Before we can build ChromiumOS, we will need to download the source code from the Chromium repositories that are hosted on Google's servers. This process will take several hours depending on the speed of your internet connection, number of CPU threads and the speed of your disk drive.
You will need to create a workspace that will house your Chromium source code. This can be done with the following command.
mkdir -p ~/Workspace/ChromiumOS/
You will now need to enter your Chromium workspace by running the following command.
cd ~/Workspace/ChromiumOS/
The next step will initialize the Chromium source tree in your workspace and pull down all of the source code from the Chromium repositories. This can be done with the following commands.
repo init -u https://chromium.googlesource.com/chromiumos/manifest.git --repo-url https://chromium.googlesource.com/external/repo.git
repo sync -j8