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

NAME
     fstab -- static information about the file systems

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 prop-
     erly 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) function.  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 system.  For swap parti-
     tions, 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 sup-
     port various file system types.  Only the root, /usr, and /tmp file systems need be stati-
     cally compiled into the kernel; everything else will be automatically loaded at mount time.
     (Exception: the FFS cannot currently be demand-loaded.)  Some people still prefer to stati-
     cally 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 options.  It contains at least the type of
     mount (see fs_type below) plus any additional options appropriate to the file system type.
     See the options 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 differently.  The arguments of the -o option can be used without the pre-
     ceding -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

	   sync,noatime,-m=644,-M=755,-u=foo,-g=bar

     in the option field of fstab.

     If the options ``userquota'' and/or ``groupquota'' are specified, the file system is auto-
     matically 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 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 path-
     name 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 ``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 implemented 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 automatically mounted at
     system startup.  Note that, for network file systems of third party types (i.e., types sup-
     ported by additional software not included 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 page.

     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 procedure.  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'', 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 deter-
     mine 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 'INT_MAX-1'.

     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 hardware.  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 system 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 com-
     pleted before starting 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 different 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).

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

EXAMPLES
     # 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

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

HISTORY
     The fstab file format appeared in 4.0BSD.

BSD					  April 14, 2014				      BSD
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