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NetBEUI
NetBEUI is similar in many ways to AppleTalk
and IPX, but it has historically been used primarily by IBM and Microsoft as
the basis for networking in DOS, Windows, and OS/2. The Linux kernel does not,
as of the 2.4.x series, include a standard
NetBEUI stack. This omission is offset by two facts, though. First, the common
uses of NetBEUI can be served by NetBIOS over TCP/IP (sometimes called NBT ), which Linux does support. Second, a third-party
NetBEUI stack is available, although it's of limited utility.
NetBEUI Features and Capabilities
Like AppleTalk and IPX, NetBEUI was designed
with small networks in mind. In fact, NetBEUI is even more limited than its
competing small-network protocols, because it's restricted to networks of just
256 computers. NetBEUI uses computer names similar to TCP/IP hostnames, but
there is no underlying numeric addressing system, as is true of TCP/IP,
AppleTalk, and IPX; NetBEUI uses the computer's name directly. These names are
two-tiered in nature, much like AppleTalk's names (which include a computer
name and a network zone name). NetBEUI calls its higher-order groupings workgroups or domains,
depending upon whether a centralized computer exists to control logins (domains
support this feature, but workgroups leave authentication to individual
servers). When it starts up and periodically thereafter, a computer configured
to use NetBEUI makes a broadcast to announce its presence.NetBEUI can theoretically be used over just
about any network medium, but it's most commonly used over Ethernet. Like
AppleTalk and IPX, NetBEUI can coexist on Ethernet with TCP/IP or other network
stacks.NetBEUI is most frequently used in
conjunction with the SMB/CIFS file- and printer-sharing protocols. These are
comparable in scope to NFS/ lpd for Unix and Linux, AppleTalk's equivalent protocols, or NCP. They
can also be used over TCP/IP, and in fact this configuration is very common,
even on networks that contain Windows computers exclusively. Because it's not
easily routed, however, NetBEUI offers some security benefitsa distant
attacker is unlikely to be able to launch a successful attack against a NetBEUI
server.
Obtaining a NetBEUI Stack for Linux
Few Linux computers participate in NetBEUI
communications because the standard kernel lacks a NetBEUI stack. In 2000,
Procom Technologies ( http://www.procom.com ) released an open source NetBEUI stack for Linux, as well as
patches to Samba (described in
and Printer Sharing via Samba), to allow Samba to operate over NetBEUI rather
than TCP/IP. These patches have not become commonplace, and in fact they aren't
posted directly on Procom's Web site, although you can request the stack from
their technical support department. The NetBEUI stack may not work properly
with kernels beyond the 2.0.x series (I was
unable to get the patches to compile with a 2.2.18 kernel, for instance). The
NetBEUI stack was also designed for versions of Samba before 2.0.7, although
there's been some talk of adding the NetBEUI support to Samba sometime before
Samba 3.0 is released. The support also requires recompiling both your kernel
and Samba. For these reasons, you're probably better off foregoing the use of
NetBEUI unless you have a very compelling reason to use it, such as a network
on which TCP/IP is forbidden. If you really must use NetBEUI, you may need to
use it with an older 2.0.x kernel and Samba 2.0.6
or earlier.In addition to patching the Linux kernel and
Samba, the NetBEUI stack comes with a number of tools that let you configure
and manipulate it. This configuration tends to be fairly simple, and in most
cases you'll use new Samba options to control the computer's NetBEUI behavior,
but the separate utilities can be useful for troubleshooting and for learning
more about NetBEUI. One utility in particular, netb , is also required to
start up the NetBIOS stack, as described shortly.
Using Linux NetBEUI Software
The NetBEUI stack includes a README file
with complete installation and use instructions. This file outlines two methods
of installation. One requires you to edit the Makefile to point to your
Linux kernel and Samba source code trees and set a few other system-specific
options. You can then recompile both Linux and Samba with a single command,
install your new kernel, and reboot the system. The second procedure also
requires you to edit the Makefile , but proceeds to give instructions on performing individual steps
in a piecemeal fashion. This second approach is likely to be superior if you
run into any difficulties, because you'll be better able to isolate and correct
the problem.Whichever way you do it, you'll need the
source code to both the Linux kernel and Samba. You can obtain these from
take several minutes to compile and install, so even if you don't run into
problems, installing NetBEUI support is likely to take several minutes.Once you've installed NetBEUI support, you
can use several commands to enable or manipulate this support. These commands,
included with the NetBEUI stack, are as follows: netb Type this command followed by start to start
NetBEUI on Linux. To stop NetBEUI, type netb stop . You must
use this utility before you can use NetBEUI on Linux. nbview Use this command if you want to check on the status of the local
NetBEUI stack. This command reads the /proc/sys/netbeui file,
which contains this information, and formats and parses the information for
easier human consumption. nbstatus This command displays information on the specified machine or
workgroup; for instance, nbstatus
SERVER displays information on the computer
called SERVER . nbadmin This command allows you to bind NetBEUI to a specific network
interface, unbind NetBEUI from a specific interface, or drop a specific NetBEUI
session. It does this using the bind , unbind , and drop commands,
respectively, as in nbadmin
bind eth0 or nbadmin drop 102 . (You
can obtain NetBEUI session numbers from nbview .) For the most part, you'll only need to issue
a netb start command, then start Samba. The NetBEUI stack adds a parameter to nmbd (the
NetBIOS name daemon), smbd (the SMB daemon), and smbclient (the text-mode Samba client) to
specify whether to use TCP/IP or NetBEUI. This parameter is -Z <NETBEUI | TCPIP> . For instance, to launch smbd to use NetBEUI,
you'd type smbd -Z
NETBEUI . You can also use the new -S NAME parameter to smbd to set the system's NetBEUI name to NAME .To sum up, you can turn Linux into a NetBEUI
SMB/CIFS server called NAME by recompiling the kernel and Samba with the Procom NetBEUI stack,
rebooting, shutting down Samba (if necessary), and typing the following
commands: # netb start # nmbd -Z NETBEUI # smbd -Z NETBEUI -S NAME
You can place these commands in a startup
script, or modify your regular Samba startup script to incorporate these
changes. Other Samba features, such as the definitions of shares, all function
as described in
advantage of this procedure boils down to two factors. First, it can be used
with some older clients that support NetBEUI but not TCP/IP, and it reduces the
chance of malicious outside access to the computer via Samba, because NetBEUI
isn't normally routed over the Internet. On the downside, NetBEUI support is
duplicated in NetBIOS over TCP/IP, which works with all recent Linux kernels
and versions of Samba, and doesn't require patching or recompiling the kernel
or Samba.
