[teacup50]

Mac OS's architecture is totally unlike systemd.

Areas of responsibility are implemented by standalone mechanisms that compose to create the larger integrated system and can:

1) Run in isolation from their upstream dependents.

2) Be replaced individually.

[gh02t]

Lol no. On many levels. MacOS does implement separate daemons, but they're all very tightly integrated, communicating over a common protocol. The core components hardly run in isolation, nor are they interchangeable. You don't, for example, just replace launchd with some other init system. You don't just say "hey, screw Aqua I want to use something else." (You can run other WMs through X11, but only on top of Aqua) Darwin is a bit more BSD-like, but nobody actually uses Darwin without the rest of MacOS.

And seriously, systemd isn't one single daemon either. It's a collection of daemons running that communicate over a common protocol. It isn't all-or-nothing, either. Only a few of the daemons are considered "core" and the rest are optional. And, because they use a common documented protocol, even the core components can be replaced. You don't hear about alternatives because nobody has really written any, but it doesn't in any way prevent you from doing it.

I think the legitimate concerns about systemd are things like losing portability of stuff like Gnome to BSD and systemd's short history, but it isn't one giant monolith executable or anything like people say.

[teacup50]

> Lol no. On many levels. MacOS does implement separate daemons, but they're all very tightly integrated, communicating over a common protocol.

What common protocol? Mac OS X doesn't have dbus. It recently acquired XPC, but XPC is NOT a system bus -- it's simply an IPC library. It's neither required, nor universally used, nor is it terminally glued to the remainder of the OS.

> You don't, for example, just replace launchd with some other init system.

You don't? Says who? All launchd does is serve as an inetd/cron-esque daemon. The system daemons themselves continue to vend standard sockets and mach ports, and launchd itself does not pervade their externally vended interface.

> You don't just say "hey, screw Aqua I want to use something else."

Actually, you can. The display stack is driven by IOKit; XDarwin can run directly atop said stack.

Likewise, none of the "Mac-like" features that you want -- for example, automatic network configuration -- rely on any sort of centralized entity that pervades all daemons. There's a seperate system -- SystemConfiguration -- that provides that functionality, abstracted through a set of well-defined APIs and modular and distinct from the remainder of the system.

> * It's a collection of daemons running that communicate over a common protocol.*

Hence it's really rather monolithic, because to play in the systemd universe, everything has to conform to systemd's tightly coupled design.

[gh02t]

What you're describing is all quite similar to how systemd operates. Your definition of "monolithic" seems to be that the components communicate with each other. My definition is that the components are difficult to replace. Systemd makes it easier to replace components, because the requisite interfaces are clearly defined.

MacOS is quite tightly integrated, it's what Apple does. Darwin is a bit different, as it's much more BSD-ish; with that I agree. But MacOS is a lot of stuff on top of Darwin and replacing any part of that would require tons of very MacOS specific code to do. Apple most definitely does not intend for their users to be able to replace logind or Aqua or pretty much any core service.

Probably a better way to phrase it would be to consided how much effort it'd take to run Aqua on BSD. You'd have to port basically everything that is MacOS. To me, that is what a monolithic system means.

[mzs]

Oh man no, go take a look at the launchd sources and see how much is hard coded in for how Apple wanted it - likely when you run into something unexpectedly not working how you wanted or expected.

[drewcrawford]

osx guy here.

Yes and no. It's true that OSX uses a variety of separate daemons, that run in different pids.

However they are all "required", "packaged together", "part of one source tree" and "shipped by a single vendor". In this respect they are a lot like systemd.

In fact it is arguably a lot more integrated. Both Python and Ruby are OSX dependencies. systemd isn't even close to that much of a power-grab.

[e7620]

GNU/Linux requires vi, perl, python... also as dependencies, but they're separate programs, the thing with systemd is that nothing can be separated, you use ALL components at the same time or change OS. Bear in mind that systemd is being integrated with the Linux kernel, so you have to update the kernel in sync with systemd.

[gh02t]

> Bear in mind that systemd is being integrated with the Linux kernel, so you have to update the kernel in sync with systemd.

I'm just feeding a troll or someone who is really ignorant, but here I go.

No it isn't, and no you don't. Systemd is closely tied to some Linux-specific features, but it generally isn't part of the kernel. And you don't have to update the kernel in sync with systemd. Systemd lives in userland, by definition.

It does impose a minimum kernel version in order for systemd to work, which is something like 2.6.39 (May 2011 vintage). They have bumped up the minimum version a couple times as they needed new features, but you don't have to upgrade both together. I routinely upgrade one or the other separately on multiple systems and distros.

And it bears repeating again... systemd is not one single executable or process. And not all of the components are required, you can turn all but a few core ones off. And the core ones could be replaced if you wanted to, because there's a documented interface that you can implement.

Also, Vi, Python and Perl aren't "required" for GNU/Linux. They're common, but definitely not required. Vi is required if you want to comply with the Single Unix standard, but that is not the same thing. GNU/Linux just refers to pairing the Linux kernel with GNU userspace utilities; it doesn't necessarily dictate any specifics. There are further standards like LSB that attempt to do so but again not relevant. On top of that, Vi, Python and Perl aren't even GNU projects, which is true of a ton of other programs common in Linux distros, which is one reason I personally find the term "GNU/Linux" a bit onerous.

[e7620]

And you don't have to update the kernel in sync with systemd

Quote from http://lists.freedesktop.org/archives/systemd-devel/2014-May...:

> > You update systemd but you don't update the kernel? How does that make > > any sense?

> > systemd and kernels are updated in lockstep (Lennart)

And it bears repeating again... systemd is not one single executable or process

https://news.ycombinator.com/item?id=8364318

Also, Vi, Python and Perl aren't "required" for GNU/Linux.

By that definition nothing is ever required. There's the same argument in my comment history, someone said, udev is not required for GNU/Linux. technically, chromium doesn't "require" blink. It's not required, you can use chromium and receive raw html, right? But in that case OSX doesn't "require" Python either, just delete the files, done :)

So again, I'm saying, I want a GNU/Linux system. (Yes, it's not required, I can install MS-DOS, HURD, HP-UX or Android.) That means POSIX, LSB... That's what 99%+ of programs targeting GNU/Linux expect.

[gh02t]

Tell me, have you actually used systemd? Because you're completely misunderstanding the first two points as they're overtly not the case. Particularly the first point, as what it is saying is that they are willing to use newish features in the kernel, not that you are forced to always be running the latest bleeding edge kernel to have an up to date systemd.

The second point has some validity, but is a distortion. Of course you couldn't plug ConsoleKit in as a replacement for logind, because ConsoleKit was never designed for that. What you can do with logind is implement a simple compatibility layer with the standard systemd interfaces and then use it; this is what Ubuntu is doing. What is mandatory to use systemd's services is to implement its protocol for communicating between the services. This is why some of the services are "core" ones- because they're implementing the basic functionality common to the other modules. They can still be replaced, as long as the replacement obeys the same interfaces. This is however a problem for BSD, as the easiest way to use the systemd components is to implement the interface, but that does require features that are only present on Linux.

> By that definition nothing is ever required.

And yes, that was exactly my point. The term "GNU/Linux" is meaningless and doesn't require anything specific. What you might want out of a GNU/Linux system is probably totally different than what I do. You might want Emacs, but I'm a Vi guy. I don't want Emacs and you might not want Vi. How do we settle this? Committee vote? Mud wrestling?

[RunningDroid]

>Bear in mind that systemd is being integrated with the Linux kernel, so you have to update the kernel in sync with systemd.

Do you have a source for this or is it FUD?

[e7620]

Before throwing such accusations, at least search Google or HN itself.

http://lists.freedesktop.org/archives/systemd-devel/2014-May...

[RunningDroid]

They're saying that after the kernel release with those features comes out they will make a release that depends on those features, not that the kernel and systemd must always be updated together.