Cannot detect any display running. Do you want NoMachine to create a new display

[Pit]

Hello

I did upgrade NoMachine on my remote machine from version 7.10.1_1 to 8.2.3_4.
Unfortunately I am no longer able to open a physical remote session to my server.
The error message says “Cannot detect any display running. Do you want NoMachine to create a new display and proceed to connect to the desktop?”.
Before the upgrade I did not face this issue.

The remote machine is a desktops with RHEL 7.6 installed.

I did several upgrades, uninstall, re-installes etc. but no change in the behavior of nomachine. I did also use different local machines, once Linux desktop with RHEL 7.6 and once a Microsoft Windows 10 client. But non of the scenario did change the behavior in any case.

If I reinstall the older 7.9.2_1 version all works fine again.

Do you have any advice for me of how to debug or even fix this issue?

Many thanks

Kind regards,
Peter

Attachments:

1. NoMachine-log-2022.12.13-13.59.01.zip

[Britgirl]

Hi, ideally we would need to see logs with debug enabled on the server machine if that’s possible (with v8 installed).

Please follow the instructions here and submit the logs to forum[at]nomachine[dot]com.

https://kb.nomachine.com/DT11R00182, section “First Step: Enable Debug Level on the Problematic Host” and then proceed with the other steps.

Thanks!

[Pit]

Hello

Please find the the requested logs attached.

Kind regards,

Peter

Attachments:

1. NoMachine-log-2022.12.14-08.42.53.zip

[Britgirl]

Apologies, I didn’t specify that the server must be restarted in order for the debug we need to be logged. Please resubmit at your earliest convenience.

We did also check on the fly to see if we can reproduce your issue, but were not able to.

[Pit]

Hello

I did reproduce the logs, this time with a restart of the nxserver before trying to connect

Kind regars,

Peter

 

Attachments:

1. NoMachine-log-2022.12.14-14.18.53.zip

[Britgirl]

In the logs we see the following server.cfg key is empty, when it should not be: AvailableSessionTypes.

What should be written there is ‘physical desktop’. Without this, no display can be started. Why it’s empty for your v8 installation, but not for v7 is not clear since we cannot reproduce this behaviour. Please check your server.cfg file has AvailableSessionTypes physical-desktop indicated. Then restart the NoMachine server.

Further reference:

The server.cfg and node.cfg files explained
https://kb.nomachine.com/AR02N00877

point (2) about the ‘AvailableSessionTypes’ key

The AvailableSessionTypes key is present in both server.cfg and node.cfg and permits to define which types of session will be made available to end-users. When server.cfg and node.cfg are on the same host, the list of session types must be the same in both keys. These keys are automatically populated at installation time. If a new session type is added later, they have to be edited manually. Restart the server to make this change effective.

 

 

[Pit]

Hello

Indeed. In our file /usr/NX/etc/server.cfg the variable “AvailableSessionTypes” was empty.

I changed it to “AvailableSessionTypes unix-remote,unix-console,unix-default,unix-application,physical-desktop,shadow,unix-xsession-default,unix-gnome,unix-xdm,windows,vnc” and it works fine again.

How come the variable “AvailableSessionTypes” was empty? Well it is the 1st time that we were using /usr/NX/etc/server-redhat.cfg.sample as the base for our server.cfg file. But I did not realize that “AvailableSessionTypes” was empty in the sample.

Many thanks for your support!

Kind regards,
Peter

[Author]

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