[systemd-devel] Boot ordering

[Michael Biebl]

2015-03-19 15:46 GMT+01:00 Uoti Urpala <uoti.urpala at pp1.inet.fi>:
> On Thu, 2015-03-19 at 14:27 +0100, Christoph Pleger wrote:
>> >> Then, I still do not understand why my definition of a new target did
>> >> not
>> >> work. What is the difference between multi-user.target waiting for
>> >> basic.target on the one hand and new.target waiting for basic.target and
>> >> multi-user.target waiting for new.target on the other hand, aside from
>> >> that one intermediate step?
>
> You're misunderstanding some of the basics of unit ordering. That
> multi-user.target has an "After:" relationship to basic.target only
> means that multi-user.target ITSELF will not be considered to have been
> successfully started before basic.target has. This does not say anything
> about the ordering of any other units, such as the services that are
> started because multi-user.target wants them - the reason why some
> service is started at boot (such as which target pulls it in via a
> "Wants/Requires" relationship) says NOTHING about where the service can
> be ordered. If multi-user.target wants some service, it's up to the
> individual dependencies of that service to determine when the service
> can be started.
>
> Typically most services started by multi-user.target run after
> basic.target, but that's only because they each have the default
> configuration "DefaultDependencies=yes", which implies "After:
> basic.target". If some service has "DefaultDependencies=no" and defines
> no other ordering requirements, it can even be the first service to run
> at boot even if it's only wanted by multi-user.target.
>
>
> Thus your "between basic.target and multi-user.target" is not a
> well-defined requirement. My best guess about what you might actually
> want to achieve (assuming you aren't so thoroughly confused that it
> makes no sense at all) is a service that runs before any service that
> has DefaultDependencies enabled, and which requires (most of)
> basic.target. I think this would be most practically implemented as a
> "DefaultDependencies=no" service, which is wanted by basic.target, and
> which has explicit dependencies on (most of) other services that are
> wanted by basic.target.
>

I already told Christoph that a week ago, since he was posting the
same question on debian-user.

The summary of my reply was "What you probably want, is hook into
basic.target or sysinit.target, use DefaultDependencies=no, and
specify the dependencies/orderings explicitly."

Apparently, this didn't stick.


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