How do I connect to Argo using X11 forwarding?

X11 forwarding allows users who have an account on a Unix server to open a connection to the X11 interface remotely from another computer. The communication between the systems is encrypted. In order to log in to Argo, you must use an SSH client, such as PuTTY, or the ssh command. 

X11 forwarding with the ssh command

To use X11 forwarding when using the ssh command, include the -X operand. For example:

ssh -X jsmith@argo.cc.uic.edu

Remember to include -X every time you want to connect.

X11 forwarding with PuTTY

To configure PuTTY to use X11 forwarding (the following assumes you have a existing Argo profile):

  1. From the main screen of the profile, click Tunnels in the lower left corner.
    PuTTY Configuration - Click Tunnels
  2. Check the box at the top labeled Enable X11 forwarding
    putty-configure-tunnels
  3. Click the Session menu at the top and save the altered profile
    putty-configure-save

It is important that you assign a new name to the modified Argo profile; a name that indicates that you are using X11 forwarding. In the above, I assigned the profile the name argo-withx11. You may use that name or one of your own selection. But, it is vital that you distinguish between a profile that uses X11 forwarding and one that does not.

DISPLAY variable

Once you connected to Argo, you must not change the environmental variable DISPLAY. The variable has the appropriate setting. When you don't use X11 forwarding, you must set the DISPLAY variable to the IP address or the fully qualified domain name of the machine running your X-server (your desktop or laptop). Examples:

export DISPLAY=128.248.5.192:0
export DISPLAY=jsmith.cc.uic.edu:0
setenv DISPLAY 128.248.5.192:0
setenv DISPLAY jsmith.cc.uic.edu:0

But, since you are using X11-Forwarding, you don't change the setting; SSH has already set it for you. If you do change it, some of the Argo software, such as GaussView, might not function correctly. To see the DISPLAY variable setting but not change it, use the echo command on Argo (don't forget the preceding dollar sign):

echo $DISPLAY

You should see the word localhost, a colon, a number, a period, and a zero. For example:

localhost:13.0

To confirm that your X-server is working with X11 forwarding, enter the following command on Argo:

xclock

Initially you will be prompted to confirm that it is okay to accept a connection from 127.0.0.1.

x11-allowconnection

x11-xclock

Important note: the IP must be 127.0.0.1. If so, click Yes. If a clock appears on the screen, then you know that X is working and is configured properly. If the IP is something other than 127.0.0.1, click No.

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Last updated: 

September 20, 2012

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