So you managed to login to your Ubuntu Linux machine with a password by using the magic of ssh keys, and you installed “apticron” to email you whenever their is a system update, you login to the system and issue the update command “sudo aptitude update” and “sudo” asks you about your password! not only it is annoying, it also can’t be automated, imaging you manage 10 servers and you have to type the password to update each machine! or you want to automate using some remote execution application like Fabric or Salt (I am Python fan, so I won’t mention Chef or Puppet here).