Samba related question.

[bscott at ntisys.com]

On Wed, 11 Feb 2004, at 11:31am, k1vp at grizzy.com wrote:
> My question relates to getting the Windows boxes to resolve the linux box
> by name.

  Ahhh.  SMB name resolution.  Never will you find a more retched hive of 
scum and kludges.

  First, it depends on the version of Windows.  Win 95, 98, ME, and NT 4.0
all support NetBIOS only.  Windows 2000 and XP add support for DNS, and have
the option to disable NetBIOS.  (95/98/ME/NT4 will appear to use DNS for SMB
name resolution, but it won't work right.)  Samba only supports NetBIOS.  
(I think Samba 3.0 might support SMB w/out NetBIOS, but I'm not sure.)

  NetBIOS is one of the worst ideas, ever.  It can resolve names by either
local broadcast or by using a WINS server.  Broadcast means just that: A box
sends a packet to every computer on the local network, and the right one is
expected to respond.  We hope.  WINS is kinda like DNS for NetBIOS, except
it (1) sucks and (2) clients automatically register their names.

  There's also the NetBIOS concept of "browse lists".  A computer on the
local network (the "local master browser") is responsible for keeping a list
of known names.  When a NetBIOS node starts, it sends a broadcast "here I
am" packet.  The LMB listens for those.  Then, when someone else wants to
find the list of names, it broadcasts to find the LMB, and then asks the
LMB.

  How does the LMB get chosen?  Well, when a NetBIOS node comes online, it
broadcasts to find the LMB.  If it doesn't get an answer, it nominates
itself to be the LMB.  If it does get an answer, then it tries to decide if
it thinks it should be the LMB instead, and if so, holds an "election" with
all the other potential LMBs on the LAN.  (I'm pretty sure the actual
process is even uglier then this, but this is close enough.)

  Oh, and NetBIOS names have to be... 14 characters or less, I think.  You 
can try for longer, but Strange Things Can Happen.

  Anyhow, the following lines in /etc/samba/smb.conf are relevant:

	workgroup = FOO

That says we're a member of workgroup "FOO".  To keep things sane, everyone
should be a member of the same workgroup.

	netbios name = BAR

That says our own NetBIOS "computer" name is "BAR".  This defaults to 
"hostname -s", but if you're having trouble, you might want to set this 
manually.

	name resolve order = lmhosts wins bcast host

That controls how Samba resolves names (not how other nodes do).  "lmhosts" 
is kinda like /etc/hosts, but with extra crap for NetBIOS.  "bcast" is 
broadcast.  "host" means the host OS (i.e., Linux), and means things like 
DNS and /etc/hosts.  Sometimes, it is a good idea to remove "host", as it 
can complicate things, and MS-Windows generally doesn't use these mechanisms 
in the same way Samba does.

	local master = yes
	os level = 90
	domain master = yes 
	preferred master = yes
	domain logons = yes

The above magic will make Linux win almost any browser election.  This can 
be useful, as Samba is often better at SMB then Windows is -- in particular, 
the diagnostics are much better.

  	wins support = yes

If "yes", Samba will be a WINS server, and use itself for WINS name 
resolution.  If "no", Samba will not be a WINS server.

	wins server = 12.23.34.45

Sets the IP address of your WINS server, if you have one.  Do not set this 
if using "wins support = yes".

> ... any local machine can ping the linux box by
> using the assigned IP, but cannot ping it by name.

  Try this command from Linux:

	nmblookup -A foo

where "foo" is the complete IP address of a Windoze machine.  This should 
list the NetBIOS names the Windoze box is using.  If this fails, 
SMB-over-NetBIOS-over-IP is not working, and neither will Samba.

  Try this command from Windoze:

	nbtstat -A bar

where "bar" is the complete IP address of the Linux machine.  If this fails, 
then Samba is not talking to Windows right.

  Next, try this on Linux:

	nmblookup ding

where "ding" is the name of a Windoze machine.  That should attempt to 
locate the NetBIOS name in question via the same mechanisms that smbd (the 
server component of Samba) would use.

  Try this on Winzoe:

	nbtstat -a dong

where "dong" is the name of the Linux box.  This will test if Windoze can 
resolve the NetBIOS name of your Samba.

  If you could resolve a Windows name from Linux, try doing this on Linux:

	smbclient -L //ding

That will list SMB information available on the Windoze box.  If this fails
when name lookup works, you might have an authentication or protocol
configuration issue.

  You can also try

	smbclient -I foo -L //ding

which gives "smbclient" the IP address to connect to, skipping name 
resolution entirely.

  On the Windoze side of things, try

	net view \\bar

and

	net view \\dong

which do similar things in the Windoze world.

  If name resolution appears to be wonky, try:

  - Make the Linux box a WINS server, and have all your Windoze boxen
    use it as the WINS server
  - Turn off DHCP on the router and turn it on on Linux.  Use Linux
    to set the WINS server ("netbios-name-servers" option).  Some
    SOHO routers have really broken DHCP implementations.

  If all else fails, try increase the "debug level" or "log level" in Samba,
restarting Samba, and looking at the Samba logs in /var/log/samba/.

  Are we sufficiently disgusted yet?

-- 
Ben Scott <bscott at ntisys.com>
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