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Arch Linux to migrate to Systemd

mailman.archlinux.org

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Re: Arch Linux to migrate to Systemd

#51

Post by comex »

dredmorbius wrote: post #11

Systemd takes a reliable, known, thoroughly debugged process (init, or various of its tweaks, including Ubuntu's upstart and Debian's insserv ), and converts booting from a deterministic, predictable process to one that's inherently unpredictable . And the stated objective? "To reduce boot times". The best way to reduce boot times is to not boot . The reason I reboot systems is to return them to a known good state (o…

As an OS X, and thus launchd user... I think you guys are crazy! :)

For launchd, the service description is a few declarative entries: on OS X, ssh.plist is 37 lines, but only because XML plists are really verbose; it could be half that in a saner format. On my Debian system, /etc/init.d/ssh is 167 lines of almost entirely boilerplate shell script that has to be maintained separately for each service (and that isn't even enough to make the script standalone; it invokes the 1400 line start-stop-daemon). The only thing simpler about SysV init is that it's the legacy everything is compatible with: the simplicity of shell scripts doesn't hold up when you need over 100 lines for a simple daemon.

launchd itself is many thousands of lines of code (too much?), but it provides cron and inetd-like services (i.e. generalized on-demand services - it is really nice to know that a daemon has zero effect on my system, no pages that had to be loaded from disk, when it's not being used, but still operates efficiently when it comes under load; this also makes the implementation for the daemon simpler in some cases), as well as automatic process termination/restarting. Its service-on-demand focused dependency model is nondeterministic in the same way that systemd is (?), but it's completely reliable, since it's standard by now so everything is designed to work with it.

Of course I usually use suspend and restore, but making rebooting really fast makes the system more fun to use.

And yes, I'm talking about launchd, not systemd, but from what I've heard systemd is pretty similar in design and goals.

Re: Arch Linux to migrate to Systemd

#52

Post by onedognight »

leif wrote: post #41
dredmorbius wrote: post #11

Systemd takes a reliable, known, thoroughly debugged process (init, or various of its tweaks, including Ubuntu's upstart and Debian's insserv ), and converts booting from a deterministic, predictable process to one that's inherently unpredictable . And the stated objective? "To reduce boot times". The best way to reduce boot times is to not boot . The reason I reboot systems is to return them to a known good state (o…

Shell scripts are awful for boot. They have no expression of a dependency graph and truly pathetic notions of state. Hell, starting a process in the background takes ACTUAL THOUGHT in a shell script. How insane is that? systemd may not be as thoroughly tested but at least it's designed thoughtfully and will eventually be more reliable. For now, let it be relegated to arch and let them test it. What are you even doing…

> For now, let it be relegated to arch and let them test it.

FWIW, Fedora moved to systemd a year or so ago.

Re: Arch Linux to migrate to Systemd

#53

Post by donniezazen »

dredmorbius wrote: post #27
sciurus wrote: post #21

Earlier quoted context omitted.

You're going to bash systemd but give a pass to upstart? Give me a break. Upstart is just as radical a departure from SysV init as systemd is, but the documentation (and IMHO, features) is much poorer. As far as I can see your arguments are 1) you boot your systems infrequently, so any work in that area isn't valuable 2) socket-based activation is somehow not predictable 3) you're familiar with shell scripting, so a…

How often do you reboot your systems? What is giving rise to the need to reboot them when you do?

Just because you don't reboot often does not mean it has to be slow. In open source community, people choose their own projects. You can't really expect for force for that matter for them to work on your favorite things.

Re: Arch Linux to migrate to Systemd

#54

Post by jpiasetz »

dredmorbius wrote: post #11

Systemd takes a reliable, known, thoroughly debugged process (init, or various of its tweaks, including Ubuntu's upstart and Debian's insserv ), and converts booting from a deterministic, predictable process to one that's inherently unpredictable . And the stated objective? "To reduce boot times". The best way to reduce boot times is to not boot . The reason I reboot systems is to return them to a known good state (o…

Is any of this really an argument against Arch adopting it? Arch and Gentoo and all the other rolling distros are the cowboy distros (I run Arch on my laptop). Literally anything can break with an update on Arch. Is Arch not the best place to try new ideas and see if they work out with a bunch of fairly technical users? I'm not about to switch all my servers to it but I'm more then willing to play around with it on my laptop.

Re: Arch Linux to migrate to Systemd

#55

Post by alrs »

FooBarWidget wrote: post #16
dredmorbius wrote: post #11

Systemd takes a reliable, known, thoroughly debugged process (init, or various of its tweaks, including Ubuntu's upstart and Debian's insserv ), and converts booting from a deterministic, predictable process to one that's inherently unpredictable . And the stated objective? "To reduce boot times". The best way to reduce boot times is to not boot . The reason I reboot systems is to return them to a known good state (o…

I'm sorry, but shell scripts suck as a language for booting the system. You need to fork() and exec() for almost anything non-trivial, wasting precious CPU cycles in the progress. It looks like every Linux distro has its own way to manage boot scripts. And when they fail, you have no idea what happened. More importantly, init only handles starting and stopping of services. They don't manage services, like restarting…

I have a Debian laptop.

ls -alh | wc -l returns 89. I can subtract "..", ".", and the "totals" lines, so that's 86 init scripts.

Big O for 86 scripts is 86 * n, which simplifies to "n". I'm not concerned.

Re: Arch Linux to migrate to Systemd

#56

Post by dredmorbius »

alrs wrote: post #55
FooBarWidget wrote: post #16

Earlier quoted context omitted.

I'm sorry, but shell scripts suck as a language for booting the system. You need to fork() and exec() for almost anything non-trivial, wasting precious CPU cycles in the progress. It looks like every Linux distro has its own way to manage boot scripts. And when they fail, you have no idea what happened. More importantly, init only handles starting and stopping of services. They don't manage services, like restarting…

I have a Debian laptop. ls -alh | wc -l returns 89. I can subtract "..", ".", and the "totals" lines, so that's 86 init scripts. Big O for 86 scripts is 86 * n, which simplifies to "n". I'm not concerned.

'ls -A | wc -l' will spare you having to account for the '.' and '..' lines. Omitting the '-l' (redundant for your case) also spares the "totals" line.

Re: Arch Linux to migrate to Systemd

#57

Post by dredmorbius »

leif wrote: post #41
dredmorbius wrote: post #11

Systemd takes a reliable, known, thoroughly debugged process (init, or various of its tweaks, including Ubuntu's upstart and Debian's insserv ), and converts booting from a deterministic, predictable process to one that's inherently unpredictable . And the stated objective? "To reduce boot times". The best way to reduce boot times is to not boot . The reason I reboot systems is to return them to a known good state (o…

Shell scripts are awful for boot. They have no expression of a dependency graph and truly pathetic notions of state. Hell, starting a process in the background takes ACTUAL THOUGHT in a shell script. How insane is that? systemd may not be as thoroughly tested but at least it's designed thoughtfully and will eventually be more reliable. For now, let it be relegated to arch and let them test it. What are you even doing…

inssrv adds the dependency graph you're looking for.

Standard on wheezy. Allows for parallel launch of services.

I'll spend more time in hardware init (especially on servers) and fsck (even just journal replays) than service startups for most part. Even my servers (minimal services starting) take a while to come live, mostly due to the actual workload stack coming up. Then caches get to warm up and all that jazz.

Boot time is still a very small part of this.

Re: Arch Linux to migrate to Systemd

#58

Post by franzus »

jpiasetz wrote: post #54
dredmorbius wrote: post #11

Systemd takes a reliable, known, thoroughly debugged process (init, or various of its tweaks, including Ubuntu's upstart and Debian's insserv ), and converts booting from a deterministic, predictable process to one that's inherently unpredictable . And the stated objective? "To reduce boot times". The best way to reduce boot times is to not boot . The reason I reboot systems is to return them to a known good state (o…

Is any of this really an argument against Arch adopting it? Arch and Gentoo and all the other rolling distros are the cowboy distros (I run Arch on my laptop). Literally anything can break with an update on Arch. Is Arch not the best place to try new ideas and see if they work out with a bunch of fairly technical users? I'm not about to switch all my servers to it but I'm more then willing to play around with it on m…

> Literally anything can break with an update on Arch.

I can confirm that. After the 3rd time such a thing happened to me I switched to Ubuntu. Arch is a testing bed for people who like screwing around with Linux. Nothing against that but from time to time I'd like to be able to do actual work on my workstation :)

Re: Arch Linux to migrate to Systemd

#59

Post by dredmorbius »

rogerbinns wrote: post #42
thaumaturgy wrote: post #29

Earlier quoted context omitted.

I'm a daily laptop linux user, specifically Chakra Linux, http://chakra-linux.org/ . My wish list goes something like this: better wireless drivers, improved sleep/suspend/hibernate/resume, better power management, a better package manager, more up-to-date applications ... At the very, very bottom of that list -- the very last item, so far at the bottom of the list that it's in danger of falling off entirely -- is "f…

Note that a better way of saying things is that systemd deals with state changes a lot better. Booting is one big state change, but when you have a laptop you go through a heck of a lot of other state changes (suspend, hibernate, resume), docking, connectivity changes (eg wifi coming and going), storage added and removed etc. You may let other people use your system (more state changes). systemd can also ensure that…

You can add state-change management to your system without mucking with really solid, stable, low-level, critical code like init.

There's already hotplug support, xinetd, ifupdown's pre/post up/down stanzas, and the like (though networkmanager's screwing that bit up wonderfully). Chroot jails too. I'm not saying that these are perfect (and some are a very pale shadow of perfect indeed), but they're independent of init.

Systemd mashes a whole bunch of crap in one place. Most of which I really don't want to have to worry about.

Now, if Arch and Fedora want to serve as test beds for this stuff -- and either perfect them or reject them as nonviable, well. Yeah, I suppose I can live with that. Though I'm definitely not a fan.

You see, there's a few things here.

For my own systems, I really like not having to fuck with useless shit. Currently I'm managing networking manually on my laptop as NetworkMangler has gone to crap again. So I run "ifconfig" and "route" from a root shell (yay for shell history and recursive reverse search).

For servers, part of my performance evaluation is based on how many nines I can deliver. Not having shit get fucked up does really nice things to my nines. Having shit change does crap things to my nines. I like my nines. I really hate change. It's an ops thing. Where I've got to have change, I like to have it compartmentalized, modularized, with loosely-linked parts and well-defined interfaces.

Startup scripts are a very much mostly solved problem. Debian gives you a nice template in /etc/init.d/skeleton. Play with it. Yes, I've written startup scripts.

Re: Arch Linux to migrate to Systemd

#60

Post by jmah »

hollerith wrote: post #38
dredmorbius wrote: post #27

Earlier quoted context omitted.

How often do you reboot your systems? What is giving rise to the need to reboot them when you do?

My computer changes location at least twice a week as I commute between my place and my girlfriend's place. A Mac mini serves my needs very well because (including AC adapter) it weighs only 2.7 pounds, and I really appreciate having more ports than most laptops have and not having to pay for and carry around a bad keyboard and a laptop display. (I consider all laptop keyboards bad keyboards, and -- maybe because I a…

You can do what you want. man pmset, or Google "hibernatemode".
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