[systemd-devel] Q: daemon-reload: when and how?

[Jérémy ROSEN]

Le jeu. 18 juin 2020 à 08:53, Ulrich Windl <
Ulrich.Windl at rz.uni-regensburg.de> a écrit :

> Hi!
>
> I have a question: systemd monitors almost everything it seems to me. So I
> wonder:
> Under what conditions is it necessary to issue a daemon-reload, and why
> can't systemd find out itself that a daemon-reload is required?
>

There are some cases where systemd can detect the proper time for a
daemon-reload, and does it implicitely
systemd also check mtime of configuration files so it can see when a
daemon-reload should be done.

However it is not because a file has been modified that systemd should
decide to reload by itself.
multiple unit files need to work together to make a working environment,
and systemd can't know when all changes are consistent and
it is safe to reload. So systemd will want an explicit order from the user.

So if I think a "manual" daemon-reload is required, is it safe to do it
> from within a unit?
>

Usually, calling daemon-reload from a unit is a sign of bad design or
misunderstanding of some tool. What exactly is the problem you are
trying to solve ?


> I have a "generator-like" type of unit that changes the configuration of
> other units. However, as it seems, systemd ignores such changes until I use
> daemon-reload...
>

Yes. you need an explicit daemon-reload here.
why can't it be a real generator ?

could you use systemd-run or the equivalent dbus API to do what you are
trying to do ?


>
> (systemd-228-157.9.1.x86_64 of SLES12)
>

Ouch that's old...
Hopefully there are not too many missing features I'm used to have in
there...

Regards
Jeremy

>
> Regards,
> Ulrich
>
>
>
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