OpenRC

It is a alternative init to systemd init thus it need to polyfills a lot of systemd functionality/api on top of it in onder to run software that needed those functionality/api.

OpenRC is a dependency-based init system that maintains compatibility with the system provided init program, normally located in /sbin/init. It does not function as a replacement for the /sbin/init file.

It is the default system in postmarketOS, and documentation can be found on the Gentoo wiki. For information related to handwriting an init script, check out Gentoos guide to initscripts

Init scripts are stored in /etc/init.d/ but it is generally recommended you do not write them by hand. User-configurable options are stored in /etc/conf.d.