sudo (change) surprise
Just a heads up that if you accept the maintainer's version of /etc/sudoers for a recent update, it removes admin group as a default sudoer from that file, leaving you unable to sudo anything if you are not a member of sudo group (which nobody is unless specifically added).
So you might want to add yourself to sudo group before doing updates. Or if like me, you were unaware of that, you can boot a (recovery) kernel and edit /etc/group from a root shell. It is a comma separated list of users in that group like:
i5 650 3.2 GHz, 8 GB, nvidia GTX 550 Ti 32" 1080p | i7-4700, 8 GB, Intel HD 4600/nvidia GTX 765M 15.6" 1080p | etc.