As you all know drupal 8 is using Symfony Components. That is the main reason of switching to symfony.
While i was reading this book Symfony.
Here is the first article how to install Symfony on Ubuntu machine.
Note: Don't copy the Dollar($) ofcourse.
1. Open your command console and execute the following commands:
$ sudo curl -LsS http://symfony.com/installer -o /usr/local/bin/symfony
$ sudo chmod a+x /usr/local/bin/symfony
2. Creating the Symfony Application