About DISPLAY, remote desktop etc

[esolve]

I want to remotely control a computer
when I type "firefox" on shell through vpn
it prompts: "

[root@canard ~]# firefox
Error: no display specified

"

a solution is

export DISPLAY=":0.0"

while I want to use tigerVNC, a remote Desktop tool, I configure the vnc server on that computer by following the article:

zeusville.wordpress.com/2012/01/27/setting-up-vncserver-on-fedora-16/

it says:

For our example I will setup vncserver to have display :3 running at a resolution of 1600×900. If you want a different number simply replace it with the number of choice.

my question is:

what is the meaning of the 3 and :0.0
if I hope tigerVNC and the vpn shell are using the same window, namely, if I type "firefox" on vpn shell and I can see the opened browser window on tigerVNC client, what numbers should I set?
thanks!

[atreyu]

think of the VNC display number "3" as "3.0". so in your vpn session, if you want to send your display to the VNC session, do:

export DISPLAY=<ip_address>:3.0

[esolve]

now I come to the remote computer, since I have ever export DISPLAY=:0.0
now I can't open firefox on this computer
how to recover?

[atreyu]

now I come to the remote computer, since I have ever export DISPLAY=:0.0
now I can't open firefox on this computer
how to recover?

i'm not sure what you mean. are you saying you are trying to open Firefox on your local machine?

please state exactly what you are trying to do, explain which machine you are on, and also show the output of:

echo $DISPLAY