5:autofs
From Linux Man Pages
autofs - Format of the automounter maps
AUTOFS(5) AUTOFS(5)
Contents |
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 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!
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
For indirect mounts this is the part of the pathname between the mountpointi and the path into the filesystem
mounted. Usually you can think about the key as a subdirectory name below the mountpoint.
For direct mounts this is the full path of the mountpoint. This map is always associated with the /- mountpoint
in the master map.
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 are two special options -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. -strict
is used to treat errors when mounting file systems as fatal. This is important when multiple file systems should
be mounted (`multimounts'). If this option is given, no file system is mounted at all if at least one file system
can't be mounted. -multi is used to specify that even if there is only one file system in this mapping, it
should be treated as a multi-mount. This is useful for auto.net, which lists all file systems exported from a
particular host. Without this option, the mount would contain the contents of a lone export rather than the name
of the export as might be expected.
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
filesystem 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
windoze -fstype=smbfs ://windoze/c
removable -fstype=ext2 :/dev/hdd
cd -fstype=iso9660,ro :/dev/hdc
floppy -fstype=auto :/dev/fd0
server -rw,hard,intr / -ro myserver.me.org:/ \
/usr myserver.me.org:/usr \
/home myserver.me.org:/home
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 Win-
dows machine available for automounting. The rest should be fairly self-explanatory. The last entry (the last
three lines) is an example of a multi-map (see below).
If you use the automounter for a filesystem without access permissions (like vfat), users usually can't write on
such a filesystem because it is mounted as user root. You can solve this problem by passing the option
gid=<gid>, e. g. gid=floppy. The filesystem is then mounted as group floppy instead of root. Then you can add the
users to this group, and they can write to the filesystem. Here's an example entry for an autofs map:
floppy-vfat -fstype=vfat,sync,gid=floppy,umask=002 :/dev/fd0
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 of indirect maps 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 pre-
fixed 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 map-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. It may return no
lines of output if there's an error, or one or more lines containing a map (with \ quoting line breaks).
To use a program map, the automount(8) daemon has to be started with the program type instead 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.
Multiple Mounts
A multi-mount map can be used to name multiple filesystems to mount. It takes the form:
key [-options] [mountpoint [-options] location...]...
This may extend over multiple lines, quoting the line-breaks with `\�. If present, the per-mountpoint mount-
options are appended to the default mount-options.
Replicated Server
Multiple replicated hosts, same path:
<path> host1,host2,hostn:/path/path
Multiple hosts, some with same path, some with another
<path> host1,host2:/blah host3:/some/other/path
Multiple replicated hosts, different (potentially) paths:
<path> host1:/path/pathA host2:/path/pathB
Mutliple weighted, replicated hosts same path:
<path> host1(5),host2(6),host3(1):/path/path
Multiple weighted, replicated hosts different (potentially) paths:
<path> host1(3):/path/pathA host2(5):/path/pathB
Anything else is questionable and unsupported, but these variations will also work:
<path> host1(3),host:/blah
UNSUPPORTED
This version of the automounter supports direct maps for FILE, NIS and LDAP maps only and handles SunOS-style
replicated filesystems only to the extent that mount(8) does.
CAVEATS
Unlike Sun's multi-mount syntax, the mountpoint is mandatory for all mounts.
RELATED
automount(8), auto.master(5), autofs(8), mount(8).