Lenovo Thinkpad X131e Chromebook

Introduction

This page contains information about the Lenovo Thinkpad X131e Chromebook that is interesting and/or useful to software developers. For general information about getting started with developing on ChromiumOS (the open-source version of the software on the Chrome Notebook), see the Chromium OS Developer Guide.

Developer Mode

Caution: Modifications you make to the system are not supported by Google, may cause hardware, software or security issues and may void warranty.

An unrelated note: Holding just Refresh and poking the Power button hard-resets the machine without entering Recovery. That's occasionally useful, but use it with care - it doesn't sync the disk or shut down politely, so there's a nonzero chance of trashing the contents of your stateful partition.

Introduction

Enabling Developer mode is the first step to tinkering with your Chromebook. With Developer mode enabled you can do things like poke around on a command shell (as root if you want), install ChromiumOS, or try other OS's. Note that Developer mode turns off some security features like verified boot and disabling the shell access. If you want to browse in a safer, more secure way, leave Developer mode turned OFF. Note: Switching between Developer and Normal (non-developer) modes will remove user accounts and their associated information from your Chromebook.

Entering

On this device, both the recovery button and the dev-switch have been virtualized. Our partners don't really like physical switches - they cost money, take up space on the motherboard, and require holes in the case.

This device has unique requirements for entering recovery mode!

You must first remove all power from the system, both the battery and the AC plug. Then when power is re-applied you have 20 seconds to enter recovery mode with the ESC+Refresh+Power button sequence.

In this system the removal of power sources will force the Embedded Controller to restart and stay in read-only code to ensure the recovery mode is secure.

To invoke Recovery mode, you hold down the ESC and Refresh (F3) keys and poke the Power button.

To enter Dev-mode you first invoke Recovery, and at the Recovery screen press Ctrl-D (there's no prompt - you have to know to do it). It will ask you to confirm, then reboot into dev-mode.

Dev-mode works the same as always: It will show the scary boot screen and you need to press Ctrl-D or wait 30 seconds to continue booting.

USB Boot

By default, USB booting is disabled. Once you are in Dev-mode and have a root shell, you can run:

sudo crossystem dev_boot_usb=1

and reboot once to boot from USB drives with Ctrl-U.

Legacy Boot

Sorry, but this device does not support a legacy BIOS mode.

Leaving

To leave Dev-mode and go back to normal mode, just follow the instructions at the scary boot screen. It will prompt you to confirm.

If you want to leave Dev-mode programmatically, you can run crossystem disable_dev_request=1; reboot from a root shell. There's no way to enter Dev-mode programmatically, and just seeing the Recovery screen isn't enough - you have to use the three-finger salute which hard-resets the machine first. That's to prevent a remote attacker from tricking your machine into dev-mode without your knowledge.

Firmware

This device uses coreboot and Das U-Boot to boot the system. You can find the source in the ChromiumOS coreboot git tree and the ChromiumOS u-boot git tree in the firmware-stout-2817.B branches.

What's inside?

WARNING: Opening the case and fiddling with the stuff inside could easily brick your system and make it unrecoverable. DO NOT ATTEMPT if you are not familiar with this process.

Stop. Don't. Come back.

Really. Opening the case will allow you to modify the read-only firmware that makes recovery possible. If someone from "teh internets" says "You need to reflash your BIOS", they're almost certainly wrong.

Disassembly

Taking apart your laptop is not encouraged. If you have hardware troubles, please seek assistance first from an authorized center. Be advised that disassembly might void warranties or other obligations, so please consult any and all paperwork your received first. If you just want to see what the inside looks like, gaze upon this (click for a high res version):

Servo Header

The X131e was not designed to use servo. A small number of debug units have a hand-wired header.