I don't want to click a confirmation or wait 60 seconds when I click Start -> shutdown. I commanded a shutdown, so just do it already! Where do I need to go to eliminate this dialog, or at least change the countdown to 5 seconds or 0 seconds?
I'm not sure why your system is waiting a whole minute, as mine does not to shut down..
Terminal - type- " shutdown now".
There's a good reason for the timer to be there. There have been a few occasions when I have told a GNU/Linux box to shut down when I have suddenly remembered I intended to write an email or some other task which prompted the need to press 'cancel'!
Tapping the shutdown icon a second time will override the timer.
You can also remove the timer and dialog with
gsettings set org.gnome.SessionManager logout-prompt false
I've actually never felt the need to cancel a shutdown, but this computer is so fast on shutdown and boot (once it starts the shutdown procedure) it wouldn't be a major issue. But your reasoning would be an excellent argument to change the timeout from 60 seconds to 5. Enough time to abort if necessary but not so much that I feel the need to make the extra mouse click to confirm shutdown. And I was unable to find any option to change that timeout setting.
I read somewhere that it does not work in earlier versions of ubuntu as it was hard coded, so perhaps it has changed. You can change settings in MATE.