MySQL how to reset root password in Linux (Debian, Ubuntu, etc)

In case you've forgotten or lost your root password from MySQL server, there is a way to reset it. Below you will find detailed guide on how to do it in Linux. In particular, all instructions and commands were tested with Debian 8 and MySQL 5.5, but they should also work on most of other distributions. So let's get started.

ssh how to disable password and allow only key authentication

Key authentication is more secure over password authentication. Just because users might have weak passwords, an attacker can easily brute force them. On the other hand, it's impossible to brute force ssh key. That's why I encourage you to use ssh key authentication and below I will show you how to configure it.