Tuesday, April 10, 2012

Having problems browsing SAMBA shares? ..README

SkyHi @ Tuesday, April 10, 2012
I've seen "SAMBA isn't working, now I can't connect to shares on my HTPC" being posted in a few places so I thought I'd post a note to educate people on what's going on. The statement that SAMBA is broken is rarely true. It's usually running fine, and the cause of the problem is simply the ugly way that NetBios over TCP/IP name resolution works. 

The reason you cannot see an smb://share "that was working 5 mins ago" is down to browser election fights between the computers on the network. An election fight is a peer-to-peer negotiation over who gets elected to be in charge of the domain(s) and/or local master browser list; the list of computer names that will appear in the Windows Network Neighbourhood (or it's current equivalent). The machine that wins the election is determined through a combination of uptime, OS version and config settings - meaning the outcome can be unpredictable, and the election process can take time (minutes not milliseconds). Over time your HTPC (as longest uptime device) has probably been elected the master browser, so if you reboot your HTPC the browser list is gone and the remaining machines on the network will restart an election process to decide who owns/creates the replacement. Once the election is over it will take time (again, minutes not milliseconds) to distribute the list and ensure every client has the same version. If you reboot other computers they will join the network and announce their availability, so an election discussion takes place to see if they should become the master browser. It's easy to see how this process may go titsup.com from time to time. Sadly, Mac and Linux computers can suffer the same issues as their Windows counterparts as they (via their local SAMBA client) are ultimately participating in the same process.

In corporate networks this issue is mitigated by having a pre-determined machine configured to win all the elections and maintain the browser list(s) - usually a domain controller. Rigging the election guarantees the election result and ensures the election process is completed quicker. The good news is that it's simple to configure SAMBA on your OE based HTPC to do the same thing. The reason for picking the HTPC to be the master browser is that it's probably the going to be the computer that has the highest uptime in your home network.

First, ensure you have /storage/.config/samba.conf. If you don't there is a sample one in the directory that can be renamed. Then add the lines indicated below to your [global] section:

  server string = Media Centre(%i)
  workgroup = HOME
  domain master = yes  <-- add this line
  local master = yes  <-- add this line
  preferred master = yes  <-- add this line
  os level = 100  <-- add this line
  netbios name = AppleTV
  security = share
  guest account = root
  wins support = yes
  syslog only = yes
  name resolve order = lmhosts wins bcast host
  printcap name = /dev/null
  load printers = no

Even if you do this the problem will never be completely eliminated, but Windows network browsing should in theory be more consistent (in theory!). If it does not clear the problem the solution is usually to "turn everything off and on again" so that the old (incorrect) browser list is lost and a new (correct) one is created, or access your HTPC directly via an IP address based URL, e.g. \\\ 

NB: in pre-RC6 setups the last two lines shown above (printcap name and load printers) were incorrectly placed under the [printers] section of the sample configuration file. If you move them to [global] as above you'll see some SAMBA startup errors in /var/log/messages go away.