Overview
Definition of systemd
According to Lennart Poettering, the developper of systemd:
"systemd is a system and session manager for Linux, compatible with SysV and LSB init scripts. systemd provides aggressive parallelization capabilities, uses socket and D-Bus activation for starting devices."
In Simpler Terms:
systemd is a more efficient method of controlling processes. It has the flexibility to start services in parallel, and have them communicate with each other, even if they are restarted (respawned). This is particularly useful for system administrators to temporarily service or update services without affecting the other dependent services.
The Old Way: init
Upon computer boot-up, and after the Kernel process is started, it traditionally launched the initprocess (usually Process ID #: 1). This important process manages (launches) other common services. In many ways, the init process is the "ancestor process" and any process that is currently running on the Unix/Linux system is either directly or indirectly related to the init process.
Traditionally, the init program would run default processes that were defined in "shell scripts" contained in appropriate run-level directory.
The Newer Way: systemd
systemd: Usage
General Concept
systdctrl
Additional Resources
- YouTube Video (beyond init: systemd): (beyond init: systemd)