How to mirror a screen in TigerVNC?

Question

How to mirror a screen?

I have an answer (VNC).
A Linux VNC server - https://help.ubuntu.com/community/VNC/Servers.

Answer 1

1. Download TigerVNC release
   (https://sourceforge.net/projects/tigervnc/files/stable/, code: https://github.com/TigerVNC/tigervnc/releases)

2. sudo cp -R [TigerVNC directory]/usr/* /usr/
   ...
   /usr/bin/vncpasswd
   ...
   /usr/bin/vncserver --help
   /usr/bin/vncserver
   ...
   

3. "Linux move window to desktop", "Linux move window to display" - Sharing an X server (session) across computers , https://superuser.com/a/315865/1514321 , How to move windows across displays in Gnome 3 with keyboard?
   / [export] DISPLAY=":1"; [app] --display=:1

4. /usr/bin/vncserver -kill :1
   

x11vnc:
sudo apt-get install x11vnc

x11vnc -usepw -display :0
...
[Ctrl-C]

x11vnc opts: -find, -clip ... -opts / info x11vnc