Upstart!

systemd is a replacement for the init daemon for Linux (either System V or BSD-style). It is intended to provide a better framework for expressing services' dependencies, allow more work to be done concurrently at system startup, and to reduce shell overhead.With systemd-nspawn and machinectl facilitate the creation and management of software containers.

The Sysvinit package contains programs for controlling the startup, running, and shutdown of the system.

OpenRC is a dependency-based init system that works with the system provided init program, normally /sbin/init. It is not a replacement for /sbin/init. OpenRC is 100% compatible with Gentoo init scripts, which means you can probably find one for the daemons you want to start in the Gentoo Portage Tree. OpenRC, however, is not exclusively used by Gentoo Linux and can be used on different Linux and BSD systems.

runit is a cross-platform Unix init scheme with service supervision, a replacement for sysvinit, and other init schemes. It runs on GNU/Linux, *BSD, MacOSX, Solaris, and can easily be adapted to other Unix operating systems.

The nosh package is a suite of system-level utilities for initializing and running a BSD or Linux system, and for managing daemons.

procd is a process and system init service for OpenWRT. It's less resource intensive as it's intended for embedded devices, works with busybox and uClib, hotplug2, libubox and ubus. It watches configuration files to start or restart services and init scripts

uselessd (the useless daemon, or the daemon that uses less... depending on your viewpoint) is a project to reduce systemd to a base initd and process supervisor, while minimizing intrusiveness and isolationism. Basically, it’s systemd with the superfluous stuff cut out, a (relatively) coherent idea of what it wants to be, support for non-glibc/non-Linux platforms, an approach that aims to minimize complicated design and various cleanups.

Faster is a very little init script aimed at Linux power-users and geek stuff oriented people. It is not industrial strength and does not comply with any other buzzwords. What it really does well is providing much better daemon handling (by means of a daemon manager e.g., daemontools) whilst offering the fastest boot times you can achieve in your machine (desktop or server).

Chaperone is a lean init-style startup manager for Docker-like containers. It runs as a single lightweight full-featured process which runs at the root of a docker container tree and provides all of the following functionality, plus much more: