A method of merging VMware disk images through file system unification

Abstract

This thesis describes a method of merging the contents of two VMware disk images by merging the file systems therein. Thus, two initially disparate file systems are joined to appear and behave as a single file system. The problem of file system namespace unification is not a new one, with predecessors dating as far back as 1988 to present-day descendants such as UnionFS and union mounts. All deal with the same major issues - merging directory contents of source branches and handling any naming conflicts (namespace de-duplication), and allowing top-level edits of file system unions in presence of read-only source branches (copy-on-write). The previous solutions deal with exclusively with file systems themselves, and most perform the bulk of the unification logic at runtime. This project is unique in that both the sources and union are disk images that can be directly run as virtual machines. This lets us exploit various features of the VMware disk image format, eventually prompting us to move the unification logic to an entirely offline process. This decision, however, carry a variety of unique implications and side effects, which we shall also discuss in the paper.