Problem Enable XDMCPServer

Support & Help Requests
1

System version: ubuntu-24.04.1 mate

After system installation, create a new configuration file /etc/lightdm/lightdm.conf

[Seat:*]
user-session=mate
allow-guest=false
greeter-show-manual-login=true
 
[XDMCPServer]
enabled=true

After restarting the lightdm service, using Xmanager 7 to remotely connect to the service shows a black screen without a graphical login interface.

Try the following two operations to make the remote Xmanager 7 client display the login graphical interface normally, but each method will cause new problems.

  1. Login to the account locally on the host, but the system will restart to recover.

  2. Add the following parameters to the /etc/lightdm/lightdm.conf configuration file

[LightDM]
start-default-seat=false

I currently choose the second method, but this will cause new problems. After the host local system is started, the command line interface is displayed and the graphical login interface is not displayed.

How to solve this problem?

Sep 23 08:39:56 *** systemd[1]: Starting lightdm.service - Light Display Manager...
Sep 23 08:39:56 *** systemd[1]: Started lightdm.service - Light Display Manager.
Sep 23 08:40:03 *** lightdm[1695]: pam_unix(lightdm-greeter:session): session opened for user lightdm(uid=110) by (uid=0)
Sep 23 08:40:03 *** lightdm[1695]: gkr-pam: couldn't unlock the login keyring.
Sep 23 08:40:03 *** lightdm[1452]: Error activating login1 session: GDBus.Error:org.freedesktop.DBus.Error.NotSupported: Operation not supported
Sep 23 08:40:05 *** lightdm[1943]: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "***"
Sep 23 08:40:15 *** lightdm[1943]: gkr-pam: unable to locate daemon control file
Sep 23 08:40:15 *** lightdm[1943]: gkr-pam: stashed password to try later in open session
Sep 23 08:40:15 *** lightdm[1943]: pam_unix(lightdm:session): session opened for user ***(uid=1000) by (uid=0)
Sep 23 08:40:15 *** lightdm[1943]: gkr-pam: unlocked login keyring
Sep 23 08:40:15 *** lightdm[1452]: Error activating login1 session: GDBus.Error:org.freedesktop.DBus.Error.NotSupported: Operation not supported
1 Like
2

Hi, @ac169 and welcome to the Ubuntu MATE Community!

3

Not familiar with xmanager7 but whenever I build a pc, I install nomachine, then put a hdmi dummy plug in the video card and I can remotely access that pc. I have um22, um24 running w/o issues. I never modify lightdm.conf REF: nomachine Current is Linux 8.13.1

2 Likes
4

Out of curiosity, I decided to figure this out. I modified /etc/lightdm/lightdm.conf on a remote pc as:

[Seat:*]
autologin-guest=false
autologin-user=user
autologin-user-timeout=0

[XDMCPServer]
enabled=true
port=177

[LightDM]
start-default-seat=false

then, sudo systemctl restart lightdm

On the main pc, I installed xnest (sudo apt install xnest). Then,
Xnest -query 192.168.0.10 -geometry 1280x1024 :1

A window popped up with lightdm of the remote pc.

On the remote pc, netstat -an | grep 177 shows protocol is active.

@ac169 Hope this help you.

4 Likes
5

Thanks

In your answer, you mentioned the autologin-user parameter. I have tried it before, and it can indeed display the graphical login interface, but the local host automatically logs in with the account to enter the system. This is not what I need.

The reason why I use mate desktop is because I want to use the default services that come with the system without installing new services. This is how I used it on the old version of the system (14). I have become accustomed to it and now I want to use it on the latest system. realize, additionally My client is windows, so I use Xmanager 7 to access the xdmcp protocol

Because the remote graphical interface can be displayed immediately after local login, the reason I analyzed should be caused by an incorrect permission of the lightdm service or the user, but I don’t know how to troubleshoot it.

Sep 23 08:39:56 *** systemd[1]: Starting lightdm.service - Light Display Manager...
Sep 23 08:39:56 *** systemd[1]: Started lightdm.service - Light Display Manager.
Sep 23 08:40:03 *** lightdm[1695]: pam_unix(lightdm-greeter:session): session opened for user lightdm(uid=110) by (uid=0)
Sep 23 08:40:03 *** lightdm[1695]: gkr-pam: couldn't unlock the login keyring.
Sep 23 08:40:03 *** lightdm[1452]: Error activating login1 session: GDBus.Error:org.freedesktop.DBus.Error.NotSupported: Operation not supported
Sep 23 08:40:05 *** lightdm[1943]: pam_succeed_if(lightdm:auth): requirement "user ingroup nopasswdlogin" not met by user "***"
Sep 23 08:40:15 *** lightdm[1943]: gkr-pam: unable to locate daemon control file
Sep 23 08:40:15 *** lightdm[1943]: gkr-pam: stashed password to try later in open session
Sep 23 08:40:15 *** lightdm[1943]: pam_unix(lightdm:session): session opened for user ***(uid=1000) by (uid=0)
Sep 23 08:40:15 *** lightdm[1943]: gkr-pam: unlocked login keyring
Sep 23 08:40:15 *** lightdm[1452]: Error activating login1 session: GDBus.Error:org.freedesktop.DBus.Error.NotSupported: Operation not supported
6

LightDM - Debian Wiki Documentation

lightdm --show-config

Comparing the parameters of the lightdm service between ubuntu mate 14 and ubuntu mate 24, we found that the default parameters of greeter-session are different. Add greeter-session=lightdm-gtk-greeter in /etc/lightdm/lightdm.conf and the problem is solved.

4 Likes