Merge pull request #182 from carla-simulator/tutorial_for_running_headless

Tutorial for running headless

Docs/carla_on_server.md

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+Running CARLA Remotely and without Display
+------
+
+
+This tutorial is designed for: 
+- Remote server users that have several nvidia  graphical cards and want to effectively use CARLA on all GPUs.
+-  Desktop users who want to use the GPU that is not plugged on the screen for rendering CARLA.
+
+
+On this tutorial you will learn.
+- How to configure your server to have nvidia working on rendering without a display attached.
+-  How to use VNC + VGL to simulate a display connected to any GPU you have in your machine.
+- And Finally, how to run CARLA in this environment
+
+This tutorial was tested in Ubuntu 16.04 and using NVIDIA 384.11 drivers.
+## Preliminaries 
+
+A few things need to be working in your server before.
+ Latest NVIDIA Drivers, OpenGL,  VirtualGL(VGL), TurboVNC 2.11, ,
+#### NVIDIA Drivers
+Download and install NVIDIA-drivers with typical tutorials
+http://www.nvidia.es/Download/index.aspx
+#### OpenGL
+Openg GL is necessary for Virtual GL. Normally OpenGL
+can be installed through apt.
+
+    sudo apt-get install freeglut3-dev mesa-utils
+####  VGL
+Follow this tutorial and install vgl
+https://virtualgl.org/vgldoc/2_2_1/#hd004001
+
+#### TurboVNC
+Follow the tutorial below to install TurboVNC 2.11
+https://cdn.rawgit.com/TurboVNC/turbovnc/2.1.1/doc/index.html#hd005001
+
+WARNING: Take care on which VNC you install as it may not be compatible with Unreal. The one above was the only one that worked for me. 
+#### Extra Packages
+These extra packages were necessary to make unreal to work.
+
+    sudo apt install x11-xserver-utils libxrandr-dev
+
+
+
+
+#### Configure your X
+
+You must generate a X compatible with your nvdia and compatible to run without display. For that, the following command worked:
+
+    sudo nvidia-xconfig -a --use-display-device=None --virtual=1280x1024
+
+
+
+## Emulating The Virtual Display
+
+Start by killing all Xorg servers. This command could change depending on your system.
+
+    sudo service lightdm stop
+
+Run your own Xorg. Here I use number 7, but it could be labeled with any free number.
+
+    sudo nohup Xorg :7 &
+
+Run an auxiliary remote VNC-Xserver. This will create a
+virtual display  "8".
+
+    /opt/TurboVNC/bin/vncserver :8
+
+If everything is working fine the following command
+should run smoothly.
+
+    DISPLAY=:8 vglrun -d :7.0 glxinfo
+Note. This will run glxinfo on Xserver 7, device 0. This means you are selecting the GPU 0 on your machine. To run on other GPU, such as GPU 1 run:
+
+    DISPLAY=:8 vglrun -d :7.1 glxinfo
+
+## Running CARLA 
+
+Now, finally, to run CARLA on a certain gpu_number placed in a certain $CARLA_PATH, run.
+
+    DISPLAY=:8 vglrun -d :7.<gpu_number> $CARLA_PATH/CarlaUE4/Binaries/Linux/CarlaUE4