04. Remote Graphical Login: VNC viewer failed to connect

albiurs

Hello,

I'm on Debian 12 and trying to setup and test vnc.

If i follow the instructions, starting the tigervnc server it returns:

$ vncserver

New Xtigervnc server 'mypc.local:2 (alu)' on port 5902 for display :2.
Use xtigervncviewer -SecurityTypes VncAuth -passwd /tmp/tigervnc.v6InDU/passwd :2 to connect to the VNC server.


=================== tail /home/username/.vnc/mypc.local:2.log ===================
X connection to :2 broken (explicit kill or server shutdown).

Wed Aug  7 09:09:08 2024
 ComparingUpdateTracker: 0 pixels in / 0 pixels out
 ComparingUpdateTracker: (1:-nan ratio)
Killing Xtigervnc process ID 37875... success!
===============================================================================

Session startup via '/etc/X11/Xtigervnc-session' cleanly exited too early (< 3 seconds)!

Maybe try something simple first, e.g.,
    tigervncserver -xstartup /usr/bin/xterm
The X session cleanly exited!
The Xtigervnc server cleanly exited!

If I try to start the server as suggested with:

$ tigervncserver -xstartup /usr/bin/xterm

The server starts. However, if try to connect I get an error:

vncviewer localhost:2

or

$ xtigervncviewer localhost:2                                                  

TigerVNC Viewer 64-bit v1.12.0
Built on: 2023-01-06 16:01
Copyright (C) 1999-2021 TigerVNC Team and many others (see README.rst)
See https://www.tigervnc.org for information on TigerVNC.

Wed Aug  7 09:19:04 2024
 DecodeManager: Detected 16 CPU core(s)
 DecodeManager: Creating 4 decoder thread(s)
 CConn:       unable to connect to socket: Connection refused (111)

Any suggestions to resolve would be appreciated.

Thanks

luisviveropena

Hi @albiurs, I couldn't find that lab. Are you sure this is Lab 4 of LFS207?

I would check at least two things:

1.- Is there any firewall running? If so, stop it and try again.

2.- Try running the command using sudo.

Regards,
Luis.

albiurs

Hi luisviveropena,

Thank you for your reply.

Yes, it's LFS207. However, it's not a lab, it's regular lesson/page of chapter 04:
https://trainingportal.linuxfoundation.org/learn/course/linux-system-administration-essentials-lfs207/user-account-management/user-account-management?page=20

As I am in chapter 04 and the firewall configuration is chapter 30, I don't know yet how to manage it. So, I uninstalled it.

And you were right. Without the fiewall I managed to start the server, but not without parameters as supposed on the linked page above...

┌──(alu@mynb)-[~]
└─$ vncserver

New Xtigervnc server 'mynb.local:2 (alu)' on port 5902 for display :2.
Use xtigervncviewer -SecurityTypes VncAuth -passwd /tmp/tigervnc.OQqCS9/passwd :2 to connect to the VNC server.


=================== tail /home/alu/.vnc/mynb.local:2.log ===================
X connection to :2 broken (explicit kill or server shutdown).
 ComparingUpdateTracker: 0 pixels in / 0 pixels out
 ComparingUpdateTracker: (1:-nan ratio)
Killing Xtigervnc process ID 5257... success!
===============================================================================

Session startup via '/etc/X11/Xtigervnc-session' cleanly exited too early (< 3 seconds)!

Maybe try something simple first, e.g.,
    tigervncserver -xstartup /usr/bin/xterm
The X session cleanly exited!
The Xtigervnc server cleanly exited!

┌──(alu@mynb)-[~]
└─$ tigervncserver -xstartup /usr/bin/xterm

New Xtigervnc server 'mynb.local:2 (alu)' on port 5902 for display :2.
Use xtigervncviewer -SecurityTypes VncAuth -passwd /tmp/tigervnc.phu6d3/passwd :2 to connect to the VNC server.

Finally, I can connect to the terminal session with the xtigervncviewer. But how do I have to start the server, so I can connect to the Gnome desktop?

Thanks.

luisviveropena

Hi @albiurs,

Finally, I can connect to the terminal session with the xtigervncviewer.

Yes, that's right.

But how do I have to start the server, so I can connect to the Gnome desktop?

You need to use sudo, like this:

sudo vncserver

Regards,
Luis.

albiurs

Hi luisviveropena,

Thanks a lot for your support. Now I'm able to start the vncserver:

┌──(alu@mynb)-[~]
└─$ sudo vncserver
[sudo] password for alu: 
Cleaning stale pidfile '/root/.vnc/mynb.local:2.pid'!

New Xtigervnc server 'mynb.local:2 (root)' on port 5902 for display :2.
Use xtigervncviewer -SecurityTypes VncAuth -passwd /tmp/tigervnc.jeWyAl/passwd :2 to connect to the VNC server.


┌──(alu@mynb)-[~]
└─$ ss -tap | grep vnc

┌──(alu@qtwixnb)-[~]
└─$ sudo ss -tap | grep vnc
LISTEN     0      5                                     127.0.0.1:5902                     0.0.0.0:*     users:(("Xtigervnc",pid=9856,fd=9))       
LISTEN     0      5                                         [::1]:5902                        [::]:*     users:(("Xtigervnc",pid=9856,fd=10))

However, I can still not connect with the VNC viewer:

┌──(alu@mynb)-[~]
└─$ xtigervncviewer localhost:2                                                           

TigerVNC Viewer 64-bit v1.12.0
Built on: 2023-01-06 16:01
Copyright (C) 1999-2021 TigerVNC Team and many others (see README.rst)
See https://www.tigervnc.org for information on TigerVNC.
Authorization required, but no authorization protocol specified

Can't open display: :0

┌──(alu@mynb)-[~]
└─$ xtigervncviewer -SecurityTypes VncAuth -passwd /tmp/tigervnc.jeWyAl/passwd localhost:2

TigerVNC Viewer 64-bit v1.12.0
Built on: 2023-01-06 16:01
Copyright (C) 1999-2021 TigerVNC Team and many others (see README.rst)
See https://www.tigervnc.org for information on TigerVNC.
Authorization required, but no authorization protocol specified

Can't open display: :0

By the way, at some point I had to set a password for the server and the file /tmp/tigervnc.jeWyAl/passwd actually exists.

What am I missing?

luisviveropena

Hi @albiurs,

You can set the user's password with the following command:

vncpasswd

You need to run it with the same user that's going to use the password.

For another hand, it seems that xtigervncviewer is not taking the parameters correctly; it tries to connect to display 0, but the one running is 2. So, let's try with another VNC client; it can be "xtightvncviewer" or any other listed here:

https://help.ubuntu.com/community/VNC/Clients

Regards,
Luis.

albiurs

Hi Luis,

Thanks again for your further suggestions.

Unfortunately, I still fail to connect also with other VNC viewers (RealVNC, Remmina).

By the way, I think, the :0 is related to the current desktop session / display:

┌──(alu@mynb)-[~]
└─$ echo $DISPLAY
:0

I guess the issue is rather at the server side (root vs. regular user privileges, Xorg vs. Wayland, Gnome vs. other desktops).

As I already spent many hours trying to resolve this issue, I have to skip this subject for now and proceed with the rest of the course. However, as the described way to setup and use VNC does not work out of the box, it would be great if one of the authors could review this lesson / page and provide a step by step tutorial to correctly setup and using VNC on a current Linux version, independently of the Linux distribution, the desktop environment and/or if Xorg or Wayland is in use.

Thank you anyway for your effort in supporting.

Best wishes,
Urs

luisviveropena

Hi @albiurs,

As I already spent many hours trying to resolve this issue, I have to skip this subject for now and >proceed with the rest of the course. However, as the described way to setup and use VNC does not >work out of the box, it would be great if one of the authors could review this lesson / page and provide >a step by step tutorial to correctly setup and using VNC on a current Linux version, independently of >the Linux distribution, the desktop environment and/or if Xorg or Wayland is in use.

Yes, I'm aware of this, as I did a test case on my system. We are checking on this and will provide a fix.

Regards,
Luis.

albiurs

Hi Luis,

Thank you very much. Could you please let me know if you will have updated the according lesson/page?

Regards,
Urs

fcioanca

Hi @albiurs
The course author will review the content and will decide what updates are needed. There is currently no ETA on this.
Regards,
Flavia
Linux Foundation Training Team