FSTAB(5) BSD Reference Manual FSTAB(5)
fstab - static information about the filesystems
#include <fstab.h>
The fstab file contains descriptive information about the various
filesystems. 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 beginning with the '#' char-
acter are comments and are ignored. The order of records in fstab is im-
portant because fsck(8), mount(8), and umount(8) sequentially iterate
through fstab doing their thing.
A line has the following format:
fs_spec fs_file fs_vfstype fs_mntops fs_freq fs_passno
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 Filesystem.
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 addi-
tional options appropriate to the filesystem type.
The option "auto" can be used in the "noauto" form to cause a filesystem
not to be mounted automatically (with mount -A or 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 alterna-
tive absolute pathname following the quota option. Thus, if the user quo-
ta 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 filesys-
tems 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/sd0j /usr/src ffs rw,nodev,nosuid,softdep 1 2
/dev/sd1b none swap sw 0 0
/dev/cd0a /cdrom cd9660 ro,noauto 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.
MirBSD #10-current June 5, 1993 2