ntp time server

I. Environmental Preparation

Two virtual machines

192.168.30.139 #Server
 192.168.30.143 #Client

2. Server side configuration:

1. Install ntp service

# 192.168.30.139 
[root@hadoop1 opt]# yum install  -y ntp

# 192.168.30.143
[root@hadoop2 opt]# yum install  -y ntp

2. Service and Set Up Startup

[root@hadoop1 opt]# service ntpd  start
# Starting ntpd:[OK]      

[root@hadoop1 opt]# chkconfig ntpd on

3. Check whether the port is started

[root@hadoop1 ~]# netstat -anput| grep 123
udp        0      0 192.168.30.139:123          0.0.0.0:*                               8239/ntpd           
udp        0      0 127.0.0.1:123               0.0.0.0:*                               8239/ntpd           
udp        0      0 0.0.0.0:123                 0.0.0.0:*                               8239/ntpd           
udp        0      0 fe80::20c:29ff:fea8:b66b:123 :::*                                    8239/ntpd           
udp        0      0 ::1:123                     :::*                                    8239/ntpd           
udp        0      0 :::123                      :::*                                    8239/ntpd  

4. Modify the configuration file:

driftfile /var/lib/ntp/drift

restrict default kod nomodify notrap nopeer noquery
restrict -6 default kod nomodify notrap nopeer noquery

restrict 127.0.0.1 
restrict -6 ::1

#Allow access to 192.168.30.0 segments
restrict 192.168.30.0 mask 255.255.255.0
server 127.127.1.0  
fudge 127.127.1.0 stratum 10 


server 0.centos.pool.ntp.org iburst
server 1.centos.pool.ntp.org iburst
server 2.centos.pool.ntp.org iburst
server 3.centos.pool.ntp.org iburst



includefile /etc/ntp/crypto/pw
keys /etc/ntp/keys

5. Restart ntpd service

[root@hadoop1 ~]# service ntpd restart
 Turn off ntpd:[OK]                              
Starting ntpd:[OK]                                

3. Client Configuration

1. Do the same in 192.168.30.143

The client does not need to restart.

IV. Verification Operation

1. Before testing, check if the firewall and selinux are off!!!

#Firewall off
[root@hadoop1 opt]# service iptables stop

#selinux off
[root@hadoop1 opt]# cat /etc/selinux/config |grep -v ^#

SELINUX=disabled
SELINUXTYPE=targeted 

2. Time Synchronization

[root@hadoop1 opt]# date
2017year 12month 17Sunday and Sunday 03:33:13 CST

# There is a significant difference between setting time on hadoop2 and hadoop1
[root@hadoop2 ~]# date -s '2017-12-10 15:14:23'
2017year 12month 10Sunday and Sunday 15:14:23 CST

#Execute Synchronization Instructions
[root@hadoop2 ~]# ntpdate 192.168.30.139
17 Dec 03:35:11 ntpdate[4405]: step time server 192.168.30.139 offset 562786.980472 sec
[root@hadoop2 ~]# date 
2017year 12month 17Sunday and Sunday 03:35:12 CST

5. Add to Timed Tasks

# Synchronize information at zero every day
[root@hadoop2 ~]# crontab -e
0 0 * * * ntpd 192.168.30.139

Tags: CentOS SELinux yum firewall

Posted on Wed, 13 May 2020 12:21:19 -0400 by infratl