Reset password using Lion Recovery

If you bought a brand new Mac with Lion pre-installed, the hard drive includes with a recovery partition that gives you access to a bunch of different tools. Here’s how to take advantage of this utility to reset your Mac’s password:

  1. Shut down your Mac and turn it back on while holding down the Command and R keys at the same time until you see the Lion Recovery screen.
  2. From the menu bar at the top, select Utilities > Terminal.
  3. In the Terminal window type resetpassword and press Enter.
  4. Use the Reset Password utility to select your hard drive, choose your user account, and enter a new password.

Reset Lion password with Single User mode

Anyone running Mac OS X Lion can take advantage of this method:

  1. Shut down your Mac and turn it back on while holding down the Command and S keys at the same time until your see a black screen with white text. This is known as Single User mode.
  2. You can skip this step, but it’s recommended that you don’t because it will check the consistency of your hard drive. At the prompt, type fsck -fy and press Enter.
  3. Once the disk check is complete and the prompt returns, type mount -uw / and press Enter.
  4. Type launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plistand press Enter.
  5. Type ls /Users and press Enter. All of the usernames on the computer will be listed, which is helpful if you don’t know or remember what these are.
  6. Type dscl . passwd /Users/username password while replacing username with one of the users displayed in the previous step and replacing password with the new password of your choice. Press Enter. You will likely get an error message about a file or directory not being found – it’s safe to ignore this.
  7. Type reboot and press Enter.

How to reset password for Mac OS X 10.7 Lion | MacYourself.