I am getting an error when I try to open the Firefox browser. I can set the variable using the command “declare -x DISPLAY=??” but I can not find what to set it to. I have tried looking on the internet as well as here and have tried “0” and “0.0”. Both of these produce an error as well. The error being “cannot open display 0”. What is the value I need to set it to?
What desktop environment are you using and how did you install Firefox?
Good question!
The tag says “server”, so perhaps there are no desktop environment. If that is the case, then the fix is to install and use a desktop environment.
Thank you for the replies. Yes I am using Fedora server 40. I have it installed on an old HP 2000-369WM laptop and keep it updated. I am currently starting a business writing IMS for the forestry industry and will be using this to simulate an intranet, ultimately a Hybrid workspace. I installed Firefox using yum. I have since found out that yum no longer exists and am now using dnf. 
An example of how I installed it is yum install firefox. I would like to be able to run Firefox from this environment also. I know that servers are almost never used by the client but I need to be able to check things on the fly.
You do need to get a desktop environment. One that is not too heavy is XFCE, which you can install using
sudo dnf group install xfce-desktop-environment
To enable that desktop environment run
sudo systemctl set-default graphical.target
Villy
That does work but not quite the way I want so now it is experiment time. If I can get it to work without going directly into a gui environment I will put another post here.