View source for Troubleshooting/Black Screen

== '''My computer boots to a Black screen''' ==

Please keep in mind that this page is just an experiment to collect the working solutions to common problems from hundreds of forum posts to a wiki-like troubleshooting page. It assumes you are running KDE Neon or another Debian based distribution.
It needs to be checked by experienced users.

====If you have a '''GPU''' and can't see the login screen====
<big>If the '''loading screen''' freezes during boot, try adding the nomodeset parameter to GRUB</big>

[https://itsfoss.com/fix-ubuntu-freezing/ Here you can find a detailed tutorial about fixing a frozen loading screen.]

The newest kernels have moved the video mode setting into the kernel. This makes it possible to have high resolution nice looking splash (boot) screens and flicker free transitions from boot splash to login screen. Unfortunately, on some video cards this doesn't work properly and you end up with a black screen. Adding the nomodeset parameter instructs the kernel to not load video drivers and use BIOS modes instead until X is loaded.

To edit Grub2 during the boot process try the following:
# Immediately after the BIOS splash screen during boot, press and hold the <keycap>SHIFT</keycap> button. This will display you grub containing a list of kernels and recovery options
# Press e to edit the first kernel displayed
# Find the line ending with quiet splash. Add your boot option before these key words - i.e. so the line looks like [...]nomodeset quiet splash
# Press CTRL+ X to boot

If you have an '''Nvidia RTX 30 series''' GPU you need to add nomodeset AND nouveau.nomodeset=1 to the boot parameters. 
While in the grub menu, hit E and then in the line with the boot options, add both of those, and also make sure any i915, amdgpu, or radeon modeset options are also disabled (if it says radeon.nomodeset=0, change it to 1, for example).
The 30 series has no support in Nouveau yet, so obviously it's not going to work. - <small>u/gatrdotd426</small>

===== Update/reinstall GPU drivers =====
<small>from linuxconfig.org/how-to-install-the-nvidia-drivers-on-ubuntu-20-04-focal-fossa-linux</small>

Press ctrl+alt+f2 to go to the terminal and log in.
You can install the recommended drivers for your GPU with: 
    sudo ubuntu-drivers autoinstall
You can install the driver version you prefer with:
    sudo apt install nvidia-driver-440
If the installation is successful reboot with:
    sudo reboot

==If you can see the cursor or the login screen==
=== Has something crashed when you turned off your PC? ===  
<big>Have you recently updated?</big>
<small>Blumen wrote on Reddit:</small>  
If you can see your cursor, but there is no wallpaper and panel, this means the process  
plasmashell crashed. Try running:  
     systemctl --user restart plasma-plasmashell.service

<small>tinny123 wrote:</small>  
===== Do you have offline updates turned off? ===== 
Then it's possible you didn't let discover finish installing updates so you have now broken packages.  
When you get to the black screen hit    ctrl+alt+f1    and log in into terminal with your username and password.  
It would be good if you can connect your pc to the internet.  

In terminal run these commands:
    sudo apt update  

    sudo apt dist-upgrade  

    sudo apt install -f   


If the system freezes in command-line mode too:
<small>emvaized wrote:</small>
Situation: The latest update included '''updated Nvidia drivers'''.
System boots up with nomodeset flag, but completely freezes in 4 or 5 seconds, even the cursor.
The same happens when I try to boot in recovery mode or the command-line mode. 

A solution to fix broken packages:
1. Boot system from Live USB
2.  Get to the current installation terminal from live usb system's terminal - as described [https://askubuntu.com/questions/34888/is-there-any-way-to-roll-back-the-most-recent-upgrade/34908#34908 here], by opening terminal from current installation drive in Dolphin and performing these commands ('sda1' was actually 'sda2' in this case, due to dual-boot with W10):
    sudo mount /dev/sda1 /mnt
    sudo mount --bind /dev /mnt/dev
    sudo mount --bind /proc /mnt/proc
    sudo mount --bind /sys /mnt/sys
    sudo chroot /mnt

3. Run the following command from here to get full list of all packages that were installed in latest 72 hours (more out of curiosity):
    find /var/lib/dpkg/info/ -name \*.list -mtime -3 | sed 's#.list$##;s#.*/##'

4.Update all installed packages (then reboot back to system to check) with:
    sudo apt update
    sudo apt full-upgrade 

5. If the issue isn't resolved run:
    sudo ubuntu-drivers autoinstall
this command finds broken packages and version mismatches between Nvidia libraries, and automatically fixed them.

===== Do you have python modules installed? =====
You can try fixing update errors with already existing python modules: remove the old version from the system installation with  
    sudo pip uninstall python-<the module to uninstall>

===== Have you installed kernel updates lately? ===== 
You can try booting with a different kernel from the GRUB menu (Advanced options for GNU/Linux).

=== If you can't see your mouse: ===

You can try hitting ctrl+alt+f2 to a terminal then running:
    startx

It's possible that your home directory is so full it stops the GUI from loading. You can try booting from a live-USB and cleaning up some space.  
If you can't boot from a live-USB it's likely you have a hardware problem with your PC.