Enable the “root” user using Single User Mode in Mac OS X

• Hold down the Command (⌘)+ S buttons whilst turning on the machine, the system will then boot into Single User Mode
• at the prompt type:/sbin/fsck -fy

• at the prompt type:/sbin/mount -uw /
• at the prompt type:launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plist
• at the prompt type:passwd root
  • you will be prompted to enter a password twice
• at the prompt type:reboot
• The Mac will now restart and take you to the logon screen, log into the Mac as the root user and use the password set in the step above.
• An additional step you can take to confirm the root user has been logged in is checking the Users & Groups in Systems Preferences, the logged on user should state System Administrator