Has anyone done a compare and contrast with the classic Unix "init" process
and the root tasks in use now?
The seL 4 root task is way more than the Unix init. The latter is all about getting initial system services started. Lot of this is just the mechanics of getting dependencies right, although it has a bit of a (minor) effect of the look and feel
of the system.
The seL4 root task pretty much defines the system, as it is in full control of all resources, and the kernel after boot is just a passive entity. It implements the fundamental policies that govern the operation of the system. In particular, it
distributes access rights to resources. In a typical system, everything else has access to just a subset of resources. Depending on how the root tasks sets things up, the system may consist of completely partitioned domains, cooperating subsystems with strictly
enforced interfaces (or, if you prefer it that way, an unstructured anarchy ;-).
Gernot