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Generating and Configuring SSH Key Pairs

Follow the steps below to configure  a new SSH key pair in anticipation of accessing a cluster with SSH. Once you have generated and configured your SSH key pair for the cluster, you do not have to do this step each time.

Note: These instructions are written generally for OpenSSH and some programs, such as VS Code, are not compatible with this configuration using alternative SSH solutions like PuTTY. 

Step 1 - Generate SSH Key Pair

First, you'll need to create and configure an SSH pair for each node you'll be connecting to, a great secure solution to connection. 

Open a Terminal

Open a terminal based on your operating system.

• Windows - Command Prompt or Git Bash
• MacOS or Linux - Terminal

Generate the SSH Key Pair

In the terminal, generate your SSH key pair with the following command. Be sure to give the key pair a comment that allows you to identify it. This could be your email address, netid, cluster name, etc.

# Example Key Generation
ssh-keygen -o -a 100 -t ed25519 -f ~/.ssh/id_ed25519 -C "<comment; ex.netid or email cluster-name>"

Next, you'll be prompted to choose a location to save the key pair. This will default to '~/.ssh/id_ed25519'. Be sure to notate if you choose another location. 

Finally, you will be prompted to set a passphrase. While this is not 'required', utilize a passphrase is highly encouraged to help keep your private key secure. If you prefer to not, simple hit 'Enter' to skip.

Step 2 - Add the SSH Public Key to the Cluster

Next, you'll need to add the public key to each node you intend to connect to using this method noting that you can certainly generate a new key for each node. 

Copy the Public Key

Begin by displaying and copying your key. 

To do so, use a corresponding terminal to display the public key so that you can copy it. 

# CMD
type %USERPROFILE%\.ssh\id_ed25519.pub

# Shell
cat ~/.ssh/id_ed25519.pub

Add the Public Key to the Login Node

Next, connect to the cluster and add the public key. Repeat this step for other nodes as needed. 

# Make the .ssh directory in your home directory
mkdir -p ~/.ssh

# Put the copied public key into your authorized_keys file
echo "your_copied_public_key" >> ~/.ssh/authorized_keys

# Ensure the .ssh locations have the correct permissions
chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

Step 3 - Configure SSH Connection

Lastly, you'll need to ensure your application is configured to make the SSH connection utilizing your new or existing SSH key pair. 

Either during connection prompt or when configuring, you'll need to know where your SSH configuration is saved. This is likely '~/.ssh/config' or 'C:\Users\<netid>\.ssh\config'. 

Next, be sure the information for your host has been given the appropriate notations including specifying the SSH key location to be used. 

# Example Global Settings for All Hosts
Host *
	User <your-netid>
	IdentityFile <your key location, ex. ~/.ssh/id_ed25519>
    AddKeysToAgent yes
    ForwardAgent yes
    ServerAliveInterval 180
    ServerAliveCountMax 3
    Protocol 2

# Example Specific Settings for an OrangeGrid and Zest Host
Host its-og-login1.syr.edu its-zest-login1.syr.edu
    HostName $h
    User <your-netid>
	IdentityFile <your key location, ex. ~/.ssh/id_ed25519>
    AddKeysToAgent yes
    ForwardAgent yes
    ServerAliveInterval 180
    ServerAliveCountMax 3
    Protocol 2

Be sure to save any configuration files if you've made any changes. 

4 - Connect to the SSH Host

Finally, connect to your host. Note that the passphrase will be needed at least once per session and you may be prompted in additional intervals depending on your ssh-agent. 

Getting Help

Question about Research Computing? Any questions about using or acquiring research computing resources or access can be directed at researchcomputing@syr.edu.