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How To Run GUI Programs as Another User in Ubuntu: Troubleshooting Mir Connection Error

Ubuntu 14

In Ubuntu, running Graphical User Interface (GUI) programs as another user can sometimes lead to a common error: “Failed to connect to Mir: Failed to connect to server socket: No such file or directory.” This error is often due to the DISPLAY environment variable not being correctly set for the user. This article will provide a step-by-step guide to troubleshoot and resolve this issue.

Quick Answer

To run GUI programs as another user in Ubuntu, you can manually set the DISPLAY variable, use the xsudo wrapper script, modify the sudoers file, or check the correct value for DISPLAY. These solutions should help troubleshoot and resolve the Mir connection error.

Understanding the Problem

The DISPLAY environment variable in Unix and Linux specifies which display server to connect to by default. It is used by GUI programs to draw on the screen. When you try to run a GUI program as another user, the system may not be able to find the correct display server, leading to the Mir connection error.

Solution 1: Manually Set the DISPLAY Variable

The first solution is to manually set the DISPLAY variable for the user. Here’s how to do it:

  1. Open a terminal. You can do this by pressing Ctrl+Alt+T.
  2. Log in as the desired user using the command sudo -u username -i. Replace “username” with the actual username.
  3. Check the current user’s home directory using the pwd command. This will confirm that you are in the correct user’s home directory.
  4. Set the DISPLAY variable to :0 or :1, depending on your system, using the command export DISPLAY=:0 or export DISPLAY=:1. This command tells the system which display server to use.
  5. Run the GUI program again.

Solution 2: Use the xsudo Wrapper Script

The second solution involves using a wrapper script called xsudo. This script automatically sets the DISPLAY variable for you.

  1. Download the wrapper script from the provided link and save it as /usr/local/bin/xsudo.
  2. Make the script executable using the command chmod +x /usr/local/bin/xsudo. The chmod command changes the file permissions, and the +x option makes the file executable.
  3. Run the GUI program using the command xsudo username program_name. Replace “username” with the actual username and “program_name” with the name of the GUI program.

Solution 3: Modify the sudoers File

The third solution is to modify the sudoers file to automatically keep the DISPLAY variable when using sudo.

  1. Open the sudoers file using the command sudo visudo. The visudo command opens the sudoers file in a safe way, checking for syntax errors before saving.
  2. Add the line Defaults env_keep+="DISPLAY" at the end of the file. This line tells sudo to keep the DISPLAY variable.
  3. Save and exit the file.
  4. Run the GUI program again.

Solution 4: Check the Correct Value for DISPLAY

In some cases, the correct value for DISPLAY may be different, such as :1 instead of :0. Try setting the DISPLAY variable to different values and run the GUI program again.

Conclusion

The Mir connection error when running GUI programs as another user in Ubuntu can be frustrating, but it is usually easy to resolve. The solutions provided in this article should help you troubleshoot and fix the problem. Remember to always use visudo when editing the sudoers file to avoid syntax errors. If none of these solutions work, there may be other underlying issues causing the problem.

What is the purpose of the DISPLAY environment variable?

The DISPLAY environment variable in Unix and Linux specifies which display server to connect to by default. It is used by GUI programs to draw on the screen.

Why am I getting the “Failed to connect to Mir” error when running GUI programs as another user?

This error is often due to the DISPLAY environment variable not being correctly set for the user. The system may not be able to find the correct display server, leading to the Mir connection error.

How can I manually set the DISPLAY variable?

To manually set the DISPLAY variable, open a terminal, log in as the desired user using sudo -u username -i, navigate to the user’s home directory, and set the DISPLAY variable to :0 or :1 using the command export DISPLAY=:0 or export DISPLAY=:1.

What is the xsudo wrapper script and how does it help with the Mir connection error?

The xsudo wrapper script is a script that automatically sets the DISPLAY variable for you. By using the xsudo command followed by the desired username and program name, the script handles the DISPLAY variable configuration, helping to resolve the Mir connection error.

How can I modify the sudoers file to keep the DISPLAY variable?

To modify the sudoers file, open it using sudo visudo, add the line Defaults env_keep+="DISPLAY" at the end of the file, save and exit. This line instructs sudo to keep the DISPLAY variable when using sudo.

What should I do if none of the provided solutions work?

If none of the solutions provided in the article work, there may be other underlying issues causing the problem. It is recommended to seek further assistance or troubleshooting resources to identify and resolve the issue.

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