[root@master ~]# yum -y install ntp

[root@master ~]# systemctl start ntpd

[root@master ~]# systemctl enable ntpd

[root@master ~]# vi /etc/ntp.conf

# 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).

#记录system clock的误差值开机时不会丢失

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.

#默认拒绝所有来源的任何访问

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.

#允许本机地址一切操作

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
#restrict 对ntp做权限控制 ignore：忽略所有类型的NTP连接请求 nomodify：限制客户端不能使用命令ntpc和ntpq来修改服务器端的时间
#noquery：不提供NTP网络校时服务 notrap：不接受远程登录请求 notrust：不接受没有经过认证的客户端的请求


#允许局域网66网段内所有client连接到这台服务器同步时间.但是拒绝让他们修改服务器上的时间和远程登录

restrict 192.168.66.0 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 0.centos.pool.ntp.org iburst

#server 1.centos.pool.ntp.org iburst

#server 2.centos.pool.ntp.org iburst

#server 3.centos.pool.ntp.org iburst

#指定ntp服务器的地址

#将当前主机作为时间服务器

server 127.127.1.0

#时间服务器层级0-15 0表示顶级 10通常用于给局域网主机提供时间服务

fudge 127.127.1.0 stratum 10

#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@master ~]# systemctl restart ntpd

[root@master ~]# ntpstat

synchronised to local net (127.127.1.0) at stratum 11

   time correct to within 7948 ms

   polling server every 64 s

[root@master ~]# 

[root@node1 ~]# vi /etc/ntp.conf

# Use public servers from the pool.ntp.org project.

# Please consider joining the pool (http://www.pool.ntp.org/join.html).

#server 0.centos.pool.ntp.org iburst

#server 1.centos.pool.ntp.org iburst

#server 2.centos.pool.ntp.org iburst

#server 3.centos.pool.ntp.org iburst
#client端仅仅加入server端IP


server master

[root@node1 ~]# systemctl restart ntpd

[root@node1 ~]# ntpq -p

     remote           refid      st t when poll reach   delay   offset  jitter

==============================================================================

*master          LOCAL(0)        11 u   43   64   37    0.223  -134.33  92.058

[root@node1 ~]#