pi-gen Scramjet Transform Hub Edition

Tool used to create Raspberry Pi OS images - with Scramjet Transform Hub installed and ready for connection with Scramjet Cloud Platform

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

Scramjet Cloud Platform

Scramjet Cloud Platform is a powerful serverless data processing platform that combines a data processing engine with serverless apps and APIs, making it easy to deploy, run, and integrate data across distributed environments.

Images and usage

This repo allows building Scramjet Transform Hub images for Raspberry Pi based on Raspberry PI OS with STH working as a service, and an optional kiosk mode browser.

STH Image

The process builds a Raspberry Pi OS image with the -sth suffix with STH installed as a service. If the platform config is provided or deployed to the SD card in the Deploy volume, it will be used to connect to Scramjet Cloud Platform.

With this you can then deploy your programs remotely via the platform panel or the si command from @scramjet/cli.

Kiosk Image

The process builds a Raspberry Pi OS image with the -sth-kiosk suffix with STH installed as a service and a kiosk mode browser with autostart. The browser waits until an API appears on //localhost:9080/api/url and redirects to the URL in the JSON response, for instance:

{"url": "http://localhost:9080/index.html"}

Such an API and website can be deployed in a Scramjet Sequence - see an example of a basic www server for a kiosk browser on a Raspberry Pi here.

Differences from upstream

• The main difference is that the image has the Transform Hub installed and automatically started with systemd.
• The additional vfat partition holds pre-deployed cloud functions for your Pi and STH configuration

Scramjet Transform Hub Configuration

For use with the Platform please register at Scramjet Cloud Platform - after completing the setup, click on Add Hub button in Space tab and copy the configuration. You'll need to copy the platform key to your config.

Here's a suggested configuration to use with Scramjet (put it on the DEPLOY partition in /conf directory as sth-config.json):

{
    "host": {
        "hostname": "0.0.0.0",
        "port": 9002,
        "instancesServerPort": 9003,
        "id": "pi-sth"
    },
    "safeOperationLimit": 64,
    "instanceRequirements": {
        "freeMem": 128
    },
    "telemetry": {
        "status": true,
        "environment": "raspberry-pi-sth"
    },
    "description": "My Pi",
    "tags": [
        "rpi",
        "demo"
    ],
    "timings": {
        "instanceLifetimeExtensionDelay": 10000
    },
    "platform": {
        "<copy>": "<json from Scramjet Cloud Platform>"
    }
}

Once that's done - start your Raspberry Pi and once it boots, it'll automatically connect to the platform. Now you can start your long running lambda functions from the panel or the CLI, wherver you are.

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

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 afer 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.

You can use your own configs with the command line switch sudo ./build.sh -c config.path.secret. If the suffix is .secret it'll be ignored by git, via .gitignore.

A sample config is as follows:

. config

IMG_NAME="${IMG_NAME}-sample"

TARGET_HOSTNAME=sth-pi
FIRST_USER_NAME=pi
ENABLE_SSH=1
# PUBKEY_SSH_FIRST_USER="<your ssh key>"
PUBKEY_ONLY_SSH=1

WPA_ESSID="<ESSID>"
WPA_PASSWORD="<password>"
WPA_COUNTRY=PL

The following environment variables are supported:

• IMG_NAME required (Default: unset)

  The name of the image to build with the current stage directories. Use this variable to set the root name of your OS, eg IMG_NAME=Frobulator. Export files in stages may add suffixes to IMG_NAME.

• PI_GEN_RELEASE (Default: Raspberry Pi reference)

  The release name to use in /etc/issue.txt. The default should only be used for official Raspberry Pi builds.

• RELEASE (Default: bookworm)

  The release version to build images against. Valid values are any supported Debian release. However, since different releases will have different sets of packages available, you'll need to either modify your stages accordingly, or checkout the appropriate branch. For example, if you'd like to build a bullseye image, you should do so from the bullseye branch.

• APT_PROXY (Default: unset)

  If you require the use of an apt proxy, set it here. This proxy setting will not be included in the image, making it safe to use an apt-cacher or similar package for development.

  If you have Docker installed, you can set up a local apt caching proxy to like speed up subsequent builds like this:

  docker-compose up -d
  echo 'APT_PROXY=http://172.17.0.1:3142' >> config
  

• BASE_DIR (Default: location of build.sh)

  CAUTION: Currently, changing this value will probably break build.sh

  Top-level directory for pi-gen. Contains stage directories, build scripts, and by default both work and deployment directories.

• WORK_DIR (Default: "$BASE_DIR/work")

  Directory in which pi-gen builds the target system. This value can be changed if you have a suitably large, fast storage location for stages to be built and cached. Note, WORK_DIR stores a complete copy of the target system for each build stage, amounting to tens of gigabytes in the case of Raspbian.

  CAUTION: If your working directory is on an NTFS partition you probably won't be able to build: make sure this is a proper Linux filesystem.

• DEPLOY_DIR (Default: "$BASE_DIR/deploy")

  Output directory for target system images and NOOBS bundles.

• DEPLOY_COMPRESSION (Default: zip)

  Set to:

  • none to deploy the actual image (.img).
  • zip to deploy a zipped image (.zip).
  • gz to deploy a gzipped image (.img.gz).
  • xz to deploy a xzipped image (.img.xz).

• DEPLOY_ZIP (Deprecated)

  This option has been deprecated in favor of DEPLOY_COMPRESSION.

  If DEPLOY_ZIP=0 is still present in your config file, the behavior is the same as with DEPLOY_COMPRESSION=none.

• COMPRESSION_LEVEL (Default: 6)

  Compression level to be used when using zip, gz or xz for DEPLOY_COMPRESSION. From 0 to 9 (refer to the tool man page for more information on this. Usually 0 is no compression but very fast, up to 9 with the best compression but very slow ).

• USE_QEMU (Default: "0")

  Setting to '1' enables the QEMU mode - creating an image that can be mounted via QEMU for an emulated environment. These images include "-qemu" in the image file name.

• LOCALE_DEFAULT (Default: "en_GB.UTF-8" )

  Default system locale.

• TARGET_HOSTNAME (Default: "raspberrypi" )

  Setting the hostname to the specified value.

• KEYBOARD_KEYMAP (Default: "gb" )

  Default keyboard keymap.

  To get the current value from a running system, run debconf-show keyboard-configuration and look at the keyboard-configuration/xkb-keymap value.

• KEYBOARD_LAYOUT (Default: "English (UK)" )

  Default keyboard layout.

  To get the current value from a running system, run debconf-show keyboard-configuration and look at the keyboard-configuration/variant value.

• TIMEZONE_DEFAULT (Default: "Europe/London" )

  Default keyboard layout.

  To get the current value from a running system, look in /etc/timezone.

• FIRST_USER_NAME (Default: pi)

  Username for the first user. This user only exists during the image creation process. Unless DISABLE_FIRST_BOOT_USER_RENAME is set to 1, this user will be renamed on the first boot with a name chosen by the final user. This security feature is designed to prevent shipping images with a default username and help prevent malicious actors from taking over your devices.

• FIRST_USER_PASS (Default: unset)

  Password for the first user. If unset, the account is locked.

• DISABLE_FIRST_BOOT_USER_RENAME (Default: 0)

  Disable the renaming of the first user during the first boot. This make it so FIRST_USER_NAME stays activated. FIRST_USER_PASS must be set for this to work. Please be aware of the implied security risk of defining a default username and password for your devices.

• WPA_COUNTRY (Default: unset)

  Sets the default WLAN regulatory domain and unblocks WLAN interfaces. This should be a 2-letter ISO/IEC 3166 country Code, i.e. GB

• ENABLE_SSH (Default: 0)

  Setting to 1 will enable ssh server for remote log in. Note that if you are using a common password such as the defaults there is a high risk of attackers taking over you Raspberry Pi.

• PUBKEY_SSH_FIRST_USER (Default: unset)

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.

• PUBKEY_ONLY_SSH (Default: 0)

• Setting to 1 will disable password authentication for SSH and enable public key authentication. Note that if SSH is not enabled this will take effect when SSH becomes enabled.

• SETFCAP (Default: unset)

  • Setting to 1 will prevent pi-gen from dropping the "capabilities" feature. Generating the root filesystem with capabilities enabled and running it from a filesystem that does not support capabilities (like NFS) can cause issues. Only enable this if you understand what it is.

• STAGE_LIST (Default: stage*)

  If set, then instead of working through the numeric stages in order, this list will be followed. For example setting to "stage0 stage1 mystage stage2" will run the contents of mystage before stage2. Note that quotes are needed around the list. An absolute or relative path can be given for stages outside the pi-gen directory.

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:

• Interate through all of the stage directories in alphanumeric order

• Bypass a stage directory if it contains a file called "SKIP"

• Run the script prerun.sh which is generally just used to copy the build directory between stages.

• In each stage directory iterate through each subdirectory and then run each of the install scripts it contains, again in alphanumeric order. These need to be named with a two digit padded number at the beginning. There are a number of different files and directories which can be used to control different parts of the build process:

  • 00-run.sh - A unix shell script. Needs to be made executable for it to run.

  • 00-run-chroot.sh - A unix shell script which will be run in the chroot of the image build directory. Needs to be made executable for it to run.

  • 00-debconf - Contents of this file are passed to debconf-set-selections to configure things like locale, etc.

  • 00-packages - A list of packages to install. Can have more than one, space separated, per line.

  • 00-packages-nr - As 00-packages, except these will be installed using the --no-install-recommends -y parameters to apt-get.

  • 00-patches - A directory containing patch files to be applied, using quilt. If a file named 'EDIT' is present in the directory, the build process will be interrupted with a bash session, allowing an opportunity to create/revise the patches.

• If the stage directory contains files called "EXPORT_NOOBS" or "EXPORT_IMAGE" then add this stage to a list of images to generate

• Generate the images for any stages that have specified them

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 0 - bootstrap. The primary purpose of this stage is to create a usable filesystem. This is accomplished largely through the use of debootstrap, which creates a minimal filesystem suitable for use as a base.tgz on Debian systems. This stage also configures apt settings and installs raspberrypi-bootloader which is missed by debootstrap. The minimal core is installed but not configured. As a result, this stage will not boot.

• Stage 1 - truly minimal system. This stage makes the system bootable by installing system files like /etc/fstab, configures the bootloader, makes the network operable, and installs packages like raspi-config. At this stage the system should boot to a local console from which you have the means to perform basic tasks needed to configure and install the system.

• Stage 2 - lite system. This stage produces the Raspberry Pi OS Lite image. Stage 2 installs some optimized memory functions, sets timezone and charmap defaults, installs fake-hwclock and ntp, wireless LAN and bluetooth support, dphys-swapfile, and other basics for managing the hardware. It also creates necessary groups and gives the pi user access to sudo and the standard console hardware permission groups.

  Note: Raspberry Pi OS Lite contains a number of tools for development, including Python, Lua and the build-essential package. If you are creating an image to deploy in products, be sure to remove extraneous development tools before deployment.

• Stage 3 - desktop system. Here's where you get the full desktop system with X11 and LXDE, web browsers, git for development, Raspberry Pi OS custom UI enhancements, etc. This is a base desktop system, with some development tools installed.

• Stage 4 - Normal Raspberry Pi OS image. System meant to fit on a 4GB card. This is the stage that installs most things that make Raspberry Pi OS friendly to new users - e.g. system documentation.

• Stage 5 - The Raspberry Pi OS Full image. More development tools, an email client, learning tools like Scratch, specialized packages like sonic-pi, office productivity, etc.

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:

• Add a file called SKIP_IMAGES into the directories containing EXPORT_* files (currently stage2, stage4 and stage5)
• Add SKIP files to the stages you don't want to build. For example, if you're basing your image on the lite image you would add these to stages 3, 4 and 5.
• Run build.sh to build all stages
• Add SKIP files to the earlier successfully built stages
• Modify the last stage
• Rebuild just the last stage using sudo CLEAN=1 ./build.sh
• Once you're happy with the image you can remove the SKIP_IMAGES files and export your image to test

Writing to SD card

Replace ${your_image} and ${card_dev} with your correct names and run.

sudo dd if=deploy/${your_image}.img of=/dev/sd${card_dev} status=progress bs=4M

Troubleshooting

64 Bit Systems

Please note there is currently an issue when compiling with a 64 Bit OS. See RPi-Distro#271

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 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-aarch64-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