On Mon, 29 Apr 2019 21:19:58 +0200 Jeff <sysi...@yandex.com> wrote: > i came across some interesting claims recently. on > http://skarnet.org/software/s6/ > it reads > > "suckless init is incorrect, because it has no supervision > capabilities, and thus, killing all processes but init can brick the > machine."
Oh, that. First of all, Suckless Init is a PID1 that forks an rc script and then hangs around reaping zombies. You could use that rc file to run supervision systems such as daemontools-encore and the supervision part of runit and s6. So Suckless Init is the PID1 part of an init system. It's 83 lines of C. There are three philosophies: 1) The supervision should be done by PID1: Supported by Laurent Bercot 2) The supervision should be done outside of PID1: Perhaps supported by Rich Felker in his http://ewontfix.com/about/ > > a rather bold claim IMO ! > where was the "correct" init behaviour specified ? > where can i learn how a "correct" init has to operate ? > or is it true since s6-svscan already provides such respawn > capabilities ? ;-) > > there is actually NO need for a "correct" working init implementation > to provide respawn capabilities at all IMO. > this can easily done in/by a subprocess and has 2 advantages: > > - it simplyfies the init implementation > > - process #1 is the default subprocess reaper on any unix > implementation and hence a lot of terminated zombie subprocesses > get assigned to it, subprocesses that were not started by it. > if it has respawn capabilities it has to find out if any of this > recently assigned but elsewhere terminated subprocesses is one of its > own childs to be respawned. if it has lots of services to respawn > this means lots of unnecessary work that could be also done > in/by a suprocess aswell. > > when do you kill a non supvervised process running with UID 0 > "accidently" ? when calling kill ( -1, SIGTERM ) ? > the kernel protects special/important processes in this case from > being killed "accidently", that's true. > but where do we usually see that ? in the shutdown stage, i guess. > and that's exactly where one wants to kill all process with PID > 1 > (sometimes excluding the calling process since it has to complete > more tasks). or when going into single user mode. > > so this looks like a rather artificial and constructed argument for > the necessity of respawn functionality in an init implementation IMO. > -- SteveT Steve Litt January 2019 featured book: Troubleshooting: Just the Facts http://www.troubleshooters.com/tjust
