I use debian jessie and I have done one of those bad mistakes and broke my system with a mistyped command and worse mistakes that follow in such situations.
Trying to fix some permissions I mistakenly used chmod recursively on root folder:
# chmod -R 0644 /
and then realizing immediately I rushed in doing something to stop it but the system was frozen and the worse mistake was the hard powering off the system.
Now I think I have some user manager problem and after booting with some "failed to start service" messages I don't have the Gnome user login and I can't also login in console. And this is what that flashes several times and then stays on screen:
[ ok ] Created slice user-113.slice Starting user manager for UID 113... [ ok ] Started user manager for UID 113 [ ok ] Stopped user manager for UID 113 [ ok ] Removed slice user-113.slice