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
1 [root@test ~]# cat /etc/redhat-release 2 CentOS release 6.9 (Final)
1.2 NTP服务器安装
1 [root@test ~]# rpm -qa ntp 2 ntp-4.2.6p5-10.el6.centos.2.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
1 [root@test ~]# cp /etc/ntp.conf{,.bak} 2 3 [root@test ~]# ll /etc/ntp.conf* 4 5 -rw-r--r--. 1 root root 1778 Jan 11 2017 /etc/ntp.conf 6 7 -rw-r--r-- 1 root root 1778 Oct 23 23:10 /etc/ntp.conf.bak
精简化配置文件
1 [root@test ~]# egrep -v "^$|#" /etc/ntp.conf.bak >/etc/ntp.conf
修改配置文件
1 # For more information about this file, see the man pages 2 # ntp.conf(5), ntp_acc(5), ntp_auth(5), ntp_clock(5), ntp_misc(5), ntp_mon(5). 3 4 driftfile /var/lib/ntp/drift 5 6 # Permit time synchronization with our time source, but do not 7 # permit the source to query or modify the service on this system. 8 restrict default kod nomodify notrap nopeer noquery 9 restrict -6 default kod nomodify notrap nopeer noquery 10 11 # Permit all access over the loopback interface. This could 12 # be tightened as well, but to do so would effect some of 13 # the administrative functions. 14 restrict 127.0.0.1 15 restrict -6 ::1 16 17 # Hosts on local network are less restricted. 18 #restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap 19 # 允许内网其他机器同步时间 20 restrict 172.16.1.0 mask 255.255.255.0 nomodify notrap 21 22 # Use public servers from the pool.ntp.org project. 23 # Please consider joining the pool (http://www.pool.ntp.org/join.html). 24 #server 0.centos.pool.ntp.org iburst 25 #server 1.centos.pool.ntp.org iburst 26 #server 2.centos.pool.ntp.org iburst 27 #server 3.centos.pool.ntp.org iburst 28 29 # 定义使用的上游 ntp服务器，将原来的注释 30 server time1.aliyun.com 31 server ntp1.aliyun.com 32 33 #broadcast 192.168.1.255 autokey # broadcast server 34 #broadcastclient # broadcast client 35 #broadcast 224.0.1.1 autokey # multicast server 36 #multicastclient 224.0.1.1 # multicast client 37 #manycastserver 239.255.254.254 # manycast server 38 #manycastclient 239.255.254.254 autokey # manycast client 39 40 # 允许上层时间服务器主动修改本机时间 41 restrict time1.aliyun.com nomodify notrap noquery 42 restrict ntp1.aliyun.com nomodify notrap noquery 43 44 # 外部时间服务器不可用时，以本地时间作为时间服务 45 server 127.127.1.0 46 fudge 127.127.1.0 stratum 10 47 48 # Enable public key cryptography. 49 #crypto 50 51 includefile /etc/ntp/crypto/pw 52 53 # Key file containing the keys and key identifiers used when operating 54 # with symmetric key cryptography. 55 keys /etc/ntp/keys 56 57 # Specify the key identifiers which are trusted. 58 #trustedkey 4 8 42 59 60 # Specify the key identifier to use with the ntpdc utility. 61 #requestkey 8 62 63 # Specify the key identifier to use with the ntpq utility. 64 #controlkey 8 65 66 # Enable writing of statistics records. 67 #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
1 [root@test ~]# /etc/init.d/ntpd start 2 Starting ntpd: [ OK ]
显示节点列表
1 [root@test ~]# ntpq -p 2 remote refid st t when poll reach delay offset jitter 3 ============================================================================== 4 time5.aliyun.co 10.137.38.86 2 u 28 64 3 5.092 6241215 185.623 5 6 132.163.96.4 .INIT. 16 u - 64 0 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
1 [root@client ~]# ntpdate 10.0.0.250 2 24 Oct 16:46:58 ntpdate[26694]: adjust time server 10.0.0.250 offset 0.320652 sec
