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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.  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 filesys-tem filesystem
     tem 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 filesystem.  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 following:

           hfs     HFS+ is the Mac OS X default filesystem.

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

           msdos   a DOS compatible filesystem

           cd966_  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 for-matted formatted
     matted 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 auto-matically automatically
     matically (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 par-titions partitions
     titions 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 filesystems should have a fs_passno of 2.  Filesystems within a drive will be checked sequen-tially, sequentially,
     tially, 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