SSH

SSH#

A plain SSH connection is a text-based terminal session to a KLC node — the fastest of the connection options, and the one that pairs most naturally with scripts, scheduled jobs, and version-controlled code.

Mac Instructions#

Mac computers come with the Terminal program already installed as a standard program.

To create a “plain” (not graphical) connection to a specific KLC node (for instance KLC0202), you would simply open Terminal and type:

ssh your-netid@klc0202.quest.northwestern.edu

If you prefer a graphical (X11) interface, just add the -Y option:

ssh -Y your-netid@klc0202.quest.northwestern.edu

Occasionally you might receive an error that says something like “host key verification failed.” Most of the time, you can fix these problems by deleting your host key file and trying again:

rm ~/.ssh/known_hosts

Note

Depending on the version of your Mac, you might need to install the free XQuartz application before X11 forwarding will work.

Windows Instructions#

Windows 10 and later come with an SSH client built in, so there’s nothing to install for a plain-text connection. Open PowerShell and type:

ssh your-netid@klc0202.quest.northwestern.edu

Occasionally you might receive an error that says something like “host key verification failed.” Most of the time, you can fix these problems by deleting your host key file and trying again:

Remove-Item ~\.ssh\known_hosts

Note

PowerShell’s built-in SSH client doesn’t include an X server, so it can’t display graphical (X11) applications. If you need a graphical interface, use KLC OnDemand or FastX instead — both are easier to set up on Windows than a third-party X11 SSH client.

If you still want a graphical (X11) interface, a saved session manager, or other conveniences PowerShell doesn’t offer, install a dedicated SSH client — MobaXterm is a popular choice with a solid free version. Note that support for MobaXterm is not provided by Research Support or KIS; consider the Pro version if you need technical help. Other options include SecureCRT, PuTTY, and Cygwin.

Common instructions for using these clients (may differ slightly for different clients):

  • In the Sessions menu, select SSH.

  • In Remote Host, give the address of the server (e.g. any KLC login node address: klc0202.quest.northwestern.edu)

  • Specify your NetID as the username.

  • Under Advanced SSH settings, check the box for X11-Forwarding if you want a graphical interface; leave it unchecked for a plain text interface.

  • If you work on remote servers regularly, you will find it convenient to save and label a set of commonly used sessions.

Passwordless SSH Login#

Passwordless SSH login allows you to securely access remote servers without typing your password each time. It uses SSH key pairs (public/private keys) for authentication instead of passwords.

Benefits:

  • Convenience: No need to repeatedly enter passwords when logging in or running automated tasks.

  • Security: Stronger authentication using cryptographic keys, reducing the risk of brute-force attacks.

  • Automation: Essential for running scripts, transferring files, or syncing data across servers without manual intervention.

  • Faster access: Speeds up workflows for data analysis, code deployment, or managing remote jobs.

Video instructions

Text instructions:

  1. Generate an SSH key pair.

    Run the following command in the Terminal app on macOS or Command Prompt/PowerShell on Windows:

    ssh-keygen -t rsa

    After running this, two files are created in your ~/.ssh directory:

    File

    Description

    id_rsa

    Your private key — keep this secure and never share it

    id_rsa.pub

    Your public key — safe to share with servers

  2. Copy the public key id_rsa.pub to KLC.

    On macOS or Linux, run the following command in the Terminal:

    ssh-copy-id your_netid@klc0202.quest.northwestern.edu

    To add it manually (works for all OS):

    • On your local machine, open id_rsa.pub in a text editor and copy its contents.

    • Open an SSH session to KLC, and create the .ssh directory if it doesn’t exist:

      mkdir -p ~/.ssh

    • Then paste the contents of id_rsa.pub into the file:

      nano ~/.ssh/authorized_keys

  3. Update permissions on KLC.

    Open an SSH session to KLC and update permissions:

    chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

Bonus#