There were many scripts, many implementations, but interestingly most were compatible with each other.

The largest issue inits had was that the flexibility they provided gave distro maintainers a lot of choice in how those scripts should operate to be consistent with the rest of the system.

Things like log locations.

The issue to be solved is: how to determine parallelism in boot, how to supervise a process with minimum complexity, and how do we do structured logging.

Interestingly: SMF solved all of these a decade before.