1, lists unit

command Explanation
systemctl list-units
 List all running unit
systemctl list-unit-files Lists all available units
systemctl --failed List all failed unit
systemctl list-unit-files --type service List all services

2, start, restart, stop, service and overloaded boot from the start the service, cancel the start-up , service is prohibited, lift the ban (such as httpd.service service)

command Explanation
systemctl start httpd.service Start httpd service
systemctl restart httpd.service Service httpd restart
systemctl stop httpd.service Stop the httpd service
systemctl reload httpd.service Service httpd reload
systemctl enable httpd.service Set boot from the start httpd service
systemctl disable httpd.service Cancel start-up service httpd
systemctl mask httpd.service
 Prohibit service httpd
systemctl unmask httpd.service Cancel service httpd ban

Note: when we start using the systemctl command, restart, stop, when the reload option, the terminal will not output anything, only the status option to print output.

3, check the service status, check whether the service starts, the service checks the boot is started (such as httpd service)

command Explanation
systemctl status httpd.service View httpd service status
systemctl is-active httpd.service
 View httpd service is started
systemctl is-enabled httpd.service Check whether the service httpd boot from the start

4, using the command kill systemctl services (such as: killing crond Service)

command Explanation
systemctl kill crond Kill crond service

5, lists all of the mount points system

command Explanation
systemctl list-unit-files --type mount All system mount points listed

6, loading, unloading and re-loading, system overload mount point, and the system checks the state of mount points (eg: tmp.mount mount point)

command Explanation
systemctl start tmp.mount Mounting
systemctl stop tmp.mount Uninstall
systemctl restart tmp.mount Remount
systemctl reload tmp.mount Overload
systemctl status tmp.mount Check Status

7, boot automatically mount, canceled boot mount, the mount point is enabled to see, to see if the boot automatically mount

command Explanation
systemctl is-active tmp.mount View mount point is enabled
systemctl enable tmp.mount Set the boot automatically mount
systemctl disable tmp.mount Cancellation boot automatically mount
systemctl is-enabled tmp.mount See if the boot automatically mount

8, prohibits any action mount point, and stop running; unblock

command Explanation
systemctl mask tmp.mount Ban
systemctl unmask tmp.mount Unblock

9, listing all available system socket system

command Explanation
systemctl list-unit-files --type socket Lists all available system socket

10, a service check of all configuration details (eg: httpd service)

command Explanation
systemctl show httpd.service Check the httpd service all configuration details

11, to obtain a service list of dependencies (eg: httpd service)

command Explanation
systemctl list-dependencies httpd.service Get httpd service dependency list

12, start rescue mode

command Explanation
systemctl rescue Start rescue mode

13, into the emergency mode

command Explanation
systemctl emergency 进入紧急模式

14、运行级别

命令 说明
systemctl get-default 查看默认的运行级别

systemctl isolate graphical.target

或

systemctl isolate runlevel5.target

 启动运行级别5（图形模式）

systemctl isolate multi-user.target

或

systemctl isolate runlevel3.target

 启动运行级别3（命令行模式）

systemctl set-default graphical.target

或

systemctl set-default runlevel5.target

 设置图形模式为默认运行级别

systemctl set-default multi-user.target

或

systemctl set-default runlevel3.target

 设置命令行模式为默认运行级别

系统运行级别说明如下：

Runlevel 0：关闭系统

Runlevel 1：单用户模式

Runlevel 2：多用户，命令行模式（无网络）

Runlevel 3：多用户，命令行模式

Runlevel 4：保留

Runlevel 5：多用户，图形化模式

Runlevel 6：重启系统