Getting "???" and no permissions when using 'adb devices' on Linux I am new to Android and ADB. This is my first time trying to install Linux on an Android device. I have been stepping though this tutorial.
I am at step 5, where the tutorial claims I will need to authorize USB debugging connections. I'm not sure it is accurate, when I booted, the device simply informed me that there was a USB connection. 

So then, I gave the Linux command:

~$ adb devices
List of devices attached 
????????????    no permissions


So then I thought it might be a Linux permissions issue, and gave it sudo, but I still get the same gibberish.

~$ adb devices
List of devices attached 
????????????    no permissions


when I unplug the device, and run the command adb devices nothing shows up... a blank line. So it would seem ADB is detecting something. 

What is this output telling me? How might I get my device recognized?
Are there any additional settings I should enable for this to work?
This Android device, is an Nextbook Ares 11.
On your device, Go to Settings > About Device and repeatedly tap "Build Number" until it says you're a developer. Then go back to Settings and into Developer Options. Turn it on and check the box for USB debugging. Then Revoke USB debugging authorisations.
Now, connect your device, install its drivers if you haven't and type any ADB command. A message will popup on your device asking for authorization. Click Allow. Once you have done that, when you type adb devices it should say &lt;device_id&gt; device