9 ms·

Systemd, 10 years later: a historical and technical retrospective

96 points by donmcc 6y ago

xwvvvvwx 6y ago
already posted 12 days ago: https://news.ycombinator.com/item?id=23062072 https://news.ycombinator.com/item?id=23062072
- christoph-heiss 6y ago
  I honestly didn’t see the post before and I’m kinda glad that I have now. Not every repost is bad, also timezones and such.
  - dang 6y ago
    You're absolutely right, but unfortunately we can't customize HN that way; we need a general approach. The problem is that no one, not even those of us who spend excessive time here, sees every thread or even every major thread. HN's front page is a tiny aperture given the firehose that flows through it. We added 'past' to the top bar a few years ago to give people a way to catch up on the biggest threads they missed. Unfortunately relatively few people use it. For example, this month about 4% of logged-in users who've viewed the front page have also used 'past'.
- wolco 6y ago
  Welcome to the weekend. Expect to see 4-5 pieces that may have appeared already but perhaps were overlooked.
beders 6y ago
Ah, hacker news, the web site that can't detect duplicates or afford a message preview. Anybody else amused that we use this bare-bones, no-frills forum to discuss high-tech? ;)
- SteveNuts 6y ago
  For me it's honestly refreshing and I wish more sites were like this.
- draw_down 6y ago
  It’s a recapitulation of how broken and crappy most tech is
- ainar-g 6y ago
  IMO, HackerNews has a few frills, mechanics-wise. Like the fact that you can't downvote direct responses to your comments. Or how you can't downvote at all until you get the right amount of karma. I also consider the lack of notifications about new responses a feature, but a lot of people will probably disagree.
  - Stierlitz 6y ago
    @ainar-g: “IMO, HackerNews has a few frills, mechanics-wise. Like the fact that you can't downvote direct responses to your comments. ” I would prefer a voting-up only option, else the down-voting option gets abused.
    - Jarwain 6y ago
      Well that's why down-voting requires a karma threshold before one can actually downvote
      - The_rationalist 6y ago
        Sadly it is easy to gain karma once your comments amplify an existing echo-chamber e.g pro mozilla/rust comments
- wolco 6y ago
  Duplicates are allowed and often stories are reposted on the weekend. Why would people who read source code for a living need a frilly marketing puff type site? Slashdot is still around if you wanted something different.
naranha 6y ago
Well, that's a lot of text to read. My (high-level) thoughts as a systemd user for 10 years is that it improved some things, made a few things worse, but I would not want to go back to the init.d days. Having a daemon around to manage the lifecycle of services is actually a good idea and most of the *ctl programs are preferable to the manual configuring they replace.
- CameronNemo 6y ago
  I think one of the more interesting takeaways is that Lennart and Kay set out to accomplish some specific goals: - universal IPC-based activation of services - kdbus with systemd being the userspace management layer for that - single writer group hierarchy with systemd being the single writer And that these goals have not (yet) been realized. My perspective is that: - socket activation was never that useful to begin with and complicates the build process for lots of services. - kdbus could have been something real, but Lennart and Kay were unwilling to compromise and listen to the kernel devs criticisms. They tried to sidestep the network maintainer by making it a character device, but forgot they did not have the clout that Google/Android does that allowed binder to get pushed through. - systemd turned out to be the worst container runtime on the market (systemd the supervisor is fundamentally that, a container runtime) and having all cgroup operations flow through its opinionated dbus api was simply unacceptable for docker, kubernetes, lxc, runc, and everybody else maintaining quality container runtimes. So many of these goals will never come to fruition. What systemd excels at is being a dependency based service supervisor with an opinionated and half functional logging layer.
  - JoshTriplett 6y ago
    > - socket activation was never that useful to begin with and complicates the build process for lots of services. One thing people often don't realize: socket activation wasn't just about simplifying daemons (though it does simplify writing daemons if you don't have to deal with the non-activation case). It was also about simplifying the boot process. There exist many different system boot configurations that are difficult to express in terms of dependencies between services; for instance, depending on your particular system configuration, you might need to launch two services in different orders, because in one configuration service A will depend on service B, and in another configuration service B will depend on service A. Socket activation means you can launch the two services simultaneously, and they'll have access to each others' sockets.
sumanthvepa 6y ago
This is an absolutely fantastic review of systemd. The technical section alone is well worth the effort to read carefully if you use Linux in any significant capacity. The history and analysis are pure gems.
- rezonant 6y ago
  Agreed. I've finished the whole thing and although it is a bit rambly it is worth it for anyone who uses systemd on the daily. I realized I have deployed units that misunderstood these core dependency primitives
- JdeBP 6y ago
  You might also enjoy these: * https://blog.darknedgy.net/technology/2015/10/11/0/ https://blog.darknedgy.net/technology/2015/10/11/0/ * https://blog.darknedgy.net/technology/2015/09/05/0/ https://blog.darknedgy.net/technology/2015/09/05/0/ * https://blog.darknedgy.net/technology/2016/01/01/0/ https://blog.darknedgy.net/technology/2016/01/01/0/ * https://blog.afoolishmanifesto.com/tags/supervisors/ https://blog.afoolishmanifesto.com/tags/supervisors/
gorgoiler 6y ago
This contributes nothing to the discussion, but towards the end of this excellent article I noticed myself reading “welcomed” phonetically as “welcome-dee”.
- rezonant 6y ago
  Haha. Knowing little about the state of the BPF developments, the line that BPF will probably supercede everything literally broke my brain

96 points by donmcc 6y ago

xwvvvvwx 6y ago

already posted 12 days ago: https://news.ycombinator.com/item?id=23062072 https://news.ycombinator.com/item?id=23062072

christoph-heiss 6y ago
I honestly didn’t see the post before and I’m kinda glad that I have now. Not every repost is bad, also timezones and such.
- dang 6y ago
  You're absolutely right, but unfortunately we can't customize HN that way; we need a general approach. The problem is that no one, not even those of us who spend excessive time here, sees every thread or even every major thread. HN's front page is a tiny aperture given the firehose that flows through it. We added 'past' to the top bar a few years ago to give people a way to catch up on the biggest threads they missed. Unfortunately relatively few people use it. For example, this month about 4% of logged-in users who've viewed the front page have also used 'past'.
wolco 6y ago
Welcome to the weekend. Expect to see 4-5 pieces that may have appeared already but perhaps were overlooked.

beders 6y ago

Ah, hacker news, the web site that can't detect duplicates or afford a message preview. Anybody else amused that we use this bare-bones, no-frills forum to discuss high-tech? ;)

SteveNuts 6y ago
For me it's honestly refreshing and I wish more sites were like this.
draw_down 6y ago
It’s a recapitulation of how broken and crappy most tech is
ainar-g 6y ago
IMO, HackerNews has a few frills, mechanics-wise. Like the fact that you can't downvote direct responses to your comments. Or how you can't downvote at all until you get the right amount of karma. I also consider the lack of notifications about new responses a feature, but a lot of people will probably disagree.
- Stierlitz 6y ago
  @ainar-g: “IMO, HackerNews has a few frills, mechanics-wise. Like the fact that you can't downvote direct responses to your comments. ” I would prefer a voting-up only option, else the down-voting option gets abused.
  - Jarwain 6y ago
    Well that's why down-voting requires a karma threshold before one can actually downvote
    - The_rationalist 6y ago
      Sadly it is easy to gain karma once your comments amplify an existing echo-chamber e.g pro mozilla/rust comments
wolco 6y ago
Duplicates are allowed and often stories are reposted on the weekend. Why would people who read source code for a living need a frilly marketing puff type site? Slashdot is still around if you wanted something different.

naranha 6y ago

Well, that's a lot of text to read. My (high-level) thoughts as a systemd user for 10 years is that it improved some things, made a few things worse, but I would not want to go back to the init.d days. Having a daemon around to manage the lifecycle of services is actually a good idea and most of the *ctl programs are preferable to the manual configuring they replace.

CameronNemo 6y ago
I think one of the more interesting takeaways is that Lennart and Kay set out to accomplish some specific goals: - universal IPC-based activation of services - kdbus with systemd being the userspace management layer for that - single writer group hierarchy with systemd being the single writer And that these goals have not (yet) been realized. My perspective is that: - socket activation was never that useful to begin with and complicates the build process for lots of services. - kdbus could have been something real, but Lennart and Kay were unwilling to compromise and listen to the kernel devs criticisms. They tried to sidestep the network maintainer by making it a character device, but forgot they did not have the clout that Google/Android does that allowed binder to get pushed through. - systemd turned out to be the worst container runtime on the market (systemd the supervisor is fundamentally that, a container runtime) and having all cgroup operations flow through its opinionated dbus api was simply unacceptable for docker, kubernetes, lxc, runc, and everybody else maintaining quality container runtimes. So many of these goals will never come to fruition. What systemd excels at is being a dependency based service supervisor with an opinionated and half functional logging layer.
- JoshTriplett 6y ago
  > - socket activation was never that useful to begin with and complicates the build process for lots of services. One thing people often don't realize: socket activation wasn't just about simplifying daemons (though it does simplify writing daemons if you don't have to deal with the non-activation case). It was also about simplifying the boot process. There exist many different system boot configurations that are difficult to express in terms of dependencies between services; for instance, depending on your particular system configuration, you might need to launch two services in different orders, because in one configuration service A will depend on service B, and in another configuration service B will depend on service A. Socket activation means you can launch the two services simultaneously, and they'll have access to each others' sockets.

sumanthvepa 6y ago

This is an absolutely fantastic review of systemd. The technical section alone is well worth the effort to read carefully if you use Linux in any significant capacity. The history and analysis are pure gems.

rezonant 6y ago
Agreed. I've finished the whole thing and although it is a bit rambly it is worth it for anyone who uses systemd on the daily. I realized I have deployed units that misunderstood these core dependency primitives
JdeBP 6y ago
You might also enjoy these: * https://blog.darknedgy.net/technology/2015/10/11/0/ https://blog.darknedgy.net/technology/2015/10/11/0/ * https://blog.darknedgy.net/technology/2015/09/05/0/ https://blog.darknedgy.net/technology/2015/09/05/0/ * https://blog.darknedgy.net/technology/2016/01/01/0/ https://blog.darknedgy.net/technology/2016/01/01/0/ * https://blog.afoolishmanifesto.com/tags/supervisors/ https://blog.afoolishmanifesto.com/tags/supervisors/

gorgoiler 6y ago

This contributes nothing to the discussion, but towards the end of this excellent article I noticed myself reading “welcomed” phonetically as “welcome-dee”.

rezonant 6y ago
Haha. Knowing little about the state of the BPF developments, the line that BPF will probably supercede everything literally broke my brain