What I'd advise you to do is live a life on the straight and narrow. To answer your question, the main part of the Tails USB is read-only by default to prevent any permanent data from being saved unless you explicitly set up a Persistent Storage Volume. You can create an encrypted PSV which is the only place data persists across reboots and give it read and write permissions. Until you set up the volume, the entire thing is read-only. GD scrubs metadata; a program generally needs the ability to both read the original file to access its current metadata and write a modified version of that file, either to remove the data or replace it with new information. Not possible using read-only, ERROR:,