Disable all console boot messages
I need to disable all boot messages in production systems. The way to handle this is to create an app that, on install, updates the system in production specific ways depending on the system the package is built for.
One of the first things this package needs to do is disable console messages. This can be achieved with two changes applied to cmdline.txt boot args.
The first disables all but absolutely fatal console messages while the second routes init script messages to tty3. Note that there is already a console=tty0 so the latter needs to be a sed change while the former is appended to the boot args.