Last Updated: June 10, 2015
Starting from Lion (Mac OS X 10.7), Apple operating systems no longer come with a bundled install DVD, which has been replaced by a hidden recovery partition that can be used for the same purpose. While this has surely meant a remarkable cost slashing for Apple, it has created some inconveniences to users. It's actually pretty easy to reinstall OS X from Recovery Partition but it requires an active Internet connection in order to download the needed files from Apple servers and it's a very slow procedure. This is a consequence of the so-called cloud computing revolution. But, what if we need to reinstall OS X without an active internet connection or we cannot access Wi-Fi from outside the operating system?
Luckily there's an easy fix for this problem: create an emergency boot disk on a bootable USB drive that will work the same way as an install DVD.
What you need: