NTP时间服务器 搭建

1.1 NTP简介

NTP（Network Time Protocol，网络时间协议）是用来使网络中的各个计算机时间同步的一种协议。它的用途是把计算机的时钟同步到世界协调时UTC，其精度在局域网内可达0.1ms，在互联网上绝大多数的地方其精度可以达到1-50ms。

NTP服务器就是利用NTP协议提供时间同步服务的。

系统版本

 [root@test ~]# cat /etc/redhat-release
 CentOS release 6.9 (Final)

1.2 NTP服务器安装

[root@test ~]# rpm -qa ntp
ntp-4.2.6p5-.el6.centos..x86_64

如果没有安装就yum install ntp -y进行安装

1.3 配置NTP服务

备份配置文件

[root@test ~]# cp /etc/ntp.conf{,.bak}
[root@test ~]# ll /etc/ntp.conf*
-rw-r--r--.  root root  Jan    /etc/ntp.conf
-rw-r--r--   root root  Oct  : /etc/ntp.conf.bak

精简化配置文件

[root@test ~]# egrep -v "^$|#" /etc/ntp.conf.bak  >/etc/ntp.conf

修改配置文件

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

 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 kod nomodify notrap nopeer noquery
 restrict - default kod 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 - ::

 # Hosts on local network are less restricted.
 #restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
 # 允许内网其他机器同步时间
 restrict 172.16.1.0 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 .centos.pool.ntp.org iburst
 #server .centos.pool.ntp.org iburst
 #server .centos.pool.ntp.org iburst
 #server .centos.pool.ntp.org iburst

 # 定义使用的上游 ntp服务器，将原来的注释
 server time1.aliyun.com
 server ntp1.aliyun.com

 #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

 # 允许上层时间服务器主动修改本机时间
 restrict time1.aliyun.com  nomodify notrap noquery
 restrict ntp1.aliyun.com  nomodify notrap noquery

 # 外部时间服务器不可用时，以本地时间作为时间服务
 server  127.127.1.0
 fudge   127.127.1.0 stratum 

 # 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   

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

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

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

1.4 启动NTP服务器

注意：如果有同步时间的定时任务要将其注销，否则会冲突

[root@test ~]# /etc/init.d/ntpd start
Starting ntpd:                                             [  OK  ]

显示节点列表

[root@test ~]# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 time5.aliyun.co 10.137.38.86      u              5.092   185.623

 132.163.96.4    .INIT.           u    -           0.000    0.000   0.000

1.5 客户机时间同步

客户机要等几分钟再与新启动的ntp服务器进行时间同步，否则会提示

no server suitable for synchronization found错误

[root@client ~]# ntpdate 10.0.0.250
 Oct :: ntpdate[]: adjust time server 10.0.0.250 offset 0.320652 sec