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FSTAB(5)                  FreeBSD 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)
     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 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;
     everything 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
     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
     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 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:


     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 supported 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'', ``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

     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
     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 completed
     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).

     /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.

FreeBSD 11.0-PRERELEASE         April 14, 2014         FreeBSD 11.0-PRERELEASE


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