https://www.chromium.org/chromium-os/quick-start-guide

root
adduser --disabled-login chromiumos
sudo apt-get install git-core gitk git-gui subversion curl lvm2 thin-provisioning-tools python-pkg-resources python-virtualenv python-oauth2client


chromiumos
git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
echo "# depot_tools
if [ -d "$HOME/depot_tools" ] ; then
    PATH="$HOME/depot_tools:$PATH"
fi" >> ~/.profile
source ~/.profile
mkdir chromiumos
repo init -u https://chromium.googlesource.com/chromiumos/manifest.git
repo sync
export BOARD=amd64-generic
cros_sdk -- ./build_packages --board=${BOARD}