You want to find the PDC Emulator for a domain using DNS.
22.214.171.124 Using a command-line interface
> nslookup -type=SRV _ldap._tcp.pdc._msdcs.<DomainDNSName>
The PDC Emulator FSMO role is the only FSMO role that is stored in DNS. Like many of the other Active Directory-related DNS records, the PDC record is stored as an SRV record under _ldap._tcp.pdc._msdcs.<DomainDNSName> where <DomainDNSName> is the domain the PDC is in.
3.28.4 See Also
Recipe 3.21 for finding domain controllers via DNS