1. Introduction and features of Systemd
Systemd is the latest initialization system (init) in the Linux system. Its main design goal is to overcome the inherent shortcomings of sysvinit and improve the startup speed of the system. systemd and ubuntu's upstart are competitors and are expected to replace UpStart. In fact, it has been reported that Ubuntu will also adopt systemd as its standard system initialization system.
Many concepts of Systemd come from launchd on the Apple Mac OS operating system, but launchd is dedicated to the Apple system, so it has not received the widespread attention it deserves for a long time. Systemd borrows a lot of ideas from launchd, and its important features are as follows:
1. Compatible with SysVinit and LSB init scripts
Systemd is a "newcomer" and many applications on Linux haven't had time to make changes for it. Like UpStart, systemd introduces new configuration methods and some new requirements for application development. If systemd is to replace the currently running init system, it must be compatible with existing programs. It is difficult for any Linux distribution to modify all service codes in a short time to adopt systemd.
Systemd provides features compatible with Sysvinit and LSB initscripts. Existing services and processes in the system do not need to be modified. This reduces the cost of system migration to systemd, making it possible for systemd to replace existing init systems.
2. Faster startup speed
Systemd provides a more radical parallel startup capability than UpStart, using technologies such as socket / D-Bus activation to start services.
An obvious result is:
- Faster startup speed.
In order to reduce system startup time, the goal of systemd is to