One of the long missing features of FreeBSD was the ability to boot up with a temporary rootfs, configure the kernel to be able to access the real rootfs, and then replace the temporary root with the real one. In Linux, the functionality is known as pivot_root. The reroot projects provides similar functionality in a different, slightly more user-friendly way: rerooting. Simply put, from the user point of view it looks like the system performs a partial shutdown, killing all processes and unmounting the rootfs, and then partial bringup, mounting the new rootfs, running init, and running the startup scripts as usual.

The project is finished. All the relevant code has been committed to FreeBSD 11-CURRENT, and is expected to ship with FreeBSD 11.0.