This feature was mainly for laptops but users:
- often don't care having the daemon running all the time;
- may not want to use the 'main-interface' option because the interface that
  provides internet access is not always the same, e.g. wifi & wired;
- may want other kinds of conditions,
  e.g. only specific wifi access points.

So in practice, main-interface is currently only use to set up a DHCP server or
provide IPv6 autoconfiguration. For such case, it is preferred to start/stop
re6stnet like a normal service.

The presence of /lib/systemd/system/*.service files masked the fact that the
/etc/init.d/ scripts were enabled, and services were not enabled under
systemd (no symlink in /etc/systemd/system/multi-user.target.wants/).

Reverting commit 4c2284e2 partially is the
easiest way to handle the case of OS upgrade (with a switch to systemd).

https://reproducible-builds.org/

debian/rules is split into reusable parts for SlapOS-based packages.