connecting to SSH server passwordless

If you have to connect to an SSH server frequently or you want to make a shell script using ssh, you might want to consider connecting to it passwordless. This trick is now new. I have heard about this long time ago but didn't have any necessity for it so I ignored it until recently.

by the time of this writing, I have just completed my script for backup using SSH passwordless. Here I want to share the way I did it in a simple way. I hope it benefits others. Bear in mind that, all ssh utilities like sftp, scp and ssh can use passwordless connection once we complete setup one.

Step 1

• Connect to SSH server and open up sshd_config in /etc/ssh or equivalent. Check your distro documentation.
• Make sure you have the following entries:

  # Allow Identity Auth for SSH1?
  RSAAuthentication yes
  
  # Allow Identity Auth for SSH2?
  PubkeyAuthentication yes
  
  # Authorized Keys File
  AuthorizedKeysFile ~/.ssh/authorized_keys

Step 2

• Make RSA keys using ssh-keygen in your home directory of ssh client.
  

  $ cd ~  
  $ mkdir identity-test
  $ cd identity-test
  $ ssh-keygen -f id_rsa -t rsa
  Generating public/private rsa key pair.
  Enter passphrase (empty for no passphrase): 
  Enter same passphrase again: 
  
  Your identification has been saved in id_rsa.
  Your public key has been saved in id_rsa.pub.
  The key fingerprint is:
  c3:af:e9:6c:2f:19:4d:b5:1a:a9:40:06:54:e6:60:08 me@localhost

• look at the created files
  

  $ ls
  id_rsa     id_rsa.pub
  
  The id_rsa.pub contains the public key and id_rsa contains private key.
  

• copy the content of id_rsa.pub to ~/.ssh/authorized_keys
  Two ways to achieve this
  1. login to ssh server and paste the content into the file
  2. using scp to copy the content into the file
• So, let's test logging in with this key. Since we have put the test key in a non-standard place, we will need to reference it explicitly on the command line:

  $ ssh username@server -i ~/identity_test/id_rsa
  $username@server$ hostname
  $server
  $username@server$ exit
  
  $ ssh username@server -i $HOME/identity_test/id_rsa "echo Success!"
  Success!
  $

• In the above examples, if you can login without password then the setup is a success. If not, please recheck the setup.

Have fun ssh'ing :)