Error in <RootX11IOErrorHandler>: fatal X11 error (connection to server lost?!) during nohup


ROOT Version: 6.04
Platform: Linux CentOS 6.4 (final)
Compiler: g++


I occasionally run into this X11 error after disconnecting from a session, while I have code running nohup’d in the background. As far as I understand nohup should be disconnecting stdout and stderr, so something like this should not happen. Is this a known problem and potentially has a known solution that would be great.

I suspect it might happen while writing TCanvas() objects, but I have set batch mode to true so it does not interact at all with X11, I would think?

Thanks,
-Alex

May be you can find some help with these posts:


https://root.cern.ch/root/roottalk/roottalk01/2640.html

It works sometimes, just not all the time. The bigger the job, the more likely that it crashes from what I have ascertained. I can’t pin down a clear pattern otherwise. I can try screen and see if it works

edit – Screen also throws X11 errors, the same ones.

You should definitely not get X11 errors in batch mode! Could you send us a reproducer? In general, libX11 (and libGX11TTF.so / libGX11.so) must not be loaded. You could check the output of gSystem->GetLibraries() and look for X11.

Hi Axel,

I can’t actually consistently reproduce this at all. It is buried in a larger multiprocessing pool based steering macro and I have never managed any reproduction, much less a minimal case.

I will try to check gSystem.GetLibraries() at various stages of the program see where X11 is missing! Is it possible that gROOT is changing settings in a wider (or shallower) scope that one might naively expect in a python script?

Thanks,
-Alex

Hi Alex,

The contrary - libX11-related libraries should not be loaded in batch mode. PyROOT is expected to obey the batch mode, too, and should not trigger loading of X11 libraries either.

Cheers, Axel

Hi Axel,

Okay! I will check to make sure they are not loaded.

Thanks,
-Alex

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