Text-mode access using PuTTY#

Prerequisite#

To access KU Leuven clusters, only an approved VSC account is needed.

To access clusters hosted at these sites, you need a public/private key pair of which the public key needs to be uploaded via the VSC account page.

Connecting to the VSC clusters#

When you start the PuTTY executable ‘putty.exe’, a configuration screen pops up. Follow the steps below to setup the connection to (one of) the VSC clusters.

Warning

In the screenshots, we show the setup for user vsc98765 to the genius cluster at KU Leuven via the login node login.hpc.kuleuven.be. You will have to

  1. replace vsc98765 with your own VSC user name, and

  2. find the name of the login node for the cluster you want to login in on in the sections on the local VSC clusters, and replace login.hpc.kuleuven.be accordingly.

  • Within the category ‘Session’, in the field ‘Host Name’, type in a valid hostname of the login node of the VSC cluster you want to connect to.

    ../_images/text_mode_access_using_putty_01.png

  • In the category Connection > Data, in the field ‘Auto-login username’, put in <vsc-account>, which is your VSC username that you have received by mail after your request was approved.

    ../_images/text_mode_access_using_putty_02.png

  • Based on the destination VSC site that you want to login to, choose one of the tabs below and proceed.

    Select the SSH > Auth > Credentials’ tab, and remove any private key from the box ‘Private key file for authentication’.

    putty private key

    In the category Connection > SSH > Auth, make sure that the option ‘Attempt authentication using Pageant’ is selected. It is also recommended to enable agent forwarding by ticking the ‘Allow agent forwarding’ checkbox.

    ../_images/text_mode_access_using_putty_03.png

    In the category Connection > SSH > Auth > Credentials, click on ‘Browse’, and select the private key that you generated and saved above.

    ../_images/text_mode_access_using_putty_04.png

    Here, the private key was previously saved in the folder C:\Users\Me\Keys. In older versions of Windows, you would have to use C:\Documents and Settings\Me\Keys.

  • In the category Connection > SSH > X11, click the ‘Enable X11 Forwarding’ checkbox:

    ../_images/text_mode_access_using_putty_05.png

  • Now go back to the ‘Session’ tab, and fill in a name in the ‘Saved Sessions’ field and press ‘Save’ to permanently store the session information.

  • To start a session, load it from Sessions > Saved Sessions, and click ‘Open’.

    putty_load_saved_session

    You will be then prompted to copy/paste the firewall link into your browser and complete the Multi Factor Authentication (MFA) procedure. With PuTTY, users only need to highlight the link with their mouse in order to copy it to the clipboard.

    PuTTY MFA URL

    Then, with the right-click from your mouse or CTRL-V, you can paste the MFA link into your browser to proceed with the authentication.

    Now pressing ‘Open’ should ask for your passphrase, and connect you to <vsc-loginnode>.

The first time you make a connection to the login node, a Security Alert will appear and you will be asked to verify the authenticity of the login node.

../_images/text_mode_access_using_putty_06.png

For future sessions, just select your saved session from the list and press ‘Open’.

Managing SSH keys with Pageant#

At this point, we highly recommend setting up an SSH agent. A widely used SSH agent is Pageant which is installed automatically with PuTTY.

Pageant can be used to manage SSH keys and certificates for multiple clients, such as PuTTY, WinSCP, FileZilla, as well as the NX client for Windows so that you don’t need to enter the passphrase all the time.

Proxies and network tunnels to compute nodes#

Network communications between your local machine and some node in the cluster other than the login nodes will be blocked by the cluster firewall. In such a case, you can directly open a shell in the compute node with an SSH connection using the login node as a proxy or, alternatively, you can also open a network tunnel to the compute node which will allow direct communication from software in your computer to certain ports in the remote system. This is also useful to run client software on your Windows machine, e.g., ParaView or Jupyter notebooks that run on a compute node.

Troubleshooting PuTTY connection issues#

If you have trouble accessing the infrastructure, the support staff will likely ask you to provide a log. After you have made a failed attempt to connect, you can obtain the connection log by

  1. right-clicking in PuTTY’s title bar and selecting Event Log.

  2. In the dialog window that appears, click the Copy button to copy the log messages. They are copied as text and can be pasted in your message to support.