Injecting a sequential job
Clint Byrum
clint at ubuntu.com
Wed Feb 29 23:28:21 UTC 2012
Excerpts from Svein Seldal's message of Wed Feb 29 14:12:35 -0800 2012:
> Hi Steve
>
> Thanks for answering.
>
> > Could you provide some more detail about what the job is that you're trying
> > to run? There's probably a solution that lets you achieve your end goal,
> > but would need to know what that end goal is to provide useful guidance
> > here.
>
> Yes sure. A bit complex I'd amit. I hope you can bear with me:
>
> Its an embedded product which has two distinct modes to run in:
> production mode and normal application mode. Application mode is
> standard rc runlevel as on a normal desktop installation. The production
> mode is a special mode used in production where no normal services
> should start except a few handpicked ones (static eth0, ssh).
>
> The decision between prod.mode is done from a script. I've been
> experimenting with starting this as a job task. One of the purposes in
> production mode is to have a very specific network setting and publish
> this on avahi.
>
> In app mode network manager provides the user's network configuration.
> One of the challenges I'm facing is how to handle network manager in
> production mode. NM holds the user's config and not the network setup
> needed in production mode. NM starts very early (even before any
> net-device-up is emitted), thus I'm experiencing a race between my
> script and NM.
>
> I've been experimenting with "start on starting dbus" (which is a common
> denominator between nm and avahi) to be able to stop nm and set the
> network manually when going to prod.mode. Yet this has a hacky feel to
> it. This script is vital for the product, so it needs to be simple.
> Complex rules will fail.
I don't think that is hacky at all.
It sounds like network-manager is not desired for production mode, and
you want to replace its functionality with something else. A job which
cancels the start of network-manager is actually *exactly* what I would
recommend in that case.
Since you also want to interact with avahi, it seems like what you need
is a two part configuration:
# prod-mode
start on starting network-manager
pre-start script
if prod_mode_active ; then
stop network-manager
else
stop # Stops prod-mode
fi
end script
# prod-mode-avahi
start on started prod-mode and started avahi-daemon
script
statically_configure_network
send_network_config
end script
Since we stop prod-mode if the machine is in 'app mode', prod-mode-avahi
only gets started after we've made sure network-manager isn't going
to start.
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