On Sun, Jul 17, 2011 at 06:51:17PM +0200, Lennart Poettering wrote: > In fact, a minimal systemd system will win in almost very aspect against > a remotely similarly powerful sysvinit system: you will need much fewer > processes to boot. That means much shorter boot times. This is, as far as I'm aware, an unproven assertion. While it's true that there is a cost to the additional processes used in init scripts, I have not seen any serious attempt at measuring how big this impact actually is - certainly not in terms that would be relevant to Debian, which uses dash as its /bin/sh and insserv by default (in squeeze and above). I'm sure that systemd does much better than a traditional sysvinit boot with /bin/bash and no dependency-based booting. But then, so does Debian's current boot system, and so does upstart; and neither of the latter two involve grandiose claims of a "shell-free boot". Trying to take the shell completely out of the boot means a definite tradeoff here between boot speed and configurability/maintainability, and in the absence of hard numbers, I suspect this is a false optimization and not a trade-off that we actually want to make in a general distribution. Which then calls into question the use of such claims as a justification for a switch to systemd at all... > > For a low-level piece of infrastructure, systemd interacts with a lot of > > high-level software; while this might be okay for a workstation running > > Gnome, it makes me wonder whether it will be usable on servers. > > A cursory look shows that systemd intrinsically depends on D-Bus (the > > *desktop* bus) and knows about Plymouth, RedHat's implementation of > > a splash screen. More on that below. > Oh, come on. > systemd does not depend on Plymouth, it merely interacts with it if it > is around it. Where interaction simply means writing a single message > every now and then to ply to keep it updated how far the boot > proceeded. It's more or a less a single line of text we send over every > now and then in very terse code. One of these days I'll get around to writing that blog entry to set the record straight on why plymouth is an indispensible component of boot with any modern boot system, because when everything is starting in parallel, you need something to handle I/O multiplexing to the user on console. So in a real sense, it *should* be a dependency. Even if you don't care about splash, you still need multiplexing. Upstart has the same dependency, though pid 1 doesn't talk directly to plymouth in the upstart model; instead this is handled by an out-of-process plymouth-upstart "bridge", as well as by the out-of-process mountall service that talks to plymouth for handling of fscks, skipping the mounting of missing filesystems, etc. > > He practices misleading advertising[2], likes to claim that the > > universal adoption of systemd by all distributions is a done thing[3], > > and attempts to bully anyone who has the gall to think that the > > discussion is still open[4]. > Juliusz practices misleading anti-advertising [1], likes to ignore the > fact that all major distros either made systemd the default or include > it in their distro with the exception of Ubuntu. Well, it's nice to see that Lennart is at least acknowledging Ubuntu as a major distribution these days, unlike in some of his earlier rhetoric. ;) Though this is still a pretty misleading comment, since both of these statements are also true: All major distros either made sysvinit the default or include it in their distro. All major distros either made upstart the default or include it in their distro. Ho-hum... -- Steve Langasek Give me a lever long enough and a Free OS Debian Developer to set it on, and I can move the world. Ubuntu Developer http://www.debian.org/ slangasek@ubuntu.com vorlon@debian.org
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