I am in the middle of a big problem.pls help me.I changed default permissions on home folder in ubuntu.(computer/filesystem/home/).Now i am not able to enter on my admin account(where i changed the permissions).i able log in on my another account.but that account is worthless.There i went to system/administration/users and group(to add a new account).But there it asked for the root password .i dont know the root password.pls help me.any help will be appriciated.