This is the guide I wish I had, when I set out get android devices on Marshmallow, when OTA updates where not to be had.
I went through lots of guides that didn't work for me, and there was a lot to learn. Basically I had to do some, or all of these things:
- Unlock the bootloader
- Reset the device
- flash the ROM
- flash google apps
This is the device list I'm working with:
- Google Nexus 4 ("mako")
- Google Nexus 7 ("grouper")
- Sony Xperia Z Ultra ("togari")
- LG G Pad 8.3 ("v500")
- Samsung Galaxy Tab Pro 12.2 ("T900")
- Alcatel One Touch POP 3 (5.5) 4G LTE
From the Device
The simplest way is to just install apps. This may not be the fastest, but it requires the least amount of knowledge of the inner workings. There is risk that one of these apps will phone home.
- Install an app that gives you root (Kingroot)
- Install an app to boot into recovery (TWRP manager)
- Flash the ROM
- Flash Google Apps
From the Shell
The quickest way is to use the shell to flash your device. Make sure you have the Android SDK and that you have
fastboot. Use fastboot to flash your
.img files and use
adb sideload <gapps> to flash google apps.