Can't run GUI apps: 'connection to ":0.0" refused

[^rooker]

[PROBLEM]
Sometimes when creating a user manually (adduser), this user may not have sufficient rights to connect to the X-server. So, when running any application with a graphical user interface (GUI), you'll receive this message:

Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

[SOLUTION]
Add the user to the access control list, using the command "xhost":

Code: Select all

xhost +si:localuser:username

Where "username" must be substituted by the actual user you want to add.