I converted a few Samba 3.0 servers from doing local authentication to using our primary domain controller. I'm not quite sure why, but I thought it would be fun. It seemed to work but every time I would try to connect I would get this error:

[2005/05/16 14:11:15, 0] auth/auth_util.c:make_server_info_info3(1134)
make_server_info_info3: pdb_init_sam failed!


Took me a while to find the right answer on google, so I figured I'd preserve it here for posterity's sake. This post had the correct answer. It was because I was using a username map to map my name on the domain controller to the local *nix user name, which happened to be different. Apparently that's the message that means "unknown local user".

The problem was in my username map. The documentation merely says the format is such:

unixuser = windowsuser


But when you're using "security = domain", you have to add the domain like this:

unixuser = DOMAIN\windowsuser


That did the trick immediately.