PI-CI

A raspberry Pi emulator in a Docker image that lets developers easily prepare and flash RPi configurations.

Overview

The PI-CI project enables developers to easily:

• Run a RPi VM.
• Prepare a configuration inside a RPi VM.
• Flash a RPi VM image to a physical SD card.

Example use cases:

• Preconfigure Raspberry Pi servers that work from first boot.
• Create reproducible server configurations using Ansible.
• Automate the distribution of configurations through a CI pipeline.
• Test ARM applications in a virtualized environment.

Key features:

• Pi 3, 4 and 5 support
• 64 bit (ARMv8) Raspberry PI OS (24.04, Bookworm) included
  • Image: 2024-07-04-raspios-bookworm-arm64-lite
  • Kernel: 6.6-y
• Internet access
• No root required
• Safe, fully reproducible from source
• Tested and stable

Usage

$ docker pull ptrsr/pi-ci
$ docker run --rm -it ptrsr/pi-ci

> usage: docker run [docker args] ptrsr/pi-ci [command] [optional args]
> 
> PI-CI: the reproducible PI emulator.
> 
> positional arguments:
>   command     [init, start, resize, flash, export]
> 
> optional arguments:
>   -h, --help  show this help message and exit
>   -v          show verbose output
> 
> Refer to https://github.com/ptrsr/pi-ci for the full README on how to use this program.

Each command has a help message, for example: docker run --rm -it ptrsr/pi-ci start -h.

Start machine

Simply run a ptrsr/pi-ci container with the start command:

docker run --rm -it ptrsr/pi-ci start

The emulator will automatically log into root.

Persistence

To save the resulting image, use a bind mount to /dist:

docker run --rm -it -v $PWD/dist:/dist ptrsr/pi-ci start

NOTE: this example will create and mount the dist folder in the current working directory of the host.

To restart the image, simply use the same bind mount.

SSH access

To enable ssh access, run the container with port 2222 exposed.

docker run --rm -p 2222:2222 ptrsr/pi-ci start

Then ssh into the virtual Pi:

ssh root@localhost -p 2222

Resize

The default image is 2 gigabytes in size. This can be increased (but not decreased!) through the resize command. Increasing the size can be done in two ways:

1. by providing a path to the target device (e.g. /dev/mmcblk0). The resulting image will be the same size as the target device.

2. By providing a specific size in gigabytes, megabytes or bytes (e.g. 8G, 8192M, 8589934592).

For an image to be flashed to a device, the image has to be the less or equal to the device size.

docker run --rm -it -v $PWD/dist:/dist --device=/dev/mmcblk0 ptrsr/pi-ci resize /dev/mmcblk0

NOTE: although an SD card will say a specific size (such as 16GB), the device is usually if not always smaller (GB vs GiB). Therefore, using a target device is recommended.

NOTE: resizing can potentially be a dangerous operation. Always make backup of the image.qcow2 file in the dist folder before proceeding.

Flash

To flash the prepared image to a storage device (such as an SD card), provide the container with the device and run the flash command:

docker run --rm -it -v $PWD/dist:/dist --device=/dev/mmcblk0 ptrsr/pi-ci flash /dev/mmcblk0

On the first boot of the real RPi, a program will automatically inflate the root partition to fill the rest of the target device.

Export

The export function converts the virtual (.qcow2) image to a raw (.img) image. This is particularly handy when it is not possible to directly flash an image (e.g. when using WSL), as the raw image can be flashed using tools like Balena Etcher. The export command takes two optional arguments; the --input and --output path;

docker run --rm -it -v $PWD/dist:/dist ptrsr/pi-ci export --input /dist/image.qcow2 --output /dist/image.img

The raw image should pop up alongside the virtual image in the mounted dist folder in the example above.

Automation

Using Ansible, it is possible to automate the whole configuration process. Ansible requires docker-py to be installed. This can be done using pip3 install docker-py.

Ansible can take care of:

1. Starting the VM
2. Running tasks in the VM
3. Stopping the VM

An example configuration can be found in the ./test folder of this repository. To start the test process, run:

ansible-playbook -i ./test/hosts.yml ./test/main.yml

Tips

• Do not forget to set a password for root and disable PermitRootLogin in the /etc/ssh/sshd_config for security.
• Do not stop or kill the Docker container while the VM is running, this WILL corrupt the image!
• Make sure to regularly back up the distro.qcow2 image.

Versions

PI-CI has automatically been tested on Ubuntu 24.04 using GitHub Actions. Any other distro should work with the following software versions (or higher, perhaps):

Software	Version
Ansible	2.5.1
docker-py	4.4.4
Docker	19.03.6

License

PI-CI is licensed under GPLv3.