Ubuntu 18.04 stuck at purple loading screen after new update

Solution 1:

This issue can have two reasons:

1- your system has Nvidia graphics card and its driver is not installed.

for this you should follow these steps:

When you start your system you can see the grub menu that has options like Ubuntu, Advanced options for ubuntu and ...( I have a Asus laptop that i must press Esc to see the grub menu) select Ubuntu but don't press Enter press E instead.

You will see boot parameters for Ubuntu. in this step we are going to use an open source graphics instead of Nvidia temporarily to install the right graphics driver. in the line which starts with linux add this at the end of the line: nauveau.modeset=0 after ... quiet splash like this: quiet splash nauveau.modeset=0

now you can press F10 to continue booting and you should see the login page and it won't be stuck. (don't do the second reasons solution if you logged in successfully. follow the final step)

2- your display manager has a problem.

When you upgrade to 18.04, Ubuntu uses gdm as a default display manager that has more code complexity than lightdm. so you should change it to lightdm (even if your Ubuntu uses lightdm do it anyway because maybe lightdm is broken)

go to recovery mode and bring up the shell(with networking enabled) as root now type these commands:

 sudo apt-get update
 sudo apt-get install --reinstall lightdm
 sudo dpkg-reconfigure lightdm

select lightdm as default display manager and reboot you should see the login page.

I recommend you to do both solutions at the same time if you are not sure which to use.

Final Step

now after logging in you should install the right version of Nvidia graphics on your system. type the following commands:

sudo apt-get purge nvidia*
sudo ubuntu-drivers devices

now you can see the drivers available for you Nvidia graphic card install the recommended version like this (the version can be different on your system but mine is 390):

sudo apt-get install nvidia-390

Warning: don't add any PPA for Nvidia

after installation is complete reboot your system normally and it must work.