sudo: /usr/bin/sudo must be owned by uid 0 and have the setuid bit set

https://askubuntu.com/questions/452860/usr-bin-sudo-must-be-owned-by-uid-0-and-have-the-setuid-bit-set

1. Log out as the current user, then log back in as root.
2. Execute chown root:root /usr/bin/sudo && chmod 4755 /usr/bin/sudo
3. Log out as root, then log back in as the current user.