[systemd-devel] Service activation

[Mantas Mikulėnas]

On Sun, Feb 13, 2022 at 2:03 AM Wol <antlists at youngman.org.uk> wrote:

> More fun getting things to work ... :-)
>
> So I've got a service, scarletdme.service, which fires up my db backend
> for running interactively. However, I also need a socket service for
> remote connections.
>
> I've got the xinetd files, but if I'm running systemd, I want to use
> systemd :-)
>
> So I've written scarletdme.socket, and scarletdme at .service, but the more
> I read, the more I don't understand ...
>
> Do I enable scarletdme.socket the same as anything else eg "systemctl
> enable scarletdme.socket"? How does it know the difference between
> scarletdme.service and scarletdme at .service? I get the impression I need
> to put something in the .socket file to make it use scarletdme@ rather
> than scarletdme?
>

If it's a 'nowait' socket (which is "[Socket] Accept=yes" in systemd
terms), then it will use the templated @.service, starting a new instance
for each "accepted" socket (i.e. instance per connection). See
oidentd.socket for comparison.

Otherwise (by default) it uses the non-templated service and directly gives
it the "listening" socket, letting the service itself handle accept().


>
>
> And once I've got all that sorted, I'm betting I'm going to have grief
> getting it to work properly, so while it's not much to do with systemd,
> is there any way I can get systemd to log all traffic back and forth so
> I can debug it?
>

No, the traffic doesn't even go through systemd in the first place.

-- 
Mantas Mikulėnas
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