I firstly installed ChromeOS with Brunch and then Kubuntu on my Laptop. Now grub doesn't recognize Chrome OS. How to add Chrome OS to Grub?

I am new to the Linux world. I recently installed Chrome OS with Brunch on my laptop. Later I installed Kubuntu but grub does not recognize the ChromeOS I installed earlier. It only allows me to boot into Kubuntu.

Here's what my partitions look like:

What should I do to add ChromeOS into grub as an option so it works as dual-boot?

Thank you so much!

So long as ChromeOS was properly working before installing Kubuntu, you can add a record for the OS in /etc/grub.d/40_custom that looks like this:

menuentry "Chrome OS" {
 insmod part_gpt
 insmod ext2
 set root=(hd0,gpt3)
 linux /boot/vmlinuz root=/dev/sda3 init=/sbin/init rootwait rw noresume console=tty2 i915.modeset=1 loglevel=1 quiet noinitrd tpm_tis.force=1
}

_{Be sure to set gpt3 and sda3 to the correct partition number if I've incorrectly identified the boot partition for ChromeOS.}

Note that the above configuration is assuming that your storage device is a GPT device. If it's not, you will need to remove the insmod part_gpt line from the configuration and change the root to (hd0,X) where X is ChromeOS's root partition number ... probably 3.

Once done, update Grub:

sudo update-grub2

Now you can reboot and find a record for "Chrome OS" in your boot list.

_{Note: If ChromeOS was not working before installing Kubuntu, you will need to confirm the STATE_DEV=${ROOTDEV_TYPE}1 setting in the /sbin/chromeos_startup on ChromeOS is changed to ${ROOTDEV_TYPE}3 (or whatever the root partition for ChromeOS happens to be). Only numbers 1 through 8 are valid, so you may want to be careful given the number of partitions on your storage device.}