Re: [ale] systemd talk from July has slide deck online now

From: Colin Booth <cathexis_at_gmail.com>
Date: Tue, 8 Sep 2015 23:20:05 -0700

On Tue, Sep 8, 2015 at 10:04 PM, Steve Litt <slitt_at_troubleshooters.com> wrote:
>
> Is s6-rc something you add to s6, or is it a totally different thing?
>
One more bit about this. s6-rc sits on top of s6 and emits s6-svc and
s6-sudo commands as necessary. For example, a dry run taking down sshd
on my laptop:
root_at_radon:~# s6-rc -n0 -d change sshd
s6-rc-dryrun: /package/admin/s6/command/s6-svc -dwD -T 0 --
/run/s6/rc/scandir/sshd-srv
s6-rc-dryrun: /package/admin/s6/command/s6-svc -dwD -T 0 --
/run/s6/rc/scandir/sshd-log

Ignoring the s6-rc-dryrun part, I have a bundle named sshd (containing
both sshd-srv and sshd-log). If I tell s6-rc to bring down sshd, it'll
tell s6-svc to stop sshd, wait until sshd has completely exited
(including any ./finish script), and then do the same with the logger.

Larger bundles, such as taking down my entire networking stack, look like this:
root_at_radon:~# s6-rc -n0 -d change ok-lan
s6-rc-dryrun: /package/admin/s6/command/s6-svc -dwD -T 0 --
/run/s6/rc/scandir/sshd-srv
s6-rc-dryrun: /package/admin/s6/command/s6-svc -dwD -T 0 --
/run/s6/rc/scandir/ntpd-srv
s6-rc-dryrun: /package/admin/s6/command/s6-svc -dwD -T 0 --
/run/s6/rc/scandir/ntpd-log
s6-rc-dryrun: /package/admin/s6/command/s6-svc -dwD -T 0 --
/run/s6/rc/scandir/dnsmasq-srv
s6-rc-dryrun: /package/admin/s6/command/s6-svc -dwD -T 0 --
/run/s6/rc/scandir/sshd-log
s6-rc-dryrun: /package/admin/s6/command/s6-svc -dwD -T 0 --
/run/s6/rc/scandir/wicd-srv
s6-rc-dryrun: /package/admin/s6/command/s6-svc -dwD -T 0 --
/run/s6/rc/scandir/dnsmasq-log
s6-rc-dryrun: /package/admin/s6/command/s6-svc -dwD -T 0 --
/run/s6/rc/scandir/wicd-log

In this case it takes down the two leaf services that nothing depends
on (sshd-srv and ntpd-srv), then stops the services that are now the
leaf services (sshd-log, ntpd-log, dnsmasq-srv), then the next new
leaf services (wicd-srv, dnsmasq-log), and finally the lone wicd-log
that nothing depends on.

Startup is, predictably the opposite:
root_at_radon:~# s6-rc -n1000 -u change ok-lan
s6-rc-dryrun: /package/admin/s6/command/s6-svc -uwu -T 0 --
/run/s6/rc/scandir/wicd-log
s6-rc-dryrun: /package/admin/s6/command/s6-svc -uwu -T 0 --
/run/s6/rc/scandir/sshd-log
s6-rc-dryrun: /package/admin/s6/command/s6-svc -uwu -T 0 --
/run/s6/rc/scandir/ntpd-log
s6-rc-dryrun: /package/admin/s6/command/s6-svc -uwu -T 0 --
/run/s6/rc/scandir/dnsmasq-log
s6-rc-dryrun: /package/admin/s6/command/s6-svc -uwu -T 0 --
/run/s6/rc/scandir/wicd-srv
s6-rc-dryrun: /package/admin/s6/command/s6-svc -uwu -T 0 --
/run/s6/rc/scandir/sshd-srv
s6-rc-dryrun: /package/admin/s6/command/s6-svc -uwu -T 0 --
/run/s6/rc/scandir/dnsmasq-srv
s6-rc-dryrun: /package/admin/s6/command/s6-svc -uwu -T 0 --
/run/s6/rc/scandir/ntpd-srv

You may notice that the ordering on loggers vs other services is
different. That's because loggers don't depend on anything changing in
this example so s6-rc will get those running first before attending to
anything else.

Cheers!

-- 
"If the doors of perception were cleansed every thing would appear to
man as it is, infinite. For man has closed himself up, till he sees
all things thru' narrow chinks of his cavern."
  --  William Blake
Received on Wed Sep 09 2015 - 06:20:05 UTC

This archive was generated by hypermail 2.3.0 : Sun May 09 2021 - 19:44:19 UTC