FSTAB(5)                    BSD File Formats Manual                   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,
     using the vifs(8) command.  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 diskarbitrationd(8), fsck(8),
     mount(8), and umount(8) sequentially iterate through fstab doing their
     thing.

     The first field, (fs_spec), describes the block special device, the local
     filesystem, or the remote filesystem to be mounted.  The diskarbitrationd
     program supports the identification of a local filesystem uniquely by its
     UUID or by its volume name, irrespective of hardware configuration and of
     hardware parallelism, using the constructs ``UUID'' and ``LABEL''.

     The second field, (fs_file), describes the mount point for the filesys-
     tem.  For swap partitions, this field should be specified as ``none''.

     The third field, (fs_vfstype), describes the type of the filesystem.  The
     system currently supports different filesystem types, including the fol-
     lowing:

           hfs     HFS+ is the Mac OS X default filesystem.

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

           msdos   a DOS compatible filesystem

           cd9660  a CD-ROM filesystem (as per ISO 9660)

           fdesc   an implementation of /dev/fd

           union   a translucent filesystem

     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.

     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).

     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 filesys-
     tems 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 will assume that the filesystem does not need to be checked.

     #define FSTAB_RW        "rw"    /* read-write device */
     #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;    /* type of filesystem */
             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), getfstype(3), and getfsfile(3).

EXAMPLES
     UUID=DF000C7E-AE0C-3B15-B730-DFD2EF15CB91 /export hfs   ro
     UUID=FAB060E9-79F7-33FF-BE85-E1D3ABD3EDEA none    hfs   rw,noauto
     LABEL=The\040Volume\040Name\040Is\040This none    msdos ro

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

SEE ALSO
     getfsent(3), diskarbitrationd(8)

HISTORY
     The fstab file format appeared in 4.0BSD.

Darwin                          March 28, 2002                          Darwin