This meta question seems somewhat ambiguous to me and does not link to the question it's asking about, so it's possible I'm making a mistake in understanding it. This answer of mine likely only applies if I am understanding this meta question correctly, which I cannot absolutely guarantee.
When your question brings you back to your original problem, often this means you did not ask about your original problem, or asked in such a way that emphasized the original problem less than some other endeavor which turned out not to be as useful toward solving the original problem as you had hoped/thought it would be.
If I understand this meta question correctly, you are saying that:
If my understanding of this meta question is correct, then what's happened is that:
- You're having a problem X, in this case that you get errors about duplicate repositories in
sources.list.
- You devised the (quite reasonable!) solution of trying to reset your software sources (repos) to their original, canonical configuration. You then went about trying to figure out how to do that. The problem of needing to know how to do that is a separate problem, problem Y.
This situation is known, on Stack Exchange sites (such as Ask Ubuntu), as the XY problem.
As the asker of the question, you can increase the likelihood of getting an answer that will solve the original, underlying problem (problem X) by asking for the solution to problem X instead of asking for the solution to problem Y.
Your question has been closed (four other users and I voted to close it because it seemed quite strongly to be asking for something answered in an already-existing question). So I think you have two main choices for how to precede:
If you believe your question, as you asked it, is close enough to the question you need to ask (about the underlying problem of fixing duplicate repos) to be worth saving, you can edit your question to improve it and make it primarily about the underlying problem which is actually what you are trying to solve.
Editing your question will get it automatically considered for reopening. Specifically, it will add it to the reopen review queue, and reviewers will be asked to decide if, given the changes you've made to it (and any other factors that might apply), it should be reopened.
If you believe you need to ask a question that's entirely different from what you've asked already, you could post a new question.
In this case I'm inclined to think the first approach--of editing your question--is the better one.
Whether you edit your existing question or post a new one, you should make sure it's clear--ideally, with an explicit explanation included in the question--as to why what you're asking is not the same as How do I restore the default repositories?, which is the question we've closed your question as a duplicate of.
Specifically, you should explain why the solutions given there have not worked to fix your problem.
In addition to the above advice that is more or less generalizable, I have some specific suggestions for this particular situation.
There are two kinds of duplicate lists mentioned in your question. Near the top you say, "I have a smooth run of update which return a notice of a duplicate in /var/lib/apt/lists." But the rest of the question seems to be about, and includes concrete quoted details confirming, that the problem you're now having is related to entries in /etc/apt/sources.list.
I recommend clarifying which of the problems you're still experiencing. A duplicate entry in /var/lib/apt/lists will not be solved with methods intended to remove duplicates from /etc/apt/sources.list. Are you seeing both messages now, or just the /etc/apt/sources.list message? (Or just the original /var/lib/apt/lists message?)
I recommend you provide the full error message (I've commented to explain how to do this in such a way that Ask Ubuntu will allow you to submit the edit, and so it appears in a readable way).
You should also show us the full contents of /etc/apt/sources.list (you can open it in a text editor or run cat /etc/apt/sources.list in a Terminal window).
And it may also be handy to see the contents of sources.list.d; I'd suggest showing us the output of:
for f in /etc/apt/sources.list.d/*.list; do printf '** %s:\n%s\n\n' "$(basename "$f")" "$(<"$f")"; done
If you're still seeing mention of /var/lib/apt/lists in any error messages, you should show us that file too (which you can do in the same way as with /etc/apt/sources.list, for example by giving the output of cat /var/lib/apt/lists).
Finally, your question is about a problem with a development release of Ubuntu (15.04 Vivid Vervet). Vivid is still in beta, though it is scheduled for release this month.
One item listed in the help under "Questions that you should avoid" is:
Now, in the final days before a release, in practice the policy becomes more lax. I'm not sure if we'll end up considering your question on-topic before Vivid is released. Even if not, if you still have the problem after the release, you should certainly feel free to continue trying to get help with it here.
(For other places to get help with alpha and beta versions of Ubuntu, see those links in the bullet point quoted from the help.)
