fstab(4) DG/UX 4.30 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. 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 swap area could be indicated using the following line:
/dev/dsk/swap1 swap1_area 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(3), which returns a structure of the following
form:
struct mntent {
char *mnt_fsname; /* file system name */
char *mnt_dir; /* file system path prefix */
char *mnt_type; /* dg/ux, nfs, swap, cdrom, or ignore */
char *mnt_opts; /* rw, ro, hard, soft, bg, fg */
int mnt_freq; /* highest dump level */
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 mnt_type field
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fstab(4) DG/UX 4.30 fstab(4)
determines how the mnt_fsname and mnt_opts 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.
cdrom mnt_fsname Must be a block special device.
mnt_opts Valid options are ro, 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 Valid options are ro, rw, hard,
soft, bg, fg.
swap mnt_fsname Must be a block special device
swap section.
mnt_opts Ignored.
If the mnt_type 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 mnt_fsname 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.
If the mnt_opts 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 options, see mount(1M).
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fstab(4) DG/UX 4.30 fstab(4)
The field mnt_freq indicates how often each file system
should be dumped by the dump(1m) command (and triggers that
command's w option, which determines what file systems
should be dumped). Most systems set the mnt_freq field to
1, indicating that file systems are dumped each day. Some
programs, like sysadm, may use a different set of entries
here.
The final field mnt_passno is used by the consistency
checking program fsck(1m) to allow overlapped checking of
file systems during a reboot. All file systems with a
mnt_passno of 1 are checked first simultaneously, then all
file systems with mnt_passno of 2 are checked, and so on. A
value of 0 indicates that the file system will not be
checked. The <mnt_passno> 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
getmntent(3), fsck(1m), mount(1m), getfsent(3x), swapon(1m),
dump(1m)
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