autofs - Format of the automounter maps
DESCRIPTION
The automounter maps are files or NIS maps referred to by
the master map of the automounter (see auto.master(5)).
The automounter maps describe how file systems below the
mountpoint of the map (given in the auto.master file) are
to be mounted. This describes the sun map format; if
another map format is specified (e.g. hesiod), this docu
mentation does not apply.
Maps can be changed on the fly and the automouter will
recognize those changes on the next operation it performs
on that map. This is not true for the auto.master map!
FORMAT
This is a description of the text file format. Other
methods of specifying these files may exist. All empty
lines or lines beginning with # are ignored. The basic
format of one line in such maps is:
key [-options] location
key
is the part of the pathname between the mountpoint and the
path into the filesystem mounted. Usually you can think
about the key as a subdirectory name below the mountpoint.
options
Options are optional. Options can also be given in the
auto.master file in which case both values are cumulative
(this is a difference from SunOS). The options are a list
of comma separated options as customary for the mount(8)
command. There is a special option -fstype= used to spec
ify a filesystem type if the filesystem is not of the
default NFS type. This option is processed by the auto
mounter and not by the mount command.
location
The location specifies from where the file system is to be
mounted. In the most cases this will be an NFS volume and
the usual notation host:pathname is used to indicate the
remote filesystem and path to be mounted. If the filesys
tem to be mounted begins with a / (such as local /dev
entries or smbfs shares) a : needs to be prefixed (e.g.
:/dev/sda1).
EXAMPLE
kernel -ro,soft,intr ftp.kernel.org:/pub/linux
boot -fstype=ext2 :/dev/hda1
removable -fstype=ext2 :/dev/hdd
cd -fstype=iso9660,ro :/dev/hdc
floppy -fstype=auto :/dev/fd0
In the first line we have a NFS remote mount of the kernel
directory on ftp.kernel.org. This is mounted read-only.
The second line mounts an ext2 volume on a local ide
drive. The third makes a share exported from a Windows
machine available for automounting. The rest should be
fairly self-explanatory.
FEATURES
Map Key Substitution
An & character in the location is expanded to the value of
the key field that matched the line (which probably only
makes sense together with a wildcard key).
Wildcard Key
A * in the key field matches all keys. An example for the
usefulness is the following entry:
* &:/home/&
This will enable you to access all the home directory of
local hosts using the path /mountpoint/hostname/local-
path.
Variable Substitution
The following special variables will be substituted in the
key and location fields of an automounter map if prefixed
with $ as customary from shell scripts (Curly braces can
be used to separate the fieldname):
ARCH Architecture (uname -m)
CPU Processor Type
HOST Hostname (uname -n)
OSNAME Operating System (uname -s)
OSREL Release of OS (uname -r)
OSVERS Version of OS (uname -v)
Additional entries can be defined with the -Dvari
able=Value option to automount(8).
Executable Maps
A map can be marked as executable. The init script that
parses the auto.master map will pass this as a program map
to the automounter. A program map will be called as a
script with the key as an argument. The script needs to
return one line of a map or no output at all if the key
cannot be matched.
To do this the automount(8) daemon has to be started with
the program type insted of the file type. This is
A executable map can return an errorcode to indicate the
failure in addition to no output at all. All output sent
to stderr is logged into the system logs.
UNSUPPORTED
The automounter does not support direct maps or mount
trees (more than one filesystem to be mounted under a spe
cific automount point), and handles SunOS-style replicated
filesystems only to the extent that mount(8) does.
SEE ALSO
automount(8), auto.master(5), autofs(8), mount(8).
AUTHOR
This manual page was written by Christoph Lameter
<chris@waterf.org>, for the Debian GNU/Linux system.
Edited by H. Peter Anvin <hpa@transmeta.com>.
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