顯示可用的運作層級
systemctl list-units --type target
顯示目前系統預設層級
systemctl get-default
切換到Run Level 3 [文字模式]
systemctl isolate multi-user.target
切換到Run Level 5 [圖形模式]
systemctl isolate graphical.target
設定開機為Run Level 3 [文字模式]
systemctl set-default multi-user.target
設定開機為Run Level 5 [圖形模式]
systemctl set-default graphical.target