A OpenRC script should be fairly simple, as should a script for the modern van Smoorenburg rc in Debian. They are both largely just scripts of variable=value assignments.

* https://manpages.debian.org/unstable/sysvinit-utils/init-d-s...

* https://sources.debian.org/src/opendnssec/1:2.0.4-3/debian/o...

> nearly any Linux distro

The service file for systemd looks pretty simple, so that's probably not a problem to port to some other init system.

But what's in the "nearly" above, do you have some other concrete requirements for the distro? Any technical reason very small busybox-based systems would be unable to support your agent?

Deviceplane sounds like a very good idea for a niche that really needs something like it!

    % printf '1,$s/^KillMode/#&/\nw\n' | ex ./deviceplane.service
    %
    % /package/admin/nosh/command/system-control convert-systemd-units --no-systemd-quirks ./deviceplane.service 
    convert-systemd-units: WARNING: ./deviceplane.service: Unused setting: [service] delegate = yes
    convert-systemd-units: WARNING: ./deviceplane.service: Unused setting: [service] tasksmax = infinity
    convert-systemd-units: WARNING: ./deviceplane.service: Unused setting: [service] timeoutstartsec = 0
    convert-systemd-units: WARNING: ./deviceplane.service: Unused setting: [unit] documentation = https://deviceplane.com/docs/
    % 
    % /package/admin/nosh/command/system-control print-service-scripts ./deviceplane                            
    start:#!/bin/nosh
    start:#Start file generated from ./deviceplane.service
    start:true
    stop:#!/bin/nosh
    stop:#Stop file generated from ./deviceplane.service
    stop:true
    run:#!/bin/nosh
    run:#Run file generated from ./deviceplane.service
    run:#Deviceplane agent
    run:hardlimit -o infinity -c infinity -p infinity
    run:softlimit -o hard -c hard -p hard
    run:/usr/local/bin/deviceplane-agent --controller=https://example.com:443/api --project=example --registration-token=example
    restart:#!/bin/sh
    restart:#Restart file generated from ./deviceplane.service
    restart:sleep 5s
    restart:exec true # ignore script arguments
    %

Delegate=yes is ignored because I did not run this on a Linux operating system.

* http://jdebp.uk./Softwares/nosh/worked-example.html

* http://jdebp.uk./FGA/run-scripts-and-service-units-side-by-s...