:: Stracca Blog :: Stefano Stracuzzi TECH blog

SSH Without a Password

In order to connect through ssh beetween linux hosts without prompting password you need to store the RSA Keys.

First log in on SERVERA as user USERA and generate a pair of authentication keys. Do not enter a passphrase:

usera@SERVERA:~> ssh-keygen -t rsa Generating public/private rsa key pair. Enter file in which to save the key (/home/usera/.ssh/id_rsa):

 Created directory '/home/usera/.ssh'. Enter passphrase (empty for no passphrase): Enter same passphrase again: Your identification has been saved in /home/usera/.ssh/id_rsa. Your public key has been saved in /home/usera/.ssh/id_rsa.pub. The key fingerprint is: 4a:4a:79:12:1b:2a:9f:3d:7c:be:f9:43:56:cb:24:e1 usera@SERVERA

Now use ssh to create a directory

~/.ssh as user userb on SERVERB. (The directory may already exist, which is fine):

usera@SERVERA:~> ssh userb@SERVERB mkdir -p .ssh userb@SERVERB's

 password:

Finally append usera's new public key to userb@SERVERB:.ssh/authorized_keys and enter userb's password for the last

time:

usera@SERVERA:~> cat .ssh/id_rsa.pub | ssh userb@SERVERB "cat - >> .ssh/authorized_keys" userb@SERVERB's password:

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

usera@SERVERA:~> ssh userb@SERVERB hostname SERVERB

In some Linux version (it depends on SSH version) you had to:

• Put the public key in .ssh/authorized_keys2
• Change the permissions of .ssh to 700
• Change the permissions of .ssh/authorized_keys2 to 640