GUI with Oracle Linux 7 doesn't launch

Are you perhaps confusing technologies trying to run a remote GUI application? Mobaxterm is SSH with X11 forwarding, hence using the X Server of Mobaxterm running on your local PC. You normally use Mobaxterm to avoid installing a GUI desktop on your Linux server.

Please explain what you're trying to accomplish?

The requirements or concepts to run a GUI app on a Linux system can be confusing because there are fundamentally different ways, and a lot of obsolete and outdated information that has piled up over decades of history. RHEL 7, and hence Oracle Linux 7, adds additional challenges with systemd and because previous tools are no longer supported or available, and do work correctly anymore.

If you have long running session, or wish to share or resume remote GUI connection, VNC over SSH is currently the best method. It's also the most complex to configure.

I won't criticize or analyze the Oracle video you posted, but you may find a better turn key solution with the following: VNCpilot - Simple And Secure Remote Access

In your case, I suppose the following should work:

yum install https://community.oracle.com/servlet/JiveServlet/downloadBody/1024832-102-9-193762/vncpilot-1.0.2-1.el7.x86_64.rpm

vncpilot --create -size=1280x800

Then use the machine specific credentials provided by the summary screen to establish a secure SSH tunnel from your PC desktop to the Linux server. Start a VNC client on the same PC desktop and connect it to localhost:5995, which is mapping localhost of the remote Linux server through the secure SSH tunnel you just created.

If you no longer need the VNC service, simply dump it.

vncpilot --delete

There are also Java based VNC clients that include an SSH client as mentioned in the tutorial.

Again, there is no need to install X Window Server on the remote Linux server and you don't want to. The TigerVNC server creates a virtual desktop session, that can only be used by a VNC client.

i did the install command but unfortunatly when writing "vncpilot --create -size=1280x800", I have "command not found"

Then it wasn't installed or your $PATH is not default. What exactly did you do?

I just tried the following:

[root@localhost ~]# yum install https://community.oracle.com/servlet/JiveServlet/downloadBody/1024832-102-9-193762/vncpilot-1.0.2-1.el7.x86_64.rpm

.... etc

Dependencies Resolved

Installing:

vncpilot     x86_64     1.0.2-1.el7     /vncpilot-1.0.2-1.el7.x86_64      18 k

.... etc

Total size: 18 k

Installed size: 18 k

Is this ok [y/d/N]: y

If you don't get this, please check your current date and time and make sure all is set correctly. Otherwise the SSL certificate may not work.

Once it's installed:

What do you see with the following:

# echo $PATH

# export PATH=/usr/local/bin:$PATH

# vncpilot -c -size=1280x800

You put an asterix or wildcard (*) in the size parameter.

Please try -size=1280x800 instead, or any other valid screen resolution you prefer.

Regarding $PATH, you may have an error in .bashrc causing to it to bail out early. /usr/local/bin is part of the environment path by default and there's no reason why you don't want to.

That's correct, you use ssh -L 5901.... at the command line of your Windows PC as shown in the summary line. MobaXterm does not come into play here at all. Once the SSH tunnel is established, you will need to make a make a VNC connection to localhost as described in the summary as well. You find examples in the mentioned document.

Your SSH command to create the tunnel timed out - that's odd. Don't you use ssh to connect to the Linux server? Can you make a regular ssh connection?