If not runlevels, then...?

Question

If not runlevels, then...?

So I'm aware that OS X does not use runlevels to denote what state the OS is in.

That said, it clearly distinguishes single-user mode from the later, 'multi-user' environment.

My coworker (who is our OS X SME) didn't seem to think that "multi-user mode" would be accepted or understood as a label by Apple experts, because according to him it's not delineated that way in OS X.

So essentially, how does Apple categorize the different stages of the OS?

There's "kernel mode", "single-user mode", and...?

Thanks in advance.

P.S. I'm wondering this partly for my own interest in understanding OS X, and partially because I'm trying to explain the boot process (from a very high level) to our lower-tier HD techs, and differentiating between problems at different stages in the boot process is very important for us.

iMac, OS X El Capitan (10.11.4)

Posted on Apr 8, 2016 1:11 PM

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Answer 1

Apr 8, 2016 2:27 PM in response to Eric Valenzuela

Here is a direct (40pp PDF) entitled, “OS X El Capitan, Core Technologies Overview, September 2015.” This may fill in some blanks for you.

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Answer 2

Apr 8, 2016 2:39 PM in response to VikingOSX

Hi Viking,

This is a nice guide to have for reference; thank you.

Unfortunately, it ends the "Boot Sequence" section right when single-user mode is effectively ready to go.

I'm interested in the semantic delineations Apple makes between the various stages of the boot and OS initialization process.

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Answer 3

Apr 8, 2016 2:40 PM in response to VikingOSX

VikingOSX wrote:

Here is a direct (40pp PDF) entitled, “OS X El Capitan, Core Technologies Overview, September 2015.” This may fill in some blanks for you.

And if that doesn't have enough detail for you, try the OS X Internals books (1st, 2nd) and/or maybe Edge's OS X Server books.

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Answer 4

Apr 8, 2016 4:35 PM in response to Eric Valenzuela

The Singh OS X Internals book has not been updated since 2006, so its content is likely based on ten-year dated OS X internals, and very likely is no longer fully accurate. Apple is about change, and there has been significant OS X technology updates since 2006. I just spent an hour in the Apple Developer's documentation site, and did not find alot of detailed information on the full boot process.

So, here is an article from 2011 that goes into detail for probably Snow Leopard behavior. Read this with tongue in cheek, as it too, may not accurately represent what is currently engaged during the boot process.

You might try the verbose boot process (holding command+V at power on) to see a sequential order of events during the boot process.

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Answer 5

etresoft

Level 8

46,200 points

Apr 8, 2016 5:13 PM in response to Eric Valenzuela

Hello Eric,

See MrHoffman's link to the 2nd edition of Mac OS X and iOS Internals. Here is a presentation from its author, Jonathan Levin, on launchd (http://technologeeks.com/docs/launchd.pdf), which is essentially what you are asking about. Unfortunately, one thing it doesn't mention is launchd domains, which is the closest Apple equivalent to run levels. See the man page for launchd for more information. If that isn't enough, you will have to look at developer documentation: https://developer.apple.com/library/mac/documentation/MacOSX/Conceptual/BPSystem Startup/Chapters/Introduction.html

The rumour is that June will bring a whole new brand of OS, named "macOS". It will likely have even more parts that are ported from iOS.

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