[systemd-devel] Why does sysv generator translate Required-Start keyword into an After= ordering dep only ?

[Lennart Poettering]

On Wed, 24.02.16 17:40, Francis Moreau (francis.moro at gmail.com) wrote:

> Hello,
> 
> It seems that the unit generator for sysv init scripts translate
> "Required-Start: X" into "After=X" native ordering deps only.
> 
> I would also have expected it to add the following dependency "Requires=X" too.
> 
> What am I missing ?

Well, on SysV the requirement in the "Required-Start:" concept is
actually a request to the tool that enables/disables a service
(i.e. the chkconfig or update-rcd tool, depending on the distro). It
means that it shall enable another service "b" if "a" is to be
enabled.

Requires= in systemd otoh is something that applies to the actual
activation time of a service. The counterpart of "Required-Start:" in
systemd concepts would actually be the Also= line in [Install], if you
follow what I mean.

systemd leaves enabling/disabling of sysv services to
chkconfig/update-rcd hence it will not act on that line regarding
requirement. It will however act on the ordering, since that's
inherently something systemd itself cares about.

Hope that makes sense?

Lennart

-- 
Lennart Poettering, Red Hat