"sudo tar xvzf *.tgz -C /" -> it seems this simply overwrote your /etc/sudoers with a version from the unpacked tarballs.
** Changed in: sudo (Ubuntu) Status: Unconfirmed => Rejected -- sudo with tar crashes /etc/sudoers https://launchpad.net/bugs/72552 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs