FSTAB(5)

NAME
fstab - static information about the filesystems

SYNOPSIS
#include <fstab.h>

DESCRIPTION
The file fstab contains descriptive information about the various file systems. 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. The order of records in fstab is important because fsck(8), mount(8), and umount(8) sequentially iterate through fstab doing their thing.

The first field, (fs_spec), describes the block special device or remote filesystem to be mounted. For filesystems of type ufs, 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 a ``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 can support various filesystem types. Only the root, /usr, and /tmp filesystems need be statically compiled into the kernel; everything else will be automatically loaded at mount time. (Exception: the UFS family - FFS, MFS, and LFS cannot currently be demand-loaded.) Some people still prefer to statically compile other filesystems as well.

ufs a local UNIX filesystem

mfs a local memory-based UNIX filesystem

nfs a Sun Microsystems compatible ``Network File System''

swap
    a disk partition to be used for swapping

msdos
    a DOS compatible filesystem

isofs
    a CD-ROM filesystem (as per ISO 9660)

procfs
    a file system for accessing process data

kernfs
    a file system for accessing kernel parameter

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 additional options appropriate to the filesystem type.

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 alternative absolute pathname following the quota option. Thus, if the user quota file for /tmp is stored in /var/quotas/tmp.user, this location can be specified as:

    userquota=/var/quotas/tmp.user

If the option ``noauto'' is specified, the filesystem will not be automatically mounted at system startup.

The type of the mount is extracted from 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 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 filesystems 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 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_RQ	"rq"	/* read/write with quotas */
    #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;	/* File system type, ufs, nfs */
    	char	*fs_mntops;	/* Mount options ala -o */
    	char	*fs_type;	/* FSTAB_* from fs_mntops */
    	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).

FILES
/etc/fstab
    The file fstab resides in /etc.

SEE ALSO
getfsent(3), getvfsbyname(3), dump(8), fsck(8), mount(8), quotacheck(8), quotaon(8), swapon(8), umount(8).

HISTORY
The fstab file format appeared in 4.0BSD.