This diploma thesis addresses the issue of unknown program execution in the GNU/Linux operating system. The need for such a solution is apparent in online submission systems for programming assignments and evaluation systems used in programming competitions. Untrusted programs must be executed in both cases. If a user obtains access to other users' files, they can steal and sabotage their solutions. In the context of this work, the program gaol has been developed. It supports this kind of security by using available mechanisms in the Linux kernel. In addition to it, an evaluation system build on top of gaol for executing and testing programming assignments has also been developed.