Putty Ubuntu SSH Autologin

With the addition of a Windows Vista computer to my small network I find myself needing to get into the Ubuntu systems via SSH when I'm on the Vista computer. This is simple with Putty, but entering my username and password every time is annoying.

I've already setup the rest of the systems on my network to have Ubuntu login to SSH automatically. I don't see why I can't have the Windows Vista computer do the same with Putty.

Having already setup the other systems, I knew I needed a key to add to the authorized_keys file on the remote system, and by looking at Putty I knew I needed a private key file.

I tried using ssh-keygen on the Ubuntu system to generate keys, but the format used for the private key was different looking than the file format of the PPK file Putty was looking for.

In order to get the key pairs I needed a tiny utility called puttygen from the Putty downloads page.


Here is what the interface looked like. I left everything default and clicked Generate.

After moving my mouse around to generate randomness while it generated a new pair of keys I clicked the Save Private Key button, selected yes when asked if I wanted to save the key without a passphrase, then selected the place I wanted to store the PPK file.

Next I copy and pasted the public key from the text area that showed up above the buttons and below where it says Public key for pasting into OpenSSH authorized_keys file, into my authorized_keys file on the remote system via nano in an open SSH session.

After closing Puttygen I closed my existing SSH session out and re-opened Putty to be presented with the settings dialog.


I entered my username in the Connection -> Data -> Autologin Username field as shown here.

Then I selected the PPK file I saved earlier in the Connection -> SSH -> Auth screen.

Viola! Autologin to Ubuntu via SSH using Putty worked like a charm.

Ubuntu SSH Autologin

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I've got a small network of Ubuntu computers at home and only one has a monitor. The rest I manage with SSH, FTP, and XDMCP logins.

Entering my password every time I want to get a terminal for one of the remote systems isn't very fun because my passwords are upwards of 16 characters. So I needed a way to login with SSH without needing to type a password.

On my main system, the one with the monitor, I used ssh-keygen at the terminal to generate a pair of public and private keys. By default ssh-keygen wants to create key files named id_rsa and id_rsa.pub but I decided to use home-network for my key files instead so I know what these ones are for.

I also just pressed enter for the passwords to leave them blank.

user@main-computer:~/Desktop$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/user/.ssh/id_rsa): /home/user/.ssh/home-network
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/user/.ssh/home-network.
Your public key has been saved in /home/user/.ssh/home-network.pub.
The key fingerprint is:
00:00:00:00:00:00:00:00:00:00:00:00:00:00:00:00 user@main-computer
The key's randomart image is:
+--[ RSA 2048]----+
|                 |
+-----------------+
user@main-computer:~/Desktop$

Once that was done I opened my FTP application and navigated the local and remote file lists to the following directory.

/home/user/.ssh/

I uploaded home-network.pub to the remote system and renamed it to authorized_keys so that on the remote system I had the following.

/home/user/.ssh/authorized_keys

If that file already existed on the remote system, I would have opened both files in my text editor and copied the contents of the *.pub file into that authorized_keys file.

Once everything was saved and uploaded I fired up SSH to login to the remote system and was logged in without needing to enter my password.