systemd

Systemd is a background program (daemon ) for Linux systems, the init process as the first process ( process ID 1 ) to start, monitor and stop other processes used. systemd is by Lennart Poettering, Kay Sievers ( Red Hat Inc.) written in C and other contributors and will be released as free software under the GNU Lesser General Public License ( LGPL).

The name corresponds with the final " d" for the usual daemons naming scheme: systemd is the daemon that starts the system and supervised.

Technology

Systemd is backwards compatible with SysVinit scripts. However, features are used deliberately, which are only available on Linux operating systems, but not on other Unix-like operating systems. Therefore, it can only run on systems with Linux kernel.

It is to the mutual dependencies of processes are better suited, by more parallelization lead to a better utilization at system startup and thus less delay cause than the older, classic SysVinit or even the older Upstart.

Basic concept for this is largely to start all processes simultaneously. To not, as in other basically translated to parallel systems, some still work from the acquired in a model interdependencies between processes with serialization, the D-Bus connections and sockets for interprocess communication be provided before the start of the associated service and buffered by the kernel eventually accumulating messages to readiness of the service. The same is done for requests to file systems using autofs.

In addition, it can only occasionally needed services based on events only start when needed and so less services start at system startup. In order to perform such tasks, which were taken over by inetd in classic Unix systems.

Furthermore, all shell - boot scripts to be replaced by declarative configuration files, which define how the various services are started. These files are usually much easier to write than init scripts and avoid the significant overhead of shell scripts.

Unified hierarchy cgroups

The Linux kernel subsystem cgroups gets kernfs support and is rewritten so that in the future a "unified hierarchy " is mapped.

History

The ideas and concepts to systemd emerged from consideration of existing modernized init systems such as launchd OSX and SMF (Service Management Facility ) Solaris. It was first published on 10 April 2010. Distributions that use systemd as default init service, are Fedora since version 15, openSUSE since version 12.1, Mandriva 2011, Mageia since version 2 and Arch Linux since October 2012, as well as Tizen. Red Hat Enterprise Linux will use systemd Version 7, Debian version 8 or Jessie and Gentoo has to systemd optional.

Unless it largely replaces the now quite widespread Upstart, is at least a substantial influence of ideas on the development of Upstart expected.

Shortly after the decision of the Debian developers continue to rely on systemd, Canonical announced that the medium also change from Upstart to systemd.