SSH login without password
Your aim : 

You want to use Linux and OpenSSH to automize your tasks. Therefore you need an automatic login 
from host A / user a to Host B / user b. You don't want to enter any passwords, because you want 
to call ssh from a within a script.
 

Host A / user a should be wifiadmin_server.name / apache user and 
host B / user b should be remoterouter.name / remoteuser


How to do it

a) Open a terminal at host A
	Log in on A as user a 

b) and generate a pair of authentication keys. *Do not enter a passphrase* :

	a@A:~> ssh-keygen -t rsa
	Generating public/private rsa key pair.
	Enter file in which to save the key (/home/a/.ssh/id_rsa): 
	Created directory '/home/a/.ssh'.
	Enter passphrase (empty for no passphrase): 
	Enter same passphrase again: 
	Your identification has been saved in /home/a/.ssh/id_rsa.
	Your public key has been saved in /home/a/.ssh/id_rsa.pub.
	The key fingerprint is:
	3e:4f:05:79:3a:9f:96:7c:3b:ad:e9:58:37:bc:37:e4 a@A

Now use ssh to create a directory ~/.ssh as user b on B. (The directory may already exist, which is fine):

a@A:~> ssh b@B mkdir -p .ssh
b@B's password: 

Finally append a's new public key to b@B:.ssh/authorized_keys and enter b's password one last time:

a@A:~> cat .ssh/id_rsa.pub | ssh b@B 'cat >> .ssh/authorized_keys'
b@B's password: 

From now on you can log into B as b from A as a without password:

a@A:~> ssh b@B hostname
B

