Chrome OS Multiboot

My approach to multiboot Chrome OS or Chromium OS on regular machines.

If you're looking for updating your Chrome OS installation, the project is move here.

Multiboot guide

Prerequisites

1. A Linux distro e.g. Ubuntu, Mint, etc. (may need installing since the files to be downloaded need a lot of space)
2. chromefy.h
3. swtpm.tar - To solve TPM related problem on modern PCs
4. @arnoldthebat's Chromium OS Special build (R74 or later)
5. Eve or similar recovery file matching your hardware specifications (check here for more info)
6. install_chromium.sh

If you're going to install Chromium OS (not Chrome OS), you don't need 2, 3, and 5 prerequisites.

Process

Creating partitions

You'll need to create 3/4 partitions in GPT mode:

1. EFI-SYSTEM: Type FAT16 (32 MB) [assume, the device id is sda4]
2. ROOT-A: Type EXT2 (at least 4 GB) [assume sda5]
3. ROOT-B: Type EXT2 (at least 4 GB) [assume sda7] (Optional if you don't want to update Chrome OS natively)
4. STATE: Type EXT4 (this is where user files will be kept, so the size of the partition depends on you; 20 GB recommended) [assume sda6]

Converting Chromium OS to Chrome OS

[Skip this step if you are not going to install Chrome OS, just Chromium OS]

• Download the prequisites at ~/Downloads/ChromeOS and extract them there as well. Don't delete the zipped files yet (as something might be broken). The file structure should look something like this:

  Camd64OS_R72-11316.B-Special.7z
  chromefy.sh
  install_chromium.sh
  chromeos_11316.165.0_eve_recovery_stable-channel_mp.bin
  chromeos_11316.165.0_eve_recovery_stable-channel_mp.bin.zip
  chromiumos_image.img
  swtpm.tar

• Now, run the following command to convert Chromium OS to Chrome OS:

  cd ~/Downloads/ChromeOS/ && sudo bash chromefy.sh chromiumos_image.img chromeos_11151.113.1_eve_recovery_stable-channel_mp.bin swtpm.tar

  At some point, the script might prompt you to know if you want to set SELINUX to permissive, just press n and enter.

Installing on HDD

• Run the following command to install chromium on HDD:

  cd ~/Downloads/ChromeOS/ && sudo bash install_chromium.sh chromiumos_image.img sda4 sda5 sda6

  Before running the above command, replace chromiumos_image.img with the chromium image (should be unchanged if you're following the guide), sda4 with EFI-SYSTEM partition's id, sda5 with ROOT-A partition's id and sda6 with STATE partition's id.

Now you can safely boot into the newly installed OS.

Updating Chrome OS

[Applied for Chrome OS only, if you're looking for updating @ArnoldTheBat's Chromium build, contact him instead]

! Warning ! This process is experimental, be sure to issue a report if you stumble upon something.

You can use the update_chromium.sh script located in this repo to update Chrome OS to the latest version (should work with regular installation as well). To do this you'll need to download the latest recovery update for your platform (e.g. eve) which can be downloaded from here. If you needed swtpm.tar, download the latest file from here.

Currently, update_chromium.sh takes three arguments (last is optional): the first argument is the recovery.bin file, the second argument is the device id of the ROOT-A partition (sda5 if you're following this guide and sda3 for regular installation) and the third argument is the optional swtpm.tar. For example:

update_chromium.sh ~/Downloads/chromeos_11647.104.3_eve_recovery_stable-channel_mp.bin sda5 swtpm.tar

You can use Ubuntu Live (ie. without installing a Linux distro) to update Chrome OS.

Want to update natively?

Move to another repo as the project appears to be more complex than I imagined. Refer here.

Mounting internal partitions

As you may have noticed, internal partitions are not mounted by default (since Chrome OS is never meant to be used this way). So, in order to mount the internal partitions, you'll need to edit /etc/fstab after you have created an user account in the Chrome OS. The idea is to mount them inside the ~/Downloads folder so that you can access these partitions from there.

Considering the fact that we may frequently need to change the partitions in the fstab, instead of editing /etc/fstab, we will be creating /usr/local/fstab which can be edited in Chrome OS later on.

Editing /usr/local/fstab

• First, you need to determine which partition(s) should be mounted on startup. You can get the device ids using various methods. For instance, in Chrome OS, you can get a list of mountable partitions using the following command:

  sudo /sbin/blkid -o full | grep -E "^/dev/sd.*TYPE" | grep -vE "EFI|STATE|ROOT-A"

  (Here EFI, STATE and ROOT-A partitions are ignored)

  You'll see something like this:

  /dev/sda2: UUID="97867245-0528-320d-94c1-c166b79375d9" LABEL="Ocean" TYPE="hfsplus" PARTUUID="864b7c8d-499e-11e7-8dc3-806e6f6e6963"
  /dev/sda3: UUID="f567c6b2-df56-37c2-b9f3-412a02695d30" LABEL="Shore" TYPE="hfsplus" PARTUUID="222c8fbe-9c8c-4ccc-a2d3-148c89b375ab"
  /dev/sda6: LABEL="WindowsOS" UUID="1EA06E1DA06DFC21" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="2ef2d893-6135-49f5-8792-a06e9eb40ef8"
  /dev/sda7: UUID="565E0E935E0E6C55" TYPE="ntfs" PARTUUID="5386f571-f91d-4c4b-b5b9-6599b2e64a5b"
  /dev/sda8: UUID="6ff85824-b561-3ffa-a1c2-171e142a9797" LABEL="macOSHighSierra" TYPE="hfsplus" PARTLABEL="Basic data partition" PARTUUID="5230f7de-347a-4091-963b-ae5cfbe9e37d"
  /dev/sda9: UUID="5e657717-36a7-3ff3-9f3b-7075104742bb" LABEL="Recovery HD" TYPE="hfsplus" PARTUUID="9b6e2c8a-bb3c-48e3-8a8b-56a26d86c5cd"
  /dev/sda12: UUID="f2d6d289-1c60-4d94-82f5-fa9132246a47" TYPE="ext4" PARTUUID="a61af699-38f7-47c3-bb97-10cbdf2dbedf"

  Note the device ids which are to be mounted on startup. (Suppose sda2, sda3, sda6, sda8, sda12)

• Open crosh and run the following:

  echo /home/$USER/u-$CROS_USER_ID_HASH/MyFiles/Downloads

  Or, if you're running Chrome OS 73 or less:

  echo /home/$USER/u-$CROS_USER_ID_HASH/Downloads

  You'll get a path which is accessible from Files app. Let call it Files path. (Suppose Files path is /home/chronos/u-910450b5b86edd74333ce14f446ec9c7a44301e0/MyFiles/Downloads)

• For each of the partitions that you've noted earlier, assign a directory name after the Files path. For instance, for sda2, I can assign Ocean, thus the whole directory becomes /home/chronos/u-910450b5b86edd74333ce14f446ec9c7a44301e0/MyFiles/Downloads/Ocean

• Create /usr/local/fstab using vim:

  sudo vim /usr/local/fstab

  Add the partition ids along with the mount points like this:

  /dev/sda2   /home/chronos/u-910450b5b86edd74333ce14f446ec9c7a44301e0/MyFiles/Downloads/Ocean            auto    defaults   0      0
  /dev/sda3   /home/chronos/u-910450b5b86edd74333ce14f446ec9c7a44301e0/MyFiles/Downloads/Shore            auto    defaults   0      0
  /dev/sda6   /home/chronos/u-910450b5b86edd74333ce14f446ec9c7a44301e0/MyFiles/Downloads/WindowsOS        auto    defaults   0      0
  /dev/sda8   /home/chronos/u-910450b5b86edd74333ce14f446ec9c7a44301e0/MyFiles/Downloads/macOSHighSierra  auto    defaults   0      0
  /dev/sda12  /home/chronos/u-910450b5b86edd74333ce14f446ec9c7a44301e0/MyFiles/Downloads/Ubuntu           auto    defaults   0      0

  Now save the file.

  (If you don't know the fstab format, see the third reference bellow.)

Copying startup script

• Download this file (mount-internals.conf) at ~/Downloads directory.
• Mount root partition for writing

  sudo mount -o rw,remount /

• Copy mount-internals.conf at /etc/init/:

  sudo cp ~/Downloads/mount-internals.conf /etc/init/

  Now, you can safely reboot. This method should work on multiple user environment as well. But beware that the CROS_USER_ID_HASH different for each user and you've to configure each of them separately in the fstab file.

NOTE: Mounted partitions don't show up on Android, further study needed.

References

1. https://github.com/imperador/chromefy
2. https://docs.google.com/document/d/1uBU4IObDI8IFhSjeCMvKw46O4vKCnfeZTGF7Jx8Brno/edit
3. https://wiki.debian.org/fstab
4. https://www.chromium.org/chromium-os/chromiumos-design-docs/disk-format