CyanogenMod 12.1 for Galaxy Nexus is brought to you by XDA Senior Member: Ziyan. Earlier he was person to bring you the CM 12 build for Nexus maguro.
Installing custom ROM requires a custom recovery to be installed on your device, which may VOID your warranty and may delete all your data.
Before proceeding further you may consider backing up your all data.
Please visit the Disclaimer page below to agree with the risks involved and proceed before flashing this ROM to your phone:
ROM Disclaimer link
Files needed for this flashing:
ROM ZIP: CyanogenMod 12.1 for Galaxy Nexus ROM download link
GAPPS: Android Lollipop 5.1 Google Apps download link
Make sure that you have the the bootloader unlocked and installed a custom recovery. If you don’t have a custom recovery then follow the below link:
RECOVERY: Installing custom recovery for Any Nexus phone.
Flashing CyanogenMod 12.1 for Galaxy Nexus:
Consider taking a backup of your OLD ROM before installing this new ROM.
Copy the ROM and GApps package to your phone.
Enter into the custom recovery.
Do a Factory Reset/Wipe Data and Cache partition.
Install the ROM and Gapps recovery flashable zip packages using the custom recovery.
Reboot your phone to enjoy the CyanogenMod 12.1 for Galaxy Nexus phone.
SuperSU is no more needed because it is embedded in CyanogenMod 12.1. To enable SuperSU you just need to enable developer options and there you will find the Root access option.
That’s all guys. This is a beta build and an unofficial build. An unofficial build means you will not get daily updates and OTA updates, but do not worry Ziyan is releasing the builds frequently. If you have some concerns regarding this ROM then head over to the source link and convey the same.