I loved this article. As a matter of fact, it cleared a few things that kept me wondering about Mac's implementation. It's a must read. Also take a look at Ubuntu Wiki on upstart at https://wiki.ubuntu.com/ReplacementInit
Upstart, an init.d replacement, is now in the Ubuntu Universe. This article also details comparisons between other approaches and why Upstart is the best. "From the start of development of edgy+2, no new packages will be accepted unless they provide upstart jobs instead of init scripts and init scripts will be considered deprecated."
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