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FSTAB(5)		    BSD	File Formats Manual		      FSTAB(5)

     fstab -- static information about the file	systems

     #include <fstab.h>

     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.  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 special device or remote	file
     system to be mounted.  The	contents are decoded by	the strunvis(3)	func-
     tion.  This allows	using spaces or	tabs in	the device name	which would be
     interpreted as field separators otherwise.

     The second	field, (fs_file), describes the	mount point for	the file sys-
     tem.  For swap partitions,	this field should be specified as "none".  The
     contents are decoded by the strunvis(3) function, as above.

     The third field, (fs_vfstype), describes the type of the file system.
     The system	can support various file system	types.	Only the root, /usr,
     and /tmp file systems need	be statically compiled into the	kernel;	every-
     thing else	will be	automatically loaded at	mount time.  (Exception: the
     FFS cannot	currently be demand-loaded.)  Some people still	prefer to
     statically	compile	other file systems as well.

     The fourth	field, (fs_mntops), describes the mount	options	associated
     with the file system.  It is formatted as a comma separated list of op-
     tions.  It	contains at least the type of mount (see fs_type below)	plus
     any additional options appropriate	to the file system type.  See the op-
     tions flag	(-o) in	the mount(8) page and the file system specific page,
     such as mount_nfs(8), for additional options that may be specified.  All
     options that can be given to the file system specific mount commands can
     be	used in	fstab as well.	They just need to be formatted a bit differ-
     ently.  The arguments of the -o option can	be used	without	the preceding
     -o	flag.  Other options need both the file	system specific	flag and its
     argument, separated by an equal sign.  For	example, mounting an
     msdosfs(5)	filesystem, the	options

	   -o sync -o noatime -m 644 -M	755 -u foo -g bar

     should be written as


     in	the option field of fstab.

     If	the options "userquota"	and/or "groupquota" are	specified, the file
     system is automatically processed by the quotacheck(8) command, and user
     and/or group disk quotas are enabled with quotaon(8).  By default,	file
     system quotas are maintained in files named quota.user and
     which are located at the root of the associated file system.  These de-
     faults may	be overridden by putting an equal sign and an alternative ab-
     solute pathname following the quota option.  Thus,	if the user quota file
     for /tmp is stored	in /var/quotas/tmp.user, this location can be speci-
     fied as:


     If	the option "failok" is specified, the system will ignore any error
     which happens during the mount of that filesystem,	which would otherwise
     cause the system to drop into single user mode.  This option is imple-
     mented by the mount(8) command and	will not be passed to the kernel.

     If	the option "noauto" is specified, the file system will not be automat-
     ically mounted at system startup.	Note that, for network file systems of
     third party types (i.e., types supported by additional software not in-
     cluded in the base	system)	to be automatically mounted at system startup,
     the extra_netfs_types rc.conf(5) variable must be used to extend the
     rc(8) startup script's list of network file system	types.

     If	the option "late" is specified,	the file system	will be	automatically
     mounted at	a stage	of system startup after	remote mount points are
     mounted.  For more	detail about this option, see the mount(8) manual

     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"	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 pro-
     cedure.  For vnode-backed swap spaces, "file" is supported	in the
     fs_mntops field.  When fs_spec is an md(4)	device file ("md" or
     "md[0-9]*") and "file" is specified in fs_mntopts,	an md(4) device	is
     created with the specified	file used as backing store, and	then the new
     device is used as swap space.  Swap entries on .eli devices will cause
     automatic creation	of encrypted devices.  The "ealgo", "aalgo", "keylen",
     "notrim", and "sectorsize"	options	may be passed to control those geli(8)
     parameters.  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	will assume
     that the file system does not need	to be dumped.  If the fifth field is
     greater than 0, then it specifies the number of days between dumps	for
     this file system.

     The sixth field, (fs_passno), is used by the fsck(8) and quotacheck(8)
     programs to determine the order in	which file system and quota checks are
     done at reboot time.  The fs_passno field can be any value	between	0 and

     The root file system should be specified with a fs_passno of 1, and other
     file systems should have a	fs_passno of 2 or greater.  A file system with
     a fs_passno value of 1 is always checked sequentially and be completed
     before another file system	is processed, and it will be processed before
     all file systems with a larger fs_passno.

     For any given value of fs_passno, file systems within a drive will	be
     checked sequentially, but file systems on different drives	will be
     checked at	the same time to utilize parallelism available in the hard-
     ware.  Once all file system checks	are complete for the current
     fs_passno,	the same process will start over for the next fs_passno.

     If	the sixth field	is not present or is zero, a value of zero is returned
     and fsck(8) and quotacheck(8) will	assume that the	file system does not
     need to be	checked.

     The fs_passno field can be	used to	implement finer	control	when the sys-
     tem utilities may determine that the file system resides on a different
     physical device, when it actually does not, as with a ccd(4) device.  All
     file systems with a lower fs_passno value will be completed before	start-
     ing on file systems with a	higher fs_passno value.	 E.g. all file systems
     with a fs_passno of 2 will	be completed before any	file systems with a
     fs_passno of 3 or greater are started.  Gaps are allowed between the dif-
     ferent fs_passno values.  E.g. file systems listed	in /etc/fstab may have
     fs_passno values such as 0, 1, 2, 15, 100,	200, 300, and may appear in
     any order within /etc/fstab.

     #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;	     /*	file system 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).

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

     # Device	     Mountpoint	     FStype  Options	     Dump    Pass#
     # UFS file	system.
     /dev/da0p2	     /		     ufs     rw		     1	     1
     # Swap space on a block device.
     /dev/da0p1	     none	     swap    sw		     0	     0
     # Swap space using	a block	device with GBDE/GELI encyption.
     # aalgo, ealgo, keylen, sectorsize	options	are available
     # for .eli	devices.
     /dev/da1p1.bde  none	     swap    sw		     0	     0
     /dev/da1p2.eli  none	     swap    sw		     0	     0
     # tmpfs.
     tmpfs	     /tmp	     tmpfs   rw,size=1g,mode=1777    0 0
     # UFS file	system on a swap-backed	md(4).	/dev/md10 is
     # automatically created.  If it is	"md", a	unit number
     # will be automatically selected.
     md10	     /scratch	     mfs     rw,-s1g	     0	     0
     # Swap space on a vnode-backed md(4).
     md11	     none	     swap    sw,file=/swapfile	     0 0
     # CDROM.  "noauto"	option is typically used because the
     # media is	removable.
     /dev/cd0	     /cdrom	     cd9660  ro,noauto	     0	     0
     # NFS-exported file system.  "serv" is an NFS server name
     # or IP address.
     serv:/export    /nfs	     nfs     rw,noinet6	     0	     0

     getfsent(3), getvfsbyname(3), strunvis(3),	ccd(4),	dump(8), fsck(8),
     geli(8), mount(8),	quotacheck(8), quotaon(8), swapon(8), umount(8)

     The fstab file format appeared in 4.0BSD.

BSD				April 14, 2014				   BSD


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