Ran into an issue today where a user had completely forgotten all passwords on the computer.
Turns out there's a way to reset it without even needing the OS X DVD.
- Boot into Single User Mode (hold down Command+S while booting)
- At the root prompt (# prompt), enter the following commands:
- /sbin/fsck -fy
This performs a disk check before making any changes to the system.
- /sbin/mount -uw /
This makes the root filesystem writable.
- launchctl load /System/Library/LaunchDaemons/com.apple.opendirectoryd.plist
This starts up the service allowing you to change the password.
- passwd username
It should prompt you to change the password of username
- Assuming it went through, type reboot and you should be able to login with your new password.