On Fri, Feb 14, 2020 at 3:22 PM Steve Litt <slitt_at_troubleshooters.com> wrote:
>
> On Fri, 14 Feb 2020 05:18:33 -0800
> Cameron Nemo <camerontnorman_at_gmail.com> wrote:
>
> > On Fri, Feb 14, 2020 at 4:45 AM Steve Litt
> > <slitt_at_troubleshooters.com> wrote:
> > >
> > > In my computer usage, I usually need about 5 minutes to gracefully
> > > exit all my programs before powering down the computer, and I have
> > > a 40 minute UPS. If this is done at all, I'd suggest a configurable
> > > amount of time, with a visible countdown, telling the user to get
> > > his or her affairs in order, and also a way to cancel the shutdown.
> > >
> > > The only reason I see to have the computer automatically power down
> > > when signaled by the UPS is that I might not be home, but in that
> > > case waiting 5 minutes wouldn't matter.
> >
> > Most init systems allow the SIGPWR behavior to be configured.
> > This includes Upstart, systemd, and my own "little init":
> >
> > https://gitlab.com/chinstrap/linit#configuration
> >
> > I provide a guide for using linit with runit here, but the process is
> > experimental:
> >
> > https://gitlab.com/chinstrap/linit/-/blob/master/README.runit.md
> >
> > Linit is packaged in Void Linux, and void images are available for
> > LXD. Lastly I want to mention that lxc.signal.halt is not available
> > with LXD.
> >
> > Regards,
> > --
> > Cameron Nemo
>
> Hi Cameron,
>
> I'm very impressed with linit. In my 20 minute perusal it looks quite a
> bit like Suckess Init, which I like. On line 54 you have
> int linit_spawn(char * restrict path) {
>
> Is path the path to the rc file that linit forks off? I've never seen
> char * restrict before: What does "restrict" mean?
I use the term hook, which could refer to /boot, /sigpwr, or /sigint.
Roughly equivalent to an rc file.
restrict keyword is described here:
https://en.wikipedia.org/wiki/Restrict
https://stackoverflow.com/questions/745870/realistic-usage-of-the-c99-restrict-keyword
It is probably not useful in this case, but the posix_spawn API
specifies it so I used it.
>
> I notice linit responds only to a couple signals, whereas Suckless
> Init responds to:
> { SIGUSR1, sigpoweroff },
> { SIGCHLD, sigreap },
> { SIGALRM, sigreap },
> { SIGINT, sigreboot },
> { SIGILL, sigillhandle},
>
SIGUSR1: I am unaware of any linux tools which use that signal. I used
SIGPWR specifically for compat with UPS tools and lxc/lxd.
SIGCHLD: linit actually ignores this signal, which reaps the child.
SIGALRM: because childs are implicitly reaped, there is no reason to
include a tick from what I can tell. (i.e. this case never happens:
https://git.suckless.org/sinit/commit/170d599d58efee6c9be675a85c6e435d68e8a2de.html)
SIGINT: same behavior as sinit here.
SIGILL: you must have added that. I would be curious to know why.
> Actually, I think I might have put one of those in, but I don't think
> you respond to most of them: Is there a reason?
>
> Anyway, I kind of like your linit PID1.
Thanks.
The only real novel details are that:
- it calls pause() in the main loop
- uses posix_spawn() to exec from signal handlers in a thread safe manner
> Steve
Regards,
Cameron
Received on Mon Feb 17 2020 - 19:46:15 UTC