“Cannot create a new display” on headless Ubuntu 22.04

[kINo204]

Hi!

I’m trying to connect to a remote headless server with Ubuntu 22.04 (NoMachine free version, latest). I’ve installed a xfce desktop and setup DefaultDesktopCommand "/usr/bin/startxfce". But when I try to connect it shows “The session negotiation failed.

Error: Cannot create a new display, please contact your system administrator”.

Here’s the server’s log in the process of connecting from client, and in attachments with debugging mode.

Info: Handler started with pid 21006 on Thu Apr  2 12:05:27 2026.
Info: Handling connection from 127.0.0.1 port 60732 on Thu Apr  2 12:05:27 2026.
21006 21006 2026-04-02 12:05:28 425.867 NXSERVER Connected from remote machine '127.0.0.1' using protocol 'NX'.
21006 21006 2026-04-02 12:05:28 425.926 NXSERVER Process initialized with arguments '-c /etc/NX/nxserver --login -H 14'.
21006 21006 2026-04-02 12:05:28 580.828 NXSERVER User 'root' logged in from '127.0.0.1' using authentication method NX-password.
21006 21022 2026-04-02 12:05:28 594.711 NameEvent/NameEvent: ERROR! Error reply 'ERR Background save already in progress'.
21055 21055 2026-04-02 12:05:29 371.767 NXSERVER Connected from remote machine '127.0.0.1' using protocol 'NX'.
21055 21055 2026-04-02 12:05:29 371.846 NXSERVER Process initialized with arguments '--virtualsession --sessionid B34F16D07AFF57E42B1503EFB80E83BE'.
21055 21055 2026-04-02 12:05:29 514.744 NXSERVER ERROR! Cannot start node to create session
21055 21055 2026-04-02 12:05:29 516.901 NXSERVER WARNING! NXRedis: field ServerStatusDump in command line 'command=hset,service=db,key=running.D049CA2F82B50B16392EE53231B2BD4D,field=ServerStatusDump,value=\n' cannot be empty.
21055 21055 2026-04-02 12:05:29 516.946 NXSERVER WARNING! NXRedis: command line 'command=hset,service=db,key=running.D049CA2F82B50B16392EE53231B2BD4D\n' cannot set nothing.
21055 21055 2026-04-02 12:05:29 516.963 NXSERVER WARNING! NXRedis: Sending command 'command=hset,service=db,key=running.D049CA2F82B50B16392EE53231B2BD4D\n' aborted.
21055 21055 2026-04-02 12:05:29 525.800 HostDescriptorClose: WARNING! Descriptor FD#29 is invalid.
21006 21006 2026-04-02 12:05:29 644.072 NXSERVER ERROR! Received error from nxserver --daemon nxFrameBuffer error while starting
Info: Connection from 127.0.0.1 port 60732 closed on Thu Apr  2 12:05:29 2026.
Info: Handler with pid 21006 terminated on Thu Apr  2 12:05:29 2026.
21006 21006 2026-04-02 12:05:29 675.125 NXSERVER Remote machine '127.0.0.1' disconnected.
21006 21006 2026-04-02 12:05:29 682.236 NXSERVER User 'root' from '127.0.0.1' logged out.
21006 21006 2026-04-02 12:05:29 683.034 NXSERVER Remote machine '127.0.0.1' disconnected.
21212 21212 2026-04-02 12:06:58 928.612 NXSERVER Connected from remote machine '127.0.0.1' using protocol 'SSH'.
21212 21212 2026-04-02 12:06:58 928.716 NXSERVER Process initialized with arguments '--restart'.
21212 21212 2026-04-02 12:06:59 255.450 NXSERVER Shutting down NoMachine server and services.
21281 21308 2026-04-02 12:07:00 345.815 ServerDBusMonitor/ServerDBusMonitor: ERROR! Connection open failed.
21281 21308 2026-04-02 12:07:00 345.911 ServerDBusMonitor/ServerDBusMonitor: ERROR! Error is 'Failed to connect to socket /var/run/dbus/system_bus_socket: No such file or directory' .
21281 21281 2026-04-02 12:07:00 353.639 NXSERVER Starting LS 9.4.14 and services.
21281 21281 2026-04-02 12:07:00 353.690 NXSERVER Process initialized with arguments 'root 21212 --daemon'.
21281 21281 2026-04-02 12:07:00 353.714 NXSERVER System information: Ubuntu 22.04.1 LTS, standalone.
21281 21281 2026-04-02 12:07:00 356.687 ServerDBusConnect: ERROR! Connection failed: Failed to connect to socket /run/dbus/system_bus_socket: No such file or directory .
21281 21315 2026-04-02 12:07:00 357.062 ServerDBusMethod: WARNING! Connection not initialized.
21212 21212 2026-04-02 12:07:00 430.864 NXSERVER Remote machine '127.0.0.1' disconnected.

Attachments:

1. log.zip

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