Passwordless SSH (Public Key Authentication) for CentOS 5, CentOS 6, Ubuntu, Debian, Linux in General

 

Passwordless login between linux host

Scenario:

You have two servers, Server-A and Server-B – you would like ServerA to be able to SSH in to ServerB without a password. Use this simple tutorial to achieve this:

Step 1: Generate public key on ServerA

SSH in to Server-A and enter the following command. Keep pressing enter (accept the defaults) – do not enter a passphrase.
 

$ssh-keygen -t dsa

This should have generated a file, /root/.ssh/id_dsa.pub

Copy the contents of the file above:
 

cat /root/.ssh/id_dsa.pub

Step2: Copy Server-A’s public key to ServerB SSH in to Server-B and paste the contents from /root/.ssh/id_dsa.pub from Server-A (above) in to /root/.ssh/authorized_keys on Server-B:

If the /root/.ssh directory does not exist, create it first:
 

$mkdir /root/.ssh
 

$vim /root/.ssh/authorized_keys

Set the required permissions on the authorized_keys file:
 

$chmod 0600 /root/.ssh/authorized_keys
 

Now try and SSH to Server-A from Server-B – you should not be prompted for a password. 

The same process can be used for other users, apart from root. If you want Server-B to have passwordless SSH access to Server-A, perform the same steps as above, but swap Server-A for Server-B the next time you do it.