Black screen connecting to physical display

[Mth]

Hello

I am very sorry I got the configuration files mixed up.
The proper configuration is:

1. In /usr/NX/etc/node.cfg:

PhysicalDisplays :0-:1200

2. In /usr/NX/etc/server.cfg:

DisplayBase 1201

Also please note the lack of ‘:’ in DisplayBase. I’m really sorry about the confusion.

/Mth

[rcasero]

Last workaround tried (editing node.cfg and server.cfg and restarting nxserver), but it doesn’t work. I still get the same black screen. I have emailed the new logs.

[Mth]

Hello.

Even if it did not work, it gave some insight to the issue.

It seems something is interfering with the session detection mechanism. Always the same X server process is detected, regardless of the display parameter. This is the reason the proper session never gets detected. Because this is a relatively new version of Gnome, even if there is user desktop running already, there will be X server for login window.

Strange thing is, we haven’t been able to reproduce that issue, at least on standard configuration of Ubuntu 19.04. Please give us some information about your configuration.

1. Is it freshly installed Ubuntu 19.04, or updated from older version?
2. Do you have any changes in gnome configuration? It looks like there is no
Wayland running, but maybe that is the issue here that it is not detected.
3. Do You have any virtual X servers running? (like vnc or xvfb)
4. If You can, please provide us with output of

‘# ps -efjH’

command. As you wrote the desktop environment is Gnome, we are mostly interested in the process tree of “/usr/sbin/gdm3” process.

And of course any information about any changes in configuration of X server or desktop environment that is present on the system will be most helpful.

Also as the problem is related to the multiple X servers running, there could be a possible workaround, that is you can try to enable the automatic login for the user, and then restart the gdm service. This will cause the X server for login window to be skipped – at least at first, any logout/login afterwards would have it back.

You can then simply kill the “Xorg” process owned by the gdm user (with kill -TERM <pid>), as there is no real need for that second inactive session to be running in background at all time. It is a very weak workaround, but may be of some help.

/Mth

[rcasero]

1. Is it freshly installed Ubuntu 19.04, or updated from older version?

Freshly installed.

2. Do you have any changes in gnome configuration? It looks like there is no
Wayland running, but maybe that is the issue here that it is not detected.

No changes, other than changing the wallpaper and adding a second keyboard layout.

3. Do You have any virtual X servers running? (like vnc or xvfb)

No.

4. If You can, please provide us with output of

‘# ps -efjH’

OK, I’ve sent it by email.

Maybe it has something to do with the nvidia driver that I mentioned in one of my first posts?

 

On a related note, it seems that when your reply #23646 started a new page in this thread, it automatically set me to “Unsubscribed”, so again I didn’t get an email notification from your last post.

[Britgirl]

@rcasero can you update to the latest version and tell us if the issue continues? (any further debug will be based on the latest version)

[rcasero]

Hi,

I’m getting the error when I try to upgrade:

$ sudo dpkg -i nomachine-workstation_6.8.1_1_amd64.deb

(Reading database … 205897 files and directories currently installed.)

Preparing to unpack nomachine-workstation_6.8.1_1_amd64.deb …

Sorry, your upgrade period has expired. To be able to

install a new version of the software, please visit the

NoMachine Web site at http://www.nomachine.com/

to acquire a valid subscription.

 

Does the NoMachine free version work with physical displays? I want to test that it works before we consider buying a subscription.

[Britgirl]

The evaluation software provides 30 days, after which you will need to make a fresh reinstall. Alternatively, you can contact the sales team and request an extension.

The free version connects to the physical display only.

[Flatline]

Hi!

I just found this thread and I guess I have the same problem of @rcasero: blank screen on Ubuntu 19.04 when connecting via NoMachine (on the monitor of the target the system behaves normally).

I upgraded (via command line) to the latest version (nomachine_6.8.1_1_amd64.deb) to no avail.

 

Output of ps command:

riccardo  1347   857  1342  1342  0 21:30 ?        00:00:00     /usr/lib/gvfs/gvfsd-fuse /run/user/1000/gvfs -f -o big_wriccardo  1382   857   927   927  0 21:30 ?        00:00:00     /usr/lib/ibus/ibus-portal

riccardo  1393   857  1393  1393  0 21:30 ?        00:00:00     /usr/libexec/xdg-permission-store

riccardo  1398   857   927   927  0 21:30 ?        00:00:00     /usr/lib/gnome-shell/gnome-shell-calendar-server

riccardo  1402   857  1402  1402  0 21:30 ?        00:00:00     /usr/libexec/evolution-source-registry

riccardo  1410   857   927   927  0 21:30 ?        00:00:00     /usr/lib/gnome-online-accounts/goa-daemon

riccardo  1416   857  1416  1416  0 21:30 ?        00:00:00     /usr/bin/pulseaudio –daemonize=no

riccardo  1429   857   927   927  0 21:30 ?        00:00:00     /usr/lib/gnome-online-accounts/goa-identity-service

riccardo  1453   857  1453  1453  0 21:30 ?        00:00:00     /usr/lib/gvfs/gvfs-udisks2-volume-monitor

riccardo  1458   857  1458  1458  0 21:30 ?        00:00:00     /usr/lib/gvfs/gvfs-goa-volume-monitor

riccardo  1462   857  1462  1462  0 21:30 ?        00:00:00     /usr/lib/gvfs/gvfs-afc-volume-monitor

riccardo  1467   857  1467  1467  0 21:30 ?        00:00:00     /usr/lib/gvfs/gvfs-gphoto2-volume-monitor

riccardo  1473   857  1473  1473  0 21:30 ?        00:00:00     /usr/lib/gvfs/gvfs-mtp-volume-monitor

riccardo  1630   857  1630  1630  0 21:30 ?        00:00:00     /usr/lib/tracker/tracker-store

riccardo  1677   857  1677  1677  0 21:30 ?        00:00:00     /usr/libexec/evolution-calendar-factory

riccardo  1705   857   927   927  0 21:30 ?        00:00:00     /usr/lib/dconf/dconf-service

riccardo  1707   857  1707  1707  0 21:30 ?        00:00:00     /usr/libexec/evolution-addressbook-factory

riccardo   902     1   901   901  0 21:30 ?        00:00:00   /usr/bin/gnome-keyring-daemon –daemonize –login

whoopsie  1149     1  1149  1149  0 21:30 ?        00:00:00   /usr/bin/whoopsie -f

kernoops  1152     1  1152  1152  0 21:30 ?        00:00:00   /usr/sbin/kerneloops –test

kernoops  1154     1  1154  1154  0 21:30 ?        00:00:00   /usr/sbin/kerneloops

riccardo  1378     1  1371   914  0 21:30 tty2     00:00:00   /usr/lib/ibus/ibus-x11 –kill-daemon

root      1413     1  1413  1413  0 21:30 ?        00:00:00   /usr/lib/upower/upowerd

rtkit     1423     1  1423  1423  0 21:30 ?        00:00:00   /usr/libexec/rtkit-daemon

root      1480     1  1480  1480 12 21:30 ?        00:00:20   /usr/lib/packagekit/packagekitd

riccardo  1581     1   914   914  0 21:30 tty2     00:00:00   /usr/lib/gnome-settings-daemon/gsd-printer

colord    1614     1  1614  1614  0 21:30 ?        00:00:00   /usr/lib/colord/colord

root      2335     1  2335  2335  0 21:31 ?        00:00:00   /usr/lib/fwupd/fwupd

root      2340     1  2340  2340  0 21:31 ?        00:00:00   /usr/lib/bolt/boltd

[Mth]

Hello

First, to answer the doubt about the Nvidia drivers, as long as there is
no problem on your side (everything is fine on physical screen), there
is no problem with them on our side. Right now as we see it from our logs
the problem is in between the Xorg display server and the NoMachine
ability to detect it.

We are still not fully sure on what causes this problem and trying to
find a solution that would fix this.

Could you please provide us with one more set of logs? This time please set
the server logs to verbose mode by editing the /usr/NX/etc/server.cfg file
and setting:

‘SessionLogLevel 9’

and then restarting the server.

‘/etc/NX/nxserver –restart’

After the restart please gather the logs as usual.

Please note that this would print much more details into the logs, so you would
want to turn it off afterwards.

Thank you for great cooperation and patience on this issue.

/Mth

[rcasero]

Hi,

I have installed nomachine_6.8.1_1_amd64.deb on client and server. I also had to make myself a trusted user on the server with

sudo /etc/NX/nxserver –useredit rcasero –trusted physical

The client establishes the connection, but still only shows a black screen.

[rcasero]

PS. I’ve emailed new logs.

[Mth]

Hello

The good news is we were able to identify the problem, and the fix
is under way. The bad news is that we cannot provide a straightforward
workaround.

The problem is happening because of the strange dbus service behavior.
By the default dbus-daemon –session should be ran by the systemd
whenever the user is logged. Here it does not happen and instead it
is invoked during the start of the graphic environment by the gdm-x-session
process.

So we have three important processes running as gdm-x-session children:
Xorg, dbus-daemon –session and gnome-session-binary. Unfortunately
the dbus-daemon started like this lacks some of expected environment
variables, and the NoMachine fails the detection badly.

Please check if there is anything wrong with the dbus service for the user e.g. by
running

‘systemctl status dbus.service’

or checking if the file /usr/lib/systemd/user/dbus.service is present and viable.

If there is nothing wrong there, or it is not a result of an accident and this
behavior is intended, we may be able to provide with patched packages.

/Mth

[rcasero]

Hi Mth,

The dbus service seems to be fine:

$ systemctl status dbus.service

● dbus.service – D-Bus System Message Bus

Loaded: loaded (/lib/systemd/system/dbus.service; static; vendor preset: enabled)

Active: active (running) since Wed 2019-10-02 17:30:43 BST; 4 days ago

Docs: man:dbus-daemon(1)

Main PID: 932 (dbus-daemon)

Tasks: 1 (limit: 4915)

Memory: 6.0M

CGroup: /system.slice/dbus.service

└─932 /usr/bin/dbus-daemon –system –address=systemd: –nofork –nopidfile –systemd-activation –syslog-only

 

Oct 07 10:24:18 lin06 dbus-daemon[932]: [system] Activating via systemd: service name=’net.reactivated.Fprint’ unit=’fprintd.service’ r

Oct 07 10:24:18 lin06 dbus-daemon[932]: [system] Successfully activated service ‘net.reactivated.Fprint’

Oct 07 10:33:09 lin06 dbus-daemon[932]: [system] Activating via systemd: service name=’org.freedesktop.PackageKit’ unit=’packagekit.ser

Oct 07 10:33:09 lin06 dbus-daemon[932]: [system] Successfully activated service ‘org.freedesktop.PackageKit’

Oct 07 10:40:38 lin06 dbus-daemon[932]: [system] Activating via systemd: service name=’org.freedesktop.PackageKit’ unit=’packagekit.ser

Oct 07 10:40:38 lin06 dbus-daemon[932]: [system] Successfully activated service ‘org.freedesktop.PackageKit’

Oct 07 11:16:46 lin06 dbus-daemon[932]: [system] Activating via systemd: service name=’org.freedesktop.hostname1′ unit=’dbus-org.freede

Oct 07 11:16:46 lin06 dbus-daemon[932]: [system] Successfully activated service ‘org.freedesktop.hostname1′

Oct 07 11:40:16 lin06 dbus-daemon[932]: [system] Activating via systemd: service name=’net.reactivated.Fprint’ unit=’fprintd.service’ r

Oct 07 11:40:17 lin06 dbus-daemon[932]: [system] Successfully activated service ‘net.reactivated.Fprint’

 

 

[Britgirl]

Please check your inbox and let us know if the patched package solves the issue.

[rcasero]

I’ve tried the patched version, and it fixes the black screen problem. Now it connects correctly.

[Author]

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