Using OS X directory services (dscl, dseditgroup) in single user mode

To access directory services you first need a writable root:

mount -uw /

Then you need the daemon loaded. On snow leopard:

launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist

And on Lion:

launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plist

On lion you might see an error about DirectoryServices.plist not existing when you connect with dscl, it can be ignored.