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NAME    [Toc]    [Back]

     fstab - static information about the filesystems

SYNOPSIS    [Toc]    [Back]

     #include <fstab.h>

DESCRIPTION    [Toc]    [Back]

     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
     For swap partitions,  this  field  should  be  specified  as

     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
           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

     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
     quota.group  which are located at the root of the associated
     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:


     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
     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).

FILES    [Toc]    [Back]


EXAMPLES    [Toc]    [Back]

     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

SEE ALSO    [Toc]    [Back]

     quota(1),  getfsent(3),  fsck(8),  mount(8),  quotacheck(8),

HISTORY    [Toc]    [Back]

     The fstab file format appeared in 4.0BSD.

OpenBSD      3.6                           June      5,      1993
[ Back ]
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