There have been countless questions on this subject, but the closest one I found was about (something like) what defines a duplicate, the question or the answer? This one is slightly different.
Then I looked better into the exact words of the description of he question and read that the poster explicitly asked for a solution that also worked without GUI log in. Since my answer (not a duplicate as far as I can see) only works when logging in with GUI, I felt silly posting it there, and came to the conclusion that although the question seemed to be a duplicate, the description of the question asked for a different solution. Therefore it could not be an exact duplicate. I have seen other examples like this, where questions were happily closed as duplicate, while indeed the title suggested a duplicate, but the description made clear the origin of the question was different.
My question is in general, since in this case there was still another duplicate that I overlooked, which was a real duplicate in my opinion.
So my question is: what defines a duplicate, a question, its description or both?