CentOS 7.x XDMCP Configuration

Gnome in CentOS 7 tries to use local hardware acceleration and this becomes a problem when trying to connect remotely using XDMCP. To avoid this problem, you have to use an alternative display manager (other than ‘gdm’) and desktop environment.

This guide explains how you can change the display manager to lightdm from gdm and desktop environment from Gnome to Xfce. You will require root privileges. Be extra careful when making any configurations with root privileges.

Switching Display Manager from gdm to lightdm

Switch to root account and install lightdm:
```
# yum install lightdm
```
If lightdm cannot be installed because of the system's default repository, extra repository information, EPEL (Extra Packages for Enterprise Linus), is required.
```
# yum install http://download.netsarang.com/files/etc/epel-release-7-0.2.noarch.rpm
```
Configure the lightdm config file. If file does not exist, create it:
# vi /etc/lightdm/lightdm.conf
```
[XDMCPServer]
enabled=true
```

Change the default display manager to lightdm:

# systemctl disable gdm ; systemctl enable lightdm

Start lightdm:
```
# systemctl start lightdm
```
Temporarily disable firewall to test connection. It is recommended that you allow incoming UDP port 177
```
# systemctl stop firewalld.service
```

Add Xfce and Configure as Default Desktop Environment

Add a new source repository:

# yum install http://download.netsarang.com/files/etc/epel-release-7-0.2.noarch.rpm

Install an alternative desktop environment:
```
# yum groupinstall xfce
```
Restart lightdm:
```
# systemctl restart lightdm
```
Connect with Xmanager and select Xfce