Bug#857452: Steps towards a patch to document disabling a daemon upon installation

[Ian Jackson]

Felipe Sateler writes ("Re: Steps towards a patch to document disabling a daemon upon installation"):
>  I suggest instead mentioning the real reasons its bad:

Thanks for providing real reasons.

> > I can't speak to the behaviour of systemd, but I think the
> >   update-rc.d add-disabled
> > operation I propose would, for sysvinit systems, do the follow:
> > 1. Are there already rc*.d links for DAEMON ?  If so, do nothing.
> > 2. If not, create them in the way that  defaults && disable
> >   would have done.
> 
> Currently, update-rc.d leaves all the hard work to insserv under sysvinit. 

Yes.

> The behaviour would have to change to check if any links exist and skip 
> invoking insserv in that case. I am not sure if that would mean a behavior 
> change though. Maybe this early in the release cycle is a good time to 
> try these kinds of changes.

I think that the right thing for `update-rc.d defaults-disabled' is to
do this:
 1. check to see if any links already exist
      if they do, do nothing else
 2. parse the init script to find the default-start and default-stop
      runlevels
 3. run
      insserv add DAEMON,stop=RLVL,RLVL,....
    (for the complete set of start and stop runlevels)

After this, the script is run for `stop' in each of those runlevels,
roughly like update-rc.d disable would do (the sequence numbers will
briefly not be identical, until insserv is re-run).

Better would be to add a feature to insserv to do (2) and (3) in one
go, but if we were to do that it should probably gain the
functionality in update-rc.d's sysv_toggle too.

Ian.