So I accidentally typed:
sudo chmod a-wrx /etc
and since etc contains
sudeors.d and many other critical stuff, I couldn't log in/out or perform any administration tasks.
I loaded GRUB and went root from there, I did:
chmod a+wrx /etc
and finally logged to the machine, but it's now messed up (can't shutdown properly, look has changed, ...etc).
How do I restore the default permissions for etc (or any file system) that came shipped with the installation (without reinstalling the system) ?