fstab(4) Kernel Interfaces Manual fstab(4)
fstab - static information about the file systems
is an ASCII file that resides in directory
contains a list of mountable file-system entries. Each file-system entry appears on a separate line, and consists of fields separated by
one or more blanks or tabs.
The order of entries in is important only for entries without a pass number field. Entries without a pass number are sequentially checked
by (see fsck(1M)) after the entries with a pass number have been checked.
Each file-system entry must contain a device special file and may additionally contain all of the following fields, in the following order:
pass number (on parallel
If any field after the name of the device special file is present, all fields must be present in the order indicated, to ensure correct
Entries from this file are accessed using (see getmntent(3X)).
The fields are separated by white space, and a as the first non-whitespace character in an entry or field indicates a comment.
device special file A block device special file name. This field is used by and other commands to identify the location of the storage
device on which the file system resides. If type is this entry is ignored since a block device is not required for a
memory file system.
directory Name of the root of the mounted file system that corresponds to the device special file. If type is there is no corre-
sponding device special file; directory is the root of the memory based file system. If type is directory can be the
name of any directory within a file system. Only one directory should be specified per file system. directory must
already exist and must be given as an absolute path name.
type Can be or a file system type (for example, or
If type is the device special file is made available as an area of swap space by the command (see swapon(1M)). The
options field is valid. The fields directory, pass number, and backup frequency are ignored for entries.
If type is the file system in which directory resides is made available as swap space by The options field is valid.
The fields device special file, pass number, and backup frequency are ignored for entries.
If type is the device special file field is ignored; the corresponding entry displayed in is Additionally, if type is
will skip the entry even for matches of directory, if a different type is specified to
If type is the device special file is made available as an area into which a system crash dump may occur, by the com-
mand (see crashconf(1M)). The fields options, directory, pass number, and backup frequency are ignored for entries.
Entries marked by the type are ignored by all commands and can be used to mark unused sections. If type is specified
as either or the entry is ignored by the and commands (see mount(1M) and fsck(1M)). fsck also ignores entries with
type specified as or
options A comma-separated list of option keywords, as found in or (see mount(1M) and swapon(1M)). The keywords used depend on
the parameter specified in type.
backup frequency Reserved for possible use by future backup utilities.
pass number Used by the command to determine the order in which file system checks are done. The root file system should be speci-
fied with a pass number of 1, to be checked first, and other file systems should have larger numbers. (A file system
with a pass number of zero is ignored by the command.)
File systems within a drive should be assigned different pass numbers, but file systems on different drives can be
checked on the same pass, to utilize possible parallelism available in the hardware. If pass number is not present,
checks each such file system sequentially after all eligible file systems with pass numbers have been checked.
comment An optional field that begins with a character and ends with a new-line character. Space from the pass number to the
comment field (if present) or to the new-line is reserved for future use.
There is no limit to the number of device special file fields in
If the field type is a remote NFS file system is implied. For NFS file systems, the device special file should be the serving machine name
followed by ":" followed by the path on the serving machine of the directory being served. The pass number and backup frequency fields are
ignored for NFS entries.
Examples of typical entries:
Add an HFS file system at using default mount options; (backup frequency 0) fsck pass 2:
Add a device to a system managed using LVM, with default options (Note, the directory field cannot be empty, even though it is
Add a swap device on a system implementing whole-disk layout to use the space after the end of the file system (options
Add file system swap space on the file system containing directory type is set options to and (see swapon(1M)) for explanation of
options). device field is ignored but must not be empty:
(Note that both a file system entry and a swap entry are required for devices providing both services.)
Use a device for dump space if the system crashes. directory field is ignored but must not be empty:
(Note that both a swap entry and a dump entry are required for devices providing both services.)
Add a MemFS file system at of The device special file field is ignored but must not be empty:
HP-UX system administration tools that provide file system mount management interfaces may read and/or write System administrators should
be careful not to simultaneously modify this file with one of these tools.
Here is an example for mounting an NFS file system on systems that support NFS file systems:
fstab was developed by HP, AT&T, Sun Microsystems, Inc., and the University of California, Berkeley.
crashconf(1M), fsck(1M), mount(1M), swapon(1M), getfsent(3X), getmntent(3X), mnttab(4).