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AppleTalk
Apple developed its AppleTalk protocol stack in conjunction
with the LocalTalk networking hardware for some of its earliest Macintoshes in the
mid-1980s. (In fact, early on, both the hardware and software went by the name AppleTalk, although today this name is reserved for
the software side.) As Ethernet grew in popularity, Apple developed a way to
use AppleTalk over Ethernet hardwarea variant that's sometimes called EtherTalk. Linux supports AppleTalk over either the
original LocalTalk hardware (if your system has a supported LocalTalk network
card, as described in
align=left border=0> Ironically, Linux doesn't support the LocalTalk hardware
built into Macintosh computers. If you run Linux on such a system, you will not be able to use the LocalTalk hardware, although
you may still use AppleTalk over Ethernet, if the computer has a built-in
Ethernet adapter or a supported Ethernet expansion card.
AppleTalk Features and
Capabilities
Like TCP/IP, AppleTalk uses a 32-bit machine address. Also
like TCP/IP, the AppleTalk address is broken down into two componentsa network
address and a computer address; however, the division of these two components
is fixed, with each consuming 16 of the 32 bits available for the address.
AppleTalk includes a procedure by which the computers on the network can
negotiate their own AppleTalk addresses, so you need not set this address
explicitly. (You can request a specific address
or an address in a specific range if you want to, but this usually isn't
necessary.) Above the AppleTalk numeric addresses lies a two-tiered
alphabetic naming system that humans use more directly. Each computer has a
name, and resides in a zone, which is a logical
group of computers. Small networks may be zoneless,
meaning that the zone name doesn't obtrude itself upon users. When you start
Netatalk, the primary AppleTalk package for Linux, the software sets the
system's AppleTalk name based upon the TCP/IP hostname, unless you override
this setting. For instance, if a computer has the TCP/IP hostname larch.threeroomco.com , the
computer's AppleTalk name becomes larch .
The domain information is lost, though. (In a zoned network, the computer
attempts to set its zone automatically, and the zone name may bear no
resemblance to anything in the TCP/IP hostname.) The two-tiered nature of
AppleTalk names is an important limiting factor on AppleTalk networks; without
more layers of names, creating an AppleTalk network with more than a few
hundred computers becomes awkward.The primary applications for AppleTalk are the file and
printer sharing for which the protocols were developed. Many network-enabled
printers "speak" AppleTalk natively, and AppleTalk file-sharing
protocols are understood by MacOS, Windows NT and 2000, Linux, BeOS, and other
systems. There's seldom any reason to use AppleTalk except on a network that
contains MacOS systems, though, because most other OSs provide better support
for other network protocols. Even in the case of Macintosh-dominated networks,
the Unix-based MacOS X supports NFS as well as AppleTalk, so you may prefer to
use NFS if your network's Macintoshes run MacOS X. The Netatalk package (see
is the main program that uses AppleTalk in Linux; it's discussed in the next
section.TIP
align=left border=0> The fact that AppleTalk packets are seldom routable by
typical routers makes AppleTalk a good choice for providing a little extra
security. You can disable TCP/IP on a Netatalk server if you want to be
absolutely certain that nobody can break into your system from outside your
local network by exploiting a flaw in your Netatalk server. Similarly,
disabling everything but AppleTalk printing on a network-enabled printer or
print server can keep this system from being abused by outsiders, unless they
first gain a foothold on another system in your local network. Good security
practices, as discussed in
though, so AppleTalk isn't the only option for improving security.
Using Linux AppleTalk
Software
The Netatalk package, which comes with most Linux
distributions, is the primary AppleTalk software for Linux. This package provides
three features: An AppleTalk file server The afpd program allows a Linux computer to
operate as a file server for Macintosh systems. The file server supports both
native AppleTalk and TCP/IP, so Linux can serve even old Macintoshes, so long
as they share a network hardware type. (In the event they don't,
LocalTalk-to-Ethernet converter devices are available to bridge the gap.) This
server is controlled through a file called afpd.conf ,
typically in /etc/atalk . In
addition, the AppleVolumes.default
file controls which directories are shared, and AppleVolumes.system maps filename extensions onto Macintosh
file and creator types, which are stored directly on MacOS-native filesystems. An AppleTalk print server The papd program allows a Linux computer to
operate as a print server for Macintosh systems. Used in conjunction with
Ghostscript (part of Linux's standard print queue), this allows you to share
even an inexpensive inkjet printer as if it were a full-featured PostScript
device. The print server features work only over the original AppleTalk, not
via TCP/IP. The papd server is
controlled through papd.conf ,
which is usually located in /etc/atalk . An AppleTalk print
client The pap program allows Linux
to submit print jobs to AppleTalk-enabled printers or print servers. This can
be useful if your Linux computer is on a Macintosh-dominated network that hosts
printers that don't understand other protocols. You can even print from one
Linux computer to another using this tool, although in most cases Linux's
native printing tools, as described in
Sharing via LPD, will be simpler to configure. The pap client has no control
file; you specify the printer to which you want to send a file with the -p parameter,
as in pap -p Laser2
sample.ps to print sample.ps to
the printer called Laser2 .The first two of these programs rely upon
another one, atalkd , which configures the computer's overall AppleTalk
presencefeatures such as the AppleTalk name and address. This program is
controlled through a file called atalkd.conf , which is also typically
stored in /etc/atalk .NOTE
align=left border=0> Netatalk doesn't include a file-sharing
client program. Therefore, you can't access AppleTalk file shares from Linux
using Netatalk. The afpfs package ( target="_blank">http://www.panix.com/~dfoster/afpfs/ ) theoretically provides this capability as of version 1.03b-alpha,
but it's very old and unreliable. If you want to access Macintosh files from
Linux, you're better off using a Macintosh NFS or SMB/CIFS server, such as
MacOS X's native NFS server or DAVE ( target="_blank">http://www.thursby.com ).
Most default installations of AppleTalk work
correctly as soon as they're installed, but they're typically configured to
share only the home directory of the user who logs in. You can alter this
configuration by editing AppleVolumes.default . For instance, the following lines in this file tell the system to
export both the user's home directory (specified by a tilde, ~ ) and the /mnt directory: ~ /mnt "Mount Points" options=noadouble
The first of these lines is the default, and
includes no special options. The second includes a name to use instead of /mnt for the
share as seen on a Macintosh client, as well as an options specification,
which sets special options. In this case, the only option set is noadouble ,
which makes Netatalk not create AppleDouble files (these are special files
stored in the .AppleDouble subdirectory to hold MacOS-specific data) unless they're absolutely
required.If your Netatalk package shipped with your
distribution, it will probably start up automatically when you start the
computer. If not, consult
Starting Servers, for general server startup information (a SysV or local startup
script are the best options for starting Netatalk). You should start atalkd first,
then afpd and papd . One of the quirks of Netatalk, and particularly of atalkd , is
that this server can take quite some time to startsometimes over a minute,
particularly on older hardware. You can avoid a pause in your system startup
procedure by including an ampersand ( & ) after the program
call in your startup script.
