FreeBSD Foundationals: rc.d - The Service Framework That Fits in Your Head

The previous article followed FreeBSD from power-on through the loader and the kernel, and stopped at a box in the diagram that just said rc(8) scripts. That box is where your machine actually becomes useful: networking comes up, filesystems get mounted, jails start, and every daemon you care about gets launched. This article opens that box. This is the fourth article in the FreeBSD Foundationals series. The first covered Jails, the second covered ZFS, and the third covered the boot process. The boot article promised that packages and ports would come next. I changed the order, because rc.d is the direct continuation of the boot story, and because nearly every FreeBSD article on this blog ends with “and here’s the rc.d script” without ever explaining how rc.d works. Packages are next, I promise. rc.d is also one of the best arguments for FreeBSD’s design approach. The whole service framework is a few thousand lines of POSIX shell that you can read in an afternoon. When something goes…