在工作中，内网环境机器的时间会有所差异，在某些测试环境下需要一毫秒都不允许出现误差，但又不想同步外网时间，那我们可以选择一台机器作为时间服务器来供其他机器进行时间同步，例如每隔1分钟同步一次时间。
一、环境
系统：Centos 6.5
ntp_client IP：192.168.0.117
ntp_server IP：192.168.0.124
二、安装ntp服务
root@fenfa ~]# yum install ntp -y [root@fenfa ~]# chkconfig --add ntpd [root@fenfa ~]# chkconfig ntpd on
三、配置/etc/ntp.conf文件：
server:
[root@fenfa ~]# vim /etc/ntp.conf 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 192.168.0.0 mask 255.255.255.0 nomodify notrap 19 20 # Use public servers from the pool.ntp.org project. 21 # Please consider joining the pool (http://www.pool.ntp.org/join.html). 22 #server 0.centos.pool.ntp.org iburst 23 #server 1.centos.pool.ntp.org iburst 24 #server 2.centos.pool.ntp.org iburst 25 #server 3.centos.pool.ntp.org iburst 26 27 server 127.127.1.0 28 fudge 127.127.1.0 stratum 1 29 30 #broadcast 192.168.1.255 autokey # broadcast server 31 #broadcastclient # broadcast client 32 #broadcast 224.0.1.1 autokey # multicast server 33 #multicastclient 224.0.1.1 # multicast client 34 #manycastserver 239.255.254.254 # manycast server 35 #manycastclient 239.255.254.254 autokey # manycast client 36 37 # Enable public key cryptography. 38 #crypto 39 40 includefile /etc/ntp/crypto/pw 41 42 # Key file containing the keys and key identifiers used when operating 43 # with symmetric key cryptography. 44 keys /etc/ntp/keys 45 46 # Specify the key identifiers which are trusted. 47 #trustedkey 4 8 42 48 49 # Specify the key identifier to use with the ntpdc utility. 50 #requestkey 8 51 52 # Specify the key identifier to use with the ntpq utility. 53 #controlkey 8 54 55 # Enable writing of statistics records. 56 #statistics clockstats cryptostats loopstats peerstats
注：红色字体的地方为新增或修改的部分
client：
[root@nfs ~]# vim /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). 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 192.168.0.0 mask 255.255.255.0 nomodify notrap 19 20 # Use public servers from the pool.ntp.org project. 21 # Please consider joining the pool (http://www.pool.ntp.org/join.html). 22 #server 0.centos.pool.ntp.org iburst 23 #server 1.centos.pool.ntp.org iburst 24 #server 2.centos.pool.ntp.org iburst 25 #server 3.centos.pool.ntp.org iburst 26 27 server 192.168.0.124 profer 28 29 #broadcast 192.168.1.255 autokey # broadcast server 30 #broadcastclient # broadcast client 31 #broadcast 224.0.1.1 autokey # multicast server 32 #multicastclient 224.0.1.1 # multicast client 33 #manycastserver 239.255.254.254 # manycast server 34 #manycastclient 239.255.254.254 autokey # manycast client 35 36 # Enable public key cryptography. 37 #crypto 38 39 includefile /etc/ntp/crypto/pw 40 41 # Key file containing the keys and key identifiers used when operating 42 # with symmetric key cryptography. 43 keys /etc/ntp/keys 44 45 # Specify the key identifiers which are trusted. 46 #trustedkey 4 8 42 47 48 # Specify the key identifier to use with the ntpdc utility. 49 #requestkey 8 50 51 # Specify the key identifier to use with the ntpq utility. 52 #controlkey 8 53 54 # Enable writing of statistics records. 55 #statistics clockstats cryptostats loopstats peerstat
四、设置client主机与时间服务器时间的同步
- serverd端从启ntp服务
- client端更改系统时间
- 执行同步命令：ntpdate -u 192.168.0.124
[root@fenfa x86_64]# service ntpd restart 关闭 ntpd： [确定] 正在启动 ntpd： [确定]
[root@nfs ~]# date 2019年 08月 19日 星期一 21:52:25 CST [root@nfs ~]# date -s 2018-08-19 2018年 08月 19日 星期日 00:00:00 CST [root@nfs ~]# date 2018年 08月 19日 星期日 00:00:05 CST [root@nfs ~]# ntpdate -u 192.168.0.124 19 Aug 21:54:22 ntpdate[1861]: step time server 192.168.0.124 offset 31614767.907398 sec [root@nfs ~]# date 2019年 08月 19日 星期一 21:54:28 CST
可以在client机器上编写一个定时脚本：
[root@nfs ~]# crontab -l ####ntpd Synchronize every 1 minute 00-59/60 * * * * /usr/sbin/ntpdate -u 192.168.0.124 >/dev/null 2>&1
修改/etc/ntp/stpe-tickers文件，内容如下（当ntpd服务启动时，会自动与该文件中记录的上层NTP服务进行时间校对
[root@nfs ~]# cat /etc/ntp/step-tickers # List of servers used for initial synchronization. server 192.168.0.124 prefer
ntp服务，默认只会同步系统时间。如果想要让ntp同时同步硬件时间，可以设置/etc/sysconfig/ntpd文件，在/etc/sysconfig/ntpd文件中，添加 SYNC_HWCLOCK=yes 这样，就可以让硬件时间与系统时间一起同步。