Learn Systemd with me.

Learn Systemd with me.Http://netkiller.github.io/journal/os.systemd.html Mr.Neo Chen(Chen Jingxian),Netkiller, Bg7nyt

China Guangdong province Shenzhen Khe Sanh Street, Longhua District, civil Administration
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2015-11-04

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Directory

• 1. What is Systemd
• 2. why-Why do
• 3. When was the SYSTEMD adopted ?
• 4. Those systems use SYSTEMD
• 5. Who developed the system ?
• 6. How to write Systemd scripts
  • 6.1. Unit
  • 6.2. Service
  • 6.3. Install

1. What is SYSTEMD

SYSTEMD is a centralized system and Setup management program (init software) under the Linux computer operating system, including daemons, libraries and applications, developed by Lennart Poettering. Its development goal is to provide a better framework to represent the dependencies between system services, and to implement the parallel startup of the service when the system is initialized, and to reduce the overhead of the shell, and eventually replace the System V and BSD-style init programs commonly used today.

2. why-Why do

Compared to the System V style init used in most distributions, SYSTEMD uses the following new technologies:

1. Using socket-activated and d-bus-activated services to improve the performance of parallel operation of each dependent service;

2. The process is tracked using cgroups instead of the process ID, so that the daemons generated even after two fork are not out of systemd control.

3. When was the SYSTEMD adopted?

CentOS 7 starts the system by default using SYSTEMD, for the user is the service is replaced by Systemctl.

4. Those systems use SYSTEMD

Basically, the Linux operating system that derives from Redhat has switched to Systemd,ubuntu and has adopted the SYSTEMD

5. Who developed the system?

Developed by Lennart Poettering

6. How to write Systemd scripts

Here is a SYSTEMD script that launches Tomcat, taking this script as an example I take you into the world of SYSTEMD.

Example 1. /usr/lib/systemd/system/tomcat.service

##################################################### homepage:http://netkiller.github.io# author:netkiller<[ Email protected]># script:https://github.com/oscm/shell# date:2015-11-03###################################### ##############[unit]description=apache Tomcat WEB Application containerafter=network.targetafter=syslog.target[ Service]type=forkinguser=wwwgroup=www#environmentfile=/etc/sysconfig/tomcatexecstartpre= "rm-rf/srv/ apache-tomcat/logs/* "Execstart=/srv/apache-tomcat/bin/startup.sh#execstartpost=execstop=/srv/apache-tomcat/bin /shutdown.sh[install]wantedby=multi-user.target

The script is installed under/usr/lib/systemd/system/tomcat.service

Systemctl Enable Tomcatsystemctl start tomcatsystemctl stop tomcatsystemctl disable tomcat

A symbolic link is created when scripting is enabled

[Email protected] ~]# Ll/etc/systemd/system/multi-user.target.wants/tomcat.service lrwxrwxrwx 1 root root  3 04:06/etc/systemd/system/multi-user.target.wants/tomcat.service-/usr/lib/systemd/system/tomcat.service

6.1. Unit

Description write a text describing the script

After waiting for network ready to run

6.2. Service

Type startup types

User, the Group that runs the Execstart script, is the equivalent of Su-user-c Execstart

Environment environment variable, environmentfile environment variable file

Execstartpre script to run before start, Execstart startup script, Execstartpost script to run after startup

Execstop Stop Script

6.3. Install

Wantedby=multi-user.target installing to multi-user mode

Learn Systemd with me.