[root@localhost /]# yum install ntp -y

# For more information about this file, see the man pages
# ntp.conf(5), ntp_acc(5), ntp_auth(5), ntp_clock(5), ntp_misc(5), ntp_mon(5).

driftfile /var/lib/ntp/drift

# Permit time synchronization with our time source, but do not
# permit the source to query or modify the service on this system.
restrict default nomodify notrap nopeer noquery

# Permit all access over the loopback interface.  This could
# be tightened as well, but to do so would effect some of
# the administrative functions.
restrict 127.0.0.1
restrict ::1

# Hosts on local network are less restricted.
#restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap

# Use public servers from the pool.ntp.org project.Please consider joining the pool (http://www.pool.ntp.org/join.html).
server 192.168.1.1 iburst       #目标服务器网络位置
#server 1.centos.pool.ntp.org iburst     #一下三个是CentOS官方的NTP服务器，我们注释掉
#server 2.centos.pool.ntp.org iburst
#server 3.centos.pool.ntp.org iburst

#broadcast 192.168.1.255 autokey        # broadcast server
#broadcastclient                        # broadcast client
#broadcast 224.0.1.1 autokey            # multicast server
#multicastclient 224.0.1.1              # multicast client
#manycastserver 239.255.254.254         # manycast server
#manycastclient 239.255.254.254 autokey # manycast client

# Enable public key cryptography.
#crypto

includefile /etc/ntp/crypto/pw

# Key file containing the keys and key identifiers used when operating
# with symmetric key cryptography.
keys /etc/ntp/keys

# Specify the key identifiers which are trusted.
#trustedkey 4 8 42

# Specify the key identifier to use with the ntpdc utility.
#requestkey 8

# Specify the key identifier to use with the ntpq utility.
#controlkey 8

# Enable writing of statistics records.
#statistics clockstats cryptostats loopstats peerstats

# Disable the monitoring facility to prevent amplification attacks using ntpdc
# monlist command when default restrict does not include the noquery flag. See
# CVE-2013-5211 for more details.
# Note: Monitoring will not be disabled with the limited restriction flag.
disable monitor

[root@localhost /]# systemctl start ntpd.service　　#启动服务
[root@localhost /]# systemctl enable ntpd.service　　#设置为开机启动

[root@localhost /]# systemctl status ntpd.service
● ntpd.service - Network Time Service
   Loaded: loaded (/usr/lib/systemd/system/ntpd.service; enabled; vendor preset: disabled)
   Active: active (running) since 二 2016-10-11 13:34:11 CST; 8min ago
 Main PID: 6497 (ntpd)
   CGroup: /system.slice/ntpd.servicess
           └─6497 /usr/sbin/ntpd -u ntp:ntp -g

10月 11 13:34:11 localhost.localdomain ntpd[6497]: Listen and drop on 1 v6wildcard :: UDP 123
10月 11 13:34:11 localhost.localdomain ntpd[6497]: Listen normally on 2 lo 127.0.0.1 UDP 123
10月 11 13:34:11 localhost.localdomain ntpd[6497]: Listen normally on 3 eno16777736 192.168.100.100 UDP 123