Fix Pi-Star to allow it to boot from USB's natively on Pi3's and Pi4's

Installation files, scripts and SYSTEMD entries to implement automatic backups and restores of Pi-Star's MMDVM logs: periodic backups, backups at shutdowns, restores on bootup.

BASH script to update a working 4.xx Pi-Star system from Debian Buster to Debian Bullseye

An augmented version of Pi-Star 4.1.x that tracks with the original

BASH script to update a working 4.xx Pi-Star system from Debian Bullseye to Debian Bookworm