[Fedora-packaging] Revised systemd Guidelines

[Bill Nottingham]

Tom Callaway (tcallawa at redhat.com) said: 
> Many thanks to Lennart for writing the initial text for the systemd
> guidelines. I've taken his draft and reworked it a bit so that it
> matches the flow and style of the existing guidelines:
> 
> https://fedoraproject.org/wiki/TomCallaway/Systemd_Revised_Draft
> 
> Keep in mind that %{_unitdir} is undefined at the moment, we would add
> it to redhat-rpm-config before this draft becomes a guideline.
> 
> Please look it over and give any feedback.

1) Typo - 'For "one-short" scripts "oneshot" is ideal'

2) On one hand, perhaps what BusName is should be elaborated on, but on the
other hand, if you need to ask, you don't need it.

3) ExecStart (and similar keys) take full pathnames as the binary/script to
execute (instead of searching $PATH); this should be mentioned.

4) Suggest changing:

The recommended parameters for WantedBy are either multi-user.target (for
most system services) or graphical.target (for services related to the UI). 

to:

The recommended parameters for WantedBy are either multi-user.target (for
most system services, analagous to runlevel 3 in System V) or graphical.target
(for services related to the UI, analagous to runlevel 5). Note that
graphical.target automatically includes services from multi-user.target.

5) In 'Support for /etc/sysconfig files', perhaps should note that variable
substitution is not supported for the initial argument for Exec<foo> lines.

Bill