Who becomes the master browser is determined by an election process using broadcasts. Each election packet contains a number of parameters that determine what precedence (bias) a host should have in the election. By default Samba uses a low precedence and thus loses elections to just about every Windows network server or client.

If you want Samba to win elections, set the os level global option in smb.conf to a higher number. It defaults to 20. Using 34 would make it win all elections over every other system (except other Samba systems).

An os level of two would make it beat Windows for Workgroups and Windows 9x/Me, but not MS Windows NT/200x Server. An MS Windows NT/200x Server domain controller uses level 32. The maximum os level is 255.

If you want Samba to force an election on startup, set the preferred master global option in smb.conf to yes. Samba will then have a slight advantage over other potential master browsers that are not preferred master browsers. Use this parameter with care, because if you have two hosts (whether they are Windows 9x/Me or NT/200x/XP or Samba) on the same local subnet both set with preferred master to yes, then periodically and continually they will force an election in order to become the LMB.

If you want Samba to be a DMB , then it is recommended that you also set preferred master to yes, because Samba will not become a DMB for the whole of your LAN or WAN if it is not also a LMB on its own broadcast isolated subnet.

It is possible to configure two Samba servers to attempt to become the DMB for a domain. The first server that comes up will be the DMB. All other Samba servers will attempt to become the DMB every 5 minutes. They will find that another Samba server is already the DMB and will fail. This provides automatic redundancy should the current DMB fail. The network bandwidth overhead of browser elections is relatively small, requiring approximately four UDP packets per machine per election. The maximum size of a UDP packet is 576 bytes.