Insert a script into boot order at a specific place

[Christoph Pleger]

Hello,

for many years and up to Debian 7, I have been using a script to configure
some things while booting the system, i.e. I had a link in /etc/rcS.d/
which was executed directly after mounting local and remote filesystems
and before doing anything else (in my Debian 7, this is after
mountnfs-bootclean.sh and before kbd). This order is necessary, otherwise
the script is not able to configure the system correcly.

After switching from SYS V boot to systemd boot, how can I achieve a
similar  order, so that only very basic tasks (bringing network up,
mounting filesystems) are performed before my script runs and all the
remaining tasks are performed after my script was finished? Without me
having to know too much about which tasks have to be performed before and
which ones afterwards, so that I can define only a few dependencies,
similar to what I used in my LSB init script, which only defines:

Required-Start:    nfs-common $remote_fs

and


X-Start-Before:    console-screen kbd

?

Regards
  Christoph

PS: I hope that this mailing list is the right place for my question.