To change the user password in Leopard(10.5.x) or SnowLeopard (10.6.x) Hold "Command + S" key on your mac keyboard to boot your mac into single user mode. Execute command "mount -uw /" in shell. Run below command " launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist" Execute command : passwd change the password of root.