Update Nexus 5 From KK 4.4.4 to M 6 I have a rooted stock Nexus 5, KitKat 4.4.4 build KTU84P with Franco kernel 3.4.88, and I would like to update to Marshmallow 6. 
Which build should I download and flash? Or do I have to upgrade before to Lollipop and only then to Marshmallow?
I would like to keep the device rooted instead of resetting it to factory defaults and then upgrading via OTA.
Is it possible?
Thanks in advance

T
You can flash directly to Marshmallow using the 6.0.1 (MMB29K) factory image. Follow the flashing instructions, which includes unlocking your bootloader.

I highly recommend then installing a custom recovery such as TWRP using the fastboot method. Having the custom recovery will enable you to flash other zip updates like SuperSU to get permanent root.

Note that Google's flash-all process replaces your custom recovery with the stock recovery, so make sure to reflash whatever custom recovery you choose right after. You can avoid this by flashing each partition manually instead of using flash-all.