Debian Graphical Issues

Introduction

When working with Debian Linux, you might occasionally encounter graphical issues that prevent your system from displaying correctly. These problems can range from minor annoyances like screen flickering to critical failures where the graphical environment refuses to start. Understanding the structure of Debian's graphical stack and common troubleshooting techniques will help you diagnose and resolve these issues efficiently.

This guide targets beginners who are new to Debian and Linux systems. We'll explore the different components of Debian's graphical subsystem, identify common problems, and learn effective troubleshooting methods.

Understanding Debian's Graphical Stack

Before diving into specific issues, it's important to understand how the graphical system in Debian works. The graphical stack consists of several layers:

1. Hardware: Your GPU (Graphics Processing Unit) and monitor
2. Kernel/Drivers: Linux kernel and specific GPU drivers
3. Display Server: X.Org (X11) or Wayland
4. Desktop Environment: GNOME, KDE, XFCE, etc.
5. Applications: Programs that run within the desktop environment

Issues can occur at any of these levels, so troubleshooting often involves identifying which component is causing the problem.

Common Debian Graphical Issues

1. Black Screen After Boot

One of the most common issues is encountering a black screen after booting Debian.

Possible Causes:

• Missing or incorrect GPU drivers
• Incompatible display server settings
• Issues with the display manager

Troubleshooting Steps:

1. Access a terminal: Press Ctrl+Alt+F2 to switch to a virtual terminal.

2. Check system logs:

sudo journalctl -b | grep -i error

3. Verify the graphics driver:

lspci -v | grep -A 10 VGA

4. Reinstall the display manager:

sudo apt update
sudo apt install --reinstall lightdm  # or gdm3, sddm depending on your system

2. Screen Resolution Problems

Another common issue involves incorrect screen resolution or refresh rate.

Troubleshooting Steps:

1. Check available resolutions:

xrandr

2. Set a specific resolution:

xrandr --output HDMI-1 --mode 1920x1080

3. Generate a mode if your desired resolution isn't listed:

# Create a new mode
xrandr --newmode "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync

# Add the mode to your output
xrandr --addmode HDMI-1 "1920x1080_60.00"

# Apply the mode
xrandr --output HDMI-1 --mode "1920x1080_60.00"

4. Make resolution changes permanent:

Create or edit the file /etc/X11/xorg.conf.d/10-monitor.conf:

sudo mkdir -p /etc/X11/xorg.conf.d
sudo nano /etc/X11/xorg.conf.d/10-monitor.conf

Add the following content:

Section "Monitor"
    Identifier "HDMI-1"
    Option "PreferredMode" "1920x1080"
EndSection

3. Graphics Driver Issues

Graphics driver issues are a common source of problems, especially with NVIDIA and AMD GPUs.

Identifying Your Graphics Card:

lspci | grep -i vga

Installing Drivers:

For Intel (open-source drivers are included by default):

sudo apt update
sudo apt install xserver-xorg-video-intel

For NVIDIA:

sudo apt update
sudo apt install nvidia-driver

For AMD:

sudo apt update
sudo apt install firmware-amd-graphics

Testing if 3D acceleration is working:

glxinfo | grep "direct rendering"

If working correctly, you should see: direct rendering: Yes

4. Screen Tearing

Screen tearing appears as horizontal lines across moving content, most noticeable in videos or games.

Solution for Intel:

Create a file /etc/X11/xorg.conf.d/20-intel.conf:

sudo nano /etc/X11/xorg.conf.d/20-intel.conf

Add the following content:

Section "Device"
    Identifier "Intel Graphics"
    Driver "intel"
    Option "TearFree" "true"
EndSection

Solution for NVIDIA:

Open the NVIDIA settings:

sudo nvidia-settings

Navigate to "X Server Display Configuration" → "Advanced" and enable "Force Composition Pipeline" or "Force Full Composition Pipeline".

5. Display Manager Fails to Start

If your display manager (login screen) fails to start, you might need to reconfigure it.

sudo dpkg-reconfigure lightdm  # or gdm3, sddm

To check the status of your display manager:

systemctl status lightdm  # or gdm3, sddm

6. Multiple Monitor Issues

Problems with multiple monitors are common, especially when using different resolutions or orientations.

Basic Configuration:

xrandr --output HDMI-1 --auto --output DP-1 --auto --right-of HDMI-1

Creating a Persistent Configuration:

Use the arandr tool for a graphical interface:

sudo apt install arandr
arandr  # arrange screens visually and save configuration

This generates a script that you can add to your startup applications.

Fixing X11 and Wayland Issues

X11 Configuration

X11 is the traditional display server in Debian. When facing issues, you might need to modify its configuration:

1. Generate a basic configuration file:

sudo Xorg -configure

2. Edit the generated file:

sudo cp /root/xorg.conf.new /etc/X11/xorg.conf
sudo nano /etc/X11/xorg.conf

Switching Between X11 and Wayland

Sometimes, switching between display servers can resolve issues:

To check which display server you're using:

echo $XDG_SESSION_TYPE

To switch from Wayland to X11 in GDM:

Edit /etc/gdm3/daemon.conf:

sudo nano /etc/gdm3/daemon.conf

Uncomment the line:

WaylandEnable=false

Then restart GDM:

sudo systemctl restart gdm3

Debugging Tools and Techniques

1. Examining Log Files

Log files are crucial for diagnosing graphical issues:

# Check X.Org logs
cat /var/log/Xorg.0.log | grep EE  # Errors
cat /var/log/Xorg.0.log | grep WW  # Warnings

# Check system logs
journalctl -b | grep -i x11
journalctl -b | grep -i wayland

2. Testing with a Minimal X Session

To test if the issue is with your desktop environment or the X server itself:

sudo apt install xterm
startx /usr/bin/xterm

If xterm starts, the problem is likely with your desktop environment rather than X11.

3. Checking GPU Status and Temperature

Overheating can cause graphical glitches:

sudo apt install lm-sensors
sudo sensors-detect  # Follow the prompts
sensors  # Check temperatures

For NVIDIA GPUs:

nvidia-smi

Real-World Examples

Example 1: Fixing Flickering Screen on Intel Graphics

A common issue with Intel graphics is screen flickering. Here's how to fix it:

1. Create a configuration file:

sudo nano /etc/modprobe.d/intel-graphics.conf

2. Add the following line:

options i915 enable_rc6=0

3. Reboot the system:

sudo reboot

Example 2: Resolving NVIDIA Driver Installation Issues

When NVIDIA drivers fail to install properly:

1. Remove existing NVIDIA packages:

sudo apt purge nvidia*

2. Blacklist the nouveau driver:

sudo nano /etc/modprobe.d/blacklist-nouveau.conf

Add:

blacklist nouveau
options nouveau modeset=0

3. Update initramfs:

sudo update-initramfs -u

4. Reboot the system:

sudo reboot

5. Install NVIDIA drivers:

sudo apt update
sudo apt install nvidia-driver

Example 3: Setting Up Automatic Screen Configuration at Login

To automatically configure screens when logging in:

1. Use arandr to visually set up your screens and save the configuration as a script.

2. Edit your autostart file:

mkdir -p ~/.config/autostart
nano ~/.config/autostart/monitor-setup.desktop

3. Add:

[Desktop Entry]
Type=Application
Exec=/path/to/your/saved/screen-setup.sh
Hidden=false
X-GNOME-Autostart-enabled=true
Name=Monitor Setup
Comment=Sets up monitors automatically

Common Command Reference

Here's a quick reference of useful commands for troubleshooting graphical issues:

Command	Description
xrandr	Display and manipulate screen outputs
lspci -v | grep -A 10 VGA	Show graphics card information
glxinfo | grep rendering	Check if direct rendering is working
sudo lshw -C display	List hardware details for display devices
inxi -G	Show graphics and display information
cat /var/log/Xorg.0.log	View X server logs
systemctl status display-manager	Check display manager status

Summary

Troubleshooting graphical issues in Debian requires understanding the graphical stack components and applying systematic debugging techniques. We've covered:

• The structure of Debian's graphical system
• Common issues and their solutions
• Driver installation and configuration
• Multiple monitor setup
• X11 and Wayland configuration
• Debugging tools and techniques

Remember that graphical issues often result from driver incompatibilities, configuration problems, or hardware limitations. By systematically identifying which component is causing the problem, you can apply the appropriate solution.

Additional Resources

• Debian Wiki: Graphics
• Debian User Forums
• X.Org Documentation
• ArchWiki: Xorg (While for Arch Linux, contains valuable information applicable to Debian)

Practice Exercises

1. Identify your graphics card and installed driver.
2. Create a script that automatically configures your preferred screen resolution.
3. Set up a dual-monitor configuration with different orientations.
4. Investigate and resolve screen tearing issues on your system.
5. Create a backup plan for recovering from graphics driver failures (what commands would you use, what files would you modify).