TL;DR: (in FAQ format)

Table of contents (for cool kids)

• Introduction
• System requirement
• Prepare the system
• Get Chromium OS source code
• Setup Raspberry Pi overlay
• Setup local chromium source
• Build Chromium OS for Raspberry Pi
• Boot Raspberry Pi from the image
• Video demonstration of the build process
• More information
• About us

Introduction

This document describes how to build and run Google Chromium OS on Raspberry Pi 3B, 3B+, 4B and the Pi 400 personal computer kit(Pi400 hereafter), from its source code and the board overlay hosted in this repository.

These overlays and the document has been tested against Raspberry Pi 3B, 3B+, 4B and Pi400 by the FydeOS team. It will not work on an earlier version of the Raspberry Pi line-up.

Goal of this project

• To provide a usable Chromium OS pre-built image that everybody can download and use that offers a similar experience to Chrome OS
• To provide an open-source code base that everybody can use to build and improve Chromium OS on Raspberry Pi.
• This project does not aim to provide support for Chromium OS itself. If you find bugs and glitches, please report to crbugs; if you have further queries regarding Chromium OS, please revert to one of the official Chromium related Google groups.

About this repository

The code and document in this repository are the results of works by the people of the FydeOS team. We previously worked on this overlay internally and released a few disk images for Raspberry Pi to the public. Now we open this to the public.

Branches and tags in this repository

• branches

  • main - the default branch of this project. It has been tested against our current release version. You are welcome to test it with future releases and send feedback and/or PRs.
  • r<revision> - branches for specific Chromium OS revision, it could be served for archiving purposes or used as a development branch for future (non-stable) code.

• tags

  • When we do release a prebuilt image, the commit would be tagged with a release number corresponding to the repo manifest. For example, if the repo manifest release is rrelease-R102-14695.B, then our release tag would be r102.
  • Often we will be doing more than one release for each repo manifest release number, so we will append a meaningful string to the tag name to identify such. For example: r102-hardware_acceleration

Typography Conventions

Shell Commands are shown with different labels to indicate whether they apply to

• your build computer (the computer on which you're doing development)
• the chroot (Chromium OS SDK) on your build computer
• your Chromium OS computer (the device on which you run the images you build)

System requirement

• An x86_64 system to perform the build. 64-bit hardware and OS are a must. The Chromium OS is a very large project, building from the source from scratch usually takes hours to over 10 hours, depending on the system configuration.

  • CPU: we recommend using a 4-core or higher processor. The Chromium OS build process runs in parallel so more cores can help shorten build time dramatically.

  • Memory: we recommend at least 16GB, plus enough swap space because for this project you will need to build Chromium from source code. Linking Chromium required between 8GB and 28GB of RAM as of March 2017, so you will run into massive swapping or OOM if you have less memory. However, if you are not building your copy of Chromium, the RAM requirements will be substantially lower at a cost of losing some of the key features provided by this project.

  • Disk: at least 100GB of free space, 200GB or more is recommended. SSD could noticeably shorten the build time as there are many gigabytes of files that need to be written to and read from the disk.

  • Network: total source code downloading will be over 10GB. Fast and stable Internet access is going to be very helpful.

• An x86_64 Linux OS, it is called the host OS later in this doc. The Chromium OS build process utilises chroot to isolate the built environment from the host OS. So theoretically any modern Linux system should work. However, only limited Linux distros are tested by the Chromium OS team and the FydeOS team. Linux versions that are known to work:

  • Ubuntu 18.04 LTS
  • Ubuntu 20.04 LTS
  • Gentoo Linux

• A non-root user account with sudo access. The build process should be run by this user, not the root user. The user needs to have sudo access. For simplicity and convenience password-less sudo could be set for this user.

Prepare the system

Install necessary tools

Git and curl as the essential tools that need to be installed in the host OS, you will also need Python3 for most of the scripting work in the build process.

(outside)
sudo apt-get install git-core gitk git-gui curl lvm2 thin-provisioning-tools \
     python-pkg-resources python-virtualenv python-oauth2client xz-utils \
     python3.6

# If Python 3.5 is the default, switch it to Python 3.6.
python3 --version
# If above version says 3.5, you'll need to run:
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.5 1
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.6 2
sudo update-alternatives --config python3

This command also installs git's graphical front end (git gui) and revision history browser (gitk).

Install Google depot_tools

The depot_tools is a software package of scripts, provided by Google, to manage source code checkouts and code reviews. We need it to fetch the Chromium OS source code.

(outside)
$ sudo mkdir -p /usr/local/repo
$ sudo chmod 777 /usr/local/repo
$ cd /usr/local/repo
$ git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git

Then add depot_tools directory to PATH and set up proper umask for the user who is going to perform the build. Add below lines to the file ~/.bash_profile of that user. Or if you are using a different shell, handle that accordingly.

(outside)
export PATH=/usr/local/repo/depot_tools:$PATH
umask 022

Then re-login to make the above changes take effect.

Configure git

Better configure git now or it may complain in some operations later.

(outside)
$ git config --global user.email "[email protected]"
$ git config --global user.name "Your Name"

Get Chromium OS source code

Create directory structure

The directory structure described here is a recommendation based on the best practice in the FydeOS team. You may host the files differently as you wish.

(outside)
# This is the directory to hold Chromium OS source code， aka cros-sdk
$ mkdir -p /path/to/cros-pi

If you are building a different release, make sure you use the actual directory name on your system, the name here mentioned is just an example.

Fetch Chromium OS source code

First, you need to find out the reference name of the release you would like to build, by visiting this page https://chromium.googlesource.com/chromiumos/manifest.git:

You will see a list of Git commit IDs and its name in the form of refs/heads/release-Rxx-xxxx.B. That release-Rxx-XXXX.B link is what you need for fetching the code of that specific Chromium OS release. For example, release-R102-14695.B for release r102.

Now run these commands to fetch the source code. Find and use a different release name if you would like to build a different release.

(outside)
#Assuming you understand what /path/to means. If not, replace it with '~'
$ cd /path/to/cros-pi

$ repo init -u https://chromium.googlesource.com/chromiumos/manifest.git --repo-url https://chromium.googlesource.com/external/repo.git -b release-R102-14695.B

# Raise this number if you have a fast internet connection
$ repo sync -j8

Fetching Chromium OS source code may take 20 to more than 40 minutes depending on your connection speed, around 10GB of data will need to be downloaded primarily from googlesource.com, it'd be helpful if you have a decent internet speed to reach Google's server.

Request for Google API key

If you would like to login into the Chromium OS GUI by using your Google account, you will need to request for Google API key and include them in the disk image you build. Since the only authentication mechanism included in Chromium OS is Google ID, you probably will need this or you will only be able to log in as a guest user.

Apply for Google API on the Google website per this document. After acquiring the client ID, client secret and API key, put them in ~/.googleapikeys file as in the below format.

'google_api_key': 'your api key',
'google_default_client_id': 'your client id',
'google_default_client_secret': 'your client secret',

Then the Chromium OS build script will read the necessary information from this file automatically, and the image you build will allow Google ID login.

Setup Raspberry Pi overlay

Now fetch this overlay and also create symlinks in the designated place.

(outside)
$ cd /path/to/overlays
$ git clone https://github.com/fydeos/chromium_os-raspberry_pi.git .

$ cd /path/to/cros-pi/src/overlays
$ ln -s /path/to/overlays/* .

By now, your cros-pi/src/overlays directory should have included symbolic links for:

• project-cros-pi
• baseboard-rpi3
• overlay-rpi3
• overlay-rpi4
• chipset-bcm2837

Setup local chromium source

It's recommended to build Chromium browser on your local setup so that your Chromium OS for Raspberry Pi could benefit from the additional functionalities like kiosk mode, you will also have the option to incorporate your modifications. If you wish to do so, you need to prepare the necessary files before entering the cros_sdk.

As far as this project is concerned, the chromium source that we use to build our releases can be found in the chromium-raspberry_pi project. You may also choose to use Google's vanilla chromium repository which can be found here.

Note that we use a much simpler way to manage releases, with our chromium-raspberry_pi project you need to select the correct branch corresponding to the repo manifest you used in the previous step to sync your Chromium OS code. For example, if you are building r102, you will then need to look out for "chromium-m102" branch under chromium-raspberry_pi. The letter "m" stands for "milestone" and it correlates to the release number for Chromium OS(r102 in this case). Choosing an unmatched chromium milestone branch and Chromium OS repo will probably result in endless build errors.

With Google's repository, you need to choose a correct release tag rather than a branch. For example, if you are building r102, you can browse all existing chromium release tags on this page and deduce that the latest tag on your desired milestone version. At the point where this was written, this would be 102.0.5005.90.

Having understood the above, now create a directory parallel to your Chromium OS repo to house the chromium source:

(outside)
$ mkdir chromium-pi
$ cd chromium-pi
$ mkdir src
$ cd src

Now clone the desired chromium project:

(outside)
# use our chromium repo
$ git clone [email protected]:FydeOS/chromium-raspberry_pi.git .

# use google's vanilla chromium
$ git clone https://chromium.googlesource.com/chromium/src.git . 

Note that chromium is an absolute HUGE project, cloning the entire repo will require ~22GB of disk space and will require about 2 hours to complete even if you have a decent internet speed.

Then choose the correct branch/tag

(outside)
#with our chromium repo
$ git checkout chromium-m102

#with Google's repo and you wish to build for r102
$ git checkout 102.0.5005.90

Now you need to create a config file known to gclient for syncing the chromium dependencies:

(outside)
$ cd ..
# now you should be in /path/to/chromium-pi
$ touch .gclient

The .gclient file should have the following content, note that you should replace the correct branch name with the url field (in this example we use chromium-m102) you may also replace the url value to Google's per your setup.

solutions = [{'custom_deps': {},
  'custom_vars': {},
  'deps_file': '.DEPS.git',
  'managed': False,
  'name': 'src',
  'url': '[email protected]:FydeOS/chromium-raspberry_pi.git@refs/remotes/origin/chromium-m102'}]
target_os = ['chromeos']

Now you can start syncing:

(outside)
$ gclient sync

Note, due to an existing issue with WebRTC, during syncing you may encounter a git related error complaining fetch failure(if you do not see such error, you can safely ignore this and move on). A temporary fix is to manually edit the src/third_party/webrtc/.git/config file under the WebRTC folder:

[core]
        repositoryformatversion = 0
        filemode = true
        bare = false
        logallrefupdates = true
[remote "origin"]
        url = https://webrtc.googlesource.com/src.git
        fetch = +refs/heads/*:refs/remotes/origin/*
        fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
[branch "master"]
        remote = origin
        merge = refs/heads/master

Once gclient sync is completed, the chromium source folder is now fully set up.

Build Chromium OS for Raspberry Pi

Create the chroot

As mentioned above, a chroot environment will be used to run the actual build process and some other related tasks. To create the chroot environment, run the below commands.

(outside)
$ cd /path/to/cros-pi
$ cros_sdk

If you wish to build your chromium and you have to follow the steps to set it up, you need to specify it when entering the cros_sdk by:

(outside)
$ cd /path/to/cros-pi
$ cros_sdk --chrome-root /path/to/your/chromium-pi #absolute path needed

It may take 10 to over 30 minutes depending on your internet connection speed and disk i/o speed. Once finished, it will enter into the chroot. The shell prompt string looks like below so it is very easy to tell whether you are currently in the chroot or not.

(inside)
(release-R102-14695.B/(xxxxxx...)) <user>@<host> ~/trunk/src/scripts $

The chroot environment is located under the /path/to/cros-pi/chroot directory.

Let's exit from the chroot first as we need to do some customisation before moving on. Type exit or ctrl + d to exit from the chroot shell.

Usually, the chroot only needs to be created once and can be used to build a board many times or build different boards. It very rarely needs to be removed/re-created.

Delete the chroot

If you would like to remove the chroot and re-create it from scratch, don't delete the chroot directory directly. As there could be directories from the host OS bind mounted in the chroot, an rm chroot command could remove files from your host OS undesirably.

The correct way to remove the chroot is by using the below commands.

(outside)
$ cd /path/to/cros-pi
$ cros_sdk --delete

Setup bind mount directories for chroot

Programs running inside the chroot will not be able to access files outside of the chroot. One way to circumvent this is to bind-mount those files into a directory inside the chroot.

When entering the Chromium OS chroot environment, a file named .local_mounts will be checked and directories listed in it will be bind-mounted inside the chroot. All we need to do is to create this file in the right place and put the necessary contents in, by using the below command.

(outside)
$ echo "/path/to/overlays" > /path/to/cros-pi/src/scripts/.local_mounts

Now, after entering the chroot, a /path/to/overlays directory will exist in the chroot and its content is the same as the /path/to/overlays directory in the host OS, as it is bind-mounted from the host OS.

If we don't do this, the /path/to/cros-pi/src/overlays/overlay-rpi4 symbolic link will not be accessible, as the top directory (/path/to/overlays) it points to doesn't exist in the chroot.

Enter the chroot

Now we can enter the chroot.

(outside)
$ cd /path/to/cros-pi
$ cros_sdk

It is the same command used to create the chroot. It creates the chroot if one does not exist and enters the chroot if there is already one.

And we can check whether the above .local_mounts setup was done correctly.

(inside)
$ ls /path/to/overlays/             # You should be able to see the same content as in the host OS.
$ ls ../overlays/overlay-rpi4/      # You should be able to see the content of this repo.

Move on if it works well. If not, check and make sure you set up .local_mounts correctly.

Set password for the chronos user

The chronos user is used to log into the command line interface of Chromium OS, via ssh, local console or the shell in crosh interface. It is recommended that a password is set for this user so you can log in as this user and also can do sudo in the Chromium OS command line, for advanced tasks.

To set a password for the chronos user, run the below command.

(inside)
$ ./set_shared_user_password.sh

Type in a password when prompted. If you would like to change the password, simply run the command again.

The password is encrypted and saved in the file /etc/shared_user_passwd.txt in the chroot. You only need to set it once and it will be used for all the images you build unless you re-create the chroot.

Setup Raspberry Pi board

In the Chromium OS terminology, a board refers to a class of computer platforms with distinct hardware configurations. The board will be used as a target in the process of building software packages and disk images for that specific computer platform.

There are many boards in the Chromium OS code base. They are either development platforms or real selling hardware products running Chrome OS, such as Chromebooks you can buy from many vendors.

The Chromium OS project utilises the Portage package management system from Gentoo Linux. Each board lives in its own "overlay", which holds distinct build configuration, system configurations, collection of software packages, system services, disk image customisation etc. for that board.

In our case here, we created a board named "rpi4" which refers to the Raspberry Pi 4B. We call the overlay "overlay-rpi4" and all its files are hosted in this repository.

To build Chromium OS for a board, the first thing is to initialise the board from its overlay.

Beginning from release 86 and onwards, we have done some efforts to add Raspberry Pi 3B/3B+ support to the Raspberry Pi 4B overlay. In the following steps, we will be using the rpi4 board as an example, the resulting image will also likely work on both Raspberry Pi 3B/3B+.

(inside)
$ setup_board --board=rpi4

Again, it may take 10 to over 30 minutes depending on the speed of your internet connection and disk i/o.

Once it's done, a directory structure for the "rpi4" board will be created under /build/rpi4 of the chroot.

Re-initialise the board

It is usually not necessary to re-initialise the board as what you have already built will be lost, and you will have to spend hours rebuilding all packages from scratch. But if you need to do so, just re-run the same setup_board command with the ---force option.

(inside)
$ setup_board --board=rpi4 --force

The --force option will remove the existing board directory /build/rpi4 and re-create it from scratch.

Build packages

Now it is time to build all software packages for the rpi4 board.

(inside)
$ ./build_packages --board=rpi4 --nowithautotest 
# Append "--nowithautotest" to speed up the build process by skipping some tests

It may take hours depending on your processor power, your memory size, your disk speed and the quality of your internet connection. Here are some examples for you to adjust your expectation:

• On a decent machine with 4 cores 8 threads, 16GB memory, files on regular HDD, and 100Mb broadband, it takes about 5 to 6 hours for the command to finish.
• On a Workstation-grade server with AMD Threadripper 3990x CPU with 64-core 128-thread, 128GB memory and 300Mb broadband, it takes 44mins for the command to finish.

Things to note

• What is happening now

  The build_packages script acts as an entry point to initialise a series of processes aiming to compile all the necessary software packages from source code and build them together forming Chromium OS as a whole. During the process there are a few required dependencies will be fetched and cloned from GitHub, so please do ensure a decent internet connection to github.com.

• When interrupted

  The build process is incremental. If it gets interrupted for any reason, you can always re-run the same build_packages command and it will resume the build instead of rebuilding from scratch.

• Read the output

  The build_packages command throws out a lot of information on the console. Fortunately, that information is very well organised.

  • Red text: these are error messages and very likely will cause the build process to break.
  • Green text: these are useful messages printed by the build script itself. They are useful when debugging problem.
  • White text: these are regular information that mostly is printed by the commands called in the build script. They provide more details about the build process and thus are also useful for debugging.

• Read the logs

  The build_packages script spends most of its airtime on running the emerge commands, to build, install and pack those hundreds of software packages required by the overlay. The emerge command is from the Portage system of Gentoo Linux.

  The emerge command saves the output of its building, installation and packing process into log files. These files are extremely useful if there is a failure when building packages. Those log files are located under the /build/rpi4/tmp/portage/logs directory of the chroot. They are plain text files so can be viewed right from your command-line interface.

Build the disk image

After the build_packages command is finished successfully, you can start building the disk image.

(inside)
$ ./build_image --board=rpi4 --noenable_rootfs_verification
# Append --noenable_rootfs_verification flag to enable root file system read/write on the built image

It may take 10 to 30 minutes, mainly depending on the speed of your disk. It will be much faster on SSD than on HDD.

Find your image

After the command finished successfully, you will have disk images generated, saved under /mnt/host/source/src/build/images/rpi4/ directory in the chroot, or /path/to/cros-pi/src/build/images/rpi4 in the host OS. These two are the same directory, just bind mounted in the chroot.

Each invocation of the build_image command will create a directory named similar to R102-XXXX.XXX.<date time>-a1 under above directory. There is a symlink named latest under the above directory, that always points to the image directory of the last successful build.

The disk image is usually named chromiumos_image.bin, under the abovementioned directory. So full path to the latest image is

/mnt/host/source/src/build/images/rpi4/latest/chromiumos_image.bin

in the chroot, and

/path/to/cros-pi/src/build/images/rpi4/latest/chromiumos_image.bin

in the host OS.

Boot Raspberry Pi from the image

The Raspberry Pi boots from the SD card so we need to write the previously generated disk image onto the SD card. An SD card of at least 8GB capacity is required.

Write the disk image to an SD card

There are two usual ways to write the Chromium OS disk image to an SD card. You can copy the image out to another Windows/macOS/Linux system and write it using your favourite GUI/CLI application. It is the same as writing other Linux images for Raspberry Pi, so will not be explained here.

Another Chromium OS-specific way is by using the cros command in the chroot.

Write the image by using the cros command

First, plug the SD card into the box used to build the image and has the chroot. Then run the below command.

(inside)
$ cros flash usb:// rpi4/latest

This asks to write the latest disk image to USB removable media. A list of USB removable media will be presented, with the index number prefixed. You can select which USB drive to write to by typing in the index number when prompted.

Boot from the SD card

After the disk image is successfully written to the SD card, plug it into the Raspberry Pi and boot it as usual. After a few seconds, you will see a Chromium logo, later on, it will boot into GUI mode and the first time setup screen (OOBE) will pop up for you to configure the system and log in.

Video demonstration of the build process

https://youtu.be/og4wzzIfGA0

More information

Chromium OS Developer Guide. This is the official source of how to build Chromium OS.

openFyde, the open-sourced version of FydeOS.

The FydeOS website, our home.

FydeOS official Telegram group, to say hi and get help.

About us

Fyde began with a vision where all applications and services we use today will be living in the Cloud. We believed that with the ever-advancing browser platform technology and web frontend performances, it’s not surprising that most things we do today with the internet can be done through a single browser window. We are stepping into an era where installable apps will soon become history. FydeOS is our answer to this new era of computing.

FydeOS is a simple, secure, fast and productive operating system. Based on the open-source Chromium Project that also powers the well-known Google Chromebooks. FydeOS inherits most of the benefits that Chromebooks have but is also bundled with our enhancements and new features. We have turned FydeOS into a more open platform, users will no longer be forced to rely on Google services and have the freedom to choose whichever services they prefer. We have also made FydeOS run on a wider range of hardware platforms ranging from x86 PCs and ARM-based single board computers, providing endless possibilities and potentials of how FydeOS can be used and applied.