Unable to find free display number when starting session

ThinLinc
1

When trying to connect via either the native OS X client or the web service, thinlinc denies access with the following message:

==> vsmagent.log <==
2025-05-14 21:42:38 WARNING vsmagent.session: Unable to find free display number when starting session for kbendl. Reporting to VSM server
2025-05-15 13:20:44 WARNING vsmagent.session: Unable to find free display number when starting session for kbendl. Reporting to VSM server
2025-05-15 13:23:02 WARNING vsmagent.session: Unable to find free display number when starting session for kbendl0. Reporting to VSM server

The user can ssh directly to the box. This appears to have come about after an upgrade.

It seems like an issue with the wondiw manager or VNC, so I tried re-installing mate-session-manager. No difference.

Side note: There are 5 hosts with agents in the cluster {02..06}, however it appears thinlinc like two of them more and only tries to commit users to 03 and 04.

Any ideas what I might look for? It’s seems like it might be the whole desktop env might be borked, post-patching.

2

Hi @kurtb.nrel,

That’s a strange one. Is this same problem happening on all agents?

It seems unlikely that you would have actually run out of display numbers, but you can check by doing something like ps aux | grep Xvnc and seeing how many processes there actually are.

Another thing to check might be your SELinux or AppArmor logs, if you have this enabled. You ould also just try disabling it temporarily and see if it resolves the problem.

Regarding the distribution of sessions across agents, the next version of ThinLinc (4.19.0) due out in a couple of months will include a bunch of changes to the load balancer. So my advice here would be to wait for the next release and see if that improves things :slight_smile:

3

It might also be worth checking that something isn’t wrong with the /tmp directory. E.g. permissions, or out of space. X11 displays need to create several files there.