Perhaps you have a new install of Ubuntu, and you are about to install docker or any other Linux packages. The first step is to update the application repositories using the sudo apt update command. There is a very small possibility that you will get the error below if you are using a fresh install of the Ubuntu 18.04 LTS (Bionic Beaver). This error simply means that Linux is unable to connect to the official repository likely due to a DNS configuration or a network issue. Here we try to help you resolve the DNS issue. To resolve this, you must specify a DNS in your network settings. Well, there is one popular DNS that works well: Google's DNS. Follow through, please. STEP 1: Go to the settings page of Linux (Ubuntu) STEP 2: This should reveal a plethora of options. On the left pane, simply scroll down and click Network as shown below. This reveals your different network connections, for me, “enp0s3” is the adapter connecter to the internet. So, I must configure DNS for “enp0s3”. ...