I generally think the command idea is a bad one, because it is intended to be the system key for app manipulation. Cmd-l appears to be unbound in the application menus, but I couldn't use any tricks to view what it's keycode may be. Thus, I would suggest Shift-Ctrl-a.
Having said that, if I understand the man page, and a resource on the Ubuntu Forums on the topic, I believe you can change it to Shift-Ctrl-a either by using the -e flag (which I suggest you use to test with before putting it in your
You should be able to run
screen -e ^AA.
^ is a common identifier for "Ctrl", and A means capital-a (shift + a), as opposed to a lowercase a, meaning the character by itself.
If that works, you should be able to add a line into your
~/.screenrc that says:
escape ^AA for it to automatically take place on any standard execution of
screen just by itself.