Linux Graphical Target Won't Start – Fix in 3 Steps

1. Systemd Default Target Changed to Multi-User

If you see a command line login instead of your desktop, someone or something changed the default target. This happens after a systemd update or if you ran systemctl set-default multi-user.target by accident.

Quick fix:

1. Log in with your username and password.
2. Run this command to check the current default target:

   systemctl get-default

   You'll probably see multi-user.target instead of graphical.target.
3. Switch it back:

   sudo systemctl set-default graphical.target

   After you hit Enter, you should see a message like Created symlink .... No error means it worked.
4. Reboot:

   sudo reboot

   This time the GUI should start.

If the GUI still doesn't appear after reboot, move to the next step.

2. Display Manager Service Won't Start (gdm3, lightdm, sddm)

Your graphical target might be set correctly, but the display manager itself crashed. This is common after a system update or after installing a new desktop environment.

Check which display manager you have:

systemctl status display-manager

You'll see something like gdm3.service (GNOME), lightdm.service (XFCE, Cinnamon), or sddm.service (KDE). If the status shows inactive (dead) or failed, do this:

1. Look at the logs to see why it failed:

   journalctl -u display-manager -b | tail -50

   Look for lines that say failed to start or error. Common reasons: missing config files, permission issues, or a broken Xorg.
2. Try to start it manually:

   sudo systemctl start display-manager

   If it says Job failed, check the logs again.
3. If the logs show something like Can't open /dev/dri/card0 or No screens found, your GPU driver is the problem (see step 3).
4. Sometimes the fix is reinstalling the display manager. On Ubuntu/Debian:

   sudo apt install --reinstall gdm3

   Replace gdm3 with your display manager.

My personal opinion: If you have multiple display managers installed, they sometimes fight. Stick with one. Remove the others with sudo apt remove lightdm sddm (adjust to what you have). Then reinstall your main one.

3. Xorg or NVIDIA Driver Crashed

This is the most annoying one. Your display manager starts, then crashes immediately because Xorg can't talk to your graphics hardware.

How to spot it:

• You see the login screen for a second, then it goes black and kicks you back to the login screen.
• Or you just get a blinking cursor on a black screen.
• Run this to see Xorg errors:

  cat /var/log/Xorg.0.log | grep EE

  Lines starting with (EE) are errors. Common ones: No devices detected, Failed to load module nvidia.

Fix for NVIDIA cards (most common culprit):

1. Boot into recovery mode or use Ctrl+Alt+F2 to get a terminal.
2. Purge the NVIDIA driver completely:

   sudo apt purge nvidia-*

3. Reinstall the recommended driver:

   sudo ubuntu-drivers autoinstall

   Or on other distros: sudo apt install nvidia-driver-545 (check what's current).
4. Reboot: sudo reboot

Fix for integrated Intel or AMD graphics:

1. Check if the modesetting driver is loaded:

   ls /usr/lib/xorg/modules/drivers/

   You should see modesetting_drv.so or intel_drv.so. If not, reinstall xserver-xorg-video-intel or xserver-xorg-video-amdgpu.
2. Rarely, the kernel mode setting (KMS) breaks. Add nomodeset to your boot parameters:

   sudo nano /etc/default/grub

   Find the line GRUB_CMDLINE_LINUX_DEFAULT and add nomodeset inside the quotes. Save, then run sudo update-grub and reboot.

One more thing: If you have both an integrated GPU and a discrete NVIDIA card (laptop), the BIOS setting or prime-select can cause this. Run sudo prime-select nvidia or sudo prime-select intel to switch.

Quick-Reference Summary Table

Start with step 1. Most people fix it there. If not, move to step 2, then step 3. Don't skip steps – they build on each other.