http://www.tkdocs.com/
Setting up an apt-mirror: https://raymii.org/s/tutorials/Set_up_a_local_Ubuntu_debian_apt_mirror.html
https://apt-mirror.github.io
https://ryanstutorials.net/bash-scripting-tutorial/bash-if-statements.php
http://wiki.bash-hackers.org/commands/classictest
