The rescue prompt gives you superuser -- as demonstrated in the video.

Funny. (pironically)
The user hasn't come back with new questions so they probably gave up and re-installed. :-)

I dug into how someone might do this from the LiveDVD while doing as much as 
possible without the command line.

I couldn't even mount the drive in that interface without the terminal.

On Mon, 31 Dec 2018, Iznogoud wrote:

>>
>> At the very least we should not ask a novice user to use vim to mess with a
>> shadow file. That's just brutal.
>>
>
> I read this and smiled. So many things wrong with this and on so many levels!
>
>
>> If the command
>>    mount -o rw,remount /
>>
>> works for them, then the user can just run
>>    passwd danny
>> to change the password for the "danny" user.
>>
>
> Superuser privilleges assumed for all the above. Now one needs only explain
> to a novice user how to get that...
>
>