Problem launching graphical user interface (GUI) applications

Any application that requires an X Window System cannot be launched.

When you attempt to start a graphical user interface (GUI), the application does not start. There are no error messages to indicate the reason for the problem.
  • The user who is attempting to run the application is not authorized to use the X Window session.
    This problem typically occurs in the following situations:
    • A user logs in to the system as user root, switches to a non-root user, and then attempts to run a GUI application.
    In these situations, the non-root user cannot start the GUI application because the X Window session was started as user root when the user initially logged on to the system as root.

  • The user who is attempting to run the application used the Linux™ ssh command to open a terminal on a remote machine but did not specify the -X option to enable X11 forwarding.
Use the following methods to determine if the user is authorized to use the X Window session:
  1. Enter xclock from a command prompt. Messages similar to the following example are displayed:
    [streamsadmin@host1 ~]$ xclock
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

  2. Enter firefox from a command prompt. Messages similar to the following example are displayed:
    [streamsadmin@host1 ~]$ firefox
Xlib: connection to ":0.0" refused by server
Xlib: No protocol specified

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

Error: cannot open display: :0.0

  • If the user is not authorized to use the X Window session:
    1. Log out of the system.
    2. Log on to the system as a non-root user.
    3. Run the GUI application.

  • If the user opened a terminal on a remote machine by using the Linux™ ssh command:
    1. Open a terminal by using the ssh -X command to enable X11 forwarding.
    2. Run the GUI application.