Put the sd card into a machine running linux anytime you want and edit the files to have root access. Another good reason to run either an external ssd as the sa drive or get a pi that has onboard memory drive. With that you boot on an sd card with the stock pi operating system and then edit the files on the sa drive then shut it down remove the sd card and start it back up on the sa drive.
This also means you can repair the sa drive is something goes wrong, back it up anytime you want and since your not using an sd card for the sa anymore it should last a loooong time. Sd cards do not like being written to very often and fail from it.
