Ubuntu系统启动至登录步骤后仅屏幕背光点亮，无画面显示求助

Been there, done that—this login screen issue is so frustrating, especially when you don’t want to drop £X00 on repairs. The good news? Since your Dell boot screen and Ubuntu’s purple loading screen work perfectly, this is almost certainly a software problem, not hardware. Let’s walk through the fixes I’ve used to resolve this exact issue for others:

1. Access a Terminal via TTY Mode #

First, we need to get into a working terminal since the GUI login screen is stuck:

• When you hit that black/grey screen (with backlight on), press Ctrl + Alt + F3 (try F2-F6 if F3 doesn’t work) to open a text-based TTY session.
• Log in with your Ubuntu username and password—you’ll have full system access here.

2. Fix Corrupted Graphics Drivers #

Misconfigured or broken graphics drivers are the #1 culprit here:

• First, identify your GPU with this command:
  lspci | grep VGA
• For NVIDIA GPUs:
  Purge old drivers and reinstall the latest compatible version:

  sudo apt purge nvidia*
  sudo apt autoremove
  sudo apt install nvidia-driver-<your-driver-version> # Replace with your GPU's correct version (e.g., 535)
  

• For Intel Integrated Graphics:
  Reinstall core display drivers to fix corruption:
  sudo apt install --reinstall mesa-utils xserver-xorg-video-intel

3. Reset Your Display Manager #

Ubuntu uses either LightDM or GDM3 to handle the login screen—let’s reset whichever you’re using:

• Check which display manager is active:
  cat /etc/X11/default-display-manager
• If using LightDM:

  sudo systemctl stop lightdm
  sudo dpkg-reconfigure lightdm
  sudo systemctl start lightdm
  

• If using GDM3:

  sudo systemctl stop gdm3
  sudo dpkg-reconfigure gdm3
  sudo systemctl start gdm3
  

• After running these, press Ctrl + Alt + F1 to switch back to the GUI—fingers crossed the login screen loads!

4. Regenerate a Fresh Xorg Configuration #

A messed-up Xorg config can block the login screen from rendering:

• Back up your current config first (just in case we need to revert):
  sudo mv /etc/X11/xorg.conf /etc/X11/xorg.conf.bak
• Generate a new, clean config file:
  sudo Xorg -configure
• Move the new config to the correct directory:
  sudo mv xorg.conf.new /etc/X11/xorg.conf
• Reboot your system with sudo reboot and test the login screen.

5. Switch to an Alternative Display Manager #

If all else fails, trying a different display manager often resolves the issue:

• Install LightDM (if you’re currently using GDM3):
  sudo apt install lightdm
• When prompted, select LightDM as your default display manager, then reboot.
• To switch back later, just run sudo dpkg-reconfigure gdm3 and select GDM3 again.

These steps have fixed this exact problem on Dell systems time and time again. Start with step 1 and work your way through—each one targets a common software cause. Let me know if any step needs clarification!

内容的提问来源于stack exchange，提问作者rca86