Could not create a virtual desktop on RHEL 8

[Karthik.V.M]

Hi,

My client is trying to log into RHEL 8 server via NoMachine from his Mac Laptop and he could not do so. After some initial investigations, it looks like it is a Kerberos issue but not fully sure. Any pointers on how to fix this issue is highly appreciated. Please find some logs below:

nxerror.log
……
……
96726 96726 13:15:42 470 RetrieveKerberosTicket: ERROR! Failed to readkerberos principal.
96726 96726 13:15:42 470 RetrieveKerberosTicket: ERROR! Kerberos error is -1765328189.
……
……

nxserver.log

97407 97407 2022-08-02 13:16:11 003.802 NXSERVER checkNodeCfg: denied services [] in node.cfg
97407 97407 2022-08-02 13:16:11 003.854 NXSERVER Services denied in node profile and deny on node: []
.......
.......
97407 97407 2022-08-02 13:16:11 144.675 NXSERVER User: mrazizad is NOT trusted on node: localhost:4000 and for user gdm.
97407 97407 2022-08-02 13:16:11 144.753 NXSERVER Physical desktop sharing is restricted by configuration.
97407 97407 2022-08-02 13:16:11 144.814 NXSERVER __checkFilterUserByFlags: user mrazizad cannot get access to desktop gdm [not ok]
97407 97407 2022-08-02 13:16:11 144.944 NXSERVER __setDataToColumns: client is supporting platform parameters
97407 97407 2022-08-02 13:16:11 145.055 NXSERVER Connection to client still open.
97407 97407 2022-08-02 13:16:11 145.112 NXSERVER NXMsg: Sent response message 'NX> 127 Session list of user 'mrazizad': '
97407 97407 2022-08-02 13:16:11 145.753 NXSERVER Check type virtual-desktops-limit user mrazizad and node: .
97407 97407 2022-08-02 13:16:11 145.922 NXSERVER Connection to client still open.
97407 97407 2022-08-02 13:16:11 145.979 NXSERVER NXMsg: Sent response message 'NX> 147 Server capacity: reached for user: mrazizad'
.....
......
97407 97407 2022-08-02 13:16:18 182.360 NXSERVER Cannot find node assigned to socket FD#25.
97407 97407 2022-08-02 13:16:18 182.427 NXSERVER ERROR! Received error message from node 'localhost:4000', 'The remote application terminated unexpectedly.'.

More info to debug the issue:
– NoMachine product and version on local and remote machine (free version, Workstation, etc)
Version – 7.10.1
Flavor:
Server: NoMachine Workstation Subscription Pack
Client: NoMachine free version for Mac

– Whether the problem arises connecting to a physical or a virtual display.
Virtual Display

– Remote and local Windows/Mac/Linux version (Windows XP/7/8, OS X 10.x, Ubuntu xyz, Mint x.y, etc.).
Remote server: RHEL 8.6
Local Mac laptop: macOS Monterey (Version 12.4)

Server side and client side logs are attached with this post.

Attachments:

1. NoMachine-log-2022.08.02-13.16.56.zip
2. nxdir.tar-1.gz

[kroy]

Hi

Logs indicate that you are trying to use VirtualGL. There are instructions how to enable it on the NoMachine: https://kb.nomachine.com/AR05P00982. After enabling VirtualGL please set default command in node.cfg:

DefaultDesktopCommand "env XDG_SESSION_TYPE=x11 /bin/dbus-launch --exit-with-session gnome-session --session=gnome"

[Karthik.V.M]

Hi Kroy,

Thank you so much for the pointers. Your solution solved the issue my client was facing. He is able to log into NoMachine now.

Furthermore, I previously modified the DefaultDesktopCommand in node.cfg as below (by reading through NoMachine KB articles) to get the GPU acceleration for the NoMachine session:

DefaultDesktopCommand "/etc/gdm/Xsession 'env XDG_SESSION_TYPE=x11 /usr/NX/scripts/vgl/vglrun gnome-session --session=gnome'"

Please note Graphics: Quadro RTX 4000/PCIe/SSE2

But changing the ‘DefaultDesktopCommand ‘ to the one suggested by you allowed the user to login but the graphics acceleration seems to be missing.

Please note Graphics: llvmpipe(LLVM 13.0.0, 256 bits)

Furthermore, when I used my version of ‘DefaultDesktopCommand ‘only one of my clients with Mac could not create a NoMachine session. Other Mac users and windows users are able to log in using my version of ‘DefaultDesktopCommand’ and get GPU acceleration. Kindly let me know your comments. Thanks for your time.

Regards,
Karthik

[Britgirl]

Can you please submit the screenshots as separate attachments? They won’t be accepted if you try to paste them in to your reply. Thanks.

[fra81]

But changing the ‘DefaultDesktopCommand ‘ to the one suggested by you allowed the user to login but the graphics acceleration seems to be missing.

Acceleration by means of VirtualGL can be enabled either explicitly by the vglrun command (even only for specific applications) or implicitly for the whole desktop by the 'nxserver --virtualgl yes' command. That DefaultDesktopCommand was provided to you assuming you were using the second method. You can find further details in https://kb.nomachine.com/AR05P00982.

Furthermore, when I used my version of ‘DefaultDesktopCommand ‘only one of my clients with Mac could not create a NoMachine session.

Can you send the logs from this specific case?

[Britgirl]

Furthermore, when I used my version of ‘DefaultDesktopCommand ‘only one of my clients with Mac could not create a NoMachine session. Other Mac users and windows users are able to log in using my version of ‘DefaultDesktopCommand’ and get GPU acceleration. Kindly let me know your comments.

If you are still encountering the problem, please open a separate topic. This topic about virtual desktop on Linux can be considered solved.

[Karthik.V.M]

Hi Britgirl,

Thanks for the notice. Sorry got caught up and could not reply earlier. The solution provided by Kroy indeed solved the problem of my client not able to log in. But since it removed virtual-gl the acceleration from GPU is missing (as shown in the attached images). I will try fra81’s pointer of setting 'nxserver --virtualgl yes' to bring back the GPU acceleration this week and keep you all posted.

Thanks,

Karthik

Attachments:

1. 

   with-virtualgl.jpg
   

2. 

   with-no-virtualgl.jpg
   

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