[linux] How do I get out of 'screen' without typing 'exit'?

In addition to the previous answers, you can also do Ctrl + A, and then enter colon (:), and you will notice a little input box at the bottom left. Type 'quit' and Enter to leave the current screen session. Note that this will remove your screen session.

Ctrl + A and then K will only kill the current window in the current session, not the whole session. A screen session consists of windows, which can be created using subsequent Ctrl + A followed by C. These windows can be viewed in a list using Ctrl + A + ".