If the title does not make any sense to you, you do not have a problem. Since nothing is broken, there is no need to fix anything. Please skip the following.
But do read on if you, like me, while trying to update the software on your computer, got an error message the kind of this:
Failed to exec method /usr/lib/apt/methods/ E: Method has died unexpectedly! E: Sub-process returned an error code (100) E: Method /usr/lib/apt/methods/ did not start correctly
It turns out this means that for some reason the cached software sources lists have been corrupted. Running ‘apt-get update’, no matter how often or with what user permissions, cannot solve this. (You got it: this is about Ubuntu-based systems.)
However, the remedy is simple: first remove the cache of sources lists, then update these. In a terminal run:
sudo rm -rf /var/lib/apt/lists/* sudo apt-get update
Done! Thanks HyRax (whose server seems to have disappeared…)