fstab(4) Kernel Interfaces Manual fstab(4)
NAME
fstab - Static information about mounted file systems
SYNOPSIS
/etc/fstab
DESCRIPTION
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 sys-
tems 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 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. Speci-
fies 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 sep-
arated list of options and must contain, at a minimum, one of the following mount options. There are no default mount options; the subse-
quent mount operation fails if you do not specify a mount option or if you specify an incorrect or undocumented mount option. See mount(8)
for a complete list and description of the legal mount options for the various file system types. 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 spec-
ify 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.
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 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 in 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 sep-
arated 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.
RELATED INFORMATION
Files: /usr/include/fstab.h
Commands: advfs(4), getfsent(3), fsck(8), mount(8),
quotaon(8), quotaoff(8), umount(8) delim off
fstab(4)