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[Debian] Survey answers part 3: systemd is not portable and what this means for our ports (2013-07-13)

post #1 of 7
Thread Starter 
Since the topic of systemd comes up quite a bit, I figured a few of you guys might be interested in this blog post about the problems with systemd's portability (as Debian runs on top of some non-Linux kernels as well).
Quote:
Some people seem to think that the systemd upstream is just hostile to users of other operating systems when they hear that systemd is not portable. However, keep in mind that Lennart, Kay and other contributors have considerable experience with writing portable software such as Avahi and PulseAudio.

The decision to only support Linux in systemd was thus not taken lightly. systemd’s design requires many kernel features and certain semantics (e.g. procfs is not enough, /proc/$PID/exe needs to be supported), which are currently only available on Linux. Point 15 of Lennart’s blog post 0pointer.de/blog/projects/the-biggest-myths.html contains an incomplete list of these features.
(the Avahi and PulseAudio comment made me laugh as they're two components I usually uninstall from any Linux box I host).

Anyhow, the blog also comments on the future of systemd within Debian:
Quote:
systemd is not portable because it relies on features only the Linux kernel provides — an example is cgroups, which systemd uses to track processes in a reliable way. Not embracing these features and staying with sysvinit indefinitely is not a viable option if Debian wants to remain relevant for today’s demands. In the short term, the migration to systemd will cause additional maintenance effort for individual package maintainers, but it will pay off in the long term.


Source: http://people.debian.org/~stapelberg//2013/07/13/systemd-not-portable.html
Edited by Plan9 - 7/18/13 at 5:21pm
post #2 of 7
Quote:
Originally Posted by Plan9 View Post

Since the topic of systemd comes up quite a bit, I figured a few of you guys might be interested in this blog post about the problems with systemd's portability (as Debian runs on top of some non-Linux kernels as well).
(the Avahi and PulseAudio comment made me laugh as they're two components I usually uninstall from any Linux box I host).

Anyhow, the blog also comments on the future of systemd within Debian:
Source: http://people.debian.org/~stapelberg//2013/07/13/systemd-not-portable.html

ProcFS could be made sufficient with symbolic links, IMO. Similar to how /dev/disks/by-uuid/[uuid] is just a symbolic link to /dev/sdX etc... All of the kernels available support and handle symlinks effectively the same to my knowledge.

EDIT: I see now that that was just one of many missing/incomplete features that are required for SystemD to work. I really don't see why the changes couldn't be made to SystemD, but the developers obviously don't want to go that route.
Edited by Xaero252 - 7/18/13 at 5:52pm
    
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post #3 of 7
Thread Starter 
Quote:
Originally Posted by Xaero252 View Post

ProcFS could be made sufficient with symbolic links, IMO. Similar to how /dev/disks/by-uuid/[uuid] is just a symbolic link to /dev/sdX etc... All of the kernels available support and handle symlinks effectively the same to my knowledge.
The /proc/$PID/exe would be harder to do with symlinks because of the frequency in which they're created and destroyed.
post #4 of 7
So? I'm probably not as hardcore as some of you, but I get the feeling that this says in the long run it is better. No?
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post #5 of 7
Quote:
Originally Posted by mushroomboy View Post

So? I'm probably not as hardcore as some of you, but I get the feeling that this says in the long run it is better. No?

There are many technical reasons systemd is better than Sysvinit. One of the most notably differences is it's parallel, so all other things being equal, a system using systemd will boot faster than one using sysvinit in most circumstances. Also, while writing sysvinit startup scripts isn't exactly hard, systemd service files are much easier.

The other thing I really like about systemd is it gives you a standard interface for making changes persistent. For instance, in a lot of cases there were small but significant differences between distribution families in how the network interfaces were configured (i.e. Debian based distros did it different than redhat based distros). Systemd standardizes that across distributions, as long as those distros are using systemd.
post #6 of 7
Nhh, I soo want to drop into this particular discussion but don't want to get my hands dirty smile.gif) Ok,... here goes. Being much of a snob and being stubbornly conservative biggrin.gif I wouldn't bend under the words "if they want to stay relevant" and so, because it sounds so very much like stuff the politicians and ambassadors love to throw at each other smile.gif
Other than that, I know that many people familiar with sysv or / and maintaining systems with sysv would disagree to learn something new just because somebody felt like he should write his own init system, with blackjack and ,... other accompanying parts, the one to unite them all. Many were against binary logs, and I, too, am comfortable that they are text files. Don't know if anything changed in this respect... Ok, to each their own, but I personally have my first objections to the ways it is propagated. edit: which arises suspicions about further technical details
(in this I am biased because of ranting over above and further mentioned and I don't need a parallelized, even more aggressively parallelized, or faster init either)
About the survey itself: from my point of view the survey sample is rather... non-representative or at least the results are not... in some way, because this sampling should be stratified to be carried out the completely proper way (which would increase its necessary size a little too) edit: the strata responds should also be separated in this case ofc
Anyway, looking at the provided results,... you could see that 63% stated "Ok let it be there in the repos, whoever needs will install it" (it's up to whoever made the survey to use a neutral formulation or not,...) and, next, following that, there is 43% pro-default against 33% not wanting it as default smile.gif Whatever decisions will be taken, this relation is not like 60 against 10, for example. So let's wait which way the Debian devs will go smile.gif
But, speculating on a sample survey results is always ungratifying (it's statistics and if you're involved in that area you know that good tools may be used properly or improperly), ... however sample survey generally boils down to the two rules: representativeness and the methods and selection must only depend on the specifics of the population and not on the goal of the survey, all other rules are meeting maths requirements like necessary minimal sample size
Edited by alexx2005 - 7/21/13 at 4:35pm
post #7 of 7

eh, systemd, upstart, sysvinit, OH MY!

 

I'm one of the hold outs, as I still don't see the benefits of systemd. I know what is says on some sites and the white docs and all that, but they really don't mean much to me.  I've used all 3, from what i can tell there isn't much difference in their speed (unless i'm just not doing it right :)). I've written startup scripts for all 3, they are all 3 a pain. dunno, we will see. I'll stick with whatever my distro of choice is using, gonna take a lot more than a init system to get me to switch. 

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Overclock.net › Forums › Software, Programming and Coding › Operating Systems › Linux, Unix › [Debian] Survey answers part 3: systemd is not portable and what this means for our ports (2013-07-13)