Force developer mode in Chrome OS

chrome-os-force-enable-developer-mode.md

Chrome OS - Force enable developer mode

Requirements

• Chromium os already installed or if you are using brunch then the chrome os image should be prepared first.
• A USB drive, bootable with Ubuntu (or any other linux distro)
  OR, a standalone Ubuntu installation
• Some basic idea about mounting and working in terminal

Common steps

1. Boot into Ubuntu
2. Open nautilus or any other file explorer
3. Mount ROOT-A partition
4. Open terminal (Ctrl+Alt+T)

PROCESS 1. This will set a password for chronos and root

For brunch images, follow the below steps to mount the correct ROOT-A partition. If you are on actual Chrome OS or on project Croissant, jump to Edit the shadow file

• Navigate to the directory of the image. Here we assume name of image is chromeos.img

• Create a directory named ROOT-A using the command:

  mkdir ROOT-A
  

• Check the partitions with fdisk

  fdisk -l chromeos.img
  

  It should output something like:

  Disk chromeos.img: 20 GiB, 21474836480 bytes, 41943040 sectors  
  Units: sectors of 1 * 512 = 512 bytes  
  Sector size (logical/physical): 512 bytes / 512 bytes  
  I/O size (minimum/optimal): 512 bytes / 512 bytes  
  Disklabel type: gpt  
  Disk identifier: D4DC4457-9899-0546-803F-AE325571D176  
    
  Device            Start      End  Sectors  Size       Type  
  chromeos.img1  19255304 41942991 22687688 10.8G Linux filesystem  
  chromeos.img2   2117638  2183173    65536   32M ChromeOS kernel  
  chromeos.img3  10866696 19255303  8388608    4G ChromeOS root fs  
  chromeos.img4   2183174  2248709    65536   32M ChromeOS kernel  
  chromeos.img5   2478088 10866695  8388608    4G ChromeOS root fs  
  chromeos.img6     16448    16448        1  512B ChromeOS kernel  
  chromeos.img7     16456  2113607  2097152    1G ChromeOS root fs  
  chromeos.img8   2248712  2281479    32768   16M Linux filesystem  
  chromeos.img9   2113608  2113608        1  512B ChromeOS reserved  
  chromeos.img10  2113609  2113609        1  512B ChromeOS reserved  
  chromeos.img11       64    16447    16384    8M unknown  
  chromeos.img12  2412552  2478087    65536   32M EFI System  
  
  Partition table entries are not in disk order.  
  

  We are interested in one of the two 4G ChromeOS root fs

• Mount the first partition

  sudo mount -o rw,loop,sync,offset=$((512*10866696)) chromeos.img ROOT-A
  

  The offset is found by the Unit size and the Start column value of the ChromeOS root fs partition. It is shown in bold.

• Check if the correct partition is mounted:
  By default brunch uses linux kernel 5.4.x. Use the command

  ls ROOT-A/lib/modules
  

  If the output begins with 5.4 as below

  5.4.88-brunch-sebanc

  then it is correct.
  If you are manually choosing to use 4.x kernel, or the output is not 5.4.x then you need to use the other ChromeOS root fs partition. Use the commands sudo umount ROOT-A and sudo mount -o rw,loop,sync,offset=$((512*2478088)) chromeos.img ROOT-A. In case that fails, you can open nautilus (the Files app) in root (sudo nautilus) and on double clicking the image, it should be able to mount all the partitions directly.

• Follow the below section Edit the shadow file

Edit the shadow file

1. cd into ROOT-A mount point.
   (mount point can be checked from GParted or from lsblk command)
2. Copy etc/shadow file (just in case you need to revert)

sudo cp etc/shadow etc/shadow.bak

3. Edit and save the original shadow file:

sudo gedit etc/shadow

The contents should be changed to:

root:$1$JustRand$Jxi2GaUx7/t2knVdSaAU11:::::::
chronos:$1$JustRand$Jxi2GaUx7/t2knVdSaAU11:::::::

The password is now password for both chronos and root

Boot into chromium os, press Alt+Ctrl+F2 to open tty
Login as chronos with password: password
OR, login as root with password: password
Enter logout to close a chronos/root session.
Press Ctrl+Alt+F1 to get out of tty.

PROCESS 2. This will allow all developer options

1. Edit the GRUB file in Ubuntu. (This is not very much recommended as this file will be needed to be updated with the changes everytime a grub is updated. If possible, create a custom menu entry in /etc/grub.d/40_custom)

sudo gedit /boot/grub/grub.cfg

Search for "Chrome" and add cros_debug in the end of the following line as shown:

linux /boot/vmlinuz-x.xx.xx root=/dev/sda7 cros_debug

This should preferably be in the main menuentry.
For brunch images, a custom menu entry is usually made in /etc/grub.d/40_custom. The entry can be edited to add the cros_debug flag. The an sudo update-grub is necessary.
DO NOT update-grub if you are editing the /boot/grub/grub.cfg directly as it will remove the change.

2. Save the file and reboot. Enjoy!

I am using the os made by Whale Is there a way to force the developer mode on this device?