AUTO_MASTER(5) File Formats Manual AUTO_MASTER(5)
NAME
auto_master – automounter master map
DESCRIPTION
The auto_master 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:
#
# Automounter master map
#
+auto_master # Use directory service
#/net -hosts -nobrowse,hidefromfinder,nosuid
/home auto_home -nobrowse,hidefromfinder
/Network/Servers -fstab
/- -static
A “#” is the comment character. All characters from it to the end of line
are ignored. A line beginning with “+” 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:
mountpoint map -options
where mountpoint is the directory on which the map is to be mounted, map
is the name of the map to be mounted, and 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 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 hidefromfinder option is used
on maps that shouldn't show up as folders in the Finder; it causes the
UF_HIDDEN flag to be set on the root directory of the map.
A 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 /etc or to
be read from Directory Service (and thus from whatever sources Directory
Service uses, such as NIS or LDAP servers).
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".
If more than one entry in the master map has the same mountpoint then all
but the first are ignored. For instance, in the following master map:
/shared my_auto_shared
+auto_master
The /shared entry overrides any /shared specification imported from the
network auto_master.
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:
key location
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 location is simply the name of an NFS server and the path
to an exported file system, e.g.
local mynfs:/export/local
A location can also represent multiple mounts, where each is associated
with a relative path, for example:
pkg \
/data mynfs:/export/pkg/data \
/bin mynfs:/export/pkg/bin \
/man mynfs:/export/pkg/man
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.
The location can be preceded by a comma-separated list of mount options
with a prepended “-”. For example:
bin -ro,nosuid mynfs:/export/bin
For file system types other than NFS, the mount option -fstype=⟨type⟩ can
be used to specify the file system type. The location would be in the
form expected by the mount command for that file system type. For
example:
smb -fstype=smb //guest@smbserver/share
afp -fstype=afp afp://;AUTH=NO%20USER%20AUTHENT@afpserver/share
If the location is a URL, with a scheme specifying AFP, NFS, or SMB,
then, if no file system type is specified, the directory referred to by
that URL will be mounted using mount_url(8). For example:
nfsurl nfs://nfsserver/path/to/mount
smburl smb://guest@smbserver/share
afpurl afp://;AUTH=NO%20USER%20AUTHENT@afpserver/share
Replicated mounts
More than one location can be specified in a map entry. At the time the
mount is done, the automounter will choose one of those 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.
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 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
data net1a:/data net1b:/data net1c(1):/otherdata
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.
If all locations have the same path, a comma-separated list of hosts
followed by the path can be used:
data net1a,net1b,net1c(1):/data
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.
Direct Map
A direct map associates filesystem locations directly with directories.
The entry key is the full path name of a directory. For example:
/usr/local eng4:/export/local
/src eng4:/export/src
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 /-.
Indirect Map
An 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 auto_home map
which determines the entries under the /home directory. For example:
bill argon:/export/home/bill
brent depot:/export/home/brent
guy depot:/export/home/guy
Executable Map
An 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 key as an argument
and receiving the 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.
If an error occurs, the executable map must return a non-zero exit status
and no output.
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
#!/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
(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).
Substituting the map key entry
If a 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
bill argon:/export/home/&
is equivalent to a map entry of
bill argon:/export/home/bill
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
bill argon:/export/home/bill
* depot:/export/home/&
as entries will mount argon:/export/home/bill on bill and will mount
depot:/export/home/{user} on {user} for all other values of {user}.
Variables
A location string in a map can contain references to variables. A
reference to a variable consists of dollar sign ($) followed by the name
of the variable. A variable name is a sequence of alphanumeric
characters and underscores; the name of the variable can be contained in
curly braces to separate the variable reference from any alphanumeric
characters or underscores following it. There are some predefined
variables:
ARCH System architecture ("macintosh" on Macintoshes).
CPU Processor type, as reported by uname -p ("powerpc" on
PowerPC Macintoshes, "i386" on Intel Macintoshes).
HOST This machine's host name.
OSNAME Operating system name, as reported by uname -s ("Darwin" in
OS X).
OSREL Operating system release, as reported by uname -r (for
example, 9.3.0 in Mac OS X 10.5.3).
OSVERS Operating system version, as reported by uname -v (this
string is a long string with spaces in Mac OS X, and is not
very useful in automounter maps).
For example, a direct map entry such as
/usr/local/bin -ro server:/export/bin/$OSNAME/$CPU
would mount on /usr/local/bin a directory from the specified server
containing executable images appropriate to the operating system and CPU
type of the machine.
In addition, any environment variable set in the environment of
automountd(8) can be used as a variable name; those variables can be set
with the AUTOMOUNTD_ENV parameter in the autofs.conf(5) file.
Quoting
Special characters, such as white space characters, a dollar sign, or an
ampersand can be quoted by escaping them with a backslash (\); 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 (").
Special Maps
The special maps have reserved names and are built into the automounter.
-fstab This map would normally be mounted on /Network/Servers. The key
is the host name of a server; the contents of the map entry are
generated from corresponding entries in fstab(5) data (as
provided by getfsent(3)) that have the net option and that
specify mounts from that server. An entry of the form
server:/path mountpoint fstype options 0 0
will be mounted in server/path under the mount point of the
-fstab map, using the specified fstype file system type and the
specified options. The mountpoint is ignored.
-hosts This map would normally be mounted on /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:
myserv \
/export/home myserv:/export/home \
/export/local myserv:/export/local \
/export/pkg myserv:/export/pkg
To access the first mount, the path would be
/net/myserv/export/home if the map was associated with /net.
-null This map has no entries. It is used to disable entries that
occur later in the auto_master file. For example:
/shared -null
+auto_master
The -null entry disables any /shared entry in +auto_master.
-static
This map is a direct map, so the mount point must be specified as
/-. The contents are generated from all entries in fstab(5) data
(as provided by getfsent(3)) that do not have the net option. An
fstab(5) entry of the form
server:/path mountpoint fstype options rw 0 0
will generate a direct map entry of the form
mountpoint options server:/path
FILES
/etc/auto_master The master map file.
SEE ALSO
automount(8), automountd(8), autofsd(8), autofs.conf(5), fstab(5),
getfsent(3), DirectoryService(8)
Darwin April 20, 2007 Darwin