A method and system for generating and restoring a backup image are disclosed. According to one aspect of the invention, a server receives a request to generate a backup image. The request includes a selection a backup path. Based on the backup path, the server generates a list of files and/or directories to backup. However, before writing the files to the backup image, the server generates an offset map to indicate where in the backup image each file will be located. The server then writes the offset map to the backup image. During a restore operation, the server receives a request to restore files, including a selection of files and/or directories to restore. The server reads the offset map from the beginning of the backup image to quickly determine the location in the backup image of selected files.