Passwordless SSH

This is a great way to perform automatic backups to a remote host over SSH. It requires shell access on both servers (obviously). Note that this is not the most secure way to do this, it is the easiest though.

  1. Login to the server that you wish to connect from, as the user you wish to connect as. We’ll call this Server1.
  2. cd into ~/.ssh (you may need to create this directory).
  3. Create
    your RSA keys (we do not want to set a passphrase here, or we will be
    prompted for it everytime we try to use it, which would defeat the
    purpose):
  1. ssh-keygen -t rsa
  2. [enter]
  3. [enter]
  4. [enter]
  • You should now have 2 newly created files: id_rsa & id_rsa.pub.
  • Copy id_rsa.pub to the user you will be logging in as on your remote system. We’ll call this Server2. I usually use SCP.
    1. scp ~/.ssh/id_rsa.pub [email protected]:~/.ssh/server1_id_rsa.pub
  • Login to Server2 as the user from the above step.
  • cd into ~/.ssh
  • Add Server1 to the users authorized keys file:
    1. cat server1_id_rsa.pub >> authorized_keys
  • Remove the key file & change the permissions on your
    authorized keys file (this will not work if the permissions are
    incorrect).
    1. rm server1_id_rsa.pub && chmod 600 authorized_keys
  • Logout, and try to login again from Server1
  • That’s it!
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