CentOS7ではntpdでなくて、chronydで時刻同期します。
systemctl start chronyd && systemctl enable chronyd
# chronyc sources 210 Number of sources = 4 MS Name/IP address Stratum Poll Reach LastRx Last sample =============================================================================== ^- ntp03.lagoon.nc 3 10 377 434 +27ms[ +27ms] +/- 140ms ^- y.ns.gin.ntt.net 2 10 377 870 -2303us[-2303us] +/- 106ms ^- time.cloudflare.com 3 10 377 199 -286us[ -286us] +/- 64ms ^* ntp.arupaka.net 2 10 377 20m +281us[ -698us] +/- 11ms
chronyc -a makestep