Setting up keys

Whenever a new repository is added to the Ubuntu repository manager, we have to make it trusted to validate the origin of the packages by adding the keys. The following key should be added to Ubuntu before starting the installation, which will ensure the download comes from an authorized server:

$ sudo apt-key adv --keyserver hkp://ha.pool.sks-keyservers.net:80 --recv-key 421C365BD9FF1F717815A3895523BAEEB01FA116