These instrucations are for updating the Nexus 7 (2012) to Android 4.4 KitKat. It should work similarly for other Nexus devices.
- First, make sure you have the Android SDK installed.
- Download the appropriate factory image for your Nexus device to your PC.
- Uncompress archive:
tar xzf nakasi-krt16s-factory-da7dee49.tgz
- Start device in bootloader mode: Power on the device with both volume buttons and the power button pressed
- Flash it:
cd nakasi-krt16s fastboot flash bootloader bootloader-grouper-4.23.img fastboot reboot-bootloader sleep 10 unzip image-nakasi-krt16s.zip flash system.img
Now choose Start using the volume and power button. The system should now boot and optimize all apps for the new version.