fistgen is a stackable file system templates and language. File system development is very difficult and time consuming. Even small changes to existing file systems require deep understanding of the inner workings of the kernel, making the barrier to entry for new developers high.Moreover, porting code from the file system of an operating system the other is almost as difficult as the first port. Earlier proposals to provide scalable (stackable) interfaces file system would have simplified the preparation of proposals systems.These new file, however, called for significant changes to the interfaces of the existing operating system and file systems ; suppliers of operating systems and maintainers to resist changes to their large core because of the stability and performance concerns. Therefore, development of system files is always difficult, long, and not portable process.The FIST (File System Translator) system combines two methods to solve the above problems a new way: a set of file system stackable models for each operating system and a high level language that can describe stackable file systems in a platform FiST fashion.Using portable, stackable file systems should be described only once. Fist tool code generation, fistgen, compiles a unique description of the file system in kernel loadable modules for several operating systems (currently Solaris, Linux and FreeBSD). The project demonstrates that the fist, the code size and development time are reduced significantly, while imposing the performance overhead of only 1-2%. These benefits are obtained, as well as portability, without changing existing operating systems or file system.