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autofs - Format of the automounter maps
The automounter maps are files or NIS maps referred to by the master map of the auto-
mounter (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 documentation
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!
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
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 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 specify a filesystem type if the filesystem is not of the default NFS
type. This option is processed by the automounter and not by the mount command.
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 filesystem to be mounted begins with a /
(such as local /dev entries or smbfs shares) a : needs to be prefixed (e.g. :/dev/sda1).
kernel -ro,soft,intr ftp.kernel.org:/pub/linux
boot -fstype=ext2 :/dev/hda1
windoze -fstype=smbfs ://windoze/c
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.
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).
A * in the key field matches all keys. An example for the usefulness is the following
This will enable you to access all the home directory of local hosts using the path
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 -Dvariable=Value option to automount(8).
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 implemented in the initialization script.
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.
The automounter does not support direct maps or mount trees (more than one filesystem to
be mounted under a specific automount point), and handles SunOS-style replicated filesys-
tems only to the extent that mount(8) does.
automount(8), auto.master(5), autofs(8), mount(8).
This manual page was written by Christoph Lameter <email@example.com>, for the Debian
GNU/Linux system. Edited by H. Peter Anvin <firstname.lastname@example.org>.
6 Apr 1998 AUTOFS(5)
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