A consistent backup, preserving data integrity across files in a file system, is of utmost importance for the purpose of correctness and minimizing system downtime during the process of data recovery. With the present day demand for continuous access to data, backup has to be taken of an active file system, putting the consistency of the backup copy at risk. We propose a scheme to take a consistent backup of an active file system assuming that the file system supports transactions. We take into consideration that file operations include, besides reading and writing of files, directory operations, file descriptor operations and operations such as append, truncate, etc. We are putting our scheme into a formal framework to prove its correctness and we have devised algorithms for implementing the scheme. We intend to simulate the algorithms and run experiments to help tune the algorithms.