fstab - Static information about mounted file systems
/etc/fstab
The /etc/fstab file contains descriptive information about
the known file systems and the disk partitions used. In
Tru64 UNIX Version 5.0, the descriptive information for
partitions used in swapping and dumping moved to the
/etc/sysconfigtab file. The /etc/fstab file is read by
various programs. When you install the operating system,
the local file systems are included in the /etc/fstab
file. Each file system is described on a separate line;
fields on each line are separated by tabs or spaces. When
you boot the system, only the file systems specified in
the /etc/fstab file are mounted.
The following is an example of an /etc/fstab file:
/dev/disk/dsk2a / ufs rw 1 1 /dev/disk/dsk0g
/usr ufs rw 1 2 /dev/disk/dsk2g /var ufs rw 1
2 /dev/disk/dsk3c /usr/users ufs rw 1 2
/usr/share/man@rabbit /usr/share/man nfs ro,bg 0 0
usr_dmn#user1 /usr/user1 advfs rw,userquota,groupquota
0 2
The order of the lines in the /etc/fstab file is important
because the fsck, mount, and umount commands read the file
sequentially from top to bottom.
The syntax of a line in the /etc/fstab file is as follows.
Note that lines beginning with a hash (#) sign are
ignored. Blank lines are also ignored.
file_spec mnt_point fs_type mnt_options backup fsck
The first field, (file_spec), describes the block special
device, the remote file system directory, or the AdvFS
fileset to be mounted. For UFS file systems, 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
inserting the letter r in the appropriate place in the
device special file name. For example, /dev/rdisk/dsk0g.
For mfs file systems, file_spec can also specify switches
to the mfs command, separated by commas. For example, you
can specify a size of 1024 sectors and the number of bytes
per inode as 1024 by passing the following arguments:
-s1024,-i2048 /mfsdir mfs rw
See mfs(8) for more information.
The second field, (mnt_point), specifies the mount point
for the file system or remote directory.
The third field, (fs_type), specifies the type of file
system. The system currently supports the following file
systems: Specifies an ISO 9660 or High Sierra Formatted
(CD-ROM) file system. Specifies a Universal Disk Format
(UDF) formatted file system. Specifies a Network File
System (NFS) protocol. The mount command tries a Version 3
mount first. If does not get a response, it then tries a
Version 2 mount. See mount(8) for more information on NFS
mount options. Specifies a /proc file system, which
allows you to access and manipulate running processes as
if they were files. The /proc file system is used for
debugging purposes. You must specify 0 (zero) in the freq
and order fields because the /proc file system should not
be backed up or checked. Specifies a local UNIX file system
(Berkeley fast file system). Specifies the memory
file system (RAM Disk). (See mfs(8).) Specifies a local
Advanced File System (AdvFS). Specifies the PC File System.
Specifies the DCE Distributed File System. Specifies
the DCE Episode File System. Specifies the File on
File Mounting system (used by streams). Specifies the
File Descriptor File System (used by streams). Specifies
the Network File System (NFS) Version 3 protocol.
The fourth field, (mnt_options), describes the mount
options associated with the file system or partition. It
is formatted as a comma separated list of options and must
contain, at a minimum, one of the mount options ro, rq, or
rw. You cannot use the options dirty, userquota, or
groupquota unless you also specify one of the minimum
options. Specifies that the file system is mounted with
read-only access. Specifies that the file system is
mounted with read-write access. Specifies that the file
system is mounted with read-write access. Specifies that
the file system can be mounted even if it was not cleanly
unmounted. This is only for UFS. If quotas are to be
enforced for users or groups, one or both of the options
must be specified. If userquota is specified, user quotas
are to be enforced. If groupquota is specified, group
quotas are to be enforced. See also quotaon(8) and quotaoff(8).
These options can also specify the location of the
quota files; either userquota, groupquota, or both
can be specified. When the quota commands (for
example, quotacheck and quotaon) are run, they
first access the quota files. By default, user and
group quotas for a file system are contained in the
quota.user and quota.group files, which are located
in the directory specified by the mount point. For
example, the quotas for the file system on which
/usr is mounted are located in the /usr directory.
You also can specify another file name and location.
For example:
userquota=/var/quotas/tmp.user
Note that quota options apply only to UFS and AdvFS
file systems. Specifies that the file system entry
should be ignored.
There are no default mount options. The mount operation
fails if you do not specify a mount option or if you specify
an incorrect mount option. See mount(8) for a complete
list and description of valid mount options for the
various file system types.
The fifth field, (backup), is used by the dump command to
determine which file systems need to be backed up. If the
fifth field is not present, a value of zero is returned
and dump assumes that the file system does not need to be
backed up. AdvFS ignores this field.
For UFS file systems, the sixth field, (pass number), is
used by the fsck and quotacheck commands to determine the
order in which file system checks are done at reboot time.
For the root file system, specify 1 in the pass field.
For other UFS file systems specify 2 or higher in the pass
number field.
For AdvFS filesets, the sixth field is a pass number field
that allows the quotacheck command to perform all of the
consistency checks needed for the fileset. For the root
file system, specify 1 n the pass field. For other AdvFS
file systems specify 2 or higher in the pass number field.
File systems that are on the same disk or domain are
checked sequentially, but file systems on different disks
or domains but with the same greater than 1 pass number
are checked at the same time to utilize parallelism available
in the hardware. When all the file systems in a pass
have completed their checks, then the file systems with
the numerically next higher pass number will be processed.
The UFS per disk drive logic is based on the
/dev/disk/dsk0a syntax where different partition letters
are treated as being on the same disk drive. Partitions
layered on top of an LSM device may not follow this naming
convention. In this case unique pass numbers may be used
to sequence fsck and quotacheck processing.
If the sixth field is not present or zero, a value of zero
is returned and the fsck command assumes that the file
system does not need to be checked.
The following information is from the /usr/include/fstab.h
file:
struct fstab {
char *fs_spec; /* block special device
name */
char *fs_file; /* file system path prefix
*/
char *fs_vfstype; /* type of file system */
char *fs_mntops; /* comma separated mount
options */
char *fs_type; /* rw, ro, or xx */
int fs_freq; /* dump frequency, in days
*/
int fs_passno; /* pass number on parallel
dump */ };
You can read records from the /etc/fstab file by using the
getfsent(), getfsspec(), getfstype(), and getfsfile() routines.
Files: /usr/include/fstab.h
Commands: advfs(4), getfsent(3), fsck(8), mount(8)
quataon(8), quotaoff(8) fsck(8), umount(8)
fstab(4)
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