Using FastX for remote desktops

Using FastX via web browser | Using the FastX desktop client

3/26/2021: This page was revised to reflect changes related to the use of PBS Pro on the Casper cluster.

The FastX remote desktop service gives users access to Casper for performing lightweight tasks such as text editing, running programs such as xxdiff and ncview, or running analysis scripts that consume little in the way of graphics resources.

A user can log out of a FastX remote desktop and return to it later. This service will remain available while NCAR and UCAR building closures are in effect.

FastX sessions that consume excessive resources are subject to being killed. For resource-intensive workloads that do not require GPU-based rendering, consider starting a Casper job instead by running an execcasper command from a FastX terminal window. For more resource-intensive work with high-end, GPU-accelerated graphics, consider using the vncmgr script rather than FastX.

FastX can be accessed through a web browser or a desktop client. How to use both of these options is described below.

Using FastX via web browser

To use FastX without installing any software, connect to the NCAR VPN and use an updated version of any common browser. See the following section for an alternative to using the VPN.

  1. Connect to the NCAR VPN.
  2. Go to
  3. Authenticate with your username and token response.
  4. Click the + button in the upper-left corner of the FastX window.

    FastX window
  5. In the next window, click the KDE button and then Launch.

    FastX bookmarks window
  6. The KDE desktop will open in a new tab or a new browser window. Right-click on the desktop to start a Kconsole terminal window.

    KDE desktop

Some users will find that their terminal environment configuration is not complete (module commands will not be available, for example). To initialize your environment, run the following command once you open the Kconsole:

bash, ksh users: source /etc/profile
csh, tcsh users: source /etc/csh.login

If you want to retain your session to return to it later, just log out or kill the browser window. When you log in again, select the icon to re-open the session.

KDE icon

If you do not want to retain your session, terminate it as shown here before logging out:

Terminating session

Using FastX via web browser and ssh tunnel

If you are not connected to or do not want to connect to the NCAR VPN, you can still use FastX via web browser by creating an ssh tunnel from your laptop or desktop to

  1. Start by running the following on your command line, inserting your own username.
ssh -L -l username
  1. Authenticate as usual and you will be in a terminal session on a Casper node.
  2. Leave that terminal session running, open your browser, and go to https://localhost:3300/. You may see a warning about the site being unsafe, but ignore the warning and continue.
  3. Authenticate with your username and token response.
  4. Continue as described in the previous section to launch the KDE desktop.

Alternatives for creating ssh tunnel

To create a tunnel using PuTTY or SecureCRT, following the examples in these video demonstrations:

After creating the tunnel, proceed as described in the previous section.

Using the FastX desktop client

If you’re not connected to the NCAR VPN or prefer to use a faster, more robust remote desktop service, consider downloading and installing the FastX desktop client. Windows users: If you do not have admin privileges to install the client on your machine, choose the “Windows Nonroot” client.

  1. Start the FastX client.
  2. Click the + button in the upper-left corner.

    FastX connections panel
  3. Fill in the fields of the pop-up boxes as follows:

    User:    Enter your username
    Port:    22
    Name:  CISL remote desktop (or any string)
    Run (advanced tab):    /ncar/opt/fastx/latest/bin/fastx-protocol

    New ssh connection Edit connection advanced tab
  4. Click OK.
  5. Select the remote desktop collection (double-click or press Enter).
  6. Authenticate with your username and token response.
  7. Click the + button in the upper-left corner of the next window.

    Selecting the plus sign
  8. Select the KDE icon that displays startkde in the required command field.
    1. Double-click the icon to start the KDE desktop. You can then right-click on the desktop to get a Kconsole menu.

    2. Double-click the xterm icon instead to get a single xterm.

Starting KDE