NTP snap安装包。通过sudo snap install --dangerous chrony-git.snap安装，安装后，见readme, 创建一个配置文件 /var/snap/chrony-git/common/chrony.conf
chrony is a versatile implementation of the Network Time Protocol (NTP). It can synchronise the system clock with NTP servers, reference clocks (e.g. GPS receiver), and manual input using wristwatch and keyboard. It can also operate as an NTPv4 (RFC 5905) server and peer to provide a time service to other computers in the network.
