1. 설치
sudo apt-get install ntp
sudo vim /etc/ntp.conf server kr.pool.ntp.org server time.kriss.re.kr # KRISS 한국표준과학연구원 server time.windows.com # Microsoft server time.bora.net # LGU+ 1.kr.pool.ntp.org 1.asia.pool.ntp.org
sudo service restart ntp
sudo ntpq -p