[systemd-devel] systemd unit timer

[Dave Howorth]

On Mon, 10 Aug 2020 20:21:51 +0200
Lennart Poettering <lennart at poettering.net> wrote:
> On So, 09.08.20 15:56, Dave Howorth (systemd at howorth.org.uk) wrote:
> 
> > Is there anywhere that explains the rationale for systemd timers?  
> 
> Probably somewhere in the git logs.

Thanks, Lennart. I'll happily poke through the logs to try to find it,
but I've no idea where to start. A starting point URL for the logs would
be helpful to me.
 
> > What's their USP? Why was it necessary to invent the facility?  
> 
> It kinda makes sense to invoke cronjobs the same way as any other
> piece of system code in userspace: as a service, so that you can take
> benefit of deps management, priv handling, logging, sandboxing and so
> on, so that you can run stuff either manually or by timers or by any
> other kind of activation, and so on, and it always ends up in exactly
> one instance. And there's tons of other stuff too.
> 
> i.e. it unifies how system programs are invoked, and that's a good
> thing. it turns time-based activation into "just another type of
> activation".

Most of that has gone over my head so some examples would probably help
me to understand. Perhaps they're in the git logs?

But I'm not normally running system code in cronjobs. I usually run
either scripts I have written myself, or backup commands and the like.

If I wanted to run a service, presumably I could just write a 'manual'
invocation as a cron or at job? I'm not seeing the big imperative to
create another new bunch of code to learn and maintain. I expect I'm
blind.