Lock screen - password incorrect

Question

I have upgraded Ubuntu to 12.04 and now I have a problem in logging in after locking the screen: it says the password is incorrect even though I provide the valid password. I found a temporary solution by switching users and logging in again with the same user.

Solution 1

I had the same issue. It is likely the ownership is wrong for /etc/shadow (See section "gnome-screensaver authentication failure with incorrect /etc/shadow permissions" of this page).

You need to sudo chown root:shadow /etc/shadow then sudo chmod u=r,g=r /etc/shadow See this bug report.

The interesting question is "Why ownership changed?". Because I don't remember changing it.

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

Comments

[nanofarad]

I'd report a bug if anybody can reproduce it. If you can reproduce it, drop a comment...

[Manu]

Having the same issue... on Ubuntu Mate 18.04... oddly this only occurred on my laptop after a clean install... I have installed other machines, including my desktop and there I've never had the issue... strange! I'll try the suggestion flagged as "accepted answer".

[guntbert]

/etc/shadow must not be owned by any other account than root!

[Manu]

Thanks it worked for me! For some unknown reason, the group ownership was "root" instead of "shadow" for /etc/shadow on my laptop. Resetting the group ownership to "shadow" solved the issue :-)

[Manu]

Albeit less informative as the answer above, this is also a correct answer, thanks! ;-)