Abstract: System and method for transaction-based versioned file system. A file system assists the users of computer systems to store data on external persistent storage media such as hard disks, the main task for the file system is to move data to and from the external media, traditional file system leaves the user with little or no control over the contents of files across system crashes. As a consequence the contents of the files are undefined after a system crash, and the file system itself may require lengthy recovery routines before the file system can be used again. The transaction based file system provides the user with control of the contents of the files in the file system across system failures, and the transaction based file system does not require lengthy recovery routines after system failure. A number of versions may be maintained at the same time and retrieved independently of each other. The version generation is based on the so-called shadow page principle.