8 ms·

How Debian managed the systemd transition

51 points by liotier 11y ago

yarrel 11y ago
I saw my first "restart to install updates" dialog in Debian this week. SystemD is cargo-culting Windows.
- throwaway7767 11y ago
  So you have not been rebooting when you update kernels up until now? That might leave you open to security vulnerabilities. You don't specify which update tool you are using, but if it hasn't shown you that screen before that sounds like a bug. EDIT: replying to digi_owl, as HN won't allow me to reply at a deeper nesting level. > 1. you can actually do a kernel update without a reboot now, using certain tools. To my knowledge, none of them are supported by debian, which was what the OP was talking about. Maybe he's using them, but then, it seems weird to complain about debian requiring reboots if he's gone to such lengths to prevent that problem in the past. > 2. dbus was a reimplementation in C of dcop, the KDE IPC system. It was aimed at allowing desktop programs to talk to each other, not carry the whole OS on its back. I'm not sure what that has to do with anything in my post. > 3. drop the attitude. Or are you deliberately trying to derail the topic? I'm not sure what attitude you refer to, it was not my intention to come off as hostile. Apologies to the GGP if that's how it sounded. I was merely pointing out that reboots for upgrades are not a new thing in debian, as the GGP seemed to be implying.
  - digi_owl 11y ago
    1. you can actually do a kernel update without a reboot now, using certain tools. 2. dbus was a reimplementation in C of dcop, the KDE IPC system. It was aimed at allowing desktop programs to talk to each other, not carry the whole OS on its back. 3. drop the attitude. Or are you deliberately trying to derail the topic?
    - iso8859-1 11y ago
      reimplementation? it's totally different!
    - icebraining 11y ago
      1. you can actually do a kernel update without a reboot now, using certain tools. Which Debian doesn't officially support, so they can't be expected to write update scripts for that use case.
  - vezzy-fnord 11y ago
    HN won't allow me to reply at a deeper nesting level Click on the timestamp of a post to get an immediate reply area.
    - digi_owl 11y ago
      Yep, the in-thread reply link seems to stay hidden for something like a minute after the post is made. I guess they want to avoid flamewars...
- shmerl 11y ago
  Reboots aren't that uncommon once you hit stuff like updating the kernel, kernel modules, systemd itself and etc. I never got that notion that Linux doesn't require rebooting with updates. It's not always necessary, but with certain updates it always happens. May be in the future there will be a way to do it all dynamically without rebooting, but it didn't happen yet.
  - gizmo686 11y ago
    Linux supports replacing the kernel without a reboot (see kexec), but I doubt we will ever see a time where the benefits of doing so outweigh the complexity and risk of error in the general case.
    - vezzy-fnord 11y ago
      It can certainly be done properly, even on relatively static systems like Unix. See Cristiano Giuffrida's Ph.D. thesis on "Safe and Automatic Live Update" [1], or, if you don't want to skim through 197 pages, the significantly shorter master's thesis "Safe and Automatic Live Update for Unix Applications" [2] by Calin Iorgulescu. The research has been supervised by AST and since incorporated into MINIX 3. [1] http://www.minix3.org/theses/Cristiano_Giuffrida_PhD_thesis.pdf http://www.minix3.org/theses/Cristiano_Giuffrida_PhD_thesis.... [2] http://www.minix3.org/theses/Calin_Iorgulescu_Master_Thesis.pdf http://www.minix3.org/theses/Calin_Iorgulescu_Master_Thesis....
    - heinrich5991 11y ago
      As I understand it, it still has to bring down the whole system (I mean all processes) in order to do that – isn't that functionally equivalent to a reboot?
      - icebraining 11y ago
        kexec does, but Ksplice and kpatch don't, they just pause the processes momentarily.
    - deleted 11y ago
      [deleted]
- GFK_of_xmaspast 11y ago
  I've been getting that for years with ubuntu.
- jryan49 11y ago
  That has NOTHING to do with systemd. I'm getting sick of people blaming everything on systemd who don't even know what they're talking about.
  - JdeBP 11y ago
    * https://fedoraproject.org/wiki/Features/OfflineSystemUpdates https://fedoraproject.org/wiki/Features/OfflineSystemUpdates * http://freedesktop.org/wiki/Software/systemd/SystemUpdates/ http://freedesktop.org/wiki/Software/systemd/SystemUpdates/ * http://www.freedesktop.org/software/systemd/man/systemd-system-update-generator.html http://www.freedesktop.org/software/systemd/man/systemd-syst... * https://lists.debian.org/debian-devel/2015/08/thrd2.html#00482 https://lists.debian.org/debian-devel/2015/08/thrd2.html#004... I look at the above; I look at what was said by the person that you're replying to; and the conclusion as to whether that person knows what xe is talking about comes out rather differently.
    - deleted 11y ago
      [deleted]
    - deleted 11y ago
      [deleted]
    - jryan49 11y ago
      This is a feature that systemd provides. It is the distro's choice to use it. Arch doesn't use this. Arch uses systemd. edit: Look how Arch dev says they won't probably ever use it: https://bbs.archlinux.org/viewtopic.php?id=145265 https://bbs.archlinux.org/viewtopic.php?id=145265, just because systemd gives you an ability to do something people actually want, you can't blame systemd for a distro that uses that feature.
throwaway7767 11y ago
It's interesting to me that debian has written systemd-shim, hadn't heard about it before. I remember that for a while, the primary criticism I heard of systemd was that it would make software linux-only because of systemd dependencies (gnome was the primary example given) and that it was impossible to write a compatibility wrapper. I guess the debian guys busted that myth.
- vezzy-fnord 11y ago
  I guess the debian guys busted that myth. Nope, they haven't. systemd-shim is a fundamentally unsustainable idea: http://homepage.ntlworld.com./jonathan.deboynepollard/FGA/debian-systemd-packaging-hoo-hah.html#systemd-shim http://homepage.ntlworld.com./jonathan.deboynepollard/FGA/de...
  - throwaway7767 11y ago
    Thanks for that link, it provides an interesting counterpoint. I'm not sure I agree that it's an unsustainable idea to keep a wrapper updated. If people really are interested in it, surely they will keep it updated. Lots of open source projects bitrot, and the general reason is lack of interest in keeping them working. Given the number of times I've seen the non-portability complaint, it's especially surprising that noone but Steve Langesek (according to your link) has seen fit to contribute code. I do agree though that it would be better if systemd standardised those interfaces that people want to use, such as the logind interface.
    - vezzy-fnord 11y ago
      The systemd interface portability and stability chart lists logind as not being independently reimplementable, and I don't see that changing soon. Steve Langasek was an Upstart project leader, and systemd-shim was never intended to be more than a temporary workaround, from what I know. Fact is, targeting the internal D-Bus interfaces is an exercise in perpetually playing catch-up.
      - 11y ago
click170 11y ago
I've been using Debian for about 10 years now and with all the FUD I was worried about the systemd switch, but its been largely uneventful for me. The only bug I've noticed after switching to Jessie is that on one of my systems that has two NICs for some reason both NICs will occasionally end up with the same IP on both NICs. I need to investigate further to figure out the root cause but a reboot always solves the problem for a couple days. I'm confident its not a dhcp server issue. I expected much more grief due to edge cases that weren't planned for but I've yet to find more than the dual nic issue.
- deleted 11y ago
  [deleted]
- currysausage 11y ago
  Maybe some glitch in your /etc/udev/rules.d/70-persistent-net.rules?
- Scramblejams 11y ago
  As a fellow Debian user, I haven't been so lucky. Installing systemd broke sleep on two of my laptops, broke a keyboard[1] (!), broke my /etc/rc.local (stopped executing it on boot)... Not a happy camper. [1] https://github.com/systemd/systemd/issues/340 https://github.com/systemd/systemd/issues/340
  - bonzini 11y ago
    At least the keyboard thing is unrelated to the systemd switch, it's just buggy hardware as usual.
    - Scramblejams 11y ago
      No, not unrelated. The hardware may be buggy but it worked fine for years and years, until I installed systemd. Only then did it break. Not good. This is what happens when you throw old software out and try to replace it wholesale -- you stub your toes on all these corner cases that the prior software got right, and now you have to get it right in the new software. And for somebody like me who personally never felt much pain from boot times or writing init scripts, the payoff from the switch has been negative so far.
iso8859-1 11y ago
Can anyone post subscriber links to LWN, or only liotier and corbet?
- DanBC 11y ago
  Click on the LWN domain in the title. You're taken to a list of articles submitted to HN from that domain. There are a bunch of people who submit articles from LWN. If you suspect shenanigans it's probably more useful to email HN. (I'm only guessing that though).
- throwaway7767 11y ago
  Any subscriber can post links. They're asked to keep it within bounds, i.e. don't just create a service where you post all the articles, but they seem to be fine with posting single articles to sites like HN.
- brobinson 11y ago
  The LWN people have stated that subscriber links are okay because they can help drive new subscribers who might otherwise not know such context existed, but obviously they don't want people posting EVERY link. I forget where I saw this discussed.
- corbet 11y ago
  Occasional subscriber links are OK. But please, if you appreciate this kind of content, consider subscribing and helping to assure its continued production. Subscribers keep the whole operation going.

51 points by liotier 11y ago

yarrel 11y ago

I saw my first "restart to install updates" dialog in Debian this week. SystemD is cargo-culting Windows.

throwaway7767 11y ago
So you have not been rebooting when you update kernels up until now? That might leave you open to security vulnerabilities. You don't specify which update tool you are using, but if it hasn't shown you that screen before that sounds like a bug. EDIT: replying to digi_owl, as HN won't allow me to reply at a deeper nesting level. > 1. you can actually do a kernel update without a reboot now, using certain tools. To my knowledge, none of them are supported by debian, which was what the OP was talking about. Maybe he's using them, but then, it seems weird to complain about debian requiring reboots if he's gone to such lengths to prevent that problem in the past. > 2. dbus was a reimplementation in C of dcop, the KDE IPC system. It was aimed at allowing desktop programs to talk to each other, not carry the whole OS on its back. I'm not sure what that has to do with anything in my post. > 3. drop the attitude. Or are you deliberately trying to derail the topic? I'm not sure what attitude you refer to, it was not my intention to come off as hostile. Apologies to the GGP if that's how it sounded. I was merely pointing out that reboots for upgrades are not a new thing in debian, as the GGP seemed to be implying.
- digi_owl 11y ago
  1. you can actually do a kernel update without a reboot now, using certain tools. 2. dbus was a reimplementation in C of dcop, the KDE IPC system. It was aimed at allowing desktop programs to talk to each other, not carry the whole OS on its back. 3. drop the attitude. Or are you deliberately trying to derail the topic?
  - iso8859-1 11y ago
    reimplementation? it's totally different!
  - icebraining 11y ago
    1. you can actually do a kernel update without a reboot now, using certain tools. Which Debian doesn't officially support, so they can't be expected to write update scripts for that use case.
- vezzy-fnord 11y ago
  HN won't allow me to reply at a deeper nesting level Click on the timestamp of a post to get an immediate reply area.
  - digi_owl 11y ago
    Yep, the in-thread reply link seems to stay hidden for something like a minute after the post is made. I guess they want to avoid flamewars...
shmerl 11y ago
Reboots aren't that uncommon once you hit stuff like updating the kernel, kernel modules, systemd itself and etc. I never got that notion that Linux doesn't require rebooting with updates. It's not always necessary, but with certain updates it always happens. May be in the future there will be a way to do it all dynamically without rebooting, but it didn't happen yet.
- gizmo686 11y ago
  Linux supports replacing the kernel without a reboot (see kexec), but I doubt we will ever see a time where the benefits of doing so outweigh the complexity and risk of error in the general case.
  - vezzy-fnord 11y ago
    It can certainly be done properly, even on relatively static systems like Unix. See Cristiano Giuffrida's Ph.D. thesis on "Safe and Automatic Live Update" [1], or, if you don't want to skim through 197 pages, the significantly shorter master's thesis "Safe and Automatic Live Update for Unix Applications" [2] by Calin Iorgulescu. The research has been supervised by AST and since incorporated into MINIX 3. [1] http://www.minix3.org/theses/Cristiano_Giuffrida_PhD_thesis.pdf http://www.minix3.org/theses/Cristiano_Giuffrida_PhD_thesis.... [2] http://www.minix3.org/theses/Calin_Iorgulescu_Master_Thesis.pdf http://www.minix3.org/theses/Calin_Iorgulescu_Master_Thesis....
  - heinrich5991 11y ago
    As I understand it, it still has to bring down the whole system (I mean all processes) in order to do that – isn't that functionally equivalent to a reboot?
    - icebraining 11y ago
      kexec does, but Ksplice and kpatch don't, they just pause the processes momentarily.
  - deleted 11y ago
    [deleted]
GFK_of_xmaspast 11y ago
I've been getting that for years with ubuntu.
jryan49 11y ago
That has NOTHING to do with systemd. I'm getting sick of people blaming everything on systemd who don't even know what they're talking about.
- JdeBP 11y ago
  * https://fedoraproject.org/wiki/Features/OfflineSystemUpdates https://fedoraproject.org/wiki/Features/OfflineSystemUpdates * http://freedesktop.org/wiki/Software/systemd/SystemUpdates/ http://freedesktop.org/wiki/Software/systemd/SystemUpdates/ * http://www.freedesktop.org/software/systemd/man/systemd-system-update-generator.html http://www.freedesktop.org/software/systemd/man/systemd-syst... * https://lists.debian.org/debian-devel/2015/08/thrd2.html#00482 https://lists.debian.org/debian-devel/2015/08/thrd2.html#004... I look at the above; I look at what was said by the person that you're replying to; and the conclusion as to whether that person knows what xe is talking about comes out rather differently.
  - deleted 11y ago
    [deleted]
  - deleted 11y ago
    [deleted]
  - jryan49 11y ago
    This is a feature that systemd provides. It is the distro's choice to use it. Arch doesn't use this. Arch uses systemd. edit: Look how Arch dev says they won't probably ever use it: https://bbs.archlinux.org/viewtopic.php?id=145265 https://bbs.archlinux.org/viewtopic.php?id=145265, just because systemd gives you an ability to do something people actually want, you can't blame systemd for a distro that uses that feature.

throwaway7767 11y ago

It's interesting to me that debian has written systemd-shim, hadn't heard about it before. I remember that for a while, the primary criticism I heard of systemd was that it would make software linux-only because of systemd dependencies (gnome was the primary example given) and that it was impossible to write a compatibility wrapper. I guess the debian guys busted that myth.

vezzy-fnord 11y ago
I guess the debian guys busted that myth. Nope, they haven't. systemd-shim is a fundamentally unsustainable idea: http://homepage.ntlworld.com./jonathan.deboynepollard/FGA/debian-systemd-packaging-hoo-hah.html#systemd-shim http://homepage.ntlworld.com./jonathan.deboynepollard/FGA/de...
- throwaway7767 11y ago
  Thanks for that link, it provides an interesting counterpoint. I'm not sure I agree that it's an unsustainable idea to keep a wrapper updated. If people really are interested in it, surely they will keep it updated. Lots of open source projects bitrot, and the general reason is lack of interest in keeping them working. Given the number of times I've seen the non-portability complaint, it's especially surprising that noone but Steve Langesek (according to your link) has seen fit to contribute code. I do agree though that it would be better if systemd standardised those interfaces that people want to use, such as the logind interface.
  - vezzy-fnord 11y ago
    The systemd interface portability and stability chart lists logind as not being independently reimplementable, and I don't see that changing soon. Steve Langasek was an Upstart project leader, and systemd-shim was never intended to be more than a temporary workaround, from what I know. Fact is, targeting the internal D-Bus interfaces is an exercise in perpetually playing catch-up.
    - 11y ago

click170 11y ago

I've been using Debian for about 10 years now and with all the FUD I was worried about the systemd switch, but its been largely uneventful for me. The only bug I've noticed after switching to Jessie is that on one of my systems that has two NICs for some reason both NICs will occasionally end up with the same IP on both NICs. I need to investigate further to figure out the root cause but a reboot always solves the problem for a couple days. I'm confident its not a dhcp server issue. I expected much more grief due to edge cases that weren't planned for but I've yet to find more than the dual nic issue.

deleted 11y ago
[deleted]
currysausage 11y ago
Maybe some glitch in your /etc/udev/rules.d/70-persistent-net.rules?
Scramblejams 11y ago
As a fellow Debian user, I haven't been so lucky. Installing systemd broke sleep on two of my laptops, broke a keyboard[1] (!), broke my /etc/rc.local (stopped executing it on boot)... Not a happy camper. [1] https://github.com/systemd/systemd/issues/340 https://github.com/systemd/systemd/issues/340
- bonzini 11y ago
  At least the keyboard thing is unrelated to the systemd switch, it's just buggy hardware as usual.
  - Scramblejams 11y ago
    No, not unrelated. The hardware may be buggy but it worked fine for years and years, until I installed systemd. Only then did it break. Not good. This is what happens when you throw old software out and try to replace it wholesale -- you stub your toes on all these corner cases that the prior software got right, and now you have to get it right in the new software. And for somebody like me who personally never felt much pain from boot times or writing init scripts, the payoff from the switch has been negative so far.

iso8859-1 11y ago

Can anyone post subscriber links to LWN, or only liotier and corbet?

DanBC 11y ago
Click on the LWN domain in the title. You're taken to a list of articles submitted to HN from that domain. There are a bunch of people who submit articles from LWN. If you suspect shenanigans it's probably more useful to email HN. (I'm only guessing that though).
throwaway7767 11y ago
Any subscriber can post links. They're asked to keep it within bounds, i.e. don't just create a service where you post all the articles, but they seem to be fine with posting single articles to sites like HN.
brobinson 11y ago
The LWN people have stated that subscriber links are okay because they can help drive new subscribers who might otherwise not know such context existed, but obviously they don't want people posting EVERY link. I forget where I saw this discussed.
corbet 11y ago
Occasional subscriber links are OK. But please, if you appreciate this kind of content, consider subscribing and helping to assure its continued production. Subscribers keep the whole operation going.