Provided is a method for implementing a file system that includes a combination of read-only and read/write parts. A file system located on a data server maintains an original copy of a data store. An “Ephemeral” file system (EFS) is created on a client computer. The data server is contacted only once for each file accessed and the copy is in an original state each time the system is mounted. Changes made to the file system by one client are not seen by other clients. The EFS maintains the file system state in memory and uses the NFS server as a backing stored for cached file data. File data for files created on the client are backed up by the client system's swapping space.