Thanks zitstif, i know have a NethunterROM + backup-android on my Nexus 4! I only did this, since my device was already rooted+unlocked:
Code:
Use the volume buttons to select Recovery/Recovery Mode and press the power button. Inside the MultiROM TWRP menu select 'Advanced > MultiROM > Swap ROMs'. Choose the action 'Copy primary ROM to secondaries'. This will create an exact copy of your Android installation, swipe across the button of the screen where it says 'Swipe to swap ROMs' to confirm.
Now wait as your ROM is copied. If your device reboots once it is done, follow the previous steps to get back into MultiROM TWRP Recovery mode. Otherwise press back untill you are on the Multirom home screen. Press 'Advanced > MultiROM > List ROMs' and tap on the ROM in the menu.
On the new screen tap on 'Flash ZIP' and navigate through the file system to '/data/local/tmp/' select the kali nethunter file that you put onto your device earlier and it will begin to flash/install. This may take a long time: ~20 minuites.
Once it is completed go back to the TWRP home screen and tap 'Reboot > System'.
Now as it loads up click on cancel so that it doesn't autoboot into your Android ROM. Here on the menu you will see two options, your internal Android ROM and your new Nethunter ROM. Select the Nethunter ROM to load it up.
Congratulations, you now have Kali-Linux Nethunter installed on your device! It will also already be rooted as it was installed on top of a copy of your rooted Android ROM. You also have a sepperate Android ROM as a backup or if you don't want to use nethunter.
You can delete the Nethunter ZIP on your device to get some space back by typeing: