really is a program that allows certain users to become whatever user they like on request. It is a bit like sudo in that respect. However, really is simpler than sudo, and doesn’t give the system administrator any false security promises. So really is less of a general security risk to the system. Unlike sudo it does not pretend that the called account can be any more secure than the calling account. so there is never a need for a password. If you wanted to restrict which commands and functions the called user can perform, use userv, not really or sudo. Also unlike sudo, really only works if the calling user is supposed to be equivalent to root. But, really can also be used by root-equivalent users to become any user, not just root; in this way it can be a replacement for certain uses of su.