Samba PDC problems after changing server IP

Samba is great, but is a real pain to configure, and very hard to diagnose problems. There’s plenty of log information to plough through once you’ve remembered how to enable it, but whenever I find myself having to change anything about my setup, I’ll spend at least a couple of hours scratching my head wondering what on earth is going on. In the interest of saving somebody else from this pain…if you find yourself banging your head against a wall primary domain controller (PDC) having weird symptoms like:

• Long hangs in Windows when browsing the domain.
• Logins fail intermittently.
• Trying to joining a machine to the domain fails with the error “domain unavailable” even though the domain is definitely there.

And you see errors in log.nmbd of the form:

domain_master_node_status_fail:
Doing a node status request to the domain master browser
for workgroup PROFACTOR at IP 192.168.200.220 failed.
Cannot sync browser lists.

…then there might be a simple explanation. If you’ve recently changed your server’s IP address, there are a number of places where the old IP will still be lurking, possibly causing the issues above.

nmbd caches browse master information in /var/cache/samba/browse.dat — your PDC’s old IP address will be listed here, and when nmbd starts up, it sees it as an existing, distinct domain master browser that then doesn’t respond to it any more. Stop nmbd and then delete the file.

In a similar way the WINS resolution system caches IPs — delete /var/lib/samba/wins.dat.

Restart the samba servers, and hopefully all will be well.