How to install Android 5.1 Lollipop on HTC One M8 with CyanogenMod 12.1 unofficial ROM

HTC's 2014 One series flagship smartphone has finally made it to the list of Android devices which have tested unofficial CaynogenMod 12.1 nightly builds.

The CyanogenMod team has confirmed in their blogpost that Android fans can expect the arrival of the official nightly featuring Android 5.1 any time.

"As we planned in the last blog post, the 5.1 code has officially migrated out of the staging branches and become the full fledged cm-12.1 branch. What does this mean? This means that we have fully merged in the upstream AOSP Android-5.1.0_r3 tag, implemented most (if not all) of the CM 12.0 features and begun focusing on hardware bring-up for our roster of devices. This also means that the buildbots can be switched over for CM 12.1 nightlies at any time."

If you cannot wait for the official version, you can try out the unofficial build on your HTC One M8 shared by XDA forum member. Since this is a test build, proceed with extreme caution.

Important points

• Before following the installation guide, create a backup of all important data of the phone using custom recovery.
• Enable USB Debugging on the phone to connect it with the computer and use Android SDK with it. [Navigate to Settings>> About phone. Tap on Build Number several times until a message appears saying 'You are now a Developer.' Now enable USB Debugging Mode by navigating to Settings>> Developer Options.]
• Your One M8 should have above 80% battery charge to avoid power off during the process which could damage the device.
• The phone should be rooted with the latest recovery system installed on it. Also, it should have an unlocked bootloader. [The guide below uses TWRP recovery.]
• As the CyanogenMod 12.1 ROM is in its testing stage, all features might not function properly.
• The Android 5.1 CyanenMod 12.1 ROM works with the HTC One M8 model. Flashing this on any incorrect variant might brick the device. Therefore, verify the model number of the device.
• After flashing the ROM, if the device gets stuck on booting animation or experiences boot loop, then perform wipe cache partition and wipe dalvik cache a few times before rebooting the device.
• Once the ROM is installed, users are advised to give 10 minutes to the ROM after the device boots up for the first time for better user experience.
• IBTimes UK will not be held liable for any damage to the device.

Download files

CyanogenMod 12.1

Gapps

TWRP recovery

How to install Android 5.1 Lollipop on HTC One M8 with CyanogenMod 12.1 unofficial build

Step-1: Connect the phone to the computer via USB cable. Without extracting, copy the downloaded files to the internal storage of the phone and remember the location

Step-2: Disconnect the phone and switch it off

Step-3: Boot the phone into recovery

Step-4: In recovery mode, create a nandroid backup of the existing ROM, which can be restored later if the new ROM does not work or, you want to revert to the current version. From recovery select Backup and do a swipe on the Swipe to Back Up button

Step-5: Perform data wiping task. Tap on Wipe then Advanced wipe, then select Cache, Dalvik/ART cache and Data. Now swipe on the Swipe to wipe option at the bottom of the screen

Step-6: Go back to recovery menu and select Install then navigate to the folder where you have saved CyanogenMod 12.1 ROM. Select it and do a swipe on Swipe to Confirm Flash

Step-7: Install the Gapps package in the similar procedure you used for flashing the ROM

Step-8: When the installation process is completed, go to recovery, select Reboot>> System

Once your One M8 boots up successfully and loads all the files, it should be ready to use with unofficial CM12.1 ROM based on Android 5.1 on board.

[Source: XDA via AndroidSoul]