logon screen wont accept details, but terminal does?

Question

My Ubuntu machine has suddenly started asking for a username and password when it starts up but does not accept the details I enter. When i go into terminal however, it seems to work fine. I have tried using the

passwd <user>

change thing but get authentication error. I know i am definately entering the correct details as I always use the same ones.

How can I change the password?

Answer 1

You need to change password for your username.

Enter command like below,

passwd YOUR_USERNAME

and make sure that you are logging in using the username you entered earlier.

Answer 2

Try running passwd as root. When you run passwd as root, unlike when you run it as yourself, you do have to specify the user whose password you want to change:

sudo passwd $USER

Either keep $USER as it is (it will expand to your username), or replace it with your username.

• If you still get an authentication error, reset the password in recovery mode.
• If even that doesn't work, you can reset it from a live CD/DVD/USB using this method or this method.