Oracle Linux 7.x XDMCP Configuration

Oracle Linux 7.x's default user environment, Gnome, uses hardware acceleration to render the graphics. Therefore, when remotely connecting with Xmanager, you may not be able to access the the desktop user environment or if you are able to connect, it will run very slowly.

As such, you will have to use a different user environment than Gnome and a different XDMCP Daemon than gdm.

Use the following instructions to install lightdm and Xfce (or KDE) as the XDMCP Daemon and desktop user environment to connect to RHEL 7. These instructions require root privileges. Be extra careful when making configurations with root privileges.

XDMCP Configuration

lightdm Installation

Add a new source repository:

# rpm -ivh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

# yum install lightdm-gtk

lightdm Configuration

Configure the /etc/lightdm/lightdm.conf file as follows. If the file does not exist, create it.
```
[XDMCPserver] 
enabled=true 
```

Change Default Display Manager to lightdm

# systemctl disable gdm ; systemctl enable lightdm

Though gdm is disabled, it is still running and will need to be stopped replaced by lightdm (This is unnecessary if you initiated a reboot after Step 3)
```
# systemctl stop gdm; sleep 3;  systemctl start lightdm
```
Temporarily Disable Firewall to Test Connection
```
# systemctl stop firewalld.service
```
Open UDP port 177 from the PC to the remote host direction. Refer to your OS manual for support concerning your firewall.

User Desktop Environment Configuration

Add a New Source Repository (If you already installed it above, you can skip this step)
```
# rpm -ivh https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm
```
Install New Desktop User Environment (Choose one or the other)

Xfce Installation
```
# yum groupinstall xfce

(In some case --skip-broken option is needed.)
```
KDE Installation(Optional)
```
# yum groupinstall kde-desktop
```
Apply New Environment and Restart XDMCP Daemon
```
# systemctl restart lightdm
```
Connect with Xmanager

Select Xfce or KDE from the login screen