|Original author(s)||Lennart Poettering, Kay Sievers|
|Developer(s)||Lennart Poettering, Kay Sievers and others|
|Initial release||30 March 2010|
|Stable release||204 / 9 May 2013|
|License||GNU LGPL 2.1+ (free software)|
In computing, systemd is a replacement for the Linux init daemon (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 (possibly in parallel) at system startup, and to reduce shell overhead. The name comes from the Unix convention of suffixing the names of system daemons (background processes) with the letter "d".
Systemd initializes a platform, but also serves to consolidate event logging, and can replace syslog. Because it replaces two administrative systems, for system administrators this means the number of in-kernel mechanisms it attends offer a steep learning curve.
Systemd is maintained by Lennart Poettering and Kay Sievers, with many other contributors. It is published as free software under the terms of the GNU Lesser General Public License version 2.1 or later.
The systemd journal subsystem can forward event messages to syslog, so both can coexist. Systemd logging is stored in binary form, and it also has mechanisms to check the source is valid as an intended source.
Some features of systemd are:
- It provides aggressive parallelization capabilities.
- Offers on-demand starting of daemons.
- Service startup is determined by a configuration file in a declarative language, rather than a shell script for each service.
- Supports Sockets and D-Bus activation for starting services.
- Supports snapshotting and restoring of the system state
- Keeps track of processes using Linux cgroups, instead of PIDs. This means that daemons cannot "escape" systemd even by double-forking.
- Support for trigger system events at a calendar-based time rather than specifying it in relative or repeating time intervals.
Distributions in which systemd is enabled by default:
- Fedora since version 15
- Frugalware 1.5+
- Mageia 2+
- Mandriva 2011+
- mer since 2012
- openSUSE 12.1+
- Arch Linux since October 2012
- Chakra Linux since October 2012
- Parabola GNU/Linux since October 2012
- NixOS since January 2013
- Red Flag Linux 8+
Distributions where systemd is available, but not enabled by default:
- Debian GNU/Linux has packages for systemd. There is reluctance amongst developers to make systemd the default, since Debian's non-Linux ports (Debian GNU/Hurd and Debian GNU/kFreeBSD) will not work with systemd.
systemd has been proposed as an external dependency of GNOME 3.2 by systemd's author. The latest decision by the GNOME release team concludes that basic functionality should not rely upon systemd.
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- "systemd", Analysis Summary (Ohloh), retrieved 2011-06-16
- Lennart Poettering (2012-04-21), systemd Status Update, retrieved 2012-04-28
- Lennart Poettering, Kay Sievers, Thorsten Leemhuis (2012-05-08), Control Centre: The systemd Linux init system, The H, retrieved 2012-09-09
- Sievers, Kay, "Commit importing udev into systemd", systemd (freedesktop.org), retrieved 25 May 2012
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- Frederic Peters (2011-11-04), "20121104 meeting minutes", release-team mailing list (GNOME), retrieved 2013-01-14
- Official website
- systemd, 0pointer
- systemd project, Fedora
- The road forward for systemd, LWN
- cgit, freedesktop