There has not been huge discussion of this issue but it has been a good time to visit the idea of merging. The following quote from the Moderator Cheat Sheet goes to the crux of the issue when merging questions:
When should I merge questions, as opposed to just closing as a duplicate?
When the exact same question gets asked twice and the answers on both are worth preserving, you should merge one into the other. You should only merge if the answers on the question-to-be-merged make perfect sense on the target question.
There certainly should not be all three question of these questions active on Ask Ubuntu, there is far too much overlap and thus dilution of community effort and the ability to find a canonical, accepted answer on AU.
But neither is there the 'exact same question' and answers that 'make perfect sense on the target question' as mentioned on the Moderator Cheat Sheet. I note as well the following statement on the Cheat Sheet:
I am not sure if I should vote to close or merge?
Merging should be much more unusual - it's in the mod menu. The answers must make sense on the target question - hence closing as duplicate first. If in doubt, ask.
And so in the presence of some variation of opinion and some doubt about the correct course of action the better course, I believe, (and @muru has agreed that this is at least better than the current situation) is to close questions 1 and 3 as Duplicates of question 2.
It is a bit of a 'line ball' call but the mechanisms are available here on meta or an Ask Ubuntu (Re-edit / Reopen Votes etc) to disagree :)