fstab - static information about the filesystems
#include <fstab.h>
The fstab file 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. 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 mounted. For filesystems of type ffs, the
special file
name is the block special file name, and not the character
special file
name. If a program needs the character special file name,
the program
must create it by appending an ``r'' after the last ``/'' in
the special
file name.
The second field, fs_file, describes the mount point for the
filesystem.
For swap partitions, this field should be specified as
``none''.
The third field, fs_vfstype, describes the type of the
filesystem. The
system currently supports twelve types of filesystems:
adosfs An AmigaDOS filesystem.
cd9660 An ISO9660 CD-ROM filesystem.
fdesc An implementation of /dev/fd.
ffs A local UNIX filesystem.
ext2fs A local Linux compatible ext2fs filesystem.
kernfs Various and sundry kernel statistics.
mfs A local memory-based UNIX filesystem.
msdos An MS-DOS FAT filesystem.
nfs A Sun Microsystems compatible Network File
System.
procfs A local filesystem containing process information.
swap A disk partition to be used for swapping.
union A translucent filesystem.
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 (see fs_type below)
plus any additional
options appropriate to the filesystem type.
The option ``auto'' can be used in the ``noauto'' form to
cause a file
system not to be mounted automatically (with mount -a, or at
system boot
time).
If the options ``userquota'' and/or ``groupquota'' are specified, the
filesystem is automatically processed by the quotacheck(8)
command, and
user and/or group disk quotas are enabled with quotaon(8).
By default,
filesystem quotas are maintained in files named quota.user
and
quota.group which are located at the root of the associated
filesystem.
These defaults may be overridden by putting an equal sign
and an alternative
absolute pathname following the quota option. Thus, if
the user
quota file for /tmp is stored in /var/quotas/tmp.user, this
location can
be specified as:
userquota=/var/quotas/tmp.user
The type of the mount is extracted from the first parameter
of the
fs_mntops field and stored separately in the fs_type field
(it is not
deleted from the fs_mntops field). If fs_type is ``rw'' or
``ro'' then
the filesystem whose name is given in the fs_file field is
normally
mounted read-write or read-only on the specified special
file. If
fs_type is ``sw'' then the special file is made available as
a piece of
swap space by the swapon(8) command at the end of the system
reboot procedure.
The fields other than fs_spec and fs_type are unused. If
fs_type is specified as ``xx'' the entry is ignored. This
is useful to
show disk partitions which are currently unused.
The fifth field, fs_freq, 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(8) 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 is zero, a value of zero
is returned
and fsck(8) will assume that the filesystem does not need to
be checked.
#define FSTAB_RW "rw" /* read-write device */
#define FSTAB_RO "ro" /* read-only device */
#define FSTAB_SW "sw" /* swap device */
#define FSTAB_XX "xx" /* ignore totally */
struct fstab {
char *fs_spec; /* block special device name
*/
char *fs_file; /* filesystem path prefix */
char *fs_vfstype; /* type of filesystem */
char *fs_mntops; /* comma separated mount options */
char *fs_type; /* rw, ro, sw, or xx */
int fs_freq; /* dump frequency, in days
*/
int fs_passno; /* pass number on parallel
fsck */
};
The proper way to read records from fstab is to use the routines
getfsent(3), getfsspec(3), getfstype(3), and getfsfile(3).
/etc/fstab
Here is a sample /etc/fstab file:
/dev/sd0a / ffs rw 1 1
/dev/sd0e /var ffs rw,nodev,nosuid 1 2
#/dev/sd0f /tmp ffs rw,nodev,nosuid 1 2
/dev/sd0b /tmp mfs rw,nodev,nosuid,-s=153600 0 0
/dev/sd0g /usr ffs rw,nodev 1 2
/dev/sd0h /usr/local ffs rw,nodev 1 2
/dev/sd0i /home ffs rw,nodev,nosuid 1 2
/dev/sd1b none swap sw 0 0
/dev/cd0a /cdrom cd9660 ro,noauto 0 0
/kern /kern kernfs ro 0 0
/proc /proc procfs rw 0 0
server:/export/ports /usr/ports nfs rw,nodev,nosuid,tcp,soft,intr 0 0
quota(1), getfsent(3), fsck(8), mount(8), quotacheck(8),
quotaon(8),
umount(8)
The fstab file format appeared in 4.0BSD.
OpenBSD 3.6 June 5, 1993
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