Kiosk terminal image builder for Raspberry Pi

This project builds an image for a Raspberry Pi that boots directly into a browser with a predefined web page. It is a soft fork of https://git.fsmpi.rwth-aachen.de/thomas/ci-vm-image (which was designed for CI VM images on amd64).

The system runs from RAM, almost all changes at runtime are ephemeral. The device can safely be unplugged without shutting down with no real risk of data loss. As the boot partition is mounted read-write in order to regularly update the software clock, there is still a minor chance, but in practice it is very unlikely to corrupt the file system.

On boot, the kiosk user is automatically logged in and launches Firefox in kiosk mode with /boot/CONFIG/kiosk.html (see below). Terminal switching is possible, both root and kiosk passwords are empty. When Firefox quits, it will automatically be relaunched, unless /tmp/noautologin exists.

:::warning Bug: Firefox will not show (only blank screen) until the first user input, such as mouse movement or a key press. :::

Building

Requirements: Podman and a native arm64 host or a correctly configured and container-compatible qemu-binfmt setup.

% make           # for arm64, RPi 3 and later
% make ARCH=arm  # for armv7, RPi 2

RPi 1 (armv6/armhf) is currently untested and unsupported, but could work. One would need to pass --variant to the podman invocation or use a single-arch image such as docker.io/arm32v6/alpine.

The results (boot.tar, root.img) are placed in the arm64 or arm directory.

SELinux

On SELinux-enabled systems (such as Fedora), the container may not have access to the directories. Either move the whole building directory to an appropriately labelled place, or customise the scripts to place the in-container directories elsewhere, or set the type context label of the build directory to container_file_t (e. g., chcon -R -t container_file_t .). You may need to install container-selinux manually on Fedora.

Flashing

1. Partition an SD card with the typical RPi layout:
   1. a small-ish (~200MiB should be enough, cf. size of boot.tar) partition at the beginning of MBR type 0x0c for the boot file system,
   2. and a partition of at least 2GiB and type 0x83 for the root file system.
2. Create a FAT32 file system (e. g., mkfs.vfat /dev/mmcblk0p1) on the first partition.
3. Mount the first partition and extract boot.tar to its root. You can ignore the error that the boot symlink cannot be created.
4. Copy root.img to the second partition (e. g., `pv -pterbaY root.img

   /dev/mmcblk0p2`)

Configuration

All configurables are stored in the CONFIG directory of the boot partition, i. e., /boot/CONFIG/ in the running system.

swclock

Software clock. On boot, system time is set to the time stamp of this file. Every hour, the time stamp of this file is updated. During normal operation, time should be updated via NTP.

interfaces

Configuration for ifupdown-ng.

hostname

System host name.

kiosk.html

Opened on boot, would typically contain a redirect to a web site.

wpa_supplicant.conf

Additional WLAN configuration, required for WPA-EAP (PSK is possible via interfaces alone).