Install Fuchsia on a Chromebook

This guide provides instructions on how to install Fuchsia on a Chromebook device.

Supported Chromebooks

Google Pixelbook Go (Atlas) is supported and regularly tested by Fuchsia developers. Some x86-based ChromeOS devices in the market may work with the instructions in this guide.

However, the following Chromebooks are not supported:

Google Pixelbook (Eve)
ARM-based ChromeOS devices

Prerequisites

This guide requires that you build a chromebook-x64 product in the Fuchsia source development environment and create a bootable USB flash drive:

Complete the Download the Fuchsia source code guide.
As part of Configure and Build Fuchsia, set your build configuration to the following Chromebook product:
```
fx set workstation_eng.chromebook-x64 --release
```
To create a bootable USB drive, follow the instructions in the Install Fuchsia from a USB flash drive guide. However, stop after creating the bootable USB drive and return to this guide.

Once the USB drive is created, follow the steps below to set up your Chromebook to boot from the USB drive.

Update ChromeOS

If your Chromebook has never been booted, boot it normally to check for updates:

Boot the Chromebook normally.
Click the Let's go button.
Connect to a wired or wireless network.
Accept the terms to proceed to check for updates.
If any updates are found, install them.
After rebooting from updates, click Browse as Guest.

From the browser UI, you go to Settings->About ChromeOS or Help->About ChromeOS to confirm the newly installed version.

Boot Chromebook into Developer Mode

To put your Chromebook into Developer Mode, do the following:

Power off the Chromebook.
To enter Recovery Mode, hold down Esc+Refresh (first and third buttons on the top row of the keyboard) and press the power button.
Press Ctrl+D to disable OS verification.
When you see "To turn OS verification OFF, press ENTER", press Enter to confirm.

When your device reboots, you get a confirmation that says "OS verification is OFF."
Press Ctrl+D again to enter Developer Mode.

Wait for the device to reconfigure itself, which will take several minutes. Initially it may not appear to be doing anything. Let the device sit for a minute or two. You will hear two loud beeps early in the process. The process is complete when you hear two more loud beeps.

The device reboots itself when the Developer Mode transition is complete. You can now go to the next Boot Chromebook from USB section.

Boot Chromebook from USB

To boot your Chromebook from USB, do the following:

Boot into ChromeOS in Developer Mode.

The screen says "OS verification is OFF." Approximately 30 seconds later the boot will continue. Wait for the welcome or login screen to load. Ignore the link for "Enable debugging features".
Press Ctrl+Alt+Refresh(F3) to enter a command shell.

If pressing this key combination has no effect, try rebooting the Chromebook once again.
Enter chronos as the user with a blank password.
To enable USB booting, run the following command on the command shell:
```
sudo crossystem dev_boot_usb=1
```
(Optional) To set USB booting to be the default, run the following command:
```
sudo crossystem dev_default_boot=usb
```
Plug the bootlable USB drive into the Chromebook.
To reboot the device, run the following command:
```
sudo reboot
```
On the "OS verification is OFF" screen, to bypass the timeout, press Ctrl+U to boot from USB immediately.

After booting from USB, the Chromebook starts the Fuchsia installer.
Press Enter on prompts to continue the installation process.

When the installation is finished, the screen displays "Success! Please restart your computer."
Unplug the USB drive from the Chromebook.

From this point, The USB drive is only needed for booting when you want to re-pave or netboot your Chromebook.
Reboot the Chromebook.

Your Chromebook is now booted into Fuchsia!

Appendices

Bypassing a long wait from the boot screen

By default the ChromeOS bootloader has a long timeout to allow you to press buttons. To shortcut this you can press Ctrl+D or Ctrl+U when on the grey screen that warns that the OS will not be verified. Ctrl+D will cause the device to skip the timeout and boot from its default source. Ctrl+U will skip the timeout and boot the device from USB.

Booting from USB

If you didn't make USB booting the default in the step 5 of the Boot Chromebook from USB section, you will need to press Ctrl+U at the grey "warning OS-not verified" screen to boot from USB when you power on your device.

If the device tries to boot from USB, either because that is the default or you pressed Ctrl+U. If the device fails to boot from USB, you'll hear a loud beep.

Note that ChromeOS bootloader USB enumeration during boot has been observed to be slow. If you're having trouble booting from USB, it may be helpful to remove other USB devices until the device is through the bootloader and also avoid using a USB hub.

Configuring boot source from Fuchsia

Fuchsia has an equivalent to crossystem called cros_nvtool. You can run cros_nvtool set dev_boot_default <usb|disk> to modify the default boot source of the system to USB or disk, respectively.

Going back to ChromeOS

To go back to ChromeOS, you must modify the priority of the Fuchsia kernel partition to be lower than that of at least one of the two ChromeOS kernel partitions:

Press Alt+Esc to get to a virtual console if not already on one.
Press Alt+Fullscreen to get to a terminal emulator on Fuchsia.

Find the disk that contains the KERN-A, KERN-B, and KERN-C partitions with the lsblk command. In the example below, 000 is the target disk – note how the device path of the kernel partitions is an extension of that device:

$ lsblk
ID  SIZE TYPE             LABEL                FLAGS  DEVICE
000 232G                                              /dev/sys/platform/pci/00:1e.4/pci-sdhci/sdhci/sdmmc/block
001   5G data             STATE                       /dev/sys/platform/pci/00:1e.4/pci-sdhci/sdhci/sdmmc/block/part-000/block
002  16M cros kernel      KERN-A                      /dev/sys/platform/pci/00:1e.4/pci-sdhci/sdhci/sdmmc/block/part-001/block
003   4G cros rootfs      ROOT-A                      /dev/sys/platform/pci/00:1e.4/pci-sdhci/sdhci/sdmmc/block/part-002/block
004  16M cros kernel      KERN-B                      /dev/sys/platform/pci/00:1e.4/pci-sdhci/sdhci/sdmmc/block/part-003/block
005   4G cros rootfs      ROOT-B                      /dev/sys/platform/pci/00:1e.4/pci-sdhci/sdhci/sdmmc/block/part-004/block
006  64M cros kernel      KERN-C                      /dev/sys/platform/pci/00:1e.4/pci-sdhci/sdhci/sdmmc/block/part-005/block
007   4G cros rootfs      ROOT-C                      /dev/sys/platform/pci/00:1e.4/pci-sdhci/sdhci/sdmmc/block/part-006/block

Use the gpt command to look at the device's (that is, 000 in the example above) partition map:

$ gpt dump /dev/class/block/000
blocksize=0x200 blocks=488554496
Partition table is valid
GPT contains usable blocks from 34 to 488554462 (inclusive)
Partition 0: STATE
    Start: 478035968, End: 488521727 (10485760 blocks)
    id:   51E8D442-0419-2447-96E5-49CB60CF0B25
    type: EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
    flags: 0x0000000000000000
Partition 1: KERN-A
    Start: 20480, End: 53247 (32768 blocks)
    id:   054CD627-F23C-5C40-8035-C188FA57DE9C
    type: FE3A2A5D-4F32-41A7-B725-ACCC3285A309
    flags: priority=2 tries=0 successful=1
Partition 2: ROOT-A
    Start: 8704000, End: 17092607 (8388608 blocks)
    id:   936E138F-1ACF-E242-9C5B-3667FAA3C10C
    type: 3CB8E202-3B7E-47DD-8A3C-7FF2A13CFCEC
    flags: 0x0000000000000000
Partition 3: KERN-B
    Start: 53248, End: 86015 (32768 blocks)
    id:   A8667891-8209-8648-9D5E-63DC9B8D0CB3
    type: FE3A2A5D-4F32-41A7-B725-ACCC3285A309
    flags: priority=1 tries=0 successful=1
Partition 4: ROOT-B
    Start: 315392, End: 8703999 (8388608 blocks)
    id:   8B5D7BB4-590B-E445-B596-1E7AA1BB501F
    type: 3CB8E202-3B7E-47DD-8A3C-7FF2A13CFCEC
    flags: 0x0000000000000000
Partition 5: KERN-C
    Start: 17092608, End: 17223679 (131072 blocks)
    id:   C7D6B203-C18F-BC4D-9160-A09BA8970CE1
    type: FE3A2A5D-4F32-41A7-B725-ACCC3285A309
    flags: priority=3 tries=15 successful=1
Partition 6: ROOT-C
    Start: 17223680, End: 25612287 (8388608 blocks)
    id:   769444A7-6E13-D74D-B583-C3A9CF0DE307
    type: 3CB8E202-3B7E-47DD-8A3C-7FF2A13CFCEC
    flags: 0x0000000000000000

Note that KERN-A and KERN-B typically have ChromeOS kernels. The Zircon kernel appears as KERN-C as in the example above, or as ZIRCON-A instead in certain setups.

To go to ChromeOS, lower the priority of KERN-C (or ZIRCON-A) by referencing the partition index on the disk that has that partition, for example:
```
$ gpt edit_cros 5 -P 0 /dev/class/block/000
```
Reboot.
When the ChromeOS bootloader appears, press Space to re-enable OS Verification.

Your device will reboot. This time, it will display a message with "Your system is repairing itself. Please wait." This operation will take around 5 minutes, after which the Chromebook will reboot one final time. The device will reboot to the initial setup screen.

From here, if you want to return to the Fuchsia kernel, you can just re-pave the Chromebook.