Version 7 Unix: /etc listing, showing init and rc
Version 7 Unix: contents of an /etc/rc Bourne shell script
sysv-rc-conf, a TUI utility that selects which SysV-style init scripts will be run in each runlevel

First process started during booting of the computer system.

- Init

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Gentoo Linux

Linux distribution built using the Portage package management system.

Installing software. For example here we see that Darktable will build with Flickr and geolocation support.

It allows very fine control of which services are installed and running, including the option to choose between systemd or OpenRC as the default init system.


Software suite that provides an array of system components for Linux operating systems.

systemd startup on Fedora 17
systemd startup on Fedora 17
The architecture of systemd as it is used by Tizen. Several systemd targets, including,,  , and   are from Tizen and are not components of systemd.
Unified-hierarchy cgroups will be accessible exclusively by systemd through
A screenshot of systemd-boot
A screenshot of timedatectl
systemd-manager, a tool to configure systemd

Its main aim is to unify service configuration and behavior across Linux distributions; Its primary component is a "system and service manager"—an init system used to bootstrap user space and manage user processes.

Daemon (computing)

Computer program that runs as a background process, rather than being under the direct control of an interactive user.

Components of some Linux desktop environments that are daemons include D-Bus, NetworkManager (here called unetwork), PulseAudio (usound), and Avahi.

In a Unix environment, the parent process of a daemon is often, but not always, the init process.

Process identifier

Number used by most operating system kernels—such as those of Unix, macOS and Windows—to uniquely identify an active process.

Computer simulation, one of the main cross-computing methodologies.

Process ID 1 is usually the init process primarily responsible for starting and shutting down the system.

Kernel panic

Safety measure taken by an operating system's kernel upon detecting an internal fatal error in which either it is unable to safely recover or continuing to run the system would have a higher risk of major data loss.

A kernel panic message from a Linux system
Kernel panic in Ubuntu 13.04 (Linux 3.8) in Oracle VM VirtualBox
Kernel panic as seen on an iKVM console
Mac OS X 10.0–10.1 kernel panic
Mac OS X 10.2 kernel panic
Mac OS X 10.3–10.5 kernel panic
Mac OS X 10.6 and 10.7 kernel panic
Message shown after the computer restarts because of a kernel panic in OS X 10.8 and later versions

For example, many Unix operating systems panic if the init process, which runs in user space, terminates.

Orphan process

Computer process whose parent process has finished or terminated, though it remains running itself.


In a Unix-like operating system any orphaned process will be immediately adopted by the special init system process: the kernel sets the parent to init.


Software suite that provides several Unix utilities in a single executable file.

As it is a complete bootstrap system, it will further replace the init daemon and udev (or the latter-day systemd) using itself to be called as init on startup and mdev at hotplug time.


Version 7 Unix: /etc listing, showing init and rc

launchd is an init and operating system service management daemon created by Apple Inc. as part of macOS to replace its BSD-style init and SystemStarter.



OpenRC is a dependency-based init system for Unix-like computer operating systems.


Init and service management scheme for Unix-like operating systems that initializes, supervises, and ends processes throughout the operating system.

Runit booting Void Linux

When running as an init daemon, Runit is the direct or indirect ancestor of all other processes.