What is the Segmentation fault (core dumped) error?

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Hi, I'm using ROS kinetic of Ubuntu 16.04, and the Gazebo version is 7.

My work is related to Deep Reinforcement Learning, and I'm doing it with the Gazebo simulation.

And I've also DONE HAVE NVIDIA Geforce 1080 and graphic driver on my laptop.

But I'm getting the error saying,

Segmentation fault (core dumped)

I really don't have any idea and googled it and I think this might be because of Nvidia GPU according to this guy

However, I've already had Nvidia graphic card!!

Just so you know, when I did

$ sudo apt-get update

I got some errors that I'm not still familiar with,

W: Target Packages (Packages) is configured multiple times in /etc/apt/sources.list:52 and /etc/apt/sources.list.d/nvidia-cuda.list:1
W: Target Translations (en_US) is configured multiple times in /etc/apt/sources.list:52 and /etc/apt/sources.list.d/nvidia-cuda.list:1
W: Target Translations (en) is configured multiple times in /etc/apt/sources.list:52 and /etc/apt/sources.list.d/nvidia-cuda.list:1
W: Target Packages (Packages) is configured multiple times in /etc/apt/sources.list:52 and /etc/apt/sources.list.d/nvidia-cuda.list:1
W: Target Translations (en_US) is configured multiple times in /etc/apt/sources.list:52 and /etc/apt/sources.list.d/nvidia-cuda.list:1
W: Target Translations (en) is configured multiple times in /etc/apt/sources.list:52 and /etc/apt/sources.list.d/nvidia-cuda.list:1

So I removed /etc/apt/sources.list.d/nvidia-cuda.list and re-update and sudo apt-get upgrade, but it still does NOT work...

I can bring up a gazebo, but it stops by itself without my order at a certain moment.

Anyone, who is familiar with this kind of error?

Thanks in advance :)

--

P.S.

I re-post this issue because an hour passed from when I posted this issue firstly.