title: Cannot scp a file into gcloud: Permission denied (publickey)
body: <p>I'm trying to copy a file into a compute instance using <code>gcloud</code> like this:</p>
  
  <pre><code>gcloud compute scp ./file.txt.bz2 root@instance-1:/home/mehran/
  </code></pre>
  
  <p>And I'm facing an error:</p>
  
  <pre><code>No zone specified. Using zone [us-central1-c] for instance: [instance-1].
  root@###.###.###.###: Permission denied (publickey).
  lost connection
  ERROR: (gcloud.compute.scp) [/usr/bin/scp] exited with return code [1].
  </code></pre>
  
  <p>I've also tested without root:</p>
  
  <pre><code>gcloud compute scp ./file.txt.bz2 instance-1:/home/mehran/
  </code></pre>
  
  <p>And facing the same error. This is in the case that I <strong>can</strong> <code>ssh</code> into the same instance without any issue:</p>
  
  <pre><code>gcloud compute ssh instance-1
  </code></pre>