Rebuild the Debian root¶

The modern firmware's root is Debian 13 (trixie) armhf with systemd, on its own ext4 partition. Rebuild it whenever firmware-modern/debian/overlay/ changes:

# run from: the repo root
./devkit build --rootfs-only        # -> firmware-modern/debian/rootfs.tar
sudo ./devkit write-card /dev/sdX   # refuses anything not removable

write-card refuses a rootfs.tar older than the overlay, and lists what it would miss. The root cannot be swapped over the network: it takes a card.

The two partitions of the card: a 128 MB FAT boot partition holding BOOT.bin, uImage, devicetree.dtb and uEnv.txt, and a Debian root partition on the rest of the card.

Where	What
`firmware-modern/debian/packages.txt`	every package, with the reason for each unobvious one
`firmware-modern/debian/overlay/`	the files laid over Debian: units, scripts, settings

A small change needs no rebuild

The root is an ordinary writable disk: apt install, or edit the file in place on the board. Rebuild when the change belongs in every card.

Why Debian, and what each unit does: why Debian · the Debian root reference.