系统：centos7
防火墙：关闭防火墙和selinux
软件：chrony

centos6我们一直用的ntp时间服务器，虽然到CentOS7上也可以装ntp。但是各种问题。所以建议centos7使用chrony同步工具。

服务端配置：

1.安装chrony软件

[root@server ~]# yum install chrony -y

2.修改配置文件

[root@server ~]# vim /etc/chrony.conf

server 0.centos.pool.ntp.org iburst     #可以修改ntp的服务器。最好用国内的。

server 1.centos.pool.ntp.org iburst

server 2.centos.pool.ntp.org iburst

server 3.centos.pool.ntp.org iburst

allow 172.19.150.0/24                   #打开允许同步的IP

阿里ntp的服务器列表

time1.aliyun.com
time2.aliyun.com
time3.aliyun.com
time4.aliyun.com
time5.aliyun.com
time6.aliyun.com
time7.aliyun.com

3.启动、开机自启动、查看状态、查看同步源

[root@server ~]# systemctl start chronyd

[root@server ~]# systemctl enable chronyd

[root@server ~]# systemctl status chronyd

● chronyd.service - NTP client/server

   Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled)

   Active: active (running) since 一 2018-04-23 11:25:38 CST; 6min ago

[root@server ~]# chronyc sources

210 Number of sources = 1

MS Name/IP address         Stratum Poll Reach LastRx Last sample

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

^* time4.aliyun.com              2   6    17    41    +87us[+1374us] +/-   28ms

客户端配置：

1. 安装chrony

[root@client ~]# yum install chrony -y

2. 修改配置文件

[root@client ~]# vim /etc/chrony.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            #注释此处

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

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

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

server 172.19.150.105 iburst                        #添加server

3.启动、开机自启动、查看状态、查看同步源

[root@client ~]# date

Sat Sep  9 00:00:02 CST 2017

[root@client ~]#  systemctl start chronyd

[root@client ~]#  systemctl enable chronyd

[root@client ~]#  systemctl status chronyd

● chronyd.service - NTP client/server

   Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled)

   Active: active (running) since Sat 2017-09-09 00:00:11 CST; 7 months 13 days ago

     Docs: man:chronyd(8)

[root@client ~]# date

Sat Sep  9 00:00:13 CST 2017

[root@client ~]# chronyc sources

210 Number of sources = 1

MS Name/IP address         Stratum Poll Reach LastRx Last sample

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

^* 172.19.150.105                3   6    17     3    +52us[ +107us] +/-   32ms

###最后一条有*号表示同步成功