Authentication token manipulation error when I try to change password

Question

I get this message when I try to change my password. Everything started when I removed password for my username, so when I go to User Accounts, it says "None" for password. But when I try to install some application in Terminal, it is still wants me to write password. When I leave blank field, doesn't help. When I type the old password, still nothing.

Do you know what's wrong?

Answer 1

I found the solution.

Open the terminal. Type passwd. Type in new password.