title: Android adb backup couldn't connect issue
body: <p>I am trying to create a backup of an android device using ADB.</p>
  
  <p>However adb backup -all gives me this error: <code>adb: unable to connect for backup</code>
  why am i getting this error?</p>
  
  <p>I know that some device ask for permission to do that, it asks you whether you want to allow the pc to take a backup, but my device isn't.</p>
  
  <p>I am developing android devices, i dont care about messing it up - so can you tell me how i can enable my device to ask for the permission, or even how i can fix this problem</p>
  
  <p>I can use <code>adb shell</code> and it works fine, and so does <code>adb pull/push</code> however i want the backup file, so i really want adb backup to work. </p>
  
  <p>Is there any other way to take an image of the entire android OS and the apps, and settings? (best is if you can point me into a direction where i can find a solution for the problem i said, but i am open to other ideas.)</p>
  
  <p>Thanks! </p>