How to fix " Ignoring file ***** as it has an invalid filename extension" [duplicate]
Solution 1:
The "ignored" message will be fixed with: cd /etc/apt/sources.list.d/ && rm rethinkdb.list.save.*. Mind that a remove is permanent but also that "ignored" is not a fatal error: the system will continue.
E: Type '“deb' is not known on line 1 in source list /etc/apt/sources.list.d/signal-xenial.list E: The list of sources could not be read.
... is fatal though. Use an editor and check /etc/apt/sources.list.d/signal-xenial.list and fix the error. OR remove the file (as it refers to xenial = 16.04) with ...
cd /etc/apt/sources.list.d/ && rm signal-xenial.list