title: SSH cannot authenticate to git@github.com
body: <p>Recently, I sign up for a free plan on Github.com.
  I follow their instructions to generate a ssh key to add to my account.
  However, when I try <code>ssh -v git@github.com</code>, I get this error:</p>
  
  <pre><code>debug1: Server accepts key: pkalg ssh-rsa blen 277
  Agent admitted failure to sign using the key.
  debug1: Trying private key: /home/phuongnd08/.ssh/identity
  debug1: Trying private key: /home/phuongnd08/.ssh/id_dsa
  debug1: No more authentication methods to try.
  Permission denied (publickey).
  </code></pre>
  
  <p>When I look into the error, I see a funny thing here, that is the .ssh/id_rsa was not tried, just .ssh/identity and .ssh/id_dsa were tried.</p>
  
  <p>How can I fix this error?
  Thanks</p>