Short Version

OSX Lion

# /sbin/fsck -fy
# /sbin/mount -uw /
# launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plist
# passwd root
# exit

Mac OS X Tiger – Snow Leopard

# /sbin/fsck -fy
# /sbin/mount -uw /
# launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist
# dscl .
 > passwd root
 > exit
# exit

Many people have been wondering what would happen if they forgot their admin password in Mac OS X. There is a solution: you have to own a Mac OS X Install DVD which provides a Password Utility application. But what if you don’t have one? There is a solution.

Important Note: This works only if there is no Firmware Password set. Firmware Password blocks the ability to boot your computer in single-user mode.

All you have to do is turn on your computer holding CMD + S. This will boot your Mac in Single-User Mode. Next, you have to wait a second while kernel will load command-line interface. It there is :/ root# line, you’re ready to go!

OSX Lion

First of all, type

# /sbin/fsck -fy

This will take a while. It will check the consistency of your filesystem. If there is no error, your output should be similar to this:

** /dev/rdisk0s2
** Root file system
   Executing fsck_hfs (version diskdev_cdms-491.6~1).
** Checking Journaled HFS Plus volume.
** Ckeching extents overflow file.
** Checking catalog file.
** Checking multi-linked files.
** Checking catalog hierarchy.
** Checking extended attributes file.
** Checking multi-linked directories.
** Checking volume bitmap.
** Checking volume information.
** The volume Macintosh HD appears to be OK.
:/ root#

The last three steps are very quick:

# /sbin/mount -uw /
# launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plist
# passwd root

Bash will ask you for the new password for your root account. Type, retype and done! You can now safely type

# exit

and your Mac will display the Login Screen.

Max OS X Tiger – Snow Leopard

For older operation system this process looks a little bit different. First of all, type these standard commands:

# /sbin/fsck -fy
# /sbin/mount -uw /

And here is the difference: the LaunchDaemon plist is located elsewhere.

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

In Snow Leopard you have to add this line too:

# dscl .

Now, type this and change your root password.

> passwd root

Note: You have to type exit twice in this case.