Purdue University

SSH Keys

Link to section 'General overview' of 'SSH Keys' General overview

To connect to Anvil using SSH keys, you must follow three high-level steps:

1. Generate a key pair consisting of a private and a public key on your local machine.
2. Copy the public key to the cluster and append it to $HOME/.ssh/authorized_keys file in your account.
3. Test if you can ssh from your local computer to the cluster directly.

Detailed steps for different operating systems and specific SSH client software are given below.

Link to section 'Mac and Linux:' of 'SSH Keys' Mac and Linux:

1. Run ssh-keygen in a terminal on your local machine.

   localhost >$ ssh-keygen
   Generating public/private rsa key pair.
   Enter file in which to save the key (localhost/.ssh/id_rsa):
   

   You may supply a filename and a passphrase for protecting your private key, but it is not mandatory. To accept the default settings, press Enter without specifying a filename.
   Note: If you do not protect your private key with a passphrase, anyone with access to your computer could SSH to your account on Anvil.

   Created directory 'localhost/.ssh'.
   Enter passphrase (empty for no passphrase):
   Enter same passphrase again:
   Your identification has been saved in localhost/.ssh/id_rsa.
   Your public key has been saved in localhost/.ssh/id_rsa.pub.
   The key fingerprint is:
   ... 
   The key's randomart image is:
   ...
   

   By default, the key files will be stored in ~/.ssh/id_rsa and ~/.ssh/id_rsa.pub on your local machine.

2. Go to the ~/.ssh folder in your local machine and cat the key information in the id_rsa.pub file.

   localhost/.ssh>$ cat id_rsa.pub
   ssh-rsa XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
   XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX= localhost-username@localhost
   

3. For your first time login to Anvil, please log in to Open OnDemand ondemand.anvil.rcac.purdue.edu using your ACCESS username and password.

4. Once logged on to OnDemand, go to the Clusters on the top toolbar. Click Anvil Shell Access and you will be able to see the terminal.

   

   =============================================================================
   ==                    Welcome to the Anvil Cluster                         ==                                            
   ……               
   =============================================================================
   
   **                        DID YOU KNOW?                                    **
   ……
   *****************************************************************************
   
   x-anvilusername@login04.anvil:[~] $ pwd
   /home/x-anvilusername
   

5. Under the home directory on Anvil, make a .ssh directory using mkdir -p ~/.ssh if it does not exist.
   Create a file ~/.ssh/authorized_keys on the Anvil cluster and copy the contents of the public key id_rsa.pub in your local machine into ~/.ssh/authorized_keys.

   x-anvilusername@login04.anvil:[~] $ pwd
   /home/x-anvilusername
   
   x-anvilusername@login04.anvil:[~] $ cd ~/.ssh
   
   x-anvilusername@login04.anvil:[.ssh] $ vi authorized_keys
   
   # copy-paste the contents of the public key id_rsa.pub in your local machine (as shown in step 2) to authorized_keys here and save the change of authorized_keys file. Then it is all set! #
   

6. Test the new key by SSH-ing to the server. The login should now complete without asking for a password.

   localhost>$ ssh x-anvilusername@anvil.rcac.purdue.edu
   =============================================================================
   ==                    Welcome to the Anvil Cluster                         ==
   ...
   =============================================================================
   x-anvilusername@login06.anvil:[~] $
   

7. If the private key has a non-default name or location, you need to specify the key by ssh -i my_private_key_name x-anvilusername@anvil.rcac.purdue.edu.

Link to section 'Windows:' of 'SSH Keys' Windows:

PuTTY:

1. Launch PuTTYgen, keep the default key type (RSA) and length (2048-bits) and click Generate button.

   

2. Once the key pair is generated:

   Use the Save public key button to save the public key, e.g. Documents\SSH_Keys\mylaptop_public_key.pub

   Use the Save private key button to save the private key, e.g. Documents\SSH_Keys\mylaptop_private_key.ppk. When saving the private key, you can also choose a reminder comment, as well as an optional passphrase to protect your key, as shown in the image below. Note: If you do not protect your private key with a passphrase, anyone with access to your computer could SSH to your account on Anvil.

   

   From the menu of PuTTYgen, use the "Conversion -> Export OpenSSH key" tool to convert the private key into openssh format, e.g. Documents\SSH_Keys\mylaptop_private_key.openssh to be used later for Thinlinc.

3. Configure PuTTY to use key-based authentication:

   Launch PuTTY and navigate to "Connection -> SSH ->Auth" on the left panel, click Browse button under the "Authentication parameters" section and choose your private key, e.g. mylaptop_private_key.ppk

   

   Navigate back to "Session" on the left panel. Highlight "Default Settings" and click the "Save" button to ensure the change is in place.

4. For your first time login to Anvil, please log in to Open OnDemand ondemand.anvil.rcac.purdue.edu using your ACCESS username and password.

5. Once logged on to OnDemand, go to the Clusters on the top toolbar. Click Anvil Shell Access and you will be able to see the terminal.

   

   =============================================================================
   ==                    Welcome to the Anvil Cluster                         ==                                            
   ……               
   =============================================================================
   
   **                        DID YOU KNOW?                                    **
   ……
   *****************************************************************************
   
   x-anvilusername@login04.anvil:[~] $ pwd
   /home/x-anvilusername
   

6. Under the home directory on Anvil, make a .ssh directory using mkdir -p ~/.ssh if it does not exist.
   Create a file ~/.ssh/authorized_keys on the Anvil cluster and copy the contents of the public key id_rsa.pub in your local machine into ~/.ssh/authorized_keys.

   x-anvilusername@login04.anvil:[~] $ pwd
   /home/x-anvilusername
   
   x-anvilusername@login04.anvil:[~] $ cd ~/.ssh
   
   x-anvilusername@login04.anvil:[.ssh] $ vi authorized_keys
   
   # copy-paste the contents of the public key id_rsa.pub in your local machine (as shown in step 2) to authorized_keys here and save the change of authorized_keys file. Then it is all set! #
   

   and copy the contents of public key from PuTTYgen as shown below and paste it into ~/.ssh/authorized_keys. Please double-check that your text editor did not wrap or fold the pasted value (it should be one very long line).

    

   

7. Test by connecting to the cluster and the login should now complete without asking for a password. If you chose to protect your private key with a passphrase in step 2, you will be prompted to enter the passphrase when connecting.