Acer C720 Chromebook
The Acer C720 Chromebook (and newer Chromebooks in general) features a "legacy boot" mode that makes it easy to boot Linux and other operating systems. The legacy boot mode is provided by the SeaBIOS payload of Coreboot. SeaBIOS behaves like a traditional BIOS that boots into the MBR of a disk, and from there into your standard bootloaders like Syslinux and GRUB.
See the libinput article on how to install and setup your touchpad.
Improving WLAN and BT performance
The C720 comes with Atheros AR9462 WLAN and Bluetooth chip which supported by
ath9k kernel module, the following options to the
ath9k module can help to affect the performance, quality and power consumption of the chip.
To add the desired module options, just create a
ath9k.conf file as shown here with some example settings:
options ath9k bt_ant_diversity=1 ps_enable=0
Details of possible settings are below.
Both Bluetooth and WiFi can use 2.4 GHz, which can cause interference. You can enable Bluetooth coexistence to improve the performance of the card with the option
You can enable power savings with the option
ps_enable=1 to reduce power usage, though it has been suggested that enabling it might be related to system freezes and also to dropouts so if you encounter such issues then you might want to make sure it's disabled (
Improving signal quality
Enable antenna diversity with the option
bt_ant_diversity=1 to improve the signal quality and boost performance. However, keep in mind that this disables the bluetooth interface and, as such, bluetooth coexistence must not be loaded at the same time.
Fixing decrease in bandwidth
If you are experiencing a decrease in bandwidth at seemingly random times try switching from hardware to software wireless encryption as explained in Wireless network configuration#ath9k.
Enabling the light sensor
Intersil ISL29018 is the light sensor in the C720, as default its module is disabled on build time so in order to use the sensor the kernel should be recompiled with
CONFIG_SENSORS_ISL29018 enabled. You can also compile just the single module. Follow the preparation instructions as Compile kernel module, enable the module in your
.config and execute
$ make SUBDIRS=drivers/staging/iio/light modules
then follow Compile kernel module#Module installation to install the module.
Fix wakeup from suspend on lid close
When the lid of the C720 is closed, the top of the screen presses against the touchpad, instantly waking the computer from suspend. To disable wakeup by touchpad, create the following file:
w /proc/acpi/wakeup - - - - TPAD
To check the current state:
# cat /proc/acpi/wakeup | grep TPAD
Alternatively, it may be toggled manually by running:
# su # echo TPAD > /proc/acpi/wakeup
This method does not persist after a reboot.
Lots of ehci errors in dmesg after resume
One symptom may be that it cannot properly shut down or reboot.
Locating the Write-Protect Screw
- Remove the bottom panel of the laptop by removing the 12 visible screws and another one underneath the warranty sticker.
- Separate the plastic starting at the back.
- Remove completely the write-protect screw from the motherboard, which is labelled as #7 in this picture.
See power saving section at Improving WLAN and BT performance.
Additionally see SSD#Troubleshooting if the system freezes are associated with hard drive errors in the system's journal.
Internal microphone not working
If your internal microphone is not working (for example, in Skype), select "Microphone (unplugged)" as your input source in the PulseAudio Volume Control. Your internal microphone should now work. 
See also Chrome OS devices#Fixing audio for another possible solution.
System shutdown on battery
If you are on battery and the system shutdown when you use the keyboard, it's probably a battery switch mulfunction (cover don't press it all time), labbeled #5 in this picture. It is a safety mechanism to prevent the Acer C720 from being powered by the battery while the cover is removed.
You can bypass this switch with a screw inserted in hole #6.