SSH Authentication without entering a password

Follow the instructions below to create and install a SSH public key on your remote server. After you followed these steps your able to login via SSH without entering a password. This is extremely useful for backups with rsync or for other automatic tasks you like to execute.

  1. Change to your user’s home directory (local system)
    cd ~
  2. create a pair of private keys
    ssh-keygen -f .ssh_key -t rsa -N ''
  3. *** upload the public key to the remote system using rsync via SSH
    rsync -e ssh ~/.ssh_key.pub [email protected]:key1.pub
  4. login to your server via SSH using the command line or Putty
    ssh [email protected]

    (you need to enter your password too)

  5. check if the .ssh directory exists, if not create it
    mkdir .ssh
  6. add the public key to the user authorized key files
    cat key1.pub >> .ssh/authorized_keys
  7. remove the uploaded key from your home directory (remote system)
    rm key1.pub
  8. test your new “private” connection
    rsync -avz -e "ssh -i .ssh_key" "someFolder" [email protected]

Now you’re able to access the remote system (YourServer) from your local system without using a password. This tutorial is for Linux only.

*** UPDATE: 12th december 2011

If you can’t create a persistent SSH connection to you backup server this way you need a small workaround:

After the creation of your “local” keys you need to download the “authorized_keys” file from the backup server

rsync -e ssh [email protected]:.ssh/authorized_keys ~/authorized_keys

(check the exact locations first)

Now add your public key to the downloaded file

cat .ssh_key.pub >> authorized_keys

Upload the modified “authorized_keys” file to the backup server

rsync -e ssh ~/authorized_keys [email protected]:.ssh/authorized_keys

Remove the downloaded file and test you connection like described in step 8.