--- title: Install Libreboot on a Chromebook x-toc-enable: true ... Open source BIOS/UEFI firmware ------------------------------ This document will teach you how to install Libreboot, on various ARM64-based Chromebook laptops. Libreboot replaces proprietary BIOS/UEFI firmware, though it should be noted that Google already ships coreboot and their own payload called Depthcharge, which is all free software; the difference with Libreboot is that it replaces Depthcharge with *U-Boot* (as a coreboot payload), which provides a lightweight UEFI boot implementation that can boot regular Linux and BSD systems more easily than Depthcharge. NOTE: daisy, peach and veyron boards were temporarily removed from lbmk. They should be re-added to Libreboot at a later date. The reasons are written on the hardware compatibility page. For now, Libreboot only officially supports the `nyan` and `gru` chromebooks. This page attempts to give a brief, general overview of how to flash custom firmware on ChromeOS devices. This guide usually refers to all of them as "Chromebook"s since it's the most common form factor. Flashrom -------- A special fork of flashrom, maintained by Google, is required for flashing these Chromebook devices. See: This document assumes you’ll be using ChromeOS to do the internal flashing. ChromeOS already comes with this special fork of flashrom pre-installed. But if you are using another OS or an external flasher, you will need to compile and use the aforementioned flashrom fork. Enable ChromeOS "Developer Mode" -------------------------------- Chromebooks are locked-down by default to only run ChromeOS. Most things you will want to do on these require you unlock it by enabling their [Developer Mode](https://chromium.googlesource.com/chromiumos/docs/+/HEAD/developer_mode.md). On most devices, you would press the `Escape + Refresh + Power` key combination to restart into the Recovery Mode, then press `Ctrl + D` and finally confirm enabling Developer Mode with `Enter`. On your next boot, it will show you an "OS Verification is disabled" screen. Waiting for 30 seconds or pressing `Ctrl + D` on this screen will proceed to boot into ChromeOS, which then erases all data on the device and reboots again into a clean ChromeOS installation. Before following steps to configure your device as new in the first screen, you should be able to see a “Enable debugging features” link that you should click on. A confirmation dialog displays. Click Proceed. The system reboots, use `Ctrl + D` again and displays a dialog with password prompts. Set the new root password. Click Enable. The screen displays messages indicating success or failure. Click OK. You'll see the first screen again. Follow the remaining prompts to configure your Chrome device. Once you are finished configuring your device, you’ll be giving the option to sign in; here you may use the guest account option in the bottom if you like. Now in the desktop we’ll set a password to use “sudo”: Use `Ctrl+Alt+Forward Arrow` (the one two key to the right of esc key, representing F2) to open a “Developer console” (similar to opening a tty) where the first line ends with “localhost login”. Enter root and the password you just set for it. Then you must run `chromeos-setdevpassword` and set another password, which is the one that is actually used when running “sudo”. Now use `Ctrl+Alt+Backward Arrow` (the key next to the right of esc, representing F1) to get back to the desktop. With Developer Mode enabled, you can launch a terminal emulator inside ChromeOS by pressing the `Ctrl + Alt + T` key combination. Run `shell` inside the resulting `crosh` prompt to actually get to a `bash` session where you can run programs. Most of the root file system is read-only, except for `/usr/local` and any mounted drives under `/media/removable`. Identify your device -------------------- It's more common to refer to ChromeOS boards by their codenames, and many compatible devices can share a single codename. Libreboot ROM images also use these, you should only use the one corresponding to your device's. There are a number of ways to find it, some are: - Check the "Model" on the Recovery Mode or Developer Mode screens - Visit `chrome://version` in ChromeOS and check the "Firmware Version" - Run `crossystem hwid` or `crossystem fwid` in a terminal Back up stock firmware ---------------------- The stock firmware on your device comes with some irreplaceable data that is unique to your device. This can include the serial number and hardware ID of the device, network MAC address, HDCP keys, maybe more. The stock firmware is also the only one that will properly boot and run ChromeOS. Make sure you back up the original firmware before trying to replace it. The version of flashrom in ChromeOS understands `host` as a programmer to flash firmware internally. To back up stock firmware you can run: sudo flashrom -p host -r depthcharge.rom sudo flashrom -p host -v depthcharge.rom Keep the resulting `depthcharge.rom` file safe and properly backed up on another device. If you can already boot a conventional Linux distro on your Chromebook, you may be able to use `flashrom -p linux_mtd` on that system instead. Check external flashability --------------------------- If a ROM image you flash is broken, you may need to restore the stock firmware to fix the board to get internal flashing working. Refer to the [external flashing guide](spi.md), and check that the result of `flashrom -r` matches what you get when you run it from the device. Chromebooks may have 1.8V as the supply voltage for the SPI NOR chip, be extra careful about that. On newer Chromebooks, there is a root-of-trust chip providing a [Closed Case Debugging](https://chromium.googlesource.com/chromiumos/platform/ec/+/cr50_stab/docs/case_closed_debugging_gsc.md) mechanism that lets you flash externally using a special USB debugging cable. However, most boards that Libreboot supports do not have this. Disable write protection ------------------------ Chromebooks have the SPI flash chip partially write-protected by default, but thankfully this protection can be disabled by the device owner. How to do so depends on the board, refer to the [ChromiumOS documentation on Write Protection](https://chromium.googlesource.com/chromiumos/docs/+/HEAD/write_protection.md) for more info. You will usually need to do this only once for the board's lifetime, unless you manually enable it again. On most boards that Libreboot supports, write-protection is enforced by a physical screw. When screwed in, it forms an electrical connection that asserts the WP pin on the flash chip. The screw can be identified by the fact that it bridges electrical contacts, but finding and removing it might require you to disassemble most of the board. In my case as an example, my kevin board had the protection screw [here](https://av.libreboot.org/board/kevin/write_protection_screw.jpg). It was tricky for me to find it since it was one of the screws that seemed to hold the heat sink in place, which I thought made it an unlikely candidate. I recommend you leave it unscrew never the less after flashing. Newer boards have a root-of-trust chip enforcing write-protection. The [Closed Case Debugging](https://chromium.googlesource.com/chromiumos/platform/ec/+/cr50_stab/docs/case_closed_debugging_gsc.md) mechanism should be used to disable hardware write-protection. Opening the case and disconnecting the battery might also disable it. Disabling the write-protect signal doesn't directly make the chip stop protecting its data, it just allows you to disable its write-protection in software. That also needs to be done in ChromeOS afterwards: sudo flashrom -p host --wp-status sudo flashrom -p host --wp-disable sudo flashrom -p host --wp-range 0x0,0x0 The *--wp* arguments are only available on the [ChromiumOS fork of flashrom](https://sites.google.com/a/chromium.org/dev/chromium-os/packages/cros-flashrom). If you are using another OS or an external flasher, you may need to compile and use that flashrom fork to disable write-protection. There is no `lbmk` support yet for automatically building it. Have a look at MrChromebox's write protect notes linked at the bottom of this page, which has some useful guidance, also see the next sections. **TODO: re-write this entire page better, with streamlined guides for the bob/kevin machines.** ### Gru BOB (ASUS Chromebook C101p) This uses a CR50-based mechanism. You must use a CR50 debug cable to unlock WP. This page has good information, and links to sellers: If you're manufacturing your own CR50 cable, something like this can be used: You could make a couple of these. But you may aswell just buy one from a seller as above, if all you need is one. **TODO: check over time if that amazon link changes, and/or find a more reliable link.** ### Gru KEVIN (Samsung Chromebook Plus XE513C24) This doesn't use CR50. This uses the old-fashioned write protect screw. It's one of the screws on the heatsink, that you loosen which removes the grounding for the WP pin. **TODO: add pics of that here.** Prepare the ROM image --------------------- Libreboot ROM image layouts are currently incompatible with the regions that should be carried over from the stock firmware. However, the released images should still be somewhat usable, since the Chromebooks supported so far don't require any non-redistributable code to be injected by the end user. Future Libreboot versions will likely require post-processing to preserve irreplaceable data in the firmware image. For now, make sure to keep backups of the original firmware. TODO: Instructions to preserve vital data when FMAPs are compatible. Flash the ROM image ------------------- You can flash the ROM image both internally and externally. For the latter, see the [external flashing guide](spi.md) and the ChromiumOS [Closed Case Debugging](https://chromium.googlesource.com/chromiumos/platform/ec/+/cr50_stab/docs/case_closed_debugging_gsc.md) documentation if your board supports it. To flash the entire ROM image internally, run within ChromeOS: sudo flashrom -p host -w libreboot.rom sudo flashrom -p host -v libreboot.rom If you can already boot a conventional Linux distro on your Chromebook, you may be able to use `flashrom -p linux_mtd` on that system instead. Install an operating system (experimental research) ------------------------------------------------ In general, ARM-compatible distros targeting U-boot can be used. There are three general methods for installing that vary depending on the distribution: 1. EFI - common u-boot methodology used by both arm64 and amd64 systems. 2. boot.scr - an older u-boot specific script used by some distributions. 3. extlinux.conf - a newer flat, bootloader-spec text file that typically lives in /boot/extlinux/extlinux.conf ### Successful installations: * [ArchLinuxARM on RK3399-based Chromebooks](../uboot/uboot-archlinux.md). * [Debian Bookworm on Samsung Chromebook Plus XE513C24](../uboot/uboot-debian-bookworm.md). * [Debian on Asus Chromebook C201](https://wiki.debian.org/InstallingDebianOn/Asus/C201). ### Unsuccessful installations: * [OpenBSD on Samsung Chromebook Plus XE513C24](../uboot/uboot-openbsd.md). ### Other promising ARM-compatible distros: * [Armbian](https://www.armbian.com/uefi-arm64/). See also -------- * [ChromiumOS Documentation](https://chromium.googlesource.com/chromiumos/docs/+/HEAD/) * [ChromiumOS Firmware Test Manual](https://chromium.googlesource.com/chromiumos/docs/+/HEAD/firmware_test_manual.md) * [ChromiumOS Flashrom Fork Information](https://www.chromium.org/chromium-os/packages/cros-flashrom/) * [MrChromebox's Unbricking Guide](https://wiki.mrchromebox.tech/Unbricking) * [MrChromebox's Write-Protection Notes](https://wiki.mrchromebox.tech/Firmware_Write_Protect) * [Coreboot Tutorial as used in ChromeOS](https://docs.google.com/presentation/d/1eGPMu03vCxIO0a3oNX8Hmij_Qwwz6R6ViFC_1HlHOYQ/preview) [//]: # "SPDX-License-Identifier: GFDL-1.3-or-later" The Canoeboot version of this page is: