VNC server set up : -auth guess: failed for display='unset'

Question

I am trying to setup vncserver(on ubuntu 18.04) remotely using putty. I was taking reference from https://tecadmin.net/setup-x11vnc-server-on-ubuntu-linuxmint/ . Although I got following message with repetition with different port numbers:

14/03/2020 19:29:18 passing arg to libvncserver: /path/.vnc/passwd
14/03/2020 19:29:18 passing arg to libvncserver: -rfbport
14/03/2020 19:29:18 passing arg to libvncserver: 5900
14/03/2020 19:29:18 x11vnc version: 0.9.13 lastmod: 2011-08-10  pid: 8026
14/03/2020 19:29:18 -auth guess: failed for display='unset'
14/03/2020 19:29:18 -auth guess: since we are root, retrying with FD_XDM=1
14/03/2020 19:29:18 -auth guess: failed for display='unset'

Do I need to set display in some file?

Answer 1

Try adding export DISPLAY=:1 before running the command described in the link.

e.g.

export DISPLAY=:1
sudo x11vnc -auth guess -forever -loop -noxdamage -repeat -rfbauth /home/YOUR_USER/.vnc/passwd -rfbport 5900 -shared