Systemd

systemd is a software suite for system and service management on Linux built to unify service configuration and behavior across Linux distributions. Its main component is an init system used to bootstrap user space and manage user processes. It also provides various daemons and utilities, including device management, login management, network connection management, and event logging. The name systemd adheres to the Unix convention of naming daemons by appending the letter d, and also plays on the French phrase Système D (a person's ability to quickly adapt and improvise in the face of problems). In Linux distributions, systemd is used as a replacement for Sysvinit and other init systems. Since 2015, nearly all Linux distributions have adopted systemd. It has been praised by developers and users of distributions that adopted it for providing a stable, fast out-of-the-box solution for issues that had existed in the Linux space for years. At the time of its adoption, it was the only parallel boot and init system offering centralized management of processes, daemons, services, and mount points. Critics of systemd contend it suffers from feature creep and has damaged interoperability across Unix-like operating systems (as it does not run on non-Linux Unix derivatives like BSD or Solaris). In addition, they contend systemd's large feature set creates a larger attack surface.…

systemd is a software suite for system and service management on Linux built to unify service configuration and behavior across Linux distributions. Its main component is an init system used to bootstrap user space and manage user processes. It also provides various daemons and utilities, including device management, login management, network connection management, and event logging. The name systemd adheres to the Unix convention of naming daemons by appending the letter d, and also plays on the French phrase Système D (a person's ability to quickly adapt and improvise in the face of problems). In Linux distributions, systemd is used as a replacement for Sysvinit and other init systems. Since 2015, nearly all Linux distributions have adopted systemd. It has been praised by developers and users of distributions that adopted it for providing a stable, fast out-of-the-box solution for issues that had existed in the Linux space for years. At the time of its adoption, it was the only parallel boot and init system offering centralized management of processes, daemons, services, and mount points. Critics of systemd contend it suffers from feature creep and has damaged interoperability across Unix-like operating systems (as it does not run on non-Linux Unix derivatives like BSD or Solaris). In addition, they contend systemd's large feature set creates a larger attack surface. This has led to the development of several minor Linux distributions replacing systemd with other init systems like SysVinit or OpenRC. === Ancillary components=== Beside its primary purpose of providing a Linux init system, the systemd suite can provide additional functionality, including the following components: is a daemon responsible for event logging, with append-only binary files serving as its logfiles. The system administrator may choose whether to log system events with , or . is the standard library for utilizing udev, which allows third-party applications to query udev resources. manages the system locale and keyboard layout. is a daemon that manages user logins and seats in various ways. It is an integrated login manager that offers multiseat improvements and replaces ConsoleKit, which is no longer maintained. For X11 display managers the switch to requires a minimal amount of porting. It was integrated in systemd version 30. manages the system hostname. is a daemon that provides portable human-user accounts that are independent of current system configuration. moves various pieces of data such as UID/GID from various places across the filesystem into one file, . manages the user's home directory in various ways such as a plain directory, a btrfs subvolume, a Linux Unified Key Setup volume, an fscrypt directory, or mounted from an SMB server. is a daemon to handle the configuration of the network interfaces; in version 209, when it was first integrated, support was limited to statically assigned addresses and basic support for bridging configuration. In July 2014, systemd version 215 was released, adding new features such as a DHCP server for IPv4 hosts, and VXLAN support. networkctl may be used to review the state of the network links as seen by systemd-networkd. Configuration of new interfaces has to be added under the /lib/systemd/network/ as a new file ending with .network extension. : provides network name resolution to local applications is a boot manager, formerly known as gummiboot. Kay Sievers merged it into systemd with rev 220. is an error reporter used to generate Blue Screen of Death. may be used to run a command or OS in a namespace container. is a daemon that can be used to control time-related settings, such as the system time, system time zone, or selection between UTC and local time-zone system clock. It is accessible through D-Bus. It was integrated in systemd version 30. : is a client NTP daemon for synchronizing the system clock across the network. is a utility that takes care of creation and clean-up of temporary files and directories. It is normally run once at startup and then in specified intervals. udev is a device manager for the Linux kernel, which handles the directory and all user space actions when adding/removing devices, including firmware loading. In April 2012, the source tree for udev was merged into the systemd source tree. In order to match the version number of udev, systemd maintainers bumped the version number directly from 44 to 183. On 29 May 2014, support for firmware loading through udev was dropped from systemd, as it was decided that the kernel should be responsible for loading firmware.

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