Root Cannot Open a PDF Ubuntu while users can

Question

I'm using Ubuntu 16.04 and I tried to open a pdf using evince.

It worked well when I'm logged in the normal user but not when I'm using sudo or switch to root user.

Answer 1

It's all about the permission to access the display server.

Generally, depending on your setup, you may need to allow root to access the xserver . https://askubuntu.com/a/175615/668478

If you run on mir, you should use gksudo to allow root to access mir .