Compile batocera.linux

The official and recommended way to compile batocera.linux is by using a development container made on purpose with Docker. Although you can do it directly on your Linux machine, if it's a supported Ubuntu Linux.

Note that it's also possible to compile batocera.linux within an LXC container but it's not recommended or officially supported.

If you are not familiar with git, you should first take a look at this page explaining the basics for contributing to Batocera Linux with git.

Make sure you have a reasonably fast CPU, and at least 8GB of RAM (even 12GB+ if you need to compile MAME). If you have a CPU with 8 cores/16 threads or more (lucky you!), you might need more than 16 GB RAM to compile batocera.linux with all threads in parallel. You also need between 80GB and 250GB of free disk space for each platform you intend to compile for in order to download and compile the final Batocera image.

For reference, here are some estimates of the space required for building certain platforms:

• sources download: up to 120GB for Batocera 41 (x86_64)
• x86_64: 165 GB for Batocera 41 (+35GB for x86_wow64)
• bcm2712 (rpi5): 105GB for Batocera 41
• bcm2711 (rpi4): 103GB for Batocera 41
• bcm2837 (rpi3): 80 GB
• bcm2836 (rpi2): 130 GB for Batocera 40
• rk3326: 74GB for Batocera 40
• rk3399: 45GB for Batocera 40
• s905gen2 (radxa zero): 65 GB
• rpizero: 45 GB

If never having compiled on the machine before you may need to install the various miscellaneous dev tools needed like git and make. These can be installed individually, or it may be more convenient to download the entire development group package for your distro (especially if planning on compiling anything else other than Batocera).

• Ubuntu:
  • To install the basic dev tools: sudo apt-get install build-essential
• Fedora:
  • To check the packages that will be installed with the group, run: sudo dnf group info "Development Tools" "Development Libraries"
  • To install them: sudo dnf groupinstall "Development Tools" "Development Libraries"
• Arch:
  • To install the dev tools: sudo pacman -S base-devel

If you wish to be frugal, the only essential packages on the host OS for compiling Batocera in Docker are git and make, the rest are already included in the Docker image itself.

If you already have a working Docker installation on your Linux system, skip to the preparations section.

Each OS and Linux distribution has a particular way to install Docker.

Please note that most developers use Docket on Ubuntu Linux to compile batocera.linux. In January 2022, Docker on Windows was not stable enough to compile Batocera.

In March 2020, with the Docker container running as non-root (regular user), you can compile Batocera on MacOS Mojave 10.14 (Darwin 18.0.0).

• Linux Ubuntu/Debian:
  • Installing Docker from the Distribution packages is not recommended. Refer to the official documentation instead: https://docs.docker.com/engine/install/ubuntu/
  • To be able to run docker without root privileges don't forget to add your user to the docker group: sudo usermod -aG docker your-user, then log out and log back in.
• Fedora:
  • Installing Docker from the snap/appimages/flatpak packages is not recommended. Refer to the official documentation instead: https://docs.docker.com/engine/install/fedora/
  • To be able to run Docker without root privileges and at boot, don't forget to add your user to the docker group. Fedora's own instructions on how to do so: https://developer.fedoraproject.org/tools/docker/docker-installation.html. In case those instructions fail, run the following sequentially in the terminal:

    sudo groupadd docker
    sudo gpasswd -a ${USER} docker
    sudo systemctl restart docker
    newgrp docker

  • To start the docker daemon at boot: sudo systemctl enable docker, then logout and log back in.
• Linux Solus: sudo eopkg install –y git docker make
• Arch Linux: sudo pacman -S docker
• (for reference) MacOS: see https://docs.docker.com/docker-for-mac/
• (for reference) Windows: see https://store.docker.com/editions/community/docker-ce-desktop-windows

cd batocera.linux
git checkout master

Choose a work directory (your $HOME?) and clone the batocera.linux source code:

git clone https://github.com/batocera-linux/batocera.linux.git

Enter the newly created directory.

cd batocera.linux

By default, the buildroot submodule will not be cloned. This is required for Batocera, run the following:

git submodule init
git submodule update

You only need to do this once.

To make things easier, there is makefile described here that makes the compilation process smoother.

1. Add your user to the docker group

If you haven't already, add your user to the “docker” group so that you can run docker commands:

and make sure that your user is in the docker group). For most Linux systems, this can be accomplished by running the following:

sudo usermod -a -G docker $USER

Enter your password when prompted to, then reboot your computer (or if connected via SSH, restart the session).

2. Start up Docker

If you haven't already configured the Docker daemon to run at boot, you have to get it up and running. On most distros, this can be accomplished with:

sudo systemctl start docker.service

then reboot in order to make sure both the service is running.

3. Install build environment

make build-docker-image

4. Customize directories

By default, Batocera will download dependencies to $(PROJECT_DIR)/dl and build to the $(PROJECT_DIR)/output folder. You can check the current default directories with the following command:

make vars

To change the directories that Batocera will build to, rename the batocera.mk.template file to batocera.mk and change the DL_DIR ?= and OUTPUT_DIR ?= lines to point to wherever you want to.

This is also how you decide which platform you are building for. If making the ordinary “PC” build, this would be x86_64.

If intending to build Raspberry Pi:

Image: broadcom/bcm2835
Hardware: rpizero rpizerow rpi1A rpi1B rpi1A+ rpi1B+ (32-bit)

Image: broadcom/bcm2836
Hardware: rpi2B rpizero2W rpi3B rpi3A+ rpi3B+ (32-bit)

Image: broadcom/bcm2837
Hardware: rpizero2W rpi3B rpi3A+ rpi3B+ (64-bit)

Image: broadcom/bcm2711
Hardware: rpi4B pi400 cm4 (64-bit)

The RPi 3 build currently uses the 64-bit build.

5. Build an image

The build command is different for each target architecture, but they all share the same syntax: make <arch>-build. For example:

make x86_64-build

If you have a lot of cores/threads on your compilation CPU, and enough RAM to support it, you can accelerate the compilation time by parallelizing package builds with:

PARALLEL_BUILD=1 make x86_64-build

You can check valid targets architectures by running make vars again.

6. Shell

It's also possible to get a shell to the desired build environment. Similar to -build, with make rockpro64-shell or:

make x86_64-shell

make x86_64-shell
make menuconfig

7. Build a single package

To build a single package, you can open a shell or use the -pkg target. Examples:

make rk3326-pkg PKG=batocera-splash
make x86_64-shell PKG=libretro-mame

8. ccache

To enable ccache for all builds, add the necessary options to batocera.mk. An example is provided there. See EXTRA_OPTS. No need to edit defconfig.

9. Compile clean builds

This will clear all the data in output/<arch> and build “from scratch”. This is useful for:

• If building an older version of Batocera, and you've already built a future version of it, always do a cleanbuild to ensure that the packages in the build cache do not cause conflicts with older packages producing unintelligible error messages.
• Avoid cherry-picking commits; every commit (in Batocera at least) may be dependent on another previous commit, and the effect daisy chains even with commits that seem otherwise independent. If a single package has been built with a cherry-picked commit, cleanbuild to ensure no future errors.
• After building an older version and wanting to build the most recent version again, do another cleanbuild. Honestly, the only time you can consistently use the regular build command is if you're solely just following master branch and continually building without modifications.
• When facing seemingly random errors that other devs are not facing when building packages, do a cleanbuild. This can also include errors that arise from the compilation process being interrupted.

make x86_64-cleanbuild

10. Build a webserver to upgrade your Batocera

You can easily upgrade your Batocera test machine with the build you have just compiled. Let's imagine your build box's IP address is 10.0.0.2. If your build machine has Python3 installed, you can run a webserver with:

make x86_64-webserver

Then, you can launch an upgrade from your Batocera test box. If your build box hosting the web server is on 10.0.0.10, you can simply upgrade to your freshly brewed build by entering from your Batocera SSH:

batocera-upgrade http://10.0.0.10:8000

11. Clean up outdated files from previous builds

Over time, there are many packages updates, and by default, all older versions of the source packages and the corresponding binary builds are kept in your Batocera working directory. Here are a few commands that will help you reclaim storage space:

Show packages that are outdated in the dl/, because a newer revision has been downloaded since then:

make find-dl-dups

Remove all these outdated packages from your dl/ directory:

make remove-dl-dups

Show directories in the x86_64/build/ tree that are outdated because a newer one has been created:

make x86_64-find-build-dups

Remove all these outdated build directories:

make x86_64-remove-build-dups

Of course x86_64 is an example in the commands above, you can use any supported arch.

Exit the container if you ran the build inside of it.

The output will be under output/images/batocera/images/<architecture> and will be gzipped. Its name contains the release version, the platform, and the build date. For instance: output/images/batocera/images/x86_64/batocera-x86_64-33-20220130.img.gz.

You can then flash it with Raspberry Pi Imager by following the install instructions, upgrading using the webserver command above, manually upgrading or by using the following command (modify appropriately for your target storage device and platform):

make DEV=/dev/TARGETDEVICE x86_64-flash

Build options in batocera.mk can further be tweaked to accommodate your preferences.

By default, Docker will take all of your computer's resources during compilation. If you'd like to continue using your computer during compilation, it is recommended to lower the MAKE_JLEVEL value down to 1.

 MAKE_JLEVEL := 1

You can also limit compilation to a single core by setting PARALLEL_BUILD to n. Be warned however, this will cause a dramatic (up to twelve times longer!) increase in compilation time.

 PARALLEL_BUILD := n

By default, buildroot will use a cache to store its most commonly compiled functions. This improves repeated compilation time at the cost of disk space. If disk space is at a premium, you can set a cap to this by appending this to the EXTRA_OPTS line:

 EXTRA_OPTS  :=  BR2_CCACHE_INITIAL_SETUP=\"--max-size=50G\"

You can download sources from Internet before compiling by running the following command, assuming you started with x86_64:

make x86_64-source

Personally, I even run it during 10 minutes and then run make in parallel.

If you want to check on the current status for your x86_64 build:

tail -f output/x86_64/build/build-time.log

If you ran make source, you can easily find what's remaining to compile by running :

for i in output/x86_64/build/*; do test -d "$i" && test -e "$i"/.stamp_built || echo "$i"; done | tee /dev/tty | wc -l

docker run -it --rm -v $PWD:/build -v $HOME/dev/batocera/DL:/build/dl batocera-docker

docker image ls

make update-docker-image

docker rmi <image_name> or docker image rm <image_name>

docker ps

docker kill [container name]

Follow this page to know more about the structure of the Batocera source code and where your modifications need to be made.

Add --security-opt seccomp:unconfined to your docker command line or update the libseccomp2 package.

As of February 2020, it looks like this step is not required any longer.

Refer to the Compiling on LXC containers page for info on how to compile Batocera inside of a LXC container.

Sometimes during compilation you may come across a package that won't compile, but you want to check for if a future package is okay or not. You can skip any partially built package by creating its stamp files to pretend like it was successfully built anyway.

For a more permanent (and somewhat easier to use) skip, a package can be skipped in compilation by removing its mention from the Config.in file for the primary package responsible for it.

For instance, to skip over the PCSX2 standalone emulator and its libretro core from compiling, comment out its respective lines in package/batocera/core/batocera-system/Config.in.

	#select BR2_PACKAGE_PCSX2                        if BR2_PACKAGE_BATOCERA_TARGET_X86_64
	#select BR2_PACKAGE_PCSX2_AVX2                   if BR2_PACKAGE_BATOCERA_TARGET_X86_64
	#select BR2_PACKAGE_LIBRETRO_PCSX2               if BR2_PACKAGE_BATOCERA_TARGET_X86_64

Let's assume you want to compile for Raspberry Pi 3. The Buildroot configuration for that platform can be refreshed by running:

make batocera-rpi3_defconfig

This step creates the file .config from configs/batocera-rpi3_defconfig.

If the .config file was manually modified for testing/dev purposes, it can reset it by running make batocera-rpi3_defconfig again.

batocera-rpi3_defconfig is a small file configuring Buildroot for the target. For example, kodi and emulationstation (and… well, a bit more ;) …).

.config is a file listing all the packages available, and for each of them, if it's going to be built or not.

In other words, batocera-rpi3_defconfig is a smaller version of the .config file without explicit dependencies. For example, if you build emulationstation which requires sdl2, in the .config, both are listed to yes (like BR2_PACKAGE_BATOCERA_EMULATIONSTATION=y) in the .config while only emulationstation is listed in the batocera-rpi3_defconfig file.

If using Docker to compile, you must add your user to the docker group before being able to compile.

In case it's not possible to do that for your user, a temporary workaround is to simply run the command with elevated privileges: sudo make x86_64-build. This is not recommended for ordinary uses, for obvious reasons.

If batocera.mk is being tracked in your local git repo, the following command may be used to explicitly ignore it:

git update-index --assume-unchanged batocera.mk	 

This usually happens when the current Linux kernel in the folder is incomplete or was halted during compilation. To fix it, run the following:

make x86_64-shell
rm -rf build/linux-*

This can also be used to “repair” packages that were interrupted during their compilation, such as you know if the power got cut out by a thunderstorm or something.

First, ensure that you have updated the Docker image.

This may happen at any point during compilation, but usually is related to a specific emulator. Hidden .stamp files are placed into each package's output/build/<package name>-<package version> folder, indicating which step was reached before the failure. Available stamps include download, extract, patch, configure, built, staging_install, target_install. Not all packages use all stamps. Once you've recognized and solved the issue, the entire package can be set to be rebuilt by deleting the respective build folder.

For example, if bsnes was the emulator causing the compilation issues, the built and target_installed stamps can be applied like so:

touch ~/batocera.linux/output/x86_64/build/libretro-bsnes-hd-0fd18e0f5767284fd373aebd75b00b5bab0d44a9/{.stamp_built,.stamp_target_installed}

If that goes to its end, then it can be recompiled with the following actions:

rm -rf ~/batocera.linux/output/x86_64/build/libretro-bsnes-hd-0fd18e0f5767284fd373aebd75b00b5bab0d44a9
make libretro-bsnes-hd

This can be used to determine if it is a local issue with that package or a global issue with Batocera.

It is possible that the downloaded code has been corrupted, or outdated. This can be remedied by performing a clean build.

make <target>-cleanbuild

This can be temporarily worked around by finding the culprit package and downloading it manually to the dl/<package name> folder. For instance, if xa-2.3.11.tar.gz were returning HTTP request sent, awaiting response… 404 Not Found, then the xa-2.3.11.tar.gz could be manually downloaded and placed into batocera.linux/dl/xa:

batocera.linux/
└─ dl/
   └─ xa/
      └─ xa-2.3.11.tar.gz

This can also happen when switching to a brand new Batocera version that you are compiling for x86_64. There is a rather large wine/wow64 package, wine-x86-<version>.tar.lzma, that is uploaded to the Batocera GitHub repository. If none for the <version> you are building has been uploaded yet, you will get a 404 error. To fix it in your build tree, run make x86_wow64-cleanbuild and put the resulting package in your dl/wine-x86/ directory.

This can happen if the MTU inside Docker isn't aligned with the MTU of your system. Check the mtu values of the host system network interface and the docker interface, through ifconfig or ip a commands.

For example, if you have a Wiregard interface, it can have a lower MTU than the default 1500 value. Let's say you have a Wiregard interface with an MTU value of 1420: then you need to put the Docker MTU at the same value by editing/adding the /etc/docker/daemon.json file with:

{
  "mtu": 1420
}

This can happen if someone merged the master branch without first compiling, meaning the PO files get outdated. They are updated once compilation is run. It's usually safe to ignore these, if your addition has no new strings then feel free to discard all batocera-es-system.po and batocera-es-system.pot files. Or include them, they'll just get updated once master gets compiled again anyway.

However, one caveat, if master has been merged without being compiled, new strings were added and a translator was really on point and has already provided a translated line for it, then your updated PO file would overwrite their translated line. In this specific situation, it's no longer “feel free to discard” but “you must discard” in the paragraph above.

If there were no version changes to the package, and the folder for it exists in output/<arch>/build/<package>, then Buildroot will skip over rebuilding it, using the older (unmodified) version. Simply remove that folder to force it to rebuild the package.

For instance, if you've added a new system which involved edits to es_systems.yml, then you would remove the build/batocera-configgen folder.