Method-1:

Create the cryptographic Key on FreeBSD / Linux / UNIX workstation, enter:

• ~/.ssh/id_rsa : identification (private) key
• ~/.ssh/id_rsa.pub : public key

scp .ssh/id_rsa.pub vivek@rh9linux.nixcraft.org:.ssh/authorized_keys2

ssh rh9linux.nixcraft.org

ssh-keygen -p

ssh-agent $BASH

ssh-add

Deleting the keys hold by ssh-agent

Method-2

To generate a public and private key run this command on your backup server:

sudo ssh-keygen -t rsa

We do not want a passphrase for this key because we want these computers to be able to connect to each other without our intervention. Press “ENTER” through all of the prompts to accept the defaults.

user@backupserver:~#: sudo ssh-keygen –t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
…
The key's randomart image is:
…

We now have a public and private key pair that will allow us to sign in to other servers from our backup server. We need to transfer our public key to the machine we will be backing up so that it knows that we are allowed to access it.

sudo ssh-copy-id -i /root/.ssh/id_rsa.pub root@example.com

Be sure to change “example.com” to the IP address or domain name of the server you will back up.

Once that command executes, you should check that you are able to log-in to your server from your backup server without a password.

sudo ssh root@example.com

Once you’ve verified that you can connect correctly, exit out so that you are able to work on your backup server again.

exit