distribution/documentation/DEVEL_BUILDING_JELOS.md

        

Developing and Building JELOS

JELOS is a fairly unique distribution as it is built to order and only enough of the operating system and applications are built for the purpose of booting and executing emulators and ports. Developers and others who would like to contribute to our project should read and agree to the Contributor Covenant Code of Conduct and Contributing to JELOS guides before submitting your first contribution.

Preparing the Build Machine

Building JELOS requires an Ubuntu 22.04 host with 200GB of free space for a single device, or 1TB of free space for a full world build. Other Linux distributions may be used when building using Docker; however this is untested and unsupported.

Docker Builds

sudo apt update
sudo apt install ca-certificates curl gnupg

sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
sudo chmod a+r /etc/apt/keyrings/docker.gpg

echo \
  "deb [arch="$(dpkg --print-architecture)" signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
  "$(. /etc/os-release && echo "$VERSION_CODENAME")" stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null

sudo apt update
sudo apt install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin

sudo groupadd docker
sudo usermod -aG docker $USER
newgrp docker

docker run hello-world

Docker installation reference (source): Install using the apt repository and Linux post-installation steps.

The final command should produce a message indicating that Docker is properly installed. If you encounter any errors, see the reference links above.

Manual Builds

To build JELOS manually, you will first need to install all packages listed in the Dockerfile.

JELOS Source Files

After preparing the build machine, clone the project git repository onto it.

cd ~
git clone https://github.com/JustEnoughLinuxOS/distribution.git

Selecting the Desired Branch

Once you have cloned the repo, decide whether you want to build the main branch which is more stable, or the development branch which is unstable but hosts our newest features.

Branch	Purpose
main	Stable JELOS sources
dev	Unstable JELOS sources

To check out our development branch, cd into the project directory and checkout dev.

cd distribution
git checkout dev

Filesystem Structure

We have a simple filesystem structure adopted from parent distributions CoreELEC, LibreELEC, etc.

.
├── build.JELOS-DEVICE.ARCHITECTURE
├── config
├── distributions
├── Dockerfile
├── licenses
├── Makefile
├── packages
├── post-update
├── projects
├── release
├── scripts
├── sources
└── tools

build.JELOS-DEVICE.ARCHITECTURE

Build roots for each device and that device's architecture(s). For ARM devices JELOS builds and uses a 32bit root for several of the cores used in the 64bit distribution.

config

Contains functions utilized during the build process including architecture specific build flags, optimizations, and functions used throughout the build workflow.

distributions

Distributions contains distribution-specific build flags and parameters and splash screens.

Dockerfile

Used to build the Ubuntu container used to build JELOS. The container is hosted at https://hub.docker.com/u/justenoughlinuxos.

licenses

All of the licenses used throughout the distribution packages are hosted here. If you're adding a package that contains a license, make sure it is available in this directory before submitting the PR.

Makefile

Used to build one or more JELOS images, or to build and deploy the Ubuntu container.

packages

All of the packages used to develop and build JELOS are hosted within the packages directory. The package structure documentation is available in DEVEL_CREATING_PACKAGES.md.

post-update

Anything that is necessary to be run on a device after an upgrade should be added here. Be sure to apply a guard to test that the change needs to be executed before execution.

projects

Hardware-specific parameters are stored in the projects folder. Anything that should not be included on every device during a world build should be isolated to the specific project or device here.

release

The output directory for all of the build images.

scripts

This directory contains all of the scripts used to fetch, extract, build, and release the distribution. Review Makefile for more details.

sources

As the distribution is being built, package source files are fetched and hosted in this directory. They will persist after a make clean.

tools

The tools directory contains utility scripts that can be used during the development process, including a simple tool to burn an image to a usb drive or sdcard.

Building JELOS

Building Device Images

Building JELOS is easy, the fastest and most recommended method is to instruct the build to use Docker, this is only known to work on a Linux system. To build JELOS with Docker use the table below.

Devices	Dependency	Docker Command
AMD64		make docker-AMD64
RK3588		make docker-RK3588
RK3326		make docker-RK3326
RK3566		make docker-RK3566
RK3566-X55		make docker-RK3566-X55
S922X		make docker-S922X
ALL DEVICES		make docker-world

Devices that list a dependency require the dependency to be built first as that build will be used as the root of the device you are building. This will be done automatically by the build tooling when you start a build for your device.

Next, build the version of JELOS for your device. See the table above for dependencies.

make AMD64

Rightsized Builds

JELOS supports various build variables which alter the behavior of the distribution for specific purposes including debugging, or hosting containers. The options are defined below and are passed on the make command line. Ex. BASE_ONLY=true make docker-RK3566.

Build Option	Default	Function
EMULATION_DEVICE	yes	Builds EmulationStation and all emulators if yes. Builds EmulationStation and NO emulators if no.
ENABLE_32BIT	yes	Builds a 32bit root and includes it in the image. Needed for 32bit cores and applications.
BASE_ONLY	false1	Builds only the bare minimum packages. Includes Weston on supported devices. Does not build EmulationStation.
CONTAINER_SUPPORT	no	Builds support for running containers on JELOS.

Note: ¹ this property will change to yes/no for consistency in a future release.

Special env Variables

For development builds, you can use the following env variables to customize the image or change build time functionality. To make them globally available to the builds, add them to ${HOME}/.JELOS/options.

Variable	Function
LOCAL_SSH_KEYS_FILE	Enables using ssh public keys for access without the root password.
LOCAL_WIFI_SSID	The SSID of the network the device should connect to automatically.
LOCAL_WIFI_KEY	The WIFI authentication key for the connection."
SCREENSCRAPER_DEV_LOGIN	Login information for screenscraper.fr.
GAMESDB_APIKEY	Login information for thegamesdb.net.
CHEEVOS_DEV_LOGIN	Login information for retroachievements.org.
CLEAN_PACKAGES	Allows specifying packages to clean during a build.

SSH Keys

export LOCAL_SSH_KEYS_FILE=~/.ssh/jelos/authorized_keys

WiFi SSID and password

export LOCAL_WIFI_SSID=MYWIFI
export LOCAL_WIFI_KEY=secret

Screenscraper, GamesDB, and RetroAchievements

To enable Screenscraper, GamesDB, and RetroAchievements, register at each site and apply the api keys in ${HOME}/.JELOS/options. Unsetting one of the variables will disable it in EmulationStation. This configuration is picked up by EmulationStation during the build.

# Apply for a Screenscraper API Key here: https://www.screenscraper.fr/forumsujets.php?frub=12&numpage=0
export SCREENSCRAPER_DEV_LOGIN="devid=DEVID&devpassword=DEVPASSWORD"
# Apply for a GamesDB API Key here: https://forums.thegamesdb.net/viewforum.php?f=10
export GAMESDB_APIKEY="APIKEY"
# Find your Cheevos Web API key here: https://retroachievements.org/controlpanel.php
export CHEEVOS_DEV_LOGIN="z=RETROACHIEVEMENTSUSERNAME&y=APIKEYID"

Cleaning Additional Packages

CLEAN_PACKAGES="linux ppsspp-sa" make AMD64

Modifying JELOS

Building a Single Package

It is also possible to build individual packages.

DEVICE=AMD64 ARCH=x86_64 ./scripts/clean busybox
DEVICE=AMD64 ARCH=x86_64 ./scripts/build busybox

Note: An EmulationStation package standalone build requires additional steps because its source code is located in a separate repository. See instructions here.

Creating a Patch for a Package

It is common to have imported package source code modifed to fit the use case. It's recommended to use a special shell script to build it in case you need to iterate over it. See below.

cd sources/wireguard-linux-compat
tar -xvJf wireguard-linux-compat-v1.0.20211208.tar.xz
mv wireguard-linux-compat-v1.0.20211208 wireguard-linux-compat
cp -rf wireguard-linux-compat wireguard-linux-compat.orig

# Make your changes to wireguard-linux-compat
mkdir -p ../../packages/network/wireguard-linux-compat/patches/AMD64
# run from the sources dir
diff -rupN wireguard-linux-compat wireguard-linux-compat.orig >../../packages/network/wireguard-linux-compat/patches/AMD64/mychanges.patch

Creating a Patch for a Package Using git

If you are working with a git repository, building a patch for the distribution is simple. Rather than using diff, use git diff.

cd sources/emulationstation/emulationstation-098226b/
# Make your changes to EmulationStation
vim/emacs/vscode/notepad.exe
# Make the patch directory
mkdir -p ../../packages/ui/emulationstation/patches
# Run from the sources dir
git diff >../../packages/ui/emulationstation/patches/005-mypatch.patch

After the patch is generated, rebuild an individual package by following the section above. The build system will automatically pick up patch files from the patches directory. For testing, one can either copy the built binary to the console or burn the whole image on SD card.

Building an Image with Your Patch

If you already have a build for your device made using the above process, it's simple to shortcut the build process and create an image to test your changes quickly using the process below.

# Update the package version for a new package, or apply your patch as above.
vim/emacs/vscode/notepad.exe
# Export the variables needed to complete your build.  We'll assume you are building AMD64; update the device to match your configuration.
export OS_VERSION=$(date +%Y%m%d) BUILD_DATE=$(date)
export PROJECT=PC ARCH=x86_64 DEVICE=AMD64
# Clean the package you are building.
./scripts/clean emulationstation
# Build the package.
./scripts/build emulationstation
# Install the package into the build root.
./scripts/install emulationstation
# Generate an image with your new package.
./scripts/image mkimage