I am totally new to Ubuntu which came pre-installed in my laptop. I upgraded to 14.04 version but I think it was not installed properly when I restarted the system. Now it is not letting me login even though I am entering the right password. I read somewhere to enter into root but I can't as I don't get any screen on pressing Alt+CRTL+F1 or F3.
I had a similar issue and resolved it by doing this:
It's not just F3 but it is Ctrl+Alt+F3 and login into the shell. Also, I've seen laptops that have the behavior of the FN and F buttons reversed, meaning that you have to press the FN button to actually press the F key. I have no idea why but the N5010 is such a model.
Assuming we get that far, run
If in the output the line is along these lines:
-rw------- 1 root root 53 Nov 29 10:19 .Xauthority
then you need to do
chown username:username .Xauthority
and try logging in.
ls -ld /tmp
Check for the first 10 letters in the left: they should read exactly so: drwxrwxrwt.
drwxrwxrwt 15 root root 4096 Nov 30 04:17 /tmp
Else, you need to do
sudo chmod a+wt /tmp
and check again.
If not both, I'd recommend you either
or uninstall, reinstall it. Now press Alt+-> until you reach the login screen again, and restart.
Please note that this was not my solution. I found the answer at this site in a post such as this one:
I'm unable to find the exact post that I initially found but this one is similar/close enough and I'd saved the information just to be able to it again if I needed it.