https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/sect-Managing_Services_with_systemd-Targets.html 

Viewing the Default Target

To determine which target unit is used by default, run the following command:

systemctl get-default

 Viewing the Current Target

To list all currently loaded target units, type the following command at a shell prompt:

systemctl list-units --type target

By default, the systemctl list-units command displays only active units. If you want to list all loaded units regardless of their state, run this command with the --all or -a command line option:

systemctl list-units --type target --all

 Changing the Default Target

To configure the system to use a different target unit by default, type the following at a shell prompt as root:

systemctl set-default name.target

 Changing the Current Target

To change to a different target unit in the current session, type the following at a shell prompt as root:

systemctl isolate name.target

本文出自 “Devops” 博客，请务必保留此出处http://yanglunkai.blog.51cto.com/7745171/1580901

CentOS 7 修改系统启动级别