I am trying to install MySql on Ubuntu 12.04 but the installation is failing with the error: "Can't change to run as user 'mysql'. Check if the user 'mysql' exits." So I go ahead type in the command : 'cat /etc/passwd | grep mysql' and result is null. I try to add a user 'mysql' by issuing the command 'useradd mysql'/. But it fails with the message: 'useradd: user 'mysql' already exists'. When I try to delete the user 'mysql' using the command 'userdel mysql' it also fails with the message "userdel: cannot remove entry 'mysql' from /etc/passwd." Can anyone explain me what's going on and suggest a solution.