: Updated some nfs stuff, [e-mail]
.\" Tue Apr  2 00:38:28 1996: added info about "noauto", "user", etc.
.\" Tue Jun 15 20:02:18 1999: added LABEL and UUID
.\" Sat Jul 14 2001: Michael K. Johnson <[e-mail]> added -O
.\"
.TH FSTAB 5 "15 June 1999" "Linux 2.2" "Linux Programmer's Manual"
.SH NAME
fstab \- static information about the filesystems
.SH SYNOPSIS
.B #include <fstab.h>
.SH DESCRIPTION
The file
.B fstab
contains descriptive information about the various file systems.
.B 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.  The order of records in
.B fstab
is important because
.BR fsck (8),
.BR mount (8),
and 
.BR umount (8)
sequentially iterate through
.B fstab
doing their thing.

The first field,
.RI ( fs_spec ),
describes the block special device or
remote filesystem to be mounted.
.LP
For ordinary mounts it will hold (a link to) a block special
device node (as created by
.BR 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'.
.LP
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.
.BR e2label (8)
or
.BR 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,
.RI ( 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 `\\040'.

The third field,
.RI ( fs_vfstype ),
describes the type of the filesystem.  Linux supports lots
of filesystem types, such as
.IR adfs ,
.IR affs ,
.IR autofs ,
.IR coda ,
.IR coherent ,
.IR cramfs ,
.IR devpts ,
.IR efs ,
.IR ext2 ,
.IR ext3 ,
.IR hfs ,
.IR hpfs ,
.IR iso9660 ,
.IR jfs ,
.IR minix ,
.IR msdos ,
.IR ncpfs ,
.IR nfs ,
.IR ntfs ,
.IR proc ,
.IR qnx4 ,
.IR reiserfs ,
.IR romfs ,
.IR smbfs ,
.IR sysv ,
.IR tmpfs ,
.IR udf ,
.IR ufs ,
.IR umsdos ,
.IR vfat ,
.IR xenix ,
.IR xfs ,
and possibly others. For more details, see
.BR mount (8).
For the filesystems currently supported by the running kernel, see
.IR /proc/filesystems .
An entry
.I swap
denotes a file or partition to be used
for swapping, cf.\&
.BR swapon (8).
An entry
.I ignore
causes the line to be ignored.  This is useful
to show disk partitions which are currently unused.

The fourth field,
.RI ( 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
.BR mount (8).
For documentation on all nfs-specific options have a look at
.BR 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 ``comment''
(e.g., for use by fstab-maintaining programs).
The ``owner'' and ``comment'' options are Linux-specific.
For more details, see
.BR mount (8).

The fifth field,
.RI ( fs_freq ),
is used for these filesystems by the
.BR 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
.B dump
will assume that the filesystem does not need to be dumped.

The sixth field,
.RI ( fs_passno ),
is used by the
.BR fsck (8)
program to determine the order in which filesystem checks are done at
reboot time.  The root filesystem should be specified with a
.I fs_passno
of 1, and other filesystems should have a 
.I 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
.B fsck
will assume that the filesystem does not need to be checked.

The proper way to read records from
.B fstab
is to use the routines
.BR getmntent (3).
.SH FILES
.I /etc/fstab
.SH "SEE ALSO"
.BR getmntent (3),
.BR mount (8),
.BR swapon (8),
.BR fs (5)
.BR nfs (5)
.SH HISTORY
The ancestor of this
.B fstab
file format appeared in 4.0BSD.
.\" But without comment convention, and options and vfs_type.
.\" Instead there was a type rw/ro/rq/sw/xx, where xx is the present 'ignore'.