參考：

• Flushing your DNS cache in Mac OS X and Linux

Mac OS X 清除DNS緩存

根據Mac OS X操作系統的版本選擇以下命令：

Mac OS X 12 (Sierra) and later:

sudo killall -HUP mDNSResponder
sudo killall mDNSResponderHelper
sudo dscacheutil -flushcache

Mac OS X 11 (El Capitan) and OS X 12 (Sierra):

sudo killall -HUP mDNSResponder

Mac OS X 10.10 (Yosemite), Versions 10.10.4+:

sudo dscacheutil -flushcache
sudo killall -HUP mDNSResponder

2018.6

Mac OS X 清除DNS緩存