A union file system allows the user to combine a read-only base directory and a writable overlay under a new read/write view. Initially, the view contains the files in the base. No changes are made as long as the contents of the view is accessed read-only. The overlay is updated as soon as the combined view is written. The idea comes from BSD's unionfs.
Under Linux, there was once an Inherited File System (IFS), but the project was abandonned. No working version existed at the time I undertook this project. In the meanwhile, I have been informed that a "real" UnionFS for Linux has appeared — and it looks good.
My version is based on LUFS (the Linux Userland Filesystem). Most operations work, with the exception of erasing files and directories from the base. Download the source code (to be unpacked in the same directory as LUFS) for the 0.1 version.
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