veyon-server doesn't start (Qt::AA_ShareOpenGLContexts must be set before QCoreApplication)

white_rabbit

Hi.
When I check the status von veyon on an Ubuntu 20.04 client I get this:

sudo systemctl status veyon
● veyon.service - Veyon Service
     Loaded: loaded (/lib/systemd/system/veyon.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 2021-05-27 11:09:42 CEST; 26min ago
       Docs: man:veyon-service(1)
   Main PID: 1519 (veyon-service)
      Tasks: 9 (limit: 9404)
     Memory: 46.3M
     CGroup: /system.slice/veyon.service
             ├─ 1519 /usr/bin/veyon-service
             └─81496 /usr/bin/veyon-worker {8e997d84-ebb9-430f-8f72-d45d9821963d}

Mai 27 11:09:42 raum1-pc systemd[1]: Started Veyon Service.
Mai 27 11:09:42 raum1-pc veyon-service[1519]: Attribute Qt::AA_ShareOpenGLContexts must be set before QCoreApplication is >

I'm not sure but is it possible (as a consequence of the last error) that veyon-server doesn't start?
Thank you?

tobydox

This is just a warning which has been fixed in Veyon 4.5.6 but unfortunately it's not related to the server start problem

Did you already try to enable advanced the "Write to logging system of operating system" option (https://docs.veyon.io/en/latest/admin/reference.html#logging) and change the log level to debug? You should then see the output of the veyon-server process in the veyon-service unit's journal. If the program catchsegv is in PATH, it will be used to dump a possible backtrace of the server if it crashes.

white_rabbit

@tobydox
Hi. I enabled the Logfiles in Debug-Mode.
Now I found this:

 /tmp]$ tail  VeyonService.log

2021-05-29T11:52:41.093: [INFO] LinuxServiceCore::startServer(): Starting server for new session "/org/freedesktop/login1/session/_32" with ID 0 at seat "/org/freedesktop/login1/seat/seat0"
2021-05-29T11:55:20.873: [ERR] LinuxServiceCore::startServer(): Can't start Veyon Server in Wayland sessions as this is not yet supported. Please switch to X11-based sessions!
2021-05-29T11:55:23.198: [DEBUG] PlatformSessionManager::closeSession(): Closing session 0 for platform session "/org/freedesktop/login1/session/_32"
2021-05-29T11:55:23.198: [INFO] LinuxServiceCore::stopServer(): stopping server for removed session "/org/freedesktop/login1/session/_32"
2021-05-29T11:55:35.946: [DEBUG] LinuxServiceCore::startServ

When I observe the process veyon-service with catchsegv I found this:

29/05/2021 12:12:03 Xinerama: number of sub-screens: 1
29/05/2021 12:12:03 Xinerama: no blackouts needed (only one sub-screen)
29/05/2021 12:12:03 

X11 MIT Shared Memory Attach failed:
  Is your DISPLAY=:0 on a remote machine?
  Suggestion, use: x11vnc -display :0 ... for local display :0

caught X11 error:
29/05/2021 12:12:03 deleted 32 tile_row polling images.
X Error of failed request:  BadAccess (attempt to access private resource denied)
  Major opcode of failed request:  130 (MIT-SHM)
  Minor opcode of failed request:  1 (X_ShmAttach)
  Serial number of failed request:  57
  Current serial number in output stream:  91

And afterwards the same with veyon-server:

2021-05-29T12:15:35.158: [DEBUG] VeyonCore::initSystemInfo(): "4.5.5" "fossa.my-domain.de" "linux" "5.8.0-53-generic" "Ubuntu 20.04.2 LTS" "ubuntu" "20.04"
2021-05-29T12:15:35.166: [ERR] VncServer::VncServer(): no VNC server plugins found!
2021-05-29T12:15:35.196: [DEBUG] [KLDAP] connection closed!
2021-05-29T12:15:35.196: [DEBUG] [KLDAP] ldap url: "ldap://server.my-domain.de:3268"
2021-05-29T12:15:35.197: [DEBUG] [KLDAP] setting version to: 3
2021-05-29T12:15:35.197: [DEBUG] [KLDAP] setting timeout to: 0
2021-05-29T12:15:35.197: [DEBUG] [KLDAP] setting security to: 1
2021-05-29T12:15:35.197: [DEBUG] [KLDAP] start TLS
2021-05-29T12:15:35.264: [DEBUG] [KLDAP] setting sizelimit to: 0
2021-05-29T12:15:35.264: [DEBUG] [KLDAP] setting timelimit to: 0
2021-05-29T12:15:35.264: [DEBUG] [KLDAP] initializing SASL client
2021-05-29T12:15:35.264: [DEBUG] [KLDAP] binding to server, bindname:  "<MY-SAMBA-DOMAIN>\\admin"  password: *****
2021-05-29T12:15:35.264: [DEBUG] [KLDAP] ldap_sasl_bind_s (simple)
2021-05-29T12:15:35.303: [DEBUG] FeatureWorkerManager::startUnmanagedSessionWorker(): Starting worker (unmanaged session process) for feature QUuid("{8e997d84-ebb9-430f-8f72-d45d9821963d}")
2021-05-29T12:15:35.304: [DEBUG] FeatureWorkerManager::sendMessageToUnmanagedSessionWorker(): User session likely not yet available - retrying worker start
2021-05-29T12:15:35.304: [DEBUG] VncProxyServer::start(): started on port 11100
2021-05-29T12:15:35.304: [DEBUG] VncServer::prepare():
2021-05-29T12:15:35.304: [DEBUG] VeyonCore::exec(): Running
2021-05-29T12:15:35.305: [DEBUG] VeyonCore::exec(): Exit
2021-05-29T12:15:35.305: [DEBUG] ComputerControlServer::~ComputerControlServer():
2021-05-29T12:15:35.305: [DEBUG] VncServer::~VncServer():
2021-05-29T12:15:35.305: [DEBUG] Logger::~Logger(): Shutdown
PluginManager::~PluginManager():
CryptoCore::~CryptoCore():
KLDAP: connection closed!

Is this helpful?

tobydox

Can you try to add -noshm as additional custom x11vnc parameter in the advanced VNC server configuration?

white_rabbit

@tobydox said in veyon-server doesn't start (Qt::AA_ShareOpenGLContexts must be set before QCoreApplication):

-noshm

Wow -- I think that's the solution! I just added this option and restarted the Client -- now "htop" shows a running veyon-server ... I can't test it in our productive environment at the moment but it looks good so far! Thank you!

hammergil

@white_rabbit where do you add this parameter? Is it in the Veyon configuration interface somewhere?

tobydox

The VNC server section is correct, make sure to enable advanced view in the menu and to select "Builtin VNC server":

hammergil

@tobydox the master computer is running Windows 10 and does not have an option for parameters. The built-in vnc is UltraVNC.

tobydox

@hammergil

Since the Linux-based student computers are affected, you have to make the configuration changes on them directly

hammergil

@tobydox Great! That did it! Thanks for the help!

hammergil

@tobydox what does the parameter "-noshm" mean out of curiosity.