How to cleanup SSH keys?

I restored my droplet to downgrade from 16.04 to 14.04. Ever since, my SSH keys are not working. I tried removing and recreating without success. I manually added the same new key on my local machine, my droplet, and updated the key via the control panel. What am I missing, or how do I clear everything out and recreate the keys? Thanks.

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I would first check SSH config, it could be that somehow is wrong there and it’s ignoring keys. Open config file with you favorite editor:

  1. sudo nano /etc/ssh/sshd_config

Now verify that following settings are as this:

sshd_config - Important settings
PubkeyAuthentication yes
ChallengeResponseAuthentication no

Make sure it is set as above and it’s uncommented (doesn’t have # in beginning of line). If you changed something make sure you restart SSH:

  1. sudo service ssh restart

If you want to clean up all keys, you can delete ~/.ssh/authorized_keys, than you can try again. I recommend you to copy keys with ssh-copy-id if that’s possible.

This tutorial can be a good reading and I recommend it.

If you do manual way, you can verify file permissions:

  1. sudo chmod 700 ~/.ssh
  2. sudo chmod 600 .ssh/authorized_keys