Memorycard initialization

This folder contains the Raspberry Pi SD card initialization. The image is based on Arch Linux ARM, plus raspi-overlayroot.

Requirements

qemu-user-static-arm  # may be qemu-user-static in some distro
podman
sudo
wget

The image build script uses podman, but regular Docker versions may work.

Make sure to initialize ad update the raspi-overlay git submodule:

git submodule update --init

Building the base image

The build script build-rpi-armv7 creates the image localhost/archlinuxarm/rpi-armv7:latest in podman. The base of the image is the tarball of the Arch Linux ARM project for Raspberry Pi devices, which defaults to http://os.archlinuxarm.org/os/ArchLinuxARM-rpi-armv7-latest.tar.gz. You can control the address of the tarball with the AARCH_URL environment variable.

The build is bound to a specific hash of the tarball. The build script will fail if the downloaded tarball md5 hash does not match ArchLinuxARM-rpi-armv7-latest.tar.gz.md5, which might happen if you run this script in the future. If you intend to run update the base tarball, first replace the md5 checksum file:

wget -O ArchLinuxARM-rpi-armv7-latest.tar.gz.md5 http://os.archlinuxarm.org/os/ArchLinuxARM-rpi-armv7-latest.tar.gz.md5
# possibly commit it

The image runs with a read-only root filesystem, with a writable in-memory overlay (see project raspi-overlayroot for details).

The script leaves in podman the imported base tarball. The import is deterministic, and so is the image hash. The image tag is localhost/archlinuxarm/rpi-armv7-import:"${date}", where ${date} is the timestamp (YYYY-MM-DD) contained in the gzip header of the tarball.

Copying to a SD card

Your SD card device should be defined with the MEMORY_CARD_DEVICE environment variable:

export MEMORY_CARD_DEVICE=/dev/mmcblk0

The sd-format, sd-mount, sd-umount scripts make use of this variable to reference the memory card.

Use the sd-format script ERASES ALL CONTENT of your memory card and replaces it with the content of the image localhost/archlinuxarm/rpi-armv7:latest, with the proper 2-partitions layout for Raspberry Pi devices. It will delete and lock the password for the root and alarm user, and initialize the machine-id and ssh host keys. If you have the public part of your ssh key in the standard path (~/.ssh/id_rsa.pub), it will use it to allow you to login to the device.

Use the sd-mount script to mount your memory card in the mounts/${device} directory. Use the sd-umount script to unmount (and flush) the device.

Modifying the SD card installation

Use the sd-exec script to login as root inside the mounted SD partitions. You can perform for example updates in this way.