[rakoo]

Imagine any single change in your system configuration (packages, configuration, startup scripts, whatever) is loaded into a source version control as you move forward.

If something fails, you can always rollback to a previous revision, and since everything is there, you know your whole system will be working.

If you want to reproduce your system, you can copy the whole content and "checkout" the relevant revision on the new system. Because the hash is the same, every single bit underneath will be the same.