MLS has been widely used in order to respect confidentiality policies inside organizations, especially into military ones. More recently, some works have been done about the use of MLS inside Security Enhanced Linux (SELinux) operating systems. Although those mechanisms have been implemented at the operating system level, that doesn't imply that the system will be usable, from an end-user point-of-view. A study is required to evaluate the usage of a real MLS system? In this paper we will study the state of the art and survey the technology about MLS/SELinux support on computer systems, for the design of a complete user oriented system with MLS at the operating system level. Keeping in mind the main objectives of MLS (i.e., preventing information flows between users), we will deeply experiment OS level mechanisms for MLS control and applications compatibility with such controls.