After we installed Ubuntu12.04, we will set up a user name and password.
The strange thing is the user's password when we sign in the desktop, open the terminal after entering the command su, enter our set. I would suggest the following:
This time do not worry, because su is being locked. And our user passwords different.
This time we su change my password on it.
FIG: input command sudo passwd
Then enter about your user password. (This password should be wrong, it is estimated can easily input, we can try it yourself)
Then enter the new password you want to change. You will be prompted to enter the password twice after the update was successful.
Again su then enter the password you just changed it.