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Funtoo Linux Installation on Chromebook Pixel 2015
Introduction
This article is a collection of thoughts, knowledge and procedures discovered while installing Funtoo linux on the Google Chromebook Pixel 2015. It is aimed to provide a concise explanation as well as a walkthrough of the components and steps required. However it will not go into the details of the applications or technologies, leaving that to external documentation.
This is an ongoing effort, e.g Under Construction
While installing this machine I first wanted to just wipe everything and install Funtoo, but decided to dual boot at first to see how it behaves, identify possible optimizations etc., before wiping the rest of the ChromeOS installation. That being said, it might be worth noting that I did remove the firmware protection and set the flags as described in #Setting seaBIOS as default boot option before setting out on actually installing anything. So verification of certain parts of this article is required.
Do anything described here or in the linked articles at your own risk, you may damage or otherwise make your device unusable and might need to contact Google for support. Be sure to read this article and all linked articles carefully, and only proceed to do something when you are sure you know what it does.
Developer Mode
Putting the Chromebook in developer mode is a requirement. Also get accustomed to opening the shell and gaining root privileges. Note that changes to ChromeOS's root filesystem are not required for this, so no need to disable root filesystem verification.
Crouton
It was suggested that crouton is a viable alternative to installing a separate Linux distribution. The advantage is that it's simple and requires no partitioning. The downside are that your are limited in distribution choice.
Dual Booting vs. Funtoo only
There are some differences in how to install the system for either dual booting with ChromeOS or removing it. Most notably, it is reported that if the "Signed boot verification" is enabled and ChromeOS is replaced with a different system, "...then your system might become corrupted on empty battery, resetting dev_boot_usb dev_boot_legacy to their default values, forcing you to recover Chrome OS..."[ Arch linux wiki ].
To avoid this, you can either Dual Boot or #Setting seaBIOS as default boot option and install Funtoo only. Another way would be to extract the kernel from ChromeOS and use that.
I already disabled "Signed boot verification", so someone needs to try this without touching the firmware to confirm that dual boot works with unsigned kernels.
Preparing for Installation
To prepare an additional or alternative operating system we will need to do some common setup, like enabling usb and legacy boot and preparing the installation media, but it is also highly recommended to make a full #Backup of the system before beginning .
Enabling USB boot
To enable usb boot run the following on ChromeOS as root:
root # crossystem dev_boot_usb=1 dev_boot_legacy=1
Preparing and testing the installation media
Installation can occur from pretty much any linux live environment, however for this article we'll be using system rescue cd. In order to make sure you can boot to the live environment, reboot your device and press ctrl+d at the white screen just before ChromeOS boots. You should now be greeted by the SeaBIOS boot system from where you can boot your live environment. Please note that you might have to play with the resolution options, especially for early boot print messages. What works for me in that case is to set vga=340 as parameter.
Backup
After booting a live environment like system rescue cd and mounting a large enough USB key (stock machines require about 2.0GB) you can take a full backup with:
root # dd if=/dev/sda | gzip > /mnt/usb_key/chromebook_pixel_2015_dd_backup.gzip
Setting SeaBIOS as default boot option
This step is only required for removing ChromeOS and installing funtoo on the whole drive. The steps in this section are all done in ChromeOS not the installation medium environment.
This may damage your system, do at your own risk. You have been warned. Follow the steps on Developer Information from Chromium to remove the firmware write protection]. After this is done, do not reassemble the Chromebook. Turn it around, put it on a non-conductive, clean, clutter free surface and follow the steps below.
The first thing we need to do is disable the software write protection. Open a root shell and enter /usr/share/vboot/bin, from there run flashrom --wp-status which will output something similar to:
flashrom v0.9.4 : 1d2f41b : Nov 12 2015 16:39:03 UTC on Linux 3.14.0 (x86_64), built with libpci 3.1.10, GCC 4.9.x-google 20150123 (prerelease), little endian WP: status: 0x0080 WP: status.srp0: 1 WP: status.srp1: 0 WP: write protect is enabled. WP: write protect range: start=0x00000000, len=0x00000000
To disable it run flashrom --wp-disable and double check if the command was successful with flashrom --wp-status.
Now it's time to set the GBB Flags, run set_gbb_flags.sh -h which will produce an output similar to the following:
root # ./set_gbb_flags -h Changes ChromeOS Firmware GBB Flags value. Usage: /usr/share/vboot/bin/set_gbb_flags.sh [option_flags] GBB_FLAGS_VALUE Defined flags (some values may be not supported by all systems): GBB_FLAG_DEV_SCREEN_SHORT_DELAY 0x00000001 GBB_FLAG_LOAD_OPTION_ROMS 0x00000002 GBB_FLAG_ENABLE_ALTERNATE_OS 0x00000004 GBB_FLAG_FORCE_DEV_SWITCH_ON 0x00000008 GBB_FLAG_FORCE_DEV_BOOT_USB 0x00000010 GBB_FLAG_DISABLE_FW_ROLLBACK_CHECK 0x00000020 GBB_FLAG_ENTER_TRIGGERS_TONORM 0x00000040 GBB_FLAG_FORCE_DEV_BOOT_LEGACY 0x00000080 GBB_FLAG_FAFT_KEY_OVERIDE 0x00000100 GBB_FLAG_DISABLE_EC_SOFTWARE_SYNC 0x00000200 GBB_FLAG_DEFAULT_DEV_BOOT_LEGACY 0x00000400 GBB_FLAG_DISABLE_PD_SOFTWARE_SYNC 0x00000800 GBB_FLAG_DISABLE_LID_SHUTDOWN 0x00001000 GBB_FLAG_FORCE_DEV_BOOT_FASTBOOT_FULL_CAP 0x00002000 GBB_FLAG_ENABLE_SERIAL 0x00004000 To get a developer-friendly device, try 0x11 (short_delay + boot_usb). For factory-related tests (always DEV), try 0x39. For early development (disable EC/PD software sync), try 0xa39. flags: -d,--[no]debug: Provide debug messages (default: false) -f,--file: Path to firmware image. Default to system firmware. (default: '') --[no]check_wp: Check write protection states first. (default: true) -h,--[no]help: show this help (default: false)
The options we are interested in are:
GBB_FLAG_DEV_SCREEN_SHORT_DELAY 0x00000001 GBB_FLAG_FORCE_DEV_SWITCH_ON 0x00000008 GBB_FLAG_FORCE_DEV_BOOT_LEGACY 0x00000080 GBB_FLAG_DEFAULT_DEV_BOOT_LEGACY 0x00000400
These options will set your device to boot to SeaBIOS by default. If we put these together we get 489, so the command we need to run becomes ./set_gbb_flags.sh 0x489. Note that ChromeOS is still available, but now the booting is reversed ( e.g. ctrl+d on the white screen is now ChromeOS).
Once this is complete, re-enable the write protection with flashrom --wp-enable. Check if it still turns on, boots to SeaBIOS by default and to ChromeOS via ctrl+d. Finally turn the device completely off shutdown -h now. Proceed to putting the write protection back into place and reassemble the device.