Comment # 3 on bug 1187656 from Coly Li

(In reply to Coly Li from comment #2)
> (In reply to Coly Li from comment #1)
> > (In reply to Daniel Molkentin from comment #0)
> > > The /usr/lib/systemd/system/mdcheck_start.service file states the following:
> > > 
> > > [Service]
> > > Type=oneshot
> > > Environment="MDADM_CHECK_DURATION=6 hours"
> > > 
> > > "oneshot" implies that the service will remain in "activating" state for the
> > > entire duration (long, up to the stated 6 hours.
> > > 
> > > It would be better to use Type=simple, which does not keep the unit in
> > > "activating" mode. This is an important difference in semantics, because
> > > monitoring tools (e.g. prometheus) tend to alert if a unit is stuck in
> > > "activating" for more than (typically) 5 minutes (which usually makes
> > > sense, but not here).
> > > 
> > > The only side effect that I could find is that systemd will not wait for
> > > follow-up units to start, but since this is a timer-triggered unit,
> > > I would not expect anyone else to depend on this service.
> > > 
> > > Verified by adding an override file.
> > 
> > IMHO the above opinion makes sense. Let me try to post a change to upstream
> > and see whether mdadm maintainer likes it or not.
> 
> It seems type=simple has more restriction like the task process should not
> do fork. There is no assurance that mdcheck won't do fork during its run
> time. Hmm, how about using an explicit RemainAfterExit=no in your case,
> let's try and see whether it works for you.
> 

If no further response, I will close this report in next several weeks.

Coly Li