Lookupd

From Mac OS X Server FAQ

Lookupd is the primary DNS resolver for Mac OS X. You can use lookupd to see just how your system is resolving DNS on your network, which can be very helpful in resolving numerous issues, including automounts.

Execute <code>lookupd -d</code> to enter an interactive lookupd shell.

Lookupd also serves all directory services requests at the unix layer. It responds to standard unix system calls and includes a bridge to DirectoryService so that the unix layer also has access to data stored in other directories, as configured with Directory Access.