On Thu, Sep 24, 2015 at 02:31:40PM +0100, Rainer Weikusat wrote:
> Laurent Bercot <ska-devel@???> writes:
>
> [...]
>
> > It manages dependencies between services, no matter whether they are
> > oneshots or longruns; it can intertwine oneshot starts and longrun
> > starts, or oneshot stops and longrun stops. When changing the machine
> > state, it always ensures the consistency of the dependency graph.
>
> I'd still very much like to see an actual example which really needs
> these depenencies which isn't either bogus or a workaround for a bug in
> the software being managed.

Well, let's see:

* cups should be started after avahi if you want zeroconf network printers
  accessible by name (note: X-Start-After or openrc "after" is suitable;
  declaring a dependency is not ideal.)
* routers:
  - you don't want networking stuff up before your firewall
  - hostapd needs to start after the interface is configured
  - the dhcp daemon needs to start after the interface is configured
    (after hostapd is best, but after networking may be adequate)
  - the ssh server needs to start after the interface is configured, if
    you want to bind to a specific interface
     Alpine example:
     I want SSH on wlan0 (192.168.64.1) only.
     I need to specify "-p 192.168.64.1:22" in /etc/conf.d/dropbear;
     wlan0 must already be 192.168.64.1 for this to work.
* to properly prioritize user-specified drivers, "modules" should run
  before driver autoload.
* an entropy-gathering daemon should start after the device used have
  been initialized, and before the services that need random bytes start.
* anything that uses the syslog should start after the syslog.
  While a failure to connect to /dev/log is recoverable, proper ordering
  will greatly simplify debugging.

Now, regarding "as long as it's working in five minutes, the users will
forget about it."
I can only speak for myself and my family, but five minutes is far too
long for me:
I can boot to a desktop with a usable internet connection in ~20 seconds
(the first 12 or so being BIOS+GRUB), and I'm annoyed if I can't start
mutt immediately without any problems.
For my parents, if the computer can't connect in the first two minutes,
they might never find out that it actually does connect.
And on a router, a minute is too long.

HTH,
Isaac Dunham