Firejail Security Sandbox - X11
Introduction
Firejail X11 #sandboxing support is built around an external #X11 server software package. Both #Xpra and #Xephyr are supported (apt-get install xpra xserver-xephyr on #Debian / #Ubuntu). To allow people to use the sandbox on headless systems, #Firejail compile and install is not be dependent on Xpra or Xephyr packages.