title: Why does SSH need a passphrase for a passphrase-less key?
body: <p>I have a SSH Key that uses no passphrase. I want to use that key to pull a private git repository when building a Docker container.</p>
  
  <p>I successfully managed to get the key into the container at build time but now SSH fails because it can't open /dev/tty to ask for the key's passphrase. The key doesn't have one, as mentioned.</p>
  
  <p>Here's some of the SSH output (-v)</p>
  
  <pre><code>debug1: SSH2_MSG_NEWKEYS sent
  debug1: expecting SSH2_MSG_NEWKEYS
  debug1: SSH2_MSG_NEWKEYS received
  debug1: SSH2_MSG_SERVICE_REQUEST sent
  debug1: SSH2_MSG_SERVICE_ACCEPT received
  debug1: Authentications that can continue: publickey
  debug1: Next authentication method: publickey
  debug1: Offering RSA public key: /root/.ssh/id_rsa
  debug1: Server accepts key: pkalg ssh-rsa blen 279
  debug1: key_load_private_type: incorrect passphrase supplied to decrypt private key
  debug1: read_passphrase: can't open /dev/tty: No such device or address
  debug1: No more authentication methods to try.
  Permission denied (publickey).
  fatal: Could not read from remote repository.
  </code></pre>