Setting up a ChromiumOS dev environment

Published 2017-02-16

Setting up a fully functional ChromiumOS development environment on actual Chromebook hardware

Set up environment

export DEV_DIR="/opt"
mkdir -p $DEV_DIR
export CHROMIUM_DIR="$DEV_DIR/chromiumos"
mkdir -p $CHROMIUM_DIR
export PATH="$DEV_DIR/depot_tools:$PATH"

# The BOARD variable used here is specific for the Chromebook that is
# being targeted, a more generic target like "amd64-generic" could
# be more useful for you needs.
export BOARD=chell

# The USB_DEVICE variable refers to the USB device that will be used
# for flashing ChromiumOS onto a Chromebook.
# Make sure that this device does not contain anything important!
export USB_DEVICE="/dev/sda"

Install dependencies

sudo apt install git-core gitk git-gui subversion curl
cd $DEV_DIR
git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git

Get ChromiumOS source

cd ${CHROMIUM_DIR}
repo init -u https://chromium.googlesource.com/chromiumos/manifest.git
repo sync -j25

Build ChromiumOS

cros_sdk -- ./build_packages --board=${BOARD}
cros_sdk -- ./build_image --board=${BOARD}

Flash ChromiumOS to storage medium

cros_sdk -- cros flash --board=${BOARD} usb:/$USB_DEVICE

Install ChromiumOS on Chromebook

Enter Chromebook into dev-mode

This part is highly device specific, and depends on how the manufacturer of your device has chosen to implement the dev-mode switch.

A partial list of devices and how to enter them into dev-mode can be found here.

Flash ChromiumOS to Chromebook

Fire up your Chrombook device and hit Ctrl+Alt+Back, followed by 'chronos' and hit enter. Followed by the below command to install the ChromiumOS build that was just flashed.

/usr/sbin/chromeos-install

Debug an application

On Chromebook

Again fire up your Chrombook device and hit Ctrl+Alt+Back, followed by 'chronos' and hit enter.

# Remount the root drive read / write
sudo mount -o remount,rw /

# Open port so that gdbserver can be reached
sudo /sbin/iptables -A INPUT  -p tcp --dport 1234 -j ACCEPT

# Run gdb server, listening on port 1234 (opened in iptables command above)
sudo gdbserver :1234 chrome

On dev machine

# On x86
cros_sdk -- sudo USE=expat emerge cross-i686-pc-linux-gnu/gdb
# On ARMv7
cros_sdk -- sudo USE=expat emerge cross-armv7a-cros-linux-gnueabi/gdb

cros_sdk -- i686-pc-linux-gnu-gdb "/build/$BOARD/opt/google/chrome/chrome"
(gdb) set sysroot /build/$BOARD/
(gdb) target remote IP_ADDR_CHROMEBOOK:1234
(gdb) continue

Conclusion

This is a bit of a rough outline, and is only suitable for Chromebook devices that already are in dev-mode.

Thanks

This post has been a part of work undertaken by my employer Collabora.

References

ChromiumOS Depo Tools
ChromiumOS Quick Start
ChromiumOS Dev Mode
ChromiumOS Debug