rsl@ubuntu:~$ sudo - root
sudo: '-' requires an argument
usage: sudo -h | -K | -k | -L | -l | -V | -v
usage: sudo [-bEHPS] [-p prompt] [-u username|#uid] [VAR=value]
            {-i | -s | }
usage: sudo -e [-S] [-p prompt] [-u username|#uid] file ...
rsl@ubuntu:~$ su - root
Password: 
rsl@ubuntu:~$