Hello Unix Lovers !!

Here, in this article, we shall learn how to login to Linux servers without username/password in PUTTY.

Just follow below simple steps and you can login to any of your linux server by just one click without entering any username or password:

• Download Putty client from here and install it.
• Search for puttygen on Start Menu and run puttygen.exe. Alternatively, you can go to Putty folder and run Puttygen.exe

• Now we are going to Generate the Public/Private Key pair using SSH algorith for password-less authentication. For that, just select Type of key to generate as SSH-2 RSA and Number of bits in generated key as 2048.
• Now click on Generate button.

• To progres with the key generation, you need to move your cursor at the empty space shown as in above picture. It helps to generate the key in random fashion.
• Once the keys are genearted, you will get the OpenSSH authorized key , public key and the private which can be saved.

• You can give a unique name in key comment field as shown in above picture. Now save the public key and private on local disk of your computer.

• Also save the authorized key generated to a text editor becuase you need this to save/append into your ~/.ssh/authorized_keys file on the Linux server to be logged on.

• Make sure no body can get the keys, specially the private key, if someone gets the private key, he/she can login to your server without password.

• Now go to the Unix server to log into, go to home directory.
• Create a folder .ssh if its not there.
• Go to .ssh folder and create a file authorized_keys if its not existing.
• Paste the authorized key which you have saved into text editor. If the file is already present and having some data, just add the new authorized_keys at new line.

• Make sure the file authorized_keys is having 700 file permissions, else set it(chmod -R 700 .ssh).
• Exit from the server.
• Now open Putty configuration window and enter server name to login to.

• Now go to SSH --> Auth Menu and Browse the private key file from local computer.
• In Session menu, enter the Host Name(or IP address) as [email protected] as shown below:

• Thats it. Now click on Open Button. You will be logged into the server using the username supplied and it will not ask you for any password!
• Enjoy password less authentication.