On Tue, 15 May 2018 23:39:24 +1000 Tom <wirelessd...@gmail.com> wrote:
> > On 14 May 2018, at 18:51, Steve Litt <sl...@troubleshooters.com> > > wrote: > > > > Way 2 is to have OpenRC run either runit or s6 from /etc/inittab > > with "respawn", and then to put all respawnable daemons in runit or > > s6. Running either runit or s6 *as a supervisor rather than an > > init* is dead-bang easy. Since about 2010 I've been doing something > > similar: I ran daemontools on top of sysvinit, and it always worked > > out great for me. > > > > SteveT > > Thanks as always for your insightful information Steve. Much > appreciated. As someone who knows very little about init systems, > can you explain what this respawning business is all about? Terminology: I call the init system we've used for 30 years "sysvinit". Yes, I'll explain. Your httpd server crashes. There are two ways of handling it: 1) Let it stay crashed until human intervention restarts it. 2) Make it restart itself (this is called respawning) Neither is better than the other: Which one to use depends on the situation. With something like httpd, perhaps it's best for a human to fix and diagnose it so it doesn't keep happening. However, some of my home-grown daemons are buggy enough that I'd rather they just log the crash and restart. * Sysvinit mainly stays crashed, but daemons identified as "respawn" in /etc/inittab respawn themselves. * OpenRC, by itself, only stays crashed. * SystemD does either. * Runit and s6 only respawn unless extraordinary measures are taken * s6 plus s6-rc does either * Bolting on either runit or s6 on top of either sysvinit or > I didn’t > realise the existing sysv-rc I assume here you mean sysvinit when you write sysv-rc. > did anything like that as I’ve never had > one of the regular system daemons (or apache2, ntp, etc.) knowingly > crash on me. In which case, you probably have little need for respawning. > > Apart from being a drop-in replacement for sysv-rc, is there any > noticeable feature that I would use as a sysadmin with OpenRC? I'm not an OpenRC expert, so everything I know is second hand. I've heard OpenRC can do parallel instantiation, for faster boots. You know, like systemd claims to do. People more knowledgeable than I can give you other OpenRC advantages. > I’ve > never encountered any boot issues or problems starting/stopping > services with says-rc. You sound like the ideal candidate for either sysvinit or OpenRC. > Perhaps there are other features of init > systems that people use regularly? YES! I use the following two features of runit regularly: 1) Simplicity 2) Run scripts are <10 lines, not the 30Megaline behemoths of sysvinit and OpenRC. 3) Daemons run by runit (or s6 or any other daemontools-inspired init or process supervisor) needn't (and shouldn't) background itself. Makes it much easier to write your own daemons. SteveT Steve Litt June 2018 featured book: Twenty Eight Tales of Troubleshooting http://www.troubleshooters.com/28 _______________________________________________ Dng mailing list Dng@lists.dyne.org https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
