Introduction to ntp + time synchronization service construction (utility tool)

Introduction to NTP

NTP is a network time synchronization protocol, which is a protocol used to synchronize the time of each computer in the network.

Prepare two centos7 environment tests

One server (136) One client (137)

1. Turn off the firewall setenforce

[root@localhost ~]# systemctl stop firewalld
[root@localhost ~]# setenforce 0

2. Install and configure the ntp service on the server side

[root@localhost ~]# yum -y install ntp
[root@localhost ~]# vim /etc/ntp.conf 

3. Start to view ntp

[root@localhost ~]# systemctl start ntpd
[root@localhost ~]# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*LOCAL(0)        .LOCL.           5 l    4   64    1    0.000    0.000   0.000
 114.118.7.161   123.139.33.3     2 u    3   64    1   80.643  271.746   0.000
 203.107.6.88    100.107.25.114   2 u    2   64    1   17.522  311.783   0.000

4. Install ntpdate on the client

[root@localhost ~]# yum -y install ntpdate

test

1. Simulate and modify the time on the server side

[root@localhost ~]#  date -s "2018-08-8 04:53"
2018年 08月 08日 星期三 04:53:00 CST

2. Check the time by synchronizing the server time on the client

[root@localhost ~]# ntpdate -u 192.168.27.136
 8 Aug 04:56:25 ntpdate[13694]: step time server 192.168.27.136 offset 38531233.207033 sec
 
[root@localhost ~]# date
2018年 08月 08日 星期三 04:56:03 CST

There may be a delay of about 30 seconds during the test