Init

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This page lists available Init systems as alternative to systemd

Init is the first process started during system boot. It is a a daemon process that continues running until the system is shut down. Init is the direct or indirect ancestor of all other processes, and automatically adopts all orphaned processes. It is started by the kernel using a hard-coded filename; if the kernel is unable to start it, panic will result. Init is typically assigned process identifier 1.

The init scripts (or rc) are launched by the init process to guarantee basic functionality on system start and shutdown. This includes (un)mounting of file systems and launching of daemons. A service manager takes this one step further by providing active control over launched processes, or process supervision. An example is to monitor for crashes and restart processes accordingly.

These components combine to the init system. Some inits include the service manager in the init process, or have init scripts in close relation to them. These inits are below referred to as integrated, though entries in different categories may explicitely depend on each other.

A nice (but still incomplete) overview of init systems can be found in this blog entry.

Contents

Alternatives to systemd

Init (integrated)

System Description Last release
dinit init system with process supervision, service dependencies and socket activation written in C++. 2017-03-30
procd OpenWrt init and process management daemon with ubus integration. 2016-06-20
Epoch Single-threaded init system designed for minimal footprint, compatibility and unified configuration. 2015-06-23
finit Fast and extensible init, originally based on EeePC fastinit. 2015-10-16
initng Dependency-based init system with parallelization and asynchronous start. 2007-11-11
eINIT Can supervise processes and start them asynchronously, possibly without shell scripts. 2007-12-18
nosh A suite of system-level utilities for initializing and running a BSD or Linux system, for managing daemons, for managing terminals, and for managing logging. 2017-07-05
runit UNIX init scheme with service supervision, a replacement for SysVinit, and other init schemes. 2014-08-10
Upstart Event-based init system which handles starting, stopping and supervising of tasks and services. This project is dead. 2014-09-04
uselessd A fork of systemd v208. This project is dead. 2014-11-16
System XVI Modular, self-healing, and interface-oriented service manager and init system.This project is dead 2015-11-07
minit A very small init with process supervision, service dependency ordering and parallel service activation. 2005 ?
s6-rc A service manager for s6-based systems, i.e. a suite of programs that can start and stop services, both long-running daemons and one-time nitialization scripts, in the proper order according to a dependency tree. 2017-07-04
anopa An init system/service manager built around s6 supervision suite. 2017-06-20
GNU PIES Program Invocation and Execution Supervisor. Inittab-compatible with a native rc format as well. 2016-10-01

Inits

System Description Last release
busybox init BusyBox init. 2017-06-03
ninit Fork from minit. See ninit Instructions. 2010-01-16
myinit Simple init with parallel execution and dependencies via reference counting (`start' and `stop' commands). 2011-07-11
sinit Simple init initially based on Rich Felker’s minimal init. 2015-06-16
SysVinit Traditional System V init. 2010-04-14
uinit Smallest init possible. 2015-09-25
simpleinit-msb A fork of simpleinit (shipped with util-linux until v2.20) by Matthias S. Benkmann currently used in Source Mage GNU/Linux. 2007-11-08

Service managers

Program Description Last release
restartd Debian restartd - A process-restarting daemon 2013-01-11
daemontools Collection of tools for managing UNIX services. 2001-07-12
daemontools encore enhanced version of daemontools github repository 2014-04-02
GNU Shepherd A service manager written in Guile scheme that is used as PID 1 by GuixSD Linux. 2016-12-04
Monit Monit is a process supervision tool for Unix and Linux. With monit, system status can be viewed directly from the command line, or via the native HTTP(S) web server. 2017-06-07
OpenRC Dependency-based parallel-process start-up rc system that works with the system-provided init, normally SysVinit. 2017-06-12
perp Persistent process (service) supervisor and managment framework for UNIX. 2013-01-11
s6 Small suite of programs for UNIX, designed to allow service supervision in the line of daemontools and runit. 2017-06-15
freedt A daemontools reimplementation. 2014-09-03
procer mongrel2's process supervisor procer 2014-03-18
god (2) Easy to configure and extend monitoring framework written in Ruby. 2014-03-06
watchman A not-so-simple service manager for Linux. 2016-03-31
Supervisor A process control system written in Python. 2016-02-06

Other

System Description Last release
startpar May be used by the SysV RC boot system executor to allow parallel process system start-up. 2014-02-09
insserv May be used with SysV-based init systems to allow dependency driven system start-up based on dependencies specified by LSB headers in the init.d scripts. 2012-11-14

This page is based on Init article at ArchLinux Wiki Content is available under GNU Free Documentation License 1.3 or later


SEE ALSO: Gentoo wiki page: Comparison of init systems presents an even more extensive / thorough "Detailed Feature Comparison Table"

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