Modifying JELOS

Before modifying JELOS, be sure you can successfully build the unmodified main or dev branch. Establish a baseline of success before introducing changes to the JELOS source.

Building a Single Package

When modifying individual packages, it's useful to regularly verify the build-ability of your changes. Rather than rebuild an entire device image, it is much faster to simply rebuild a single package using the following commands:

make docker-shell
export PROJECT=PC DEVICE=AMD64 ARCH=x86_64
./scripts/clean busybox
./scripts/build busybox
exit

PROJECT is one of Amlogic, PC, or Rockchip (i.e. the subdirectories of the project directory).

!!! note "The first and last lines should be omitted if building outside of Docker."

!!! info "If you are interested in an EmulationStation package build it requires additional steps because its source code is located in a separate repository. Please 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 a Modified Image

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.

make docker-shell

# Update the package version for a new package, or apply your patch as above.
vim/emacs/vscode/notepad.exe

export OS_VERSION=$(date +%Y%m%d) BUILD_DATE=$(date)
export PROJECT=PC DEVICE=AMD64 ARCH=x86_64
./scripts/clean emulationstation
./scripts/build emulationstation
./scripts/install emulationstation
./scripts/image mkimage

exit

!!! note "The first and last lines should be omitted if building outside of Docker."

Pushing Modified Images to a Device

You can of course reflash the SD card with the modified image.

Alternatively, you may install the image through the JELOS update mechanism, which retains your ES and emulator settings. If the device is networked and reachable from the build machine, this can be done as follows.

# Replace with your device values
HOST=192.168.0.123
DEVICE=RK3566
ARCH=aarch64

# Assume today is the same UTC day that the image was built
TIMESTAMP=$(date -u +%Y%m%d)

SSH_OPTS="-o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null"
scp ${SSH_OPTS} ~/distribution/release/JELOS-${DEVICE}.${ARCH}-${TIMESTAMP}.tar root@${HOST}:~/.update && \
    ssh ${SSH_OPTS} root@{HOST} reboot

Common File Locations

Below is a reference for the locations of files you may frequently interact with while modifying JELOS

File	Location	Description
bootloader mkimage	projects/Rockchip/bootloader/mkimage
busybox package	packages/sysutils/busybox
init	packages/sysutils/busybox/scripts/init
kernel config	projects/Rockchip/devices/RK3566-ML/linux/linux.aarch64.conf
running kernel config	build.JELOS-RK3566-ML.aarch64/linux-6.5-rc7/.config
boot.scr	projects/Rockchip/devices/RK3566/boot/boot.scr
uboot package.mk	projects/Rockchip/packages/u-boot/package.mk
uboot	sources/u-boot/u-boot-976fb2f
uboot config	sources/u-boot/u-boot-976fb2f/configs/anbernic-rgxx3-rk3566_defconfig
dts sources	sources/u-boot/u-boot-976fb2f/arch/arm/dts/rk3566-anbernic-rgxx3.dts
kernel sources/build	build.JELOS-RK3566-ML.aarch64/linux-6.6-rc3
final.img	releases
$EXTRA_CMDLINE	projects/Rockchip/devices/RK3566-ML/options
$INSTALL	/config $BUILD/image/system, /scripts ${BUILD}/initramfs
$LE_TEMP	scripts/mkimage mktemp -d -p $TARGET_IMG

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