Some time ago I got an idea on granting access to my Linux machine which had the passwd and shadow files CRC protected, the SSH and Single User Mode both disabled.
To apply this method, the user needs some sort of physical access to the machine. So, finally I put together a script – all the other instructions are included in description (see below the link from the end of this article). You may also want to read the following post too: http://www.techtipsforsmartchicks.com/recover-root-password-single-user-mode-disabled/
Before going ahead with the reading, please also read the disclaimer below.
DISCLAIMER: This technique is presented for educational purposes only and you take full responsibility for all your actions.
You can download the script from here: http://pastebin.com/pbJ5iCJR