[X2Go-Dev] Bug#1117: Bug#1117: x2goclient "stuck session" for select users that cannot be resumed or terminated

[Jordan Poppenk]

Dear Stephan,

Thanks for your quick help and suggestions! 

The session listing commands you mentioned didn’t reveal the users’ sessions. 
But while I was investigating those ideas, I was advising my users to try using 
an ssh -X session in an xquartz terminal as a workaround. that produced similar 
errors as were being reported in x2go (X11 connection rejected because of wrong 
authentication). Even when attempting to log onto the server in person using 
their user accounts, they were booted back to the login screen. So the problem 
was clearly outside of x2go.

I googled this new but related X11 message, and noticed it was sometimes 
associated with users having exceeded their disk quotas:
https://www.cyberciti.biz/faq/x11-connection-rejected-because-of-wrong-authentication/

This was the problem! I have home folder quotas, and the users had neglected 
our server rules and were saving large image files to their documents folder 
rather than our data volume. With quota enforced on their home folders, x11 and 
x2go were unable to write any of the files needed for authentication. This 
manifests as an “authentication error” even though this is a red herring. I 
will now know what to check if I see this error again for specific users.

I’m guessing this arises because a server can’t reveal errors during 
authentication for security reasons, so there's no way for a client to know 
whether there’s free disk space on the server until it has successfully 
authenticated. This likely means there's nothing an x2go client can do to know 
this was the problem, but perhaps it would be worth considering a helpful 
suggestion in this error that the problem *could* be attributable to 
insufficient disk space in the user’s home folder on the host machine?

As for brains: it's thoughtful of you to make these suggestions, although I’m 
afraid I'm not a radiologist or clinician, just a brain scientist who likes to 
use the interface for persistent matlab desktop sessions and running numbers. 
We do have quite a few users, so you'd be forgiven for thinking my lab was an 
outfit with actual resources, but all are students and we operate on a 
shoestring :-)  This just makes us all the more grateful for your development 
efforts.

Cheers,
Jordan
 

Jordan Poppenk, Ph.D.
Canada Research Chair in Cognitive Neuroimaging
Department of Psychology and Centre for Neuroscience Studies
Queen's University
http://popmem.com
613-533-6009

 

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[X2Go-Dev] Bug#1117: x2goclient "stuck session" for select users that cannot be resumed or terminated

[Jordan Poppenk]

Package: x2goclient (mac)
Version: 4.0.5.2

Above is my best guess as to the affected package, although I am not certain it 
is on the client end. Also, my issue is similar to the one reported here:
http://lists.x2go.org/pipermail/x2go-dev/2015-October/010734.html
...but that thread concludes without a solution that works for me.

x2go had been working for a dozen users of my server. One day, two of the users 
reported that they were no longer able to log in -- they were kicked back to 
the login screen after entering their ssh private key encryption password. 
After entering this, the users get the result: 
- Session: Session session started at: (date)
- Warning: Protocol mismatch or no X authentication data.
- Session: Terminating session at (date)
- Info: Your session was closed before reaching a usable state.
- Info: This can be due to the local X server refusing access to the client.
- Info: Please check authorization provided by the remote X application.
- Session: Session terminated at (date)
Sometimes, they are presented with a list of sessions that shows their 
"running" session. It allows them to terminate the session, then brings them 
back to the screen where they would terminate the session.

It is worth noting that their configuration was previously working. Also, I am 
sometimes able to fix issues like this by deleting the user's .Xauthority 
files, their .x2go folder, and their cache/lxsession folder; and rebooting. In 
this case, none of these things influenced the outcome of their login attempts. 
But, many other users are still able to access x2go normally on the same 
machine.

Both affected users are using the mac x2goclient (4.0.5.2) with xquartz 2.7.9 
on OSX 10.11.6. On my server (running Ubuntu 16.04), x2goversion reports the 
following:
x2goagent: 3.5.0.32
x2godesktopsharing: 3.1.1.3
x2golxdebindings: 1.0.2.4
x2goserver: 4.0.1.19
x2goserver-extensions: 4.0.1.19
x2goserver-xsession: 4.0.1.19
It is worth noting that I sometimes experienced similar issues while still 
using Ubuntu 14.04.

A third user recently reported that after a crash that occurred after opening 
too many windows in her session, she started getting the same errors, which I 
have also been unable to resolve. Are you able to suggest any remedy? Where 
might the information about the "stuck session" live -- perhaps I could try 
deleting some session file that is stored on the user's machine?

Thank you in advance for any help you can offer, as well as your extremely 
helpful ongoing development of this portable desktop solution.

Cheers,
Jordan


Jordan Poppenk, Ph.D.
Canada Research Chair in Cognitive Neuroimaging
Department of Psychology and Centre for Neuroscience Studies
Queen's University
http://popmem.com
613-533-6009






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