init/README.md

About

This directory contains the source code for a tiny service supervision framework devised for the Pygos system, consisting of an init daemon and accompanying command line utilities.

The programs of this package are developed first and foremost for GNU/Linux systems, so there are some GNU and some Linux extensions used and some of the code may unintentionally rely on Linux specific behavior.

Nevertheless, if sufficient interest exists, it should be possible to make it run on BSDs or other Unix-like systems, but some effort may be required.

The init system tries to mimic the concept of unit files from systemd as those were considered to be a good design choice.

In a typical setup, the parameterizeable service description files are stored in /usr/share/init by default. Services are enabled by creating a symlink in /etc/init.d. This can be done more conveniently using the service command line tool.

A default setup for the Pygos system, including helper scripts for setting up mount points and for network configuration, is provided in a seperate package. This package only contains the bare init framework without any default configuration.

Right now, the system is in a "basically works" proof of concept stage and needs some more work to become usable.

There are plans for maybe eventually adding more fancy features like support for Linux name spaces, seccomp filters and cgroups, but right now, features are added only when the need arises.

See docs/init.md for more information on the design, implementation and caveats of the init daemon.

See docs/cmdline.md for an explanation on the available command line tools.

See docs/services.md for more information on service description files.

Why

There are already a bunch of similar projects out there that have been considered for use in the Pygos system. The reason for starting a new one was mainly dissatisfaction with the existing ones. Other Projects that have been considered include:

• systemd

  Contains a lot of good ideas, but it is HUGE. It has tons of dependencies. It implements tons of things that it simply shouldn't. It has a horrid, "modern", python based, hipster build system. It's simply too damn large and complex.

• SystemV init

  A bad combination of unnecessary complexity where it isn't needed and a complete lack of abstraction where it would be needed. Shell script copy and paste madness. There are reasons people started developing alternatives (other than "hurr-durr-parallel-boots").

• upstart

  Seems nice overall, but needlessly big and complex for the intended use case in Pygos. Would have needlessly added D-Bus to the system.

• OpenRC

  Was already integrated into Pygos. Things turned out to be broken. Upstream developers did not accept fixes (after ignoring them for weeks and preferring typo fixes instead). Complaints from other people who tried to contribute fixes were observed on GitHub. Complaints from package maintainers about deteriorating code quality were observed on the official IRC channel. Documentation is non-existent.

• daemon tools and similar (runnit, s6, minit, ...)

  The sixties are over. And even code from that era is more readable. The source code for those projects should better be tossed out the window and rewritten from scratch. If you are a first semester CS student and you hand something like this in as a homework, the best you might get is a well deserved slap on the back of your head.

• busybox init

  Nice and simple. Probably the best fit if the rest of your user space is busybox as well.