RHEL 8.x XDMCP Configuration(RHEL 8.0, RHEL 8.1)

XDMCP configuration

1. Install Extra Packages for Enterprise Linux

   [root@yourhost ~]# dnf install https://dl.fedoraproject.org/pub/epel/epel-release-latest-8.noarch.rpm
   Or
   [root@yourhost ~]# dnf install https://cdn.netsarang.com/utils/epel-release-8-5.el8.noarch.rpm

2. Download lightdm-greeter and install the greeter first
   (There is no greeter for lightdm in RHEL 8's epel packages. Therefore, you'll need to install lightdm-gtk-greeter from epel 7's packages. Because of dependencies, other lightdm packages will be downloaded and installed.)

   [root@yourhost ~]# wget https://cdn.netsarang.com/utils/lightdm-gtk-1.8.5-19.el7.x86_64.rpm https://cdn.netsarang.com/utils/lightdm-gtk-common-1.8.5-19.el7.noarch.rpm
   [root@yourhost ~]# dnf install ./lightdm-gtk-common-1.8.5-19.el7.noarch.rpm
   ...
   Installed:
     lightdm-gtk-common-1.8.5-19.el7.noarch                                                                                                   
     
   Complete!
   [root@yourhost ~]# dnf install ./lightdm-gtk-1.8.5-19.el7.x86_64.rpm 
   Last metadata expiration check: 0:16:11 ago on Tue 24 Dec 2019 04:43:34 AM GMT. 
   Dependencies resolved. 
   ============================================================================================
   Package Arch Version Repository Size 
   ============================================================================================
   Installing: 
   lightdm-gtk x86_64 1.8.5-19.el7 @commandline 58 k 
   Installing dependencies: 
   lightdm x86_64 1.30.0-3.el8 epel 229 k 
   lightdm-gobject x86_64 1.30.0-3.el8 epel 77 k 
   
   Transaction Summary 
   ============================================================================================
   Install 3 Packages 
   
   Total size: 364 k 
   Total download size: 307 k 
   Installed size: 938 k 
   Is this ok [y/N]:y

3. Configure lightdm.conf for XDMCP

   [root@yourhost ~]# vi /etc/lightdm/lightdm.conf
   ... 
   [XDMCPServer] 
   enabled=true 
   ...

4. Stop gdm and disable it to prevent it from starting after rebooting.

   [root@yourhost ~]# systemctl disable gdm; systemctl stop gdm

5. Start lightdm and enable it to have it start after rebooting.

   [root@yourhost ~]# systemctl enable lightdm; systemctl start lightdm

6. Disable the OS's firewall or allow UDP port 177 from the firewall's configuration.

   [root@yourhost ~]# systemctl stop firewalld

How to check if XDMCP is configured properly.

1. Process running

   [root@yourhost ~]# ps -aef |grep lightdm root 8079 1 0 05:31 ? 00:00:00 /usr/sbin/lightdm ...

2. Port listening

   [root@yourhost ~]# netstat -anep |grep :177 
   udp        0      0 0.0.0.0:177             0.0.0.0:*                           0          90932      8079/lightdm
   udp6       0      0 :::177                  :::*                                0          90933      8079/lightdm

3. Checking the Firewall
   The firewall status should be one of the following:
   In case of an enabled firewall:

   [root@yourhost ~]# firewall-cmd --zone=`firewall-cmd --get-default-zone` --list-all 
   public (active) 
   	...
   	ports: 177/udp 
   	...

   In case of a disabled firewall:

   [root@yourhost ~]# firewall-cmd --zone=`firewall-cmd --get-default-zone` --list-all 
   FirewallD is not running 
   FirewallD is not running

Xfce-desktop installation for a user's desktop environment

1. Download and extract Xfce-desktop packages
   (EPEL 8 does not contain packages related to Xfce-desktop. The following packages are those of EPEL 7.)

   [root@yourhost ~]# wget https://cdn.netsarang.net/utils/Xfce-desktop-4.12.4.3.tar.gz 
   [root@yourhost ~]# tar xvzf Xfce-desktop-4.12.4.3.tar.gz

2. Install all packages

   [root@yourhost ~]# cd Xfce-desktop-4.12.4.3; rpm -i --nodeps --force *.rpm

3. Restart lightdm

   [root@yourhost ~]# systemctl restart lightdm

4. Select the Xfce session at the XDMCP greeter