SSH is the typical manner most Linux/UNIX administrators use to remotely access and run commands against a Linux/UNIX server or desktop. Occasionally typing a username and password becomes tedious. Having to type your username and password can put a halt to automating processes.

This guide will help in automating SSH login without a password from a Linux/UNIX system to another Linux/UNIX system.

The things you will need before starting:

• Access to 2 Linux Desktops or Servers.
• Basic understanding of Linux/UNIX folder structure.

Steps:

1. Log in to the first Linux Desktop/Server.
2. Generate your pubic and private keys.

   user1@server1:~$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/user1/.ssh/id_rsa): [Press Enter Here]
   Enter passphrase (empty for no passphrase): [Press Enter Here]
   Enter same passphrase again: [Press Enter Here]
   Your identification has been saved in /home/user1/.ssh/id_rsa.
Your public key has been saved in /home/user1/.ssh/id_rsa.pub.
The key fingerprint is:
17:0c:23:02:f7:8c:c0:4a:1a:e3:99:ab:30:2b:8f:0f user1@server1
The key's randomart image is:
+--[ RSA 2048]----+
| .o.o . o |
|o..o = . + |
|++o . o o |
|o+ . |
| . S . |
|o. . |
|Eo |
|+o |
|ooo |
+-----------------+

3. Copy your public key to the remote server

   user1@server1:~$ ssh-copy-id -i ~/.ssh/id_rsa.pub user2@server2
user2@server2's password:
Now try logging into the machine, with "ssh 'user2@server2'", and check in:

~/.ssh/authorized_keys

to make sure we haven't added extra keys that you weren't expecting.

4. Finally we need to test our automatic remote login

   user1@server1:~$ ssh user2@server2
Last login: Tue Mar 4 20:51:33 2014 from 192.168.1.100
user2@server2:~$ [Congrats you can login without a password]

If these steps don't work, you can delete the ~/.ssh directory on the remote server and try again. You can now use this password-less ssh login to either shorten your login processes or to help script cronjobs such as rsync.