auto_master.5   [plain text]


.Dd April 20, 2007
.Dt AUTO_MASTER 5
.Os Darwin
.Sh NAME
.Nm auto_master
.Nd
automounter master map
.Sh DESCRIPTION
The
.Nm
file contains a list of the directories that are to be automounted.
Associated with each directory is the name of a map that lists the
locations of the filesystems to be automounted there.
The default map looks like this:
.Bd -literal -offset indent
#
# Automounter master map
#
+auto_master		# Use directory service
/net			-hosts		-nobrowse,hidefromfinder,nosuid
/home			auto_home	-nobrowse,hidefromfinder
/Network/Servers	-fstab
/-			-static
.Ed
.Pp
A
.Dq #
is the comment character. All characters from it to the end of
line are ignored.
A line beginning with
.Dq +
and followed by a name, indicates the name of a file or map accessible
from a Directory Service source such as NIS or LDAP;
the master map entries in that file or map are included at this point
in the master map.
A line that specifies a map to be mounted has the format:
.Pp
.Dl Va mountpoint map -options
.Pp
where
.Va mountpoint
is the directory on which the map is to be mounted,
.Va map
is the name of the map to be mounted, and
.Va options
is an optional, comma-separated list of default
mount options to be used by any entries in the map
that do not have their own mount options.
The
.Cm nobrowse
option is used on maps that have the potential to
produce entries too numerous for browsing to
be practical. This option as used in the master
map is distinct from nobrowse used as a Mac OS X
mount option, which affects the visibility of the
mount to the Finder.
The
.Cm hidefromfinder
option is used on maps that shouldn't show up as folders in the Finder;
it causes the
.Dv UF_HIDDEN
flag to be set on the root directory of the map.
.Pp
A
.Va map
name beginning with / is
the pathname of a file containing the map, otherwise
the name represents a map to be found as a file in
.Pa /etc
or to be read from Directory Service (and thus from whatever sources
Directory Service uses, such as NIS or LDAP servers).
.Pp
Note that, in order to get automounter maps from NIS, the "BSD Flat File
and NIS" plugin must, in the Directory Utility application, be enabled
and configured to "Use NIS domain for authentication".
.Pp
If more than one entry in the master map has the same
.Va mountpoint
then all but the first are ignored.
For instance, in the following master map:
.Bd -literal -offset indent
/shared		my_auto_shared
+auto_master
.Ed
.Pp
The
.Pa /shared
entry overrides any
.Pa /shared
specification imported from the network
.Nm .
.Sh AUTOMOUNTER MAPS
Automounter maps associate directories with the locations of
filesystems that are to be mounted when the directory is accessed.
Map entries have the general form:
.Pp
.Dl Va key location
.Pp
These map entries may be represented by lines in a file,
NIS or LDAP tables indexed by the key, or from output of
an executable map.
Most commonly, the
.Va location
is simply the name of an NFS
server and the path to an exported file system, e.g.
.Bd -literal -offset indent
local	mynfs:/export/local
.Ed
.Pp
A
.Va location
can also represent multiple mounts, where each
is associated with a relative path, for example:
.Bd -literal -offset indent
pkg	\\
	/data	mynfs:/export/pkg/data \\
	/bin	mynfs:/export/pkg/bin  \\
	/man	mynfs:/export/pkg/man
.Ed
.Pp
Reference to this entry will provide access to any
of three exported file systems from the server, each via
its own subdirectory.
Each of these sub-mounts will be done only when referenced.
Note the use of a backslash to escape the newline so that
the automounter will read these lines as a single map entry.
.Pp
The
.Va location
can be preceded by a comma-separated list of mount options
with a prepended
.Dq - .
For example:
.Bd -literal -offset indent
bin	-ro,nosuid  mynfs:/export/bin
.Ed
.Sh Replicated mounts
More than one
.Va location
can be specified in a map entry.  At the time the mount is done, the
automounter will choose one of those
.Va locations
to mount.  Locations not responding to an NFS null request at that time
will not be considered, so that servers that are unavailable will not be
chosen.  Servers that are on the same subnet as the client will be
chosen in preference to servers on different subnets.
.Pp
By default, in each of those sets of servers, the server with the
shortest response time to the aforementioned NFS null request will be
chosen.  A
.Va location
can be given a weighting factor; the higher the weighting factor, the
lower the preference for that server.  For example, with an entry such
as
.Bd -literal -offset indent
data	net1a:/data net1b:/data net1c(1):/otherdata
.Ed
.Pp
if either host net1a or net1b is available, the one with the shortest
response time will be chosen; host net1c will be chosen only if it is
available and neither hosts net1a nor net1b are available.
.Pp
If all
.Va locations
have the same path, a comma-separated list of hosts followed by the path
can be used:
.Bd -literal -offset indent
data	net1a,net1b,net1c(1):/data
.Ed
.Pp
If a server that has been mounted becomes unavailable, the NFS client
will not automatically fail over to another server; the mount must be
unmounted and remounted in order for failover to occur.
.Sh Direct Map
A
.Em direct
map associates filesystem locations directly with directories.
The entry key is the full path name of a directory.
For example:
.Bd -literal -offset indent
/usr/local	eng4:/export/local
/src		eng4:/export/src
.Ed
.Pp
Since the direct map as a whole isn't associated with a single
directory, it is specified in the master map with a dummy
directory name of
.Pa /- .
.Sh Indirect Map
An
.Em indirect
map is used where a large number of entries are to be associated
with a single directory.  Each map entry key is the simple name of a
directory entry.  A good example of this is the
.Pa auto_home
map which determines the entries under the
.Pa /home
directory.
For example:
.Bd -literal -offset indent
bill	argon:/export/home/bill
brent	depot:/export/home/brent
guy	depot:/export/home/guy
.Ed
.Pp
.Sh Executable Map
An
.Em executable
map is an indirect map represented by a file that has its execute bit set.
Instead of reading entries from the file directly, the automounter
executes the program or script passing the
.Va key
as an argument and receiving the
.Va location
string on stdout.
If the automounter needs to enumerate map keys for a directory listing,
it invokes the map with no arguments and expects a newline-separated
list of keys on stdout.
.Pp
If an error occurs, the executable map must return a non-zero
exit status and no output.
.Pp
For example, a map that, when bound to an Open
Directory server, has one entry for every user, with the key being the
user's login name and the entry being the URL of the user's home
directory, could be implemented as
.Bd -literal -offset indent
#!/bin/sh
if [ $# = 0 ]; then # List keys
	dscl /Search -list Users
	exit
fi
# Return location
homedirloc=`dscl /Search -read Users/$1 HomeDirectory`
case "$homedirloc" in

"No such key: HomeDirectory"*)
	homedirloc=`dscl /Search -read Users/$1 NFSHomeDirectory`
	case "$homedirloc" in

	"NFSHomeDirectory: /Network/Servers/"*)
		#
		# NFS home directory
		#
		echo "$homedirloc" | sed 's;NFSHomeDirectory: /Network/Servers/\([^/]*\)/\(.*\);\1:/\2;'
		;;

	*)
		#
		# Unknown
		#
		exit 1
		;;
	esac
	;;

"HomeDirectory: <home_dir><url>smb://"*)
	#
	# SMB home directory
	#
	echo "$homedirloc" | sed -e 's;HomeDirectory: <home_dir><url>;;' -e 's;</url><path>;/;' -e 's;</path></home_dir>;;'
	;;

*)
	#
	# Unknown
	#
	exit 1
	;;
esac
.Ed
.Pp
(this is a simplified example; it does not handle users who do not have
a network home directory, but includes them in the directory listing).
.Sh Substituting the map key entry
If a
.Va location
in a map entry contains an ampersand (&), the ampersand will be replaced
by the value of the key for the map entry.  For example, a map entry of
.Bd -literal -offset indent
bill	argon:/export/home/&
.Ed
.Pp
is equivalent to a map entry of
.Bd -literal -offset indent
bill	argon:/export/home/bill
.Ed
.Sh Wildcards
If the key in an indirect map entry is an asterisk (*), that entry will
match any name that isn't matched by any other entry.  For example, a
map with
.Bd -literal -offset indent
bill	argon:/export/home/bill
*	depot:/export/home/&
.Ed
.Pp
as entries will mount
.Pa argon:/export/home/bill
on
.Pa bill
and will mount
.Pa depot:/export/home/{user}
on
.Pa {user}
for all other values of
.Pa {user} .
.Sh Variables
A
.Va location
string in a map can contain references to variables.  A reference to a
variable consists of dollar sign ($) followed by the name of the
variable.  A variable name is a sequence of alphanumeric characters and
underscores; the name of the variable can be contained in
curly braces to separate the variable reference from any alphanumeric
characters or underscores following it.
There are some predefined variables:
.Bl -tag -width "OSNAME" -offset indent
.It Sy ARCH
System architecture ("macintosh" on Macintoshes).
.It Sy CPU
Processor type, as reported by
.Ic "uname -p"
("powerpc" on PowerPC Macintoshes, "i386" on Intel Macintoshes).
.It Sy HOST
This machine's host name.
.It Sy OSNAME
Operating system name, as reported by
.Ic "uname -s"
("Darwin" in OS X).
.It Sy OSREL
Operating system release, as reported by
.Ic "uname -r"
(for example, 9.3.0 in Mac OS X 10.5.3).
.It Sy OSVERS
Operating system version, as reported by
.Ic "uname -v"
(this string is a long string with spaces in Mac OS X, and is not very
useful in automounter maps).
.El
.Pp
For example, a direct map entry such as
.Bd -literal -offset indent
/usr/local/bin	-ro	server:/export/bin/$OSNAME/$CPU
.Ed
.Pp
would mount on
.Pa /usr/local/bin
a directory from the specified server containing executable images
appropriate to the operating system and CPU type of the machine.
.Pp
In addition, any environment variable set in the environment of
.Xr automountd 8
can be used as a variable name; those variables can be set
with the
.Dv AUTOMOUNTD_ENV
parameter in the
.Xr autofs.conf 5
file.
.Sh Quoting
Special characters, such as white space characters, a dollar sign, or an
ampersand can be quoted by escaping them with a backslash (\e); this
prevents white space from being interpreted as a field separator,
prevents a dollar sign from being interpreted as the beginning of a
variable name, and prevents an ampersand from being interpreted as the
key field for the entry in which it occurs.  A sequence of characters
can also be quoted by enclosing it in double-quotes (").
.Sh Special Maps
The special maps have reserved names and are built into the automounter.
.Bl -tag
.It Dv -fstab
This map would normally be mounted on
.Pa /Network/Servers .
The key is the host name of a server; the contents of the map entry are
generated from corresponding entries in
.Xr fstab 5
data (as provided by
.Xr getfsent 3 Ns )
that have the
.Li net
option and that specify mounts from that server.  An entry of the form
.Bd -literal -offset indent
server:/path mountpoint fstype options 0 0
.Ed
.Pp
will be mounted in
.Va server Ns / Ns Va path
under the mount point of the
.Dv -fstab
map, using the specified
.Va fstype
file system type and the specified
.Va options .
The
.Va mountpoint
is ignored.
.It Dv -hosts
This map would normally be mounted on
.Pa /net .
The key is the host name of an NFS server; the contents of the map are
generated from the list of file systems exported by that server.
For example, a server that exports three NFS filesystems might have
an equivalent map entry of:
.Bd -literal -offset indent
myserv	\\
	/export/home	myserv:/export/home \\
	/export/local	myserv:/export/local \\
	/export/pkg	myserv:/export/pkg
.Ed
.Pp
To access the first mount, the path would be
.Pa /net/myserv/export/home
if the map was associated with
.Pa /net .
.It Dv -null
This map has no entries.
It is used to disable entries that occur later in the
.Nm
file.
For example:
.Bd -literal -offset indent
/shared		-null
+auto_master
.Ed
.Pp
The -null entry disables any
.Pa /shared
entry in +auto_master.
.It Dv -static
This map is a direct map, so the mount point must be specified as
.Pa /- Ns .
The contents are generated from all entries in
.Xr fstab 5
data (as provided by
.Xr getfsent 3 Ns )
that do not have the
.Li net
option.  An
.Xr fstab 5
entry of the form
.Bd -literal -offset indent
server:/path mountpoint fstype options rw 0 0
.Ed
.Pp
will generate a direct map entry of the form
.Bd -literal -offset indent
mountpoint options server:/path
.Ed
.Pp
.El
.Sh FILES
.Bl -tag -width /etc/auto_master -compact
.It Pa /etc/auto_master
The master map file.
.El
.Sh SEE ALSO
.Xr automount 8 ,
.Xr automountd 8 ,
.Xr autofsd 8 ,
.Xr autofs.conf 5 ,
.Xr fstab 5 ,
.Xr getfsent 3 ,
.Xr DirectoryService 8