Generating Public and Private SSH Keys

Generating SSL Public and Private key pairs is a good idea if you are automating things such as rsync because it allows you to authenticate between a primary and secondary server without having to provide a password every time. I am using this to rsync the backup of my LDAP server, and I am setting this up so only the backup user will  be able to connect to both servers without a password, as the backup user is the only user that will need to do this. This means that you will need to set up a crontab for the backup user.

To enable the remote login you need to create a pair of keys, one of which will be added to a file on the remote server. The key pairs will be stored in the following files:

* ~/.ssh/id_rsa

*~/.ssh/id_rsa.pub

You will need to create the .ssh directory and the id_rsa and id_rsa.pub files before you can generate the keys.

To generate the keys you will need to run:

ssh-keygen -t rsa

You will be asked where you want the key file to be saved, as I am using the key for the backup user I am saving it in /home/backup/.ssh/id_rsa.

Next you will be asked to enter a pass phrase, you can choose to leave this blank and have no pass phrase. If you create the files without a passphrase the key files will be available to be used without being unlocked, which is what you want if you are wishing to automate things.

Now that you have a pair of key files you need to append the contents of the.pub file to the right location on the remote server.

To do this you will need to run the following command:

ssh-copy-id -i /home/backup/.ssh/id_rsa.pub otheruser@remotehost

chown -R backup:users .ssh

cd .ssh

chmod 600 id * # This means that the key files can only be read by the owner, which in this case is the backup user, this is vital to keeping the server secure.

Once you've done this you'll be able to log in remotely and run commands without being prompted for a password!