How to get the root permission of android

Now we build the android-5.1.1_r2, while after we flash the img into the nexus 9. we need get the root permission to push out library into the device.

The following steps is how to get the root permission:

1. adb kill-server

2. adb start-server

3. adb root

4. adb remount

after it remount success.

5. adb shell

6. you will get the root permission, you can run mkdir in the /system/lib/