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pi-gen

Tool used to create Raspberry Pi OS images, and custom images based on Raspberry Pi OS, which was in turn derived from the Raspbian project.

Note: Raspberry Pi OS 32 bit images are based primarily on Raspbian, while Raspberry Pi OS 64 bit images are based primarily on Debian.

Note: 32 bit images should be built from the master branch. 64 bit images should be built from the arm64 branch.

Dependencies

pi-gen runs on Debian-based operating systems released after 2017, and we always advise you use the latest OS for security reasons.

On other Linux distributions it may be possible to use the Docker build described below.

To install the required dependencies for pi-gen you should run:

apt-get install coreutils quilt parted qemu-user-static debootstrap zerofree zip \
dosfstools libarchive-tools libcap2-bin grep rsync xz-utils file git curl bc \
gpg pigz xxd arch-test

The file depends contains a list of tools needed. The format of this package is <tool>[:<debian-package>].

Getting started with building your images

Getting started is as simple as cloning this repository on your build machine. You can do so with:

git clone https://github.com/RPI-Distro/pi-gen.git

--depth 1 can be added after git clone to create a shallow clone, only containing the latest revision of the repository. Do not do this on your development machine.

Also, be careful to clone the repository to a base path NOT containing spaces. This configuration is not supported by debootstrap and will lead to pi-gen not running.

After cloning the repository, you can move to the next step and start configuring your build.

Config

Upon execution, build.sh will source the file config in the current working directory. This bash shell fragment is intended to set needed environment variables.

The following environment variables are supported:

Setting this to a value will make that value the contents of the FIRST_USER_NAME's ~/.ssh/authorized_keys. Obviously the value should therefore be a valid authorized_keys file. Note that this does not automatically enable SSH.

A simple example for building Raspberry Pi OS:

IMG_NAME='raspios'

The config file can also be specified on the command line as an argument the build.sh or build-docker.sh scripts.

./build.sh -c myconfig

This is parsed after config so can be used to override values set there.

How the build process works

The following process is followed to build images:

It is recommended to examine build.sh for finer details.

Docker Build

Docker can be used to perform the build inside a container. This partially isolates the build from the host system, and allows using the script on non-debian based systems (e.g. Fedora Linux). The isolation is not complete due to the need to use some kernel level services for arm emulation (binfmt) and loop devices (losetup).

To build:

vi config         # Edit your config file. See above.
./build-docker.sh

If everything goes well, your finished image will be in the deploy/ folder. You can then remove the build container with docker rm -v pigen_work

If you encounter errors during the build, you can edit the corresponding scripts, and continue:

CONTINUE=1 ./build-docker.sh

To examine the container after a failure you can enter a shell within it using:

sudo docker run -it --privileged --volumes-from=pigen_work pi-gen /bin/bash

After successful build, the build container is by default removed. This may be undesired when making incremental changes to a customized build. To prevent the build script from remove the container add

PRESERVE_CONTAINER=1 ./build-docker.sh

There is a possibility that even when running from a docker container, the installation of qemu-user-static will silently fail when building the image because binfmt-support must be enabled on the underlying kernel. An easy fix is to ensure binfmt-support is installed on the host machine before starting the ./build-docker.sh script (or using your own docker build solution).

Passing arguments to Docker

When the docker image is run various required command line arguments are provided. For example the system mounts the /dev directory to the /dev directory within the docker container. If other arguments are required they may be specified in the PIGEN_DOCKER_OPTS environment variable. For example setting PIGEN_DOCKER_OPTS="--add-host foo:192.168.0.23" will add '192.168.0.23 foo' to the /etc/hosts file in the container. The --name and --privileged options are already set by the script and should not be redefined.

Stage Anatomy

Raspbian Stage Overview

The build of Raspbian is divided up into several stages for logical clarity and modularity. This causes some initial complexity, but it simplifies maintenance and allows for more easy customization.

Stage specification

If you wish to build up to a specified stage (such as building up to stage 2 for a lite system), place an empty file named SKIP in each of the ./stage directories you wish not to include.

Then add an empty file named SKIP_IMAGES to ./stage4 and ./stage5 (if building up to stage 2) or to ./stage2 (if building a minimal system).

# Example for building a lite system
echo "IMG_NAME='raspios'" > config
touch ./stage3/SKIP ./stage4/SKIP ./stage5/SKIP
touch ./stage4/SKIP_IMAGES ./stage5/SKIP_IMAGES
sudo ./build.sh  # or ./build-docker.sh

If you wish to build further configurations upon (for example) the lite system, you can also delete the contents of ./stage3 and ./stage4 and replace with your own contents in the same format.

Skipping stages to speed up development

If you're working on a specific stage the recommended development process is as follows:

Troubleshooting

64 Bit Systems

A 64 bit image can be generated from the arm64 branch in this repository. Just replace the command from this section by the one below, and follow the rest of the documentation:

git clone --branch arm64 https://github.com/RPI-Distro/pi-gen.git

If you want to generate a 64 bits image from a Raspberry Pi running a 32 bits version, you need to add arm_64bit=1 to your config.txt file and reboot your machine. This will restart your machine with a 64 bits kernel. This will only work from a Raspberry Pi with a 64-bit capable processor (i.e. Raspberry Pi Zero 2, Raspberry Pi 3 or Raspberry Pi 4).

binfmt_misc

Linux is able to execute binaries from other architectures, meaning that it should be possible to make use of pi-gen on an x86_64 system, even though it will be running ARM binaries. This requires support from the binfmt_misc kernel module.

You may see one of the following errors:

update-binfmts: warning: Couldn't load the binfmt_misc module.

W: Failure trying to run: chroot "/pi-gen/work/test/stage0/rootfs" /bin/true
and/or
chroot: failed to run command '/bin/true': Exec format error

To resolve this, ensure that the following files are available (install them if necessary):

/lib/modules/$(uname -r)/kernel/fs/binfmt_misc.ko
/usr/bin/qemu-arm-static

You may also need to load the module by hand - run modprobe binfmt_misc.

If you are using WSL to build you may have to enable the service sudo update-binfmts --enable