On Thu, 10 Aug 2017 09:22:38 -0500 "Jamey Fletcher" <[email protected]> wrote:
> Take what he's written, add in your thoughts, more clearly specify the > differences between inits, supervisors, hypervisors, and containers, > and write up your own explanation. This will probably fail due to a lack of agreed upon definitions. I'll discuss just inits and supervisors here. There are folks who say if it's not part of PID1, it's not part of the init system. That means that runit's rc files and process supervisor aren't part of the init system. But on very similar s6, where the supervisor *is* part of PID1, the whole thing is an init. And what about OpenRC, which has no PID1 at all but must borrow one from somewhere else, typically from sysvinit? Is OpenRC not an init system? As far as the word supervisor, Laurent Bercot is working very hard to keep a pure definition. I'm not sure I agree with all elements of his definition, but could live with it if he would write very tight definitions for both "process supervisor", "supervisor" if any different, and "process manager". We'd then have to correct the millions using different terminology. We see this definition mess all the time when people talk about "window managers" and "desktop environments". That's a distinction that never should have been made. I suggest everyone read and do their best to understand https://skarnet.org/software/s6/s6-svscan-1.html. This page does a great job of defining and explaining the three stages of the initialization process, and if you read carefully, it explains that there's not necessarily a relationship between stage and PID. In runit, stage1 is done in PID1, but a fork to an rc file culminating in runsvdir does all the stage2 work, while PID1 continues to check for zombies. In s6, PID1 does the first part of stage1, then the rest of stage1 is forked, and then supervisor s6-svscan is execed into PID1, and s6-svscan not only supervises, but also checks for zombies. I'm a little confused on stage3, shutdown. When I've built my own init systems, I've always had stage3 just be a shellscript to shut everything down. Sometimes I shut down by manually running the shellscript, rather than sending a signal. Crude, but effective. https://skarnet.org/software/s6/s6-svscan-1.html has an excellent bullet list on the four things a stage3 must do. https://skarnet.org/software/s6/s6-svscan-1.html is one of a few documents I read before beginning the Manjaro Experiments, along with such classics as ewontfix.com/14 and the Daemontools documentation. It helped me immensely, and I highly recommend it. SteveT Steve Litt July 2017 featured book: Quit Joblessness: Start Your Own Business http://www.troubleshooters.com/startbiz _______________________________________________ Dng mailing list [email protected] https://mailinglists.dyne.org/cgi-bin/mailman/listinfo/dng
