Can't log into Linux?
Can’t log into Kubuntu and possibly other KDE / Gnome distributions? Get a black screen and then you go back to the login screen?
This has happened to me twice, the latest time being about 10 minutes ago, luckily I remembered how to fix it from the first time so might as well put it up here, you never know when someone might have the same trouble (Or to remind myself if / when it happens again).
Symptoms
You Linux machine boots up to the graphical login prompt perfectly. Everything appears to be running nicely but, when you type in your password and continue, the following happens.
1. The screen goes black for a few seconds
2. The login prompt re-appears with the password field blank again as if you had just booted.
The Fix
There may be other reasons for this behaviour but whenever it happened to me it was due to a lack of disk space. I was using almost everything on my hard drive and this was causing issues with logging in.
Ok, so we know what the problem is but I can’t log in to fix it! No problem, the easiest way to fix this in my opinion is to press the following keys when you are in the graphical login prompt
CTRL + ALT + F1
This is a time machine command that will whip you back to the early 1980s and give you an old fashioned terminal prompt. From here you can log into your account using your normal username and password.
You will then be (in terminal form) logged in and inside your home directory where you can probably delete something like, purely for example you understand, a 200mb game demo installer that you forgot to delete a while ago.
A list of terminal commands can be found here. The main ones that interest you are cd (Change Directory) and rm (Remove)
Once you have deleted a file or two (preferably large ones) you can go back to the graphical login screen with
CTRL + ALT + F7
and then try logging in again normally. If it still doesn’t work go back to the terminal screen with CTRL + ALT + F1 and delete something else. Use the above mentioned F1/F7 key combinations to flit back and forth between 1980s terminal and slick 2008 GUI and keep deleting and trying again.
Once you are able to login with the GUI it is a good idea to reboot. Starting up with low memory can cause some start-up procedures to fail and rebooting now will avoid possible strange behaviour.
