[systemd-devel] Upstream service file for NTP daemon chrony

[David Strauss]

On Mon, Jul 2, 2012 at 4:20 PM, Paul Menzel
<paulepanter at users.sourceforge.net> wrote:
>> "Before=, After=
>> Configures ordering dependencies between units. If a unit foo.service
>> contains a setting Before=bar.service and both units are being
>> started, bar.service's start-up is delayed until foo.service is
>> started up.
>
> So »started up« does not mean is started up and finished with execution?

Kay's post is correct, but I think he was answering a different
question (when a service is considered "started up") versus your
question, which seems to be whether After= delays a service until the
unit(s) identified with After= are finished starting.

The key to your understanding here is the "If ... both units are being
started" part of the documentation. Without Requires=, Before= and
After= are like "yield" in road traffic control; *when* there is
concurrency, there is a defined ordering. However, just like in
traffic, putting up a "yield" sign does not, itself, create
concurrency.

-- 
David Strauss
   | david at davidstrauss.net