Updated: 2022/Sep/29
Please read Privacy Policy. It's for your privacy.
FSTAB(5) File Formats Manual FSTAB(5)
NAME
fstab - file system table for devices, types, and mount points
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 file system is described on a separate line; fields on each line are
separated by tabs or spaces. Lines beginning with "#" are comments. The
order of records in fstab is important because fsck(8), mount(8), and
umount(8) sequentially iterate through fstab doing their respective
tasks.
Each configuration line/record in fstab has the format:
fs_spec fs_file fs_vfstype fs_mntops fs_freq fs_passno
The first field, (fs_spec), describes the block special device or remote
file system to be mounted. For file systems of type ffs, 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. (Note that for some file systems, e.g., kernfs,
procfs, and tmpfs, this field has no applicable use, and any string may
be supplied as a placeholder. It is present simply for consistency of
argument number and order.)
If the first field is of the form "NAME=<value>" then all the dk(4) wedge
partitions are searched for one that has a wedge name equal to <value>
and the device corresponding to it is selected.
If the first field starts with the prefix "ROOT." the prefix is replaced
with "/dev/[root_device]", where [root_device] is the value of the
"kern.root_device" sysctl.
The second field, (fs_file), describes the mount point for the file
system. For swap and dump partitions, this field should be specified as
"none".
The third field, (fs_vfstype), describes the type of the file system.
The system currently supports these file systems:
adosfs an AmigaDOS file system.
cd9660 an ISO 9660 CD-ROM file system.
ext2fs an implementation of the Linux "Second Extended
File-system".
fdesc an implementation of /dev/fd.
ffs a local UNIX file system.
filecore a file system for RISC OS.
kernfs various and sundry kernel statistics.
lfs a log-structured file-system.
mfs a local memory-based UNIX file system.
msdos an MS-DOS "FAT file system".
nfs a Sun Microsystems compatible "Network File System".
ntfs a file system used by Windows NT. Still experimental.
null a loop-back file system, allowing parts of the system to
be viewed elsewhere.
overlay a demonstration of layered file systems.
portal a general file system interface, currently supports TCP
and FS mounts.
procfs a local file system of process information.
ptyfs a pseudo-terminal device file system.
swap a disk partition to be used for swapping and paging.
tmpfs an efficient memory file system.
umap a user and group re-mapping file system.
union a translucent file system.
zfs a ZFS file system.
The fourth field, (fs_mntops), describes the mount options associated
with the file system. 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 file system type.
The option "auto" can be used in the "noauto" form to cause a file system
not to be mounted automatically (with "mount -a" , or system boot time).
If the options "userquota" and/or "groupquota" are specified, the file
system is automatically processed by the quotacheck(8) command, and
legacy user and/or group disk quotas are enabled with quotaon(8). By
default, file system quotas are maintained in files named quota.user and
quota.group which are located at the root of the associated file system.
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
It is recommended to turn on the new, in-file system quota with tunefs(8)
or at newfs(8) time, and to not use the "userquota" or "groupquota"
options. Migration of limits to the new in-file system quota can be
handled via quotadump(8) and quotarestore(8).
The option "rump" is used to mount the file system using a rump(3)
userspace server instead of the kernel server.
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 file system 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" or "dp" then the special
file is made available as a piece of swap or dump space by the swapctl(8)
command towards the beginning of the system reboot procedure. See
swapctl(8) for more information on configuring swap and dump devices.
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 file systems by the dump(8)
command to determine which file systems need to be dumped. If the fifth
field is not present, a value of zero is returned and dump(8) will assume
that the file system does not need to be dumped.
The sixth field, (fs_passno), is used by the fsck(8) program to determine
the order in which file system checks are done at reboot time. The root
file system should be specified with a fs_passno of 1, and other file
systems should have a fs_passno of 2. Filesystems within a drive will be
checked sequentially, but file systems on different drives will be
checked at the same time to use 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 file system 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_DP "dp" /* dump device */
#define FSTAB_XX "xx" /* ignore totally */
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, sw, or xx */
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), and getfsfile(3).
FILES
/etc/fstab The location of fstab configuration file.
/usr/share/examples/fstab/
Some useful configuration examples.
EXAMPLES
To use "NAME" on a non-GPT disk, use:
NAME=sb2k5Root/a / ffs rw,log 1 1
NAME=sb2k5Root/b none swap sw,dp 0 0
For a gpt(8) disk, use:
NAME=firstpartition / ffs rw,log 1 1
NAME=secondpartition none swap sw,dp 0 0
SEE ALSO
getfsent(3), getfsspecname(3), mount(8), swapctl(8)
HISTORY
The fstab file format appeared in 4.0BSD.
NetBSD 10.99 April 19, 2020 NetBSD 10.99