Comparison of init systems
From Gentoo Wiki
This article compares and contrasts init systems for Unix(like) OSs, irrespective of whether they are available for Gentoo or not. See the init system (meta) article for init system software available in Gentoo.
Init system comparison table
| Feature | Init system | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| sysvinit | OpenRC | systemd | SMF | launchd | Epoch | finit | runit | s6 + s6-rc | 66 + 66-rc | BSD rc.d | dinit | ||
| Supported in Gentoo | partially (used by OpenRC) | Yes (default init) | Yes | No | No | Yes | No | Yes | No | No | No | No | |
| Package / Bug# | sys-apps/sysvinit | sys-apps/openrc | sys-apps/systemd | - | - | sys-apps/epoch | - | sys-process/runit | sys-apps/s6 + sys-apps/s6-rc | - | - | - | |
| Supported platforms | Linux / BSD | Linux + BSD | Linux | Solaris | Darwin | Linux | Linux | Linux / BSD / Darwin | Linux / BSD / Darwin | Linux | BSD | Linux / BSD / Darwin | |
| Main coding language | C | POSIX shell (+ C) | C | C | C | C | C | C | C | C | POSIX shell (+ C) | C++ | |
| Main dependencies | - | init (sysv or BSD) | D-Bus | init(sysv?) | - | libc, /bin/sh | ? | - | skalibs, execline | s6, s6-rc | rcorder | - | |
| Init script/service format | single config file | shell scripts | config files (ini) | XML (+ shell scripts) | plist | multiple or single .conf | multiple or single .conf | shell scripts | execline or shell scripts | config files + execline fragments | shell scripts | config files | |
| Per-service configuration | No | Yes (conf.d) | Yes | Yes (service instances) | ? | Yes (v1.1+) | ? | No | No | Yes | No | Yes | |
| Running as a daemon | Yes (PID 1) | Yes (PID 1) | Yes (PID 1) | Yes (invoked) | Yes (PID 1) | Yes (PID 1) | Yes (PID 1) | Yes (PID 1) | Yes (sys-apps/s6-linux-init) | Yes (PID 1) | Yes (PID 1) | Yes (PID 1) | |
| Cross-service dependencies/events | No | Yes | Yes | Yes | No | Yes (basic support, v1.3+) | ? | Yes | Yes | Yes | Yes | Yes | |
| Parallel service startup | Yes | Yes (optional) | Yes | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | |
| Keeping daemons alive | Yes | Yes (optional v0.21+ via supervise-daemon) | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | Yes | |
| Preferred service file supplier | n/a | Gentoo | upstream | Solaris | MacOS | n/a | n/a | Void Linux | Artix Linux | Obarun | NetBSD, FreeBSD, OpenBSD | Artix Linux, Chimera Linux | |
| License | GPL v2+ | 2-cl. BSD | LGPL v2.1+ | ? | Apache License 2.0 | Unlicense | MIT | BSD | ISC | ISC | BSD | Apache License 2.0 | |
OpenRC compared to systemd
| Feature | OpenRC | systemd |
|---|---|---|
| Filesystem mounting | One script per group (root, local, network, swap, etc.). | Two units per mount point (fsck + mount), runtime-generated with dependencies. |
| getty (terminal prompts) | Started through /etc/inittab or via agetty script | One unit per console, instantiated from template on-demand. |
| Networking setup | Several options like dhcpcd[1][2], netifrc, iwd, or NetworkManager.[3] | Integrated (systemd-networkd), or using any of the external options mentioned prior. |
| X11 Display Manager setup | Single service for all (required to auto-restart). | Separate Display Manager units. |
See also
- OpenRC — a dependency-based init system for Unix-like systems that maintains compatibility with the system-provided init system (see the openrc-init sub-article).
- Runit — lightweight process supervision suite, originally inspired by daemontools-inspired that offers fast and reliable service management.
- S6 and s6-rc-based init system — an init system built using components from the s6, s6-rc and s6-linux-init packages
- systemd — a modern SysV-style init and rc replacement for Linux systems.
- User:AdibSaad/66 — 66 + 66-rc guide. Warning: status of instructions unknown.
External resources
- s6 - Forum thread
- Forum thread
- openrc-init
- GNU shepherd - service manager for the GNU OS.
- Finit - Fast init for Linux systems.
- 66tools-overlay
- Dinit
- "Comparison of Dinit with other supervision / init systems" - by the developer of Dinit