The on-board system is a complete ready-to-use Debian distribution; however, it may happen that we may need another image (maybe during some developing stages) or just for backup purposes (just in case, the default image is corrupted for some reason). So, it's important to see how we can install an alternate image on our board.
There are many ways to install a Debian OS on our BeagleBone Black. I'm going to use the simplest and quickest one using a prebuild image to be put on a microSD. This solution has the advantage that by simply removing the microSD from the system, the board will boot with the original default image.
A similar procedure may be used to install a different OS too.
Note that the microSD should be a class ...