A: RedirFS or redirecting filesystem is a new layer between virtual filesystem switch (VFS) and filesystem drivers. It is implemented as an out-of-kernel module for Linux 2.6 and it provides framework allowing modification of filesystem calls in the VFS layer.

Q: What is Filter?

A: Filter is a linux kernel module (LKM) using the RedirFS framework. Each filter can add some useful functionality to existing filesystems like transparent compression, transparent encryption, merging contents of several directories into the one, allowing writing to a read-only media and other.

Q: Is RedirFS hacking Linux kernel?

A: It depends how you look at it. RedirFS is using just symbols exported by the Linux kernel and derives benefit from feature that pointer assignment is atomic. This allows RedirFS to stay out-of-kernel. Nevertheless I guess that it can be implemented in cleaner way directly in the Linux kernel.

Q: Which operating systems are supported?

A: At this moment only systems using Linux kernel 2.6.

Q: Which architectures are supported?

A: RedirFS was by now tested mainly on x86 and x86_64(SMP) architectures. One exeption is the Sun Microsystems' UltraSPARC T1 Niagara with logical domain with 20 CPUs. On this architecture were made some basic SMP tests. Generally RedirFS should not be dependent on any architecture.

Q: What has GRISOFT in common with the RedirFS project?

A: The first work on the RedirFS project started as a diploma thesis for GRISOFT. The original intention was to find out possible ways how to implement an on-access scanning for Linux kernel as an alternative to the Dazuko project. The RedirFS project then evolved to the general framework allowing much more than only the on-access scanning. GRISOFT in these days supports this project.