Is there any 'usual' way to port kernel functionalities to user space?
For example, I looked for a solution to access an ext3 filesystem in an disk image file without root privileges. So I thought of running the ext3 module code in userspace, instead of relying on tools that mimic the ext3 fs.
So I wonder how to get kernel code running in user space.
There are a bunch of container mechanisms for Linux now: LXC, Docker, lmctfy, OpenVZ, Linux-VServer, etc. All of these either involve kernel patches or recently added Linux features like cgroups and seccomp.
I'm wondering if it would be possible to implement similar (OS-level) virtualization purely in userspace.
There's already a precedent for this - User Mode Linux.