fstab(4) DG/UX R4.11MU05 fstab(4)
NAME
fstab - static information about file systems
SYNOPSIS
#include <mntent.h>
DESCRIPTION
The file /etc/fstab describes the file systems and swapping areas
used by the local machine. The system administrator can modify it
with a text editor or by invoking the sysadm(1M) system
administration utility. It is read by commands that mount, dump,
restore, and check the consistency of file systems, as well as by the
system in providing swap space. The file consists of a number of
lines like this:
fsname dir type opts freq passno
for example:
/dev/dsk/usr /usr dg/ux rw 1 1
would indicate a mount for a local file system, and
titan:/usr/titan /usr/titan nfs rw,hard 0 0
would indicate an NFS file system mount.
A High Sierra CDROM would be indicated using the following line:
/dev/pdsk/4 /cdrom cdrom ro 0 0
A DOS floppy would be indicated using the following line:
/dev/pdsk/3 /pdd/floppy dos rw 0 0
The third partition of a DOS hard disk is indicated using the
following line (first partition is c, last is z):
/dev/pdsk/3:e /pdd/partition3 dos rw 0 0
A swap area could be indicated using the following line:
/dev/dsk/swap1 swap1area swap sw 0 0
The fstab format was changed in order to support NFS file systems as
well as local file systems. The old-style fstab entries are
supported, but not recommended.
The entries from this file are accessed using the routines in
getmntent(3C), which returns a structure of the following form:
struct mntent {
char *mnt_fsname; /* name of mounted file system */
char *mnt_dir; /* file system path prefix */
char *mnt_type; /* eg. dg/ux, nfs, swap, cdrom */
char *mnt_opts; /* eg. rw, ro, hard, soft, bg, fg */
int mnt_freq; /* dump frequency, in days */
int mnt_passno; /* pass number on parallel fsck */
};
Fields are separated by white space; a #, as the first non-white
character, indicates a comment. The mnttype field determines how
the mntfsname and mntopts fields will be interpreted. The
following is a list of the file system types currently supported, and
the way each of them interprets these fields:
Type Field Interpretation
dg/ux mnt_fsname Must be a block special device
unless this is a ramdisk, in which
case, it is a symbolic link to the
mounted memory file system.
mnt_opts Valid options are ro, rw, bg, and
fg. If this has the ramdisk option,
other options include
use_wired_memory, max_file_space and
max_file_count.
dg/cfs mnt_fsname Must be a block special device.
mnt_opts Valid options are ro, rw, bg, and
fg.
cdrom mnt_fsname Must be a block special device.
mnt_opts Valid options are ro, bg, fg.
dos mnt_fsname Must be a block special device.
mnt_opts Common options are ro, rw, bg, fg.
nfs mnt_fsname The hostname of the server and the
pathname on the server of the
directory to be served. A colon
separates the pathname and hostname.
mnt_opts Common options are ro, rw, hard,
soft, bg, fg.
swap mnt_fsname Must be a block special device swap
section.
mnt_opts Ignored.
The mnttype of dg/cfs, specifying a DG/UX Cluster File System, is
valid only with the DG/UX Cluster Software product.
If the mnttype is specified as ignore, the entry is ignored. This
is useful to show disks not currently used.
Entries identified as swap are made available as swap space by the
swapon(1M) command at the end of the system reboot procedure.
When the mntfsname field is interpreted as a block special device,
programs that require the corresponding character special device must
construct the name by changing dsk to rdsk in the pathname.
mntopts could also be selected from the command line using mount -o.
If the mntopts field is a comma-separated list of options that
includes rw or ro, the file system is mounted read-write or read-
only. If this includes hard or soft, the NFS file system is mounted
hard or soft. If the list includes bg or fg, and failed attempt to
mount will cause mount to retry in the background or in the
foreground. For more details on these mntopts and others, see
mount(1M).
The field mntfreq indicates how often each file system should be
dumped by the dump2(1M) command (and triggers that command's w
option, which determines what file systems should be dumped). Most
systems set the mntfreq field to 1, indicating that file systems are
dumped each day. Some programs, like sysadm, may use a different set
of entries here; see the description of -d in admfilesystem(1M).
The final field mntpassno is used by the consistency checking
program fsck(1M) to allow overlapped checking of file systems during
a reboot. All file systems with a mntpassno of 1 are checked first
simultaneously, then all file systems with mntpassno of 2 are
checked, and so on. A value of 0 indicates that the file system will
not be checked. The <mntpassno> of the root file system should be
0, as the root cannot be checked since it is already mounted.
Programs read the /etc/fstab file but never write to it. It is the
duty of the system administrator to maintain this file. The order of
records in /etc/fstab is important because fsck and mount process the
file sequentially; file systems must appear after file systems they
are mounted within. For example, if you have an entry for
/usr/spool, it must appear after the entry for /usr.
FILES
/etc/fstab
SEE ALSO
admfilesystem(1M), dump2(1M), fsck(1M), mount(1M), swapon(1M),
sysadm(1M), getfsent(3C), getmntent(3C).
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