I have a different problem.When first time I used ubuntu old to new in every version I can easily type password in terminal after sudo command.But now a day I can't because In terminal after sudo command in password i can't able to type any thing like char or number ,but just in password other part in terminal I can type. Now,probelm is there that it don't show password means not that in terminal password is in hide mode.Every time I type in after that it show me" sorry,try again" error message after three time wrong password means empty password it's again come into first position. For solve this problem I used old to new version of ubuntu also format it many time but same problem occured. Please help me because without terminal password I can't install anything.