HOWTO : Flash CyanogenMod 12.1 ROM to OnePlus One

Hardware : OnePlus One 64GB (Black) (CyanogenMod 12, Android 5.0.2)
Desktop : Ubuntu Desktop 14.04.2 LTS
Accessories : OTG USB cable and 32GB USB thumb drive

I am running Ubuntu Desktop 14.04.2 LTS. However, the android-tools-adb is out of date to operate with Android 5.1. So, we use OTG USB to copy all the required files to the OnePlus One ("storage" directory) instead of using adb command.

Step 1 :

Install Android tools :

sudo apt-get update
sudo apt-get install android-tools-adb android-tools-fastboot

Step 2 :

Enable the Developer options at OnePlus One :

"Settings" -- "About phone"

Then tap on "Build number" for seven times

"Settings" -- "Developer options"

Enable Android debugging
Enable Advanced reboot
Disable Cyanogen recovery

Step 3 :

Unlock the bootloader :
*** Please note that all user data will be destoryed for this step ***

sudo adb reboot bootloader

or

Reboot to bootloader by selecting "Bootloader" from OnePlus One

Then,

sudo fastboot oem unlock

OnePlus One will be reboot.

Step 4 :

TWRP Recovery (TeamWin Recovery) for OnePlus One :

https://twrp.me/devices/oneplusone.html

Download the latest TWRP for OnePlus One :

https://dl.twrp.me/bacon/
e.g. twrp-2.8.7.0-bacon.img

Then rename it to twrp.img and copy to "storage" directory of OnePlus One.

Flash TWRP Recovery :

Reboot to Fastboot by selecting "Bootloader" from OnePlus One

or

sudo adb reboot bootloader
sudo fastboot devices
sudo flash recovery twrp.img

* Make sure your computer has been allowed to communicate with the OnePlus One (there will be a pop up for your to confirm).

OnePlus One will be shutdown and then you boot it up to TWRP Recovery by holding "Volume Down" and "Power" button.

Step 5 :

CyanogenMod 12.1 Nightly ROM (Android 5.1.1) for OnePlus One (There is no stable CyanogenMod 12.x ROM for OnePlus One) :

http://download.cyanogenmod.org/?device=bacon&type=nightly

Copy the CyanogenMod ROM, such as cm-12.1-20150729-NIGHTY-bacon.zip, to "storage" directory of OnePlus One.

Flash CyanogenMod ROM :

Reboot to TWRP Recovery. Select "Backup". To backup the OnePlus One stock ROM (CyanogenMod 12).

Select "Wipe". To delete all data EXCEPT "System" and "Internal storage" as your CyanogenMod 12.1 ROM is there. This step must do, otherwise; your flash will be failed due to "incorrect signature".

Select "Install". To select "/0" and then "/storage", select the CyanogenMod 12.1 Nightly image file.

Step 6 :

Get Android 5.1 Google Play :

sudo apt-get update
sudo apt-get install git

git clone https://github.com/cgapps/vendor_google.git

For OnePlus One, you need to get :

~/vendor_google/arm/gapp-5.1-arm-2015-07-17-13-29.zip

Copy the gapp-5.1-arm-2015-07-17-13-29.zip to "storage" directory of OnePlus One.

Boot to TWRP Recovery and select "Install" to install Google Play.

Now you can configure your OnePlus One with CyanogenMod 12.1 ROM and download the Apps from Google Play.

Optional :

If you want to replace the TWRP Recovery with the CyanogenMod Recovery, you can enable "Cyanogen recovery" at "Developer options". When the next Nightly update is available, you can OTA it and it will replace the TWRP Recovery with CyanogenMod Recovery :

Enable Cyanogen recovery

You can consider to lock your bootloader back too :

sudo fastboot oem lock

*** If you unlock the bootloader, all your data will be destroyed ***

You can also consider to turn off the "Developer options" and disable "Advanced root" as well as "Android debugging".

Remark

CyanogenMod stated that the recent Stagefright vulnerabilities has been fixed in CyanogenMod 12 and 12.1 Nightlies before the time of this writing. Please refer to here.

Since Android ROM may have vulnerabilities, it is better to buy Google Android products as it will provide the most latest fix or update to their devices. Or you can consider to flash responsible 3rd party ROM developers, such as CyanogenMod. However, my Google Nexus 5 (5.1.1) does not have the fix OTA at the time of this writing. So sad.

UPDATE on August 06, 2015

I confirmed that CyanogenMod 12.1 Nightly for OnePlus One is fixed the Stagefright vulnerabilities by using Google Play - Stagefright Detector by Zimperium INC while OnePlus One v5.0.2 (Cyanogen OS version 12.0-YNG1TAS2I3) and Google Nexus 5 v5.1.1 (Build number LMY48B) are still vulnerable to Stagefright vulnerabilities.

That's all! See you.