|Original author(s)||Lennart Poettering, Kay Sievers|
|Developer(s)||Lennart Poettering, Kay Sievers and others|
|Initial release||30 March 2010|
|Stable release||208 / 1 October 2013|
|License||first GPLv2+, currently GNU LGPL 2.1+ |
systemd is a system management daemon designed exclusively for the Linux kernel API. In the Linux startup process, it is the first process to execute in user land; therefore, it is also the parent process of all child processes in user land.
systemd was developed for Linux to replace the init system inherited from UNIX System V and Berkeley Software Distribution (BSD) operating systems. Like init, systemd is a daemon that manages other daemons. All daemons, including systemd, are background processes. systemd is the first daemon to start (during booting) and the last daemon to terminate (during shutdown).
Lennart Poettering and Kay Sievers, the software engineers who initially developed systemd, sought to surpass the efficiency of the init daemon in several ways. They wanted to improve the software framework for expressing dependencies; to allow more processing to be done concurrently or in parallel during system booting; and to reduce the computational overhead of the shell.
systemd's initialization instructions for each daemon are recorded in a declarative configuration file rather than a shell script. For inter-process communication, systemd makes Unix domain sockets and D-Bus available to the running daemons. Because systemd tracks processes using Linux cgroups instead of process identifiers (PIDs), daemons cannot "escape" systemd; not even by double-forking. Systemd is also capable of aggressive parallelization.
Among systemd's auxiliary features are a cron-like job scheduler called systemd Calendar Timers, and an event logging subsystem called journal. The system administrator may choose whether to log system events with systemd or syslog. systemd's logfile is a binary file. The state of systemd itself can be preserved in a snapshot for future recall.
Linux startup process
Userspace utility programs
|Linux distribution||Date added to software repository1||Enabled by default?|
|Arch Linux||October 2012||Yes|
|Debian GNU/Linux2||April 2012||No|
|Fedora||May 2011 (v15)||Yes|
|Frugalware Linux||August 2011 (v1.5)||Yes|
|Mageia||May 2012 (v2.0)||Yes|
|openSUSE||March 2011 (v11.4)||Yes, since 2012-09-15 (v12.2)|
|Red Hat Enterprise Linux||Pending||No|
|Sabayon Linux||August 2013 (v13.08)||Yes|
|Ubuntu3||April 2013 (v13.04)||No|
- 1.^ Dates are for the general availability release.
- 2.^ Debian developers are reluctant to make systemd the default, since Debian's non-Linux ports (Debian GNU/Hurd and Debian GNU/kFreeBSD) will not work with systemd.
- 3.^ Canonical Ltd. provides experimental instructions for installing systemd as an unsupported, alternative init system.
In the interest of enhancing the interoperability between systemd and GNOME, systemd coauthor Lennart Poettering asked the GNOME Project to consider making systemd an [clarify] of GNOME 3.2. In November 2012, the GNOME Project concluded that basic GNOME functionality should not rely on systemd.
- "README", systemd (freedesktop.org), retrieved 2012-09-09
- "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
- ConsoleKit office website
- "systemd.index", freedesktop.org
- "F15 one page release notes", fedoraproject.org, 2001-05-24
- systemd is now the default on new installations, Arch Linux News, 2012-10-13, retrieved 2012-10-29
- systemd, Debian Wiki, retrieved 2011-07-21
- D. J. Walker-Morgan (2011-05-24), Fedora 15's Lovelock released, The H, retrieved 2012-08-22
- Phayz (2012-01-17), Review of 2011, Frugalware Project, retrieved 2012-08-22
- "Comment #210", systemd – bug #318365 (Gentoo's Bugzilla), retrieved 2011-07-05
- systemd, Gentoo's Documentation, retrieved 2011-07-05
- systemd, Gentoo wiki, retrieved 2012-08-26
- Fabian Scherschel (2012-05-23), Mageia 2 arrives with GNOME 3 and systemd, The H, retrieved 2012-08-22
- Directory view of the 11.4 i586 installation showing presence of the systemd v18 installables, 2011-02-23, retrieved 2013-09-24
- Tim Burke (2012-06-27), "Red Hat Enterprise Linux Roadmap Highlights" (PDF), presentation
- Jake Edge (2011-07-27), Debian debates systemd, LWN.net
- Michael Stapelberg (2013-05-27), Results of the Debian systemd survey
- systemd - An alternative boot manager, Ubuntu Wiki, retrieved 2013-06-24
- Lennart Poettering (2011-05-18), "systemd as an external dependency", desktop-devel mailing list (GNOME), retrieved 2011-05-26
- 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
- Interface Portability And Stability Chart, freedesktop