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) sequen-
tially 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
Mac OS X 10.8 - Generated Sat Sep 1 10:31:07 CDT 2012