Opened 8 months ago

Closed 6 months ago

#3331 closed defect (answered)

X DISPLAY lost on PUMA after some time

Reported by: pmcguire Owned by: um_support
Component: PUMA Keywords: Xwindows, PUMA, JASMIN
Cc: Platform: PUMA
UM Version:


Hi CMS Helpdesk
I am logging in to PUMA directly from my Mac, with ssh. I start jobs on PUMA to run on ARCHER and I study the output on JASMIN by ssh'ing from PUMA to JASMIN. The problem I am having is that my Xwindows dies periodically (with DISPLAY not found), and the easiest way to fix this is to log out of PUMA and ssh again to PUMA.

How can I fix this more permanently?

Normally before, I was doing Xwindows on JASMIN by using the University of Reading VPN, and logging in to JASMIN directly from my Mac, when logged in to the VPN. I don't remember having these Xwindows issues so often when I was doing it this way.

But I have to turn off the VPN now, to log in to PUMA, so that I can monitor my UM jobs on ARCHER from PUMA. I can't log in to PUMA from my Mac with the VPN on (this is a known issue right now). Therefore, I can't use the VPN at the same time (as I am logged in to PUMA) to log in to JASMIN (jasmin-sci1) without going through PUMA.

Right now, the VPN is down anyways, so I can't do Xwindows on JASMIN without going through PUMA. But on PUMA, the Xwindows stops working after 5-20 minutes. (The exact time period is not known to me, or even if there is an exact time period). I can check that the Xwindows is not working for both my Mac→PUMA connection and my Mac→PUMA→jasmin-sci1 connection by trying to start xclock.

Any suggestions or help would be much appreciated.
Patrick McGuire

Change History (7)

comment:1 Changed 8 months ago by ros

Hi Patrick,

It's not going to be much help but I ssh direct from my Mac to PUMA and don't get any problems with XWindows dying on PUMA at all. I've not done anything special to my knowledge. I very rarely run Xwindows on JASMIN so can't comment on that part.

I'm using macOS 10.15.5 & XQuartz 2.7.11


comment:2 Changed 8 months ago by pmcguire

Thanks, Ros:
I am using the same versions of the !macOS and !XQuartz.
Is there any chance of getting PUMA fixed sometime soon by IT so that I can use it when I have the VPN on?
That way, I can go direct from my Mac to JASMIN with the VPN on, and maybe I won't have the Xwindows problem since I won't need to go through PUMA.

comment:3 Changed 8 months ago by jeff

Hi Patrick

Have you tried using act-ssh to login into jasmin? See here


comment:4 Changed 8 months ago by andy

Hi Patrick,

There have been issues with the Reading VPN and logging into PUMA for some time that IT haven't managed to get to the bottom of. Do you have server keep alives in your .ssh/config file on both your laptop and PUMA:

Host *

ForwardX11 yes
ForwardAgent? yes
ServerAliveInterval? 30

The last line sends a keep alive signal every 30 seconds and is one that seems to help a lot in not losing sessions. You shouldn't need to be on the VPN to login PUMA and to jasmin. You can use the jasmin ssh keys direct from your laptop to login to as this doesn't require a address.


comment:5 Changed 7 months ago by pmcguire

Hi Andy & Jeff & Ros
I tried Andy's suggestion, adding or adapting those three lines. Previously, my ServerAliveInterval was 120 instead 30.
But that didn't help. I logged in to PUMA and started an xclock. This worked. Some time later, I closed the xclock, and tried to start another xclock, but the !XWindows had failed and the 2nd xclock failed to start, citing a lack of DISPLAY variable. There was no extra logging into JASMIN from PUMA in this test.

I haven't tried Jeff's suggestion yet of using act-ssh. Maybe I will find some time soon to try that.

Unless things have changed, I often need to use jasmin-login1 instead of jasmin-login2, since jasmin-login1 allows much better access to file transfer from JASMIN to/from my !Mac. That's why one reason I use the VPN. But I can't use the VPN and PUMA at the same time.

comment:6 Changed 7 months ago by pmcguire

I have found a decent temporary solution.
When I am using the VPN, I can first ssh to jasmin-sci1 (via jasmin-login1). And then from there, I can ssh to puma. When I do this, the !XWindows doesn't die on puma, and I have access to both jasmin-sci1 and puma.

comment:7 Changed 6 months ago by ros

  • Resolution set to answered
  • Status changed from new to closed
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