Update Nexus 7 to Android 4.3 manually without loosing data

Sometimes one has modified some system files and OTA is failing due to those modifications. The easiest way in that case would be to do the update manually by using the factory image. Unfortunately applying the factory image directly does a factory reset, so all data will be lost, but knowing the principles behind, you can go to the lastest Androis version without loosing your data.

Get the factory image from Google and extract the following files from it:

• bootloader-grouper-4.23.img
• boot.img
• system.img

If you have root and want to keep it, get
- UPDATE-SuperSU-v1.51.zip
and copy it to /sdcard and be sure, that you have a custom recovery installed on your device.

Then do a nandroid backup before starting (it's always better to have it) and then do a

fastboot flash bootloader bootloader-grouper-4.23.img
fastboot reboot-bootloader
fastboot flash boot boot.img
fastboot flash system system.img

reboot into recovery and flash UPDATE-SuperSU-v1.51.zip

Do a reboot system and, congrats, you should be on Android 4.3 without loosing any data.

Enable usbnet on ADS_Magpie / ezGingerbread

Currently I am playing around with my old G1 to set up a communication channel to a different android / Linux device. WiFi / Bluetooth is no problem at all, but I wanted to use a direct USB connection.
Having an USB Host mode available I was wondering how easy / complicate it would be to set up usbnet on the G1. As it turned out, it was surprisingly easy, because everything is already prepared within the kernel (which is available from Github):

echo 1 > /sys/devices/virtual/usb_composite/rndis

Afterwards one can configure an IP address and set the link up:

ip addr add dev usb0 10.0.0.2/24
ip link set usb0 up

There is only one thing to be regarded: after enabling usbnet, adb over usb will no longer work, so it's better to switch to WiFi before.