Revert the Pixel C from Oreo to Nougat

The bleeding edge is where you bleed

I was pleasantly surprised to find Oreo (Android 8) ready to install on my Pixel C tablet a few days ago. The OTA update went smoothly but it had one unacceptable flaw: Oreo broke the only action game I play regularly (War Robots, if you must know). Here’s how I fixed it.

Download platform tools

This step was precautionary. One could probably use the fastboot and adb tools already installed on Ubuntu 17.04. Oh well, this worked. I downloaded the Linux tools from the Android Studio site. After download, I opened a terminal and configured the software.

  mkdir PixelC
  mv ~/Downloads/ ./PixelC

  # Add tools to path
  cd PixelC
  export PATH=`pwd`/platform-tools:$PATH

Download latest Nougat

I downloaded the latest ryu build for the Pixel C release August 2017 from the offical Google Android image site, moved it to a PixelC directory, and then unzipped it.

  mv ~/Downloads/ ~/PixelC/
  cd ~/PixelC

Prepare the tablet

Warning: The following procedure erases all your data. Do not proceed without a backup!

First I enabled developer options by vistiting Settings > About Tablet and tapping on the Build seven times. A message on the bottom confirms that I’m now a “developer” - thanks Google! Next selected Settings > Developer options and enabled USB debugging and OEM unlock. I then attached the tablet to the computer using USB C cable and unlocked its bootloader as shown below.

  sudo adb start-server
  sudo adb devices # should show tablet
  sudo adb reboot bootloader
  sudo fastboot oem unlock

The last step took about 5 minute and erased all user data on the tablet. The tablet then rebooted and presented me with plain “Waiting for fastboot command” message.

Flash the image

Here is were things got tricky. The official means to flash failed because the archive does not contain boot.sig, recovery.sig, or system.sig files. But an Android Central forum post and a Nexus 7 article from five years ago saved the day. Back to our trusty terminal to work the magic.

  cd ryu-n2g48c

  # Running sudo ./ failed.
  # This is the alternate solution that worked.


  sudo fastboot devices # should show tablet, if not, fix before proceeding
  sudo fastboot flash bootloader bootloader-dragon-google_smaug.7900.50.0.img
  sudo fastboot reboot-bootloader
  sleep 5

  sudo fastboot flash boot boot.img
  sudo fastboot flash system system.img
  sudo fastboot flash cache cache.img
  sudo fastboot flash vendor vendor.img
  sudo fastboot flash recovery recovery.img

  # IMPORTANT Do this here as it erases all user data again!
  # sudo fastboot oem lock

  sudo fastboot reboot

After this the device warned the the bootloader was unlocked and that I would have to wait 30s for a reboot. In retrospect, I should have relocked the bootloader before rebooting as shown above. Instead I set up the like-factory-new tablet from a backup and patiently wait for all the apps to reinstall - around 45 minutes.

Relock the bootloader

If you’re playing along at home and still haven’t relocked your boot loader you’re in trouble now. That’s because fixing this is going to completely delete all user data again. I had to re-enabled developer options and USB debugging as before and attach the tablet to the computer via USB C and executed these commands in the terminal:

  sudo adb start-server
  sudo adb devices # should show tablet, if not, fix before proceeding

  sudo adb reboot-bootloader

  # This will again erase all user apps and data
  # and requires confirmation on the tablet
  sudo fastboot oem lock

  # And now to reinstall everything...
  sudo fastboot reboot

Then I had to install my apps and data all over again.

I hope someone finds this useful!

Cheers, Mike


Written on September 10, 2017