You can create a backup (system restore point) on your DietPi system. This will allow you to revert the root filesystem back to a previous state.
dietpi-backup
As an example:
When I do a fresh DietPi install for testing, once the basic installation process is completed (eg: nothing installed), I create a dietpi-backup before doing anything else.
Once I’ve finished “fiddling” and testing, i simply restore the previous backup. Means I dont need to rewrite the DietPi image
