Suddenly unable to "create a new desktop or custom session"

[ggt-pcs]

Hello Forum,

we are using 2 NoMachine Workstation licenses on two Red Hat Enterprise Linux 7 since February 2017.

All of a sudden we are not able to “create a new desktop or custom session” any more. We are using this way in order to get a virtual desktop in the client’s screen resolution. When creating this new session, and:

a) specifying “run the console” we get a console window which works as expected.

b) specifying “Run the default X client script on the server” we get a window “Oh no! Something has gone wrong.”

Connecting to the physical display, however, works.

 

Any idea, what could be wrong?

Any logs, I could provide to debug this issue?

 

 

Software versions
———————-

NoMachine Enterprise Client 5.2.11 running on Windows Server 2012 R2

NoMachine Workstation 5.3.9-8.x86_64 running on Red Hat Enterprise Linux Server release 7.3 (Maipo) (GNOME)

 

kind regards,

Thorsten

 

[kroy]

Which Desktop Environment do you use on that server? Can you try “Create a new virtual desktop” (not “Create a new custom session”) and check that it works?

Node keys DefaultDesktopCommand and DefaultXCommand are responsible for starting -in sequence – a new virtual desktop and default X client script.

Can you paste here the output of the command:

grep -E “DefaultDesktopCommand|DefaultXCommand” /usr/NX/etc/node.cfg

[ggt-pcs]

Hi,

• we’re using the RHEL default Desktop Environment (gnome-desktop3-3.14.2-2.el7.x86_64)
• creating a “new virtual desktop” works but there seems to be the issue that “user elevation” does not work. When opening Settings -> Users I cannot activate the “unlock” button (ref. attachment “RHEL_NX_User__not_unlockable.png”)
  When opening a new custom session (in client resolution) or connecting to physical desktop, this is possible. (ref. attachment RHEL_NX_User_unlockable.png from connection to physical desktop)
•  grep -E “DefaultDesktopCommand|DefaultXCommand” /usr/NX/etc/node.cfg
  DefaultDesktopCommand “/etc/gdm/Xsession ‘gnome-session –session=gnome'”

Hope this helps 🙂

Attachments:

1. 

   RHEL_NX_User__not_unlockable.png
   

2. 

   RHEL_NX_User_unlockable.png
   

[kroy]

creating a “new virtual desktop” works but there seems to be the issue that “user elevation” does not work.

It’s not an issue. User which is not in the sudo group shouldn’t be allowed to change system settings. Are you sure that custom session was ran as user which wasn’t belong to sudo group? If yes – can you paste here command which was executed to start that custom session?

Excuse my mistake. I wrote wrong key in previous post. It should be DefaultXSession. Can you paste here output of command:
grep DefaultXSession /usr/NX/etc/node.cfg? It looks that there is changed value to some not working command. Thats why “Run the default X client script on the server” fails.

[ggt-pcs]

Hi,

It’s not an issue. User which is not in the sudo group shouldn’t be allowed to change system settings. Are you sure that custom session was ran as user which wasn’t belong to sudo group? If yes – can you paste here command which was executed to start that custom session?

Both sessions were run as the user “a_garrth” as you can see in attached screenshots. a_garrth is member of the group “wheel”, which, in turn, has sudo privileges.
I’m not sure I get what you mean by ” can you paste here command which was executed to start that custom session?” Since the custom session will not start. Where would I find this information?

Can you paste here output of command:

grep DefaultXSession /usr/NX/etc/node.cfg
DefaultXSession "/etc/X11/xinit/Xsession default"

Attachments:

1. 

   RHEL_NX_physical_desktop.png
   

2. 

   RHEL_NX_virtual_desktop.png
   

[kroy]

Thanks for the report. We will try to fix problem as soon as it’s possible.

About your question with the custom session in your previous post you wrote “When opening a new custom session (in client resolution) or connecting to physical desktop, this is possible”.

Can you point to exactly which option in nxplayer you used during the creation of a new custom session that you have possibility to activate “unlock” button inside?

[ggt-pcs]

kroy wrote:

Can you point to exactly which option in nxplayer you used during the creation of a new custom session that you have possibility to activate “unlock” button inside?

I’m sorry but currently I cannot accommodate your request since I am unable to create a custom session. This was the original reason for opening this topic. If you can show me how to get it working again (“create a new session”) I’ll be happy to provide you with any debug information you need.

 

 

[kroy]

Logs will be necessary. Please remove .xsession-error (in home directory user a_garrth, if you are trying on the same user), enable logs and restart nxserver (sudo /usr/NX/bin/nxserver --restart). If you are able to reproduce problem with not working custom session, collect logs and send them to forum[at]nomachine[dot]com. Instructions about debug and collecting logs you can find there: https://www.nomachine.com/DT07M00098.

[ggt-pcs]

Logs have been sent with the following subject “NoMachine issue “Suddenly unable to “create a new desktop or custom session”  #15474 — requested logs”

[ggt-pcs]

Forgot to attach the .xsession-errors. Please find output below:

 

$ cat .xsession-errors

xrandr: Failed to get size of gamma for output default

xrandr: Failed to get size of gamma for output default

xrandr: cannot find output “VGA-0”

xrandr: Failed to get size of gamma for output default

warning: output VGA-0 not found; ignoring

gnome-session-is-accelerated: No composite extension.

gnome-session-check-accelerated: Helper exited with code 256

gnome-session-is-accelerated: No composite extension.

gnome-session-check-accelerated: Helper exited with code 256

 

** (process:44883): WARNING **: software acceleration check failed: Child process exited with code 1

 

[kroy]

You need to try to start the custom session specifying “Run the default X client script on the server” and “Run the command in a virtual desktop”.

Option “Run the command in a floating window” won’t work because it looks that your version of Gnome uses Composite Extension which is not available in the rootless session.

[JoeD]

Did you ever find a solution to this? We’re having the same problem.

Thanks!

-Joe

[Britgirl]

Are you getting exactly the same error messages as originally reported?

[ggt-pcs]

Hi, this is OP:

I have debugged quit a lot and have some information to share and some problems still remaining.

i) Information about physical setup: Two DELL Servers R720 running RHEL 7.4. Both servers are connected to a Raritan KVM switch and a Raritan rackmounted monitor.

ii) There was a problem with the screen resolution if the server was restarted while not connected to the monitor. Screen resolution was way off. This problem was solved by using xrandr and adding the modelines to a config file in /etc/X11/xorg.conf.d.

iii) After rebooting both servers and verifying that they have full HD resolution regardless of their connection state to the monitor, NoMachine NX was running much more stable.

iv) I also uninstalled and reinstalled the package nomachine-workstation-5.3.9-8.x86_64 on both servers.

v) Now, when logging on to server-A after choosing “Create a new desktop or custom session” -> “Create a new custom session” -> “Run the default X client script on the server” + “Run the command in a virtual desktop”  and the display “Creating a new custom session” I see a black screen for aprox. 60 seconds with a popup from NX in the upper right corner “User a_garrth connected”. After aprox. 60 seconds the virtual session is displayed and I have the problem stated above (no user name displayed in Logout dialogue, unable to perform elevation (cannot create users)..

vi) during the same on server-B until “and the display “Creating a new custom session” I get the virtual session after aprox. 7 seconds and my name is displayed under “Logoff” as well as user elevation works.

 

BTW: I had rather poor performance in NX (not much better then VNC) because the machine running the NX client is also a DELL server without a dedicated GPU. After googleing I found the notice that I should copy ffmpeg into the program directory of NX Client. Now the performance has really improved — however I’m still stuck with VP8 instead of H.264 even though ffmpeg is installed on the client and NoMachine Workstation should include H.264 encoder.

Any thought about this? Will try to install a dedicated GPU on that server next week to see if this helps.

Any help / tips about solving the user elevation problem on server-A would be appreciated.

kind regards,

ggt-pcs

[kroy]

There was a problem with the screen resolution if the server was restarted while not connected to the monitor. Screen resolution was way off. This problem was solved by using xrandr and adding the modelines to a config file in /etc/X11/xorg.conf.d.

It depends on the OS. NoMachine does not modify the list of available resolutions on the system.

About point v) – is the same situation taking place when you try to “Create a new virtual session”?

…however I’m still stuck with VP8 instead of H.264 even though ffmpeg is installed on the client and NoMachine Workstation should include H.264 encoder.

Do you have the evaluation of Workstation installed or did you purchase a subscription? AVC Pack is not available as evaluation (https://www.nomachine.com/AR10K00706), but installing the libraries and codecs to enable H.264 by hand is possible:

http://www.nomachine.com/AR10K00696 for client side
https://www.nomachine.com/AR09M00863 for server side

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