Lock screen does not unlock with correct password Gnome and Ubuntu 14.04

Question

I had to reinstall recently. I installed normal Ubuntu 14.04. I then installed gnome/gnome shell/gdm. I then logged in my user to gnome. Since then I have been configuring my system.

Yesterday, unlock was working fine. Today, the automatic lock screen is not accepting my password as valid. It just takes the input like it's processing it, then takes me right back to the same password prompt. If I click the 'login as a new user' link, it takes me right back to the lock screen. Ctrl+Alt+F1, etc, does nothing.

I had to resort to a hard boot. I've tried this more then once. (first time was from automatic, idle time lock, second time was from my triggering the lock screen with the keyboard command).

I'm certain I have my password right, as I am able to get logged in after the cold boot.

Solution 1

Neither of the other two answers solved the problem for me, but some additional searching led to this bug report:

sudo chown root:shadow /sbin/unix_chkpwd
sudo chmod 2755 /sbin/unix_chkpwd

which solved the issue for me.

Solution 2

I could resolve this issue with the following permission changes:

sudo chown root:shadow /etc/gshadow
sudo chown root:shadow /etc/gshadow-
sudo chown root:shadow /etc/shadow
sudo chown root:shadow /etc/shadow-

Found here: http://ubuntuforums.org/showthread.php?t=1006366

Check also this question: Lock screen - password incorrect

Solution 3

Open a terminal and type ll | grep '.Xauthority' and make sure it is owned by you and not root.

You can chown it or just remove it, it'll come back! Now just log out and log back in.

This is one of the main reasons why you shouldn't use sudo to open GUIs, as root will take ownership of some of your files in your home directory.

Solution 4

I had a similar issue after upgrading to 20.04. If I suspended the computer and tried to log back in I could not enter my password at the login screen.

I was able to fix this by purging and then reinstall lightdm the issue was solved.

So

sudo apt purge lightdm
sudo apt install lightdm

View more solutions

Comments

[ElefantPhace]

Check your permissions on ~/.Xauthority sounds like root owns it now. You can simply delete it and you should be fine. One reason why you don't use sudo to open GUIs

[Eliah Kagan]

@ElefantPhace You might want to post that (or something like it) as an answer.

[Cris Holdorph]

I will add just a little bit. Since I asked this question originally, I still have this problem happen on a regular basis. Usually about once a month. I have noticed, that for some reason, the most often (NOT EVERYTIME), this seems to happen on days where I've found myself booting more then once. I can not see how that would related to anything, but it's the only other piece of evidence I've gathered so far.

[ALX]

It is possible your keyboard layout was reset to a different language. For example changing from UK to US would have the result of some of the non-alphanumeric characters not printing what you think they are.

[Cris Holdorph]

the .Xauthority file is owned by my user. So, as much as I would love a simple fix like this. It is unfortunately not my problem.

[ElefantPhace]

Check your .xsession-errors and see if you can find any clues there

[Cris Holdorph]

No .xsession-errors file, but I haven't locked my screen since the most recent reboot. And if I did, I wouldn't be able to get back in, until I rebooted. So, if it's a file that persists across reboot/relogins/restarting x, then it's not present.

[X09]

Solved my problem too on Ubuntu 16.04.

[Nimish]

Worked for me ubuntu 16.04 LTS

[ccpizza]

these are already the permissions that ubuntu comes with ootb

[Nick Orlando]

@ccpizza And? That doesn't mean they can't get corrupted or changed.

[ccpizza]

@NickOrlando: only mentioning this in order to encourage people to check the current permissions first before attempting to 'fix' them.

[John Timberlake]

How can you enter your password regardless of what lock screen is showing off? How do you change your language on lock screen then?

[1mi]

@SergeyBushmanov Just pretend you've another layout than what is shown and type your password. You can't change the layout from what was set when you locked the screen despite what it is shown. That's why the bug is reported.

[John Timberlake]

Whatever I pretend none of the passwords is accepted.

[WoJ]

This (or Nick's solution above) helped on 18.04.

[WoJ]

This (or fret's solution below) helped on 18.04.