systemd

目前centos使用的就是systemd。

wikipedia systemd

systemd is a software suite that provides an array of system components for Linux operating systems.

NOTE: 1、它是一套软件

Official site systemd

NOTE:

1、内容并不完全

freedesktop systemd System and Service Manager

What is this?

systemd is a suite of basic building blocks for a Linux system. It provides a system and service manager that runs as PID 1 and starts the rest of the system.

NOTE:

ps --pid=1 -l
F S   UID     PID    PPID  C PRI  NI ADDR SZ WCHAN  TTY          TIME CMD
4 S     0       1       0  0  80   0 - 61488 -      ?        00:00:02 systemd

systemd provides aggressive parallelization capabilities, uses socket and D-Bus activation for starting services, offers on-demand starting of daemons, keeps track of processes using Linux control groups, maintains mount(安装) and automount points, and implements an elaborate(精心制作的) transactional dependency-based service control logic.

NOTE:

1、上面描述的是systemd的特性、它的一些实现方式

2、"keeps track of processes using Linux control groups" 中的"Linux control groups"要如何理解？参见 Virtualization\Linux-control-groups 章节

systemd supports SysV and LSB init scripts and works as a replacement for sysvinit. Other parts include a logging daemon, utilities to control basic system configuration like the hostname, date, locale, maintain a list of logged-in users and running containers and virtual machines, system accounts, runtime directories and settings, and daemons to manage simple network configuration, network time synchronization, log forwarding, and name resolution. See the introductory blog story and three status updates for a longer introduction. Also see the Wikipedia article.

freedesktop systemd man page

NOTE:

1、这是需要阅读的

使用指南

查看哪些服务是开机自动启动

csdn Linux查看哪些服务是开机自动启动的

服务如果需要自动启动，需要在/etc/systemd/system/multi-user.target.wants/***.service添加链接文件到/usr/lib/systemd/system/***.service

如果去除自动启动，移除此文件即可。/etc/systemd/system/multi-user.target.wants/***.service

ll /etc/systemd/system/multi-user.target.wants/

csdn Linux查看设置开机启动的服务列表

systemctl list-units --type=service

NOTE:

下面是我的系统中的样例输出

UNIT	LOAD	active	SUB	DESCRIPTION
mcelog.service	loaded	active	running	Machine Check Exception Log>
ModemManager.service	loaded	active	running	Modem Manager
NetworkManager-dispatcher.service	loaded	active	running	Network Manager Script Disp>
NetworkManager-wait-online.service	loaded	active	exited	Network Manager Wait Online
NetworkManager.service	loaded	active	running	Network Manager
nis-domainname.service	loaded	active	exited	Read and set NIS domainname>
packagekit.service	loaded	active	running	PackageKit Daemon
plymouth-quit-wait.service	loaded	active	exited	Hold until boot process fin>
plymouth-read-write.service	loaded	active	exited	Tell Plymouth To Write Out >
plymouth-start.service	loaded	active	exited	Show Plymouth Boot Screen
polkit.service	loaded	active	running	Authorization Manager
rhsmcertd.service	loaded	active	running	Enable periodic update of e>
rngd-wake-threshold.service	loaded	active	exited	Hardware RNG Entropy Gather>
rngd.service	loaded	active	running	Hardware RNG Entropy Gather>
rpc-statd-notify.service	loaded	active	exited	Notify NFS peers of a resta>
rpcbind.service	loaded	active	running	RPC Bind
rsyslog.service	loaded	active	running	System Logging Service
rtkit-daemon.service	loaded	active	running	RealtimeKit Scheduling Poli>
smartd.service	loaded	active	running	Self Monitoring and Reporti>
sshd.service	loaded	active	running	OpenSSH server daemon
sssd-kcm.service	loaded	active	running	SSSD Kerberos Cache Manager
sssd.service	loaded	active	running	System Security Services Da>
systemd-journal-flush.service	loaded	active	exited	Flush Journal to Persistent>
systemd-journald.service	loaded	active	running	Journal Service
systemd-logind.service	loaded	active	running	Login Service

设置开机自启动

csdn centos7设置NetworkManager开机自启动

启动：systemctl start NetworkManger 关闭：systemctl stop NetworkManager 开机启动：systemctl enable NetworkManager 查看是否开机启动：systemctl is-enabled NetworkManager 禁用开机启动：systemctl disable NetworkManager

`systemctl`

redhat Getting started with systemctl

Here is a syntax example:

systemctl subcommand argument

Service status

# systemctl status sshd

Starting and stopping services

# systemctl restart sshd
# systemctl stop sshd
# systemctl start sshd
# systemctl kill sshd

Enable and disable services

Previously, you used the chkconfig command to define the service's startup setting for each runlevel. Here is an example:

# chkconfig --level 35 sshd on

This command enables sshd to start up in runlevels 3 and 5.

With systemctl, configuring the default startup setting is the work of the enable and disable subcommands. The syntax is the same as with the start, stop, and restart subcommands. For example, to set SSH to start when the server boots, enter:

# systemctl enable sshd

Likewise, to configure SSH not to start during bootup, type:

# systemctl disable sshd

Use start and enable together

# systemctl start sshd

# systemctl enable sshd

geeksforgeeks systemctl in Unix

TODO

1、where dose systemd log？