How I Fixed a Boot Loop during a LineageOS Upgrade

Today I upgraded my Android smartphone from LineageOS 16.0 to 17.1 and I decided to share some insights since I ran into several issues.

Upgrading the Recovery Image

According to the LineageOS upgrade documenation, “a newer LineageOS version may not install due to an outdated recovery”. When upgrading from 16.0 to 17.1, a new recovery image is mandatory. This is how you install it (you need to have adb and fastboot installed for that):

  • Download the recovery image for your smartphone
  • Reboot your phone into bootloader mode using the command adb reboot bootloader (the LED should now flash blue)
  • Check if the phone is properly connected using fastboot devices
  • Upload the new recovery image with fastboot flash recovery <your recovery filename>.img

The output should be similar to this:

Sending 'recovery' (13528 KB) OKAY [ 0.496s]
Writing 'recovery' OKAY [ 0.917s]
Finished. Total time: 1.426s

Note that the new recovery has no touch display input anymore. Instead, you can navigate using the the volume up and volume down keys. The power button is used as enter key.

Upgrading LineageOS and Google Apps

First, you need to download the new LineageOS image for your phone. In case you have Google Apps installed, you also need a new Google Apps package your the processor architecture of your phone (in my case this was arm and I chose the nano package).

The required steps are:

  • If not already enabled, activate USB debugging in your phone’s settings (Settings | System | Developer Options | Root Debugging or in older versions Root Access Options / ADB only)
  • Start sideloading in recovery using adb reboot sideload
  • Sideload the LineageOS image with adb sideload <your LineageOS image>.zip Note: on the phone a confirmation message will be shown that the process was successful, but on the computer the following confusing error message will appear: adb: failed to read command: Undefined error: 0. You can simple ignore this error as long the phone reports success.
  • Directly after sideloading the OS image, sideload the Google Apps (without rebooting in between!): Apply Update | Apply from ADB, then on your computer type adb sideload <google apps filename>.zip
  • Navigate to the back arrow at the top left of the screen using the volume up key and confirm with the power button, then choose Reboot system now.

If you’re lucky, you’re already done now. If you encounter issues, continue reading.

Possible Issues

I encountered the following issues:

  • I tried installing 17.1 with the 16.0 recovery image. It does not work, you need to flash the 17.1 recovery first.
  • After sideloading my computer displayed the error adb: failed to read command: Undefined error: 0, while the phone displayed a success message. This is very confusing, but the error in the terminal can be ignored as long as the phone displays a success message.
  • My phone got stuck in a boot loop. With the old recovery image, there was no way to solve it. With the new recovery image, after a few minutes a screen appeared saying that “the Andorid system could not be started” with the options Try again and Factory Reset. At this point do not immediately perform the factory reset, in my case I was able to repair the installation. Apparently, a faulty Google Apps package caused the problems. The problematic package was open_gapps-arm-10.0-nano-20200919.zip. When I looked at the download page again, a package from the day before was provided: open_gapps-arm-10.0-nano-20200918.zip. With the “older” package it suddenly worked. Before, I had also tried different LineageOS image versions.

Bottom line: if you are in a boot loop situation, first try different versions of LineageOS images and also different Google Apps images. Remember to always install the LineageOS package first and then the Google Apps package directly afterwards. In some cases the boot loop can be solved like this.

The combination that ultimately worked for me was:

  • lineage-17.1-20200915-recovery
  • lineage-17.1-20200915-nightly
  • open_gapps-arm-10.0-nano-20200918

Now I can enjoy Android 10 Features on a 6 year old smartphone 😎

Creating Full Backups of your Android Smartphone Without Root Access

In this blog post I will explain how you can create a full backup of your Android smartphone, even if you don’t have root access.

“Become” a Developer

The first step is to activate the developer options in your system settings menu. To do that, locate the build number in your device info menu. This is usually located somewhere under Settings -> Device Info. Once you located it, you have to tap the build number seven times in order to unlock the developer features of your phone.

Enable USB Debugging

Once you unlocked the developer mode, there is a new menu in your settings called Developer Options. Find this menu and enable USB Debugging.

Install the Android Debug Bridge

The next step is to install a tool called adb (Android Debug Bridge). It is part of the Android SDK (Software Developer Kit). The problem is that the current version as of the time of writing (1.0.32) is unusable due to a bug (see bug report). As soon as this bug is fixed, you can dowload the SDK Command Line Tools from the official download page or install a current version using Homebrew.

Update March 9th, 2017: Tested again with version 1.0.36 (Revision 0e9850346394-android), and the backup works. However, an app blocked the backup process. After uninstalling the app, the full backup was successful.

Connect Your Device

After you installed a working version of adb, you can check the connection between your device and your computer. To do this, you need to locate the adb executable file in your SDK installation or your extracted folder. Open a terminal and type the following command:

/path/to/adb devices

where /path/to/adb must be replaced with the absolute path to the adb executable. Mac users can drag and drop the adb file from the Finder into the terminal in order to insert the complete path automatically. This should result in an output similar to:

List of devices attached 
3204226a921e227d    device

Make the Backup

If your device is connected, you can perform the backup with the following command:

/path/to/adb backup -all -apk -shared

This starts a backup process including all apps (-all), APK archives (-apk) as well as the internal and external storage data (internal memory and SD cards, -shared). If you don’t need all of this data, you can skip the correspondent parameter.

After issuing the command, you will be asked to confirm the backup operation on your smartphone. You can enter a password to encrypt your backup, which I recommend. Note that the backup process can take a long time depending on how much data is persisted on your phone. The process should result in a large file called backup.ab which is stored in the current folder (if you did not navigate to another directory: in your user home folder). If you want the backup to be stored elsewhere, you can supply the parameters -f <path> specifiying the target file path.

If the file is empty or contains only 41 bytes (when using no password) or 549 bytes (when using password) then you have a buggy version installed and need to get an older version (see previous sections).

Restoring Backups

Backups can be restored using the command

adb restore /path/to/backup.ab