Section 10 - NTP

Synchronize Time Using Other NTP Peers - set up local time server

## install required packages [root@rhel7server1 ~]# yum install -y ntp ## check currently configured NTP servers [root@rhel7server1 ~]# grep ^server /etc/ntp.conf server 0.rhel.pool.ntp.org iburst server 1.rhel.pool.ntp.org iburst server 2.rhel.pool.ntp.org iburst server 3.rhel.pool.ntp.org iburst ## enable and start ntpd service [root@rhel7server1 ~]# systemctl enable ntpd Created symlink from /etc/systemd/system/multi-user.target.wants/ntpd.service to /usr/lib/systemd/system/ntpd.service. [root@rhel7server1 ~]# systemctl start ntpd [root@rhel7server1 ~]# ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== +nets.org.sg .NMC1. 1 u 41 64 1 6.095 0.583 0.797 *time1.maxonline .GPS. 1 u 40 64 1 6.558 6.094 1.767 -time.cloudflare 10.35.14.16 3 u 39 64 1 10.726 8.551 4.313 +time.cloudflare 10.35.14.16 3 u 11 64 3 3.591 5.652 1.406 ## edit /etc/ntp.conf and comment out the following #server 0.rhel.pool.ntp.org iburst #server 1.rhel.pool.ntp.org iburst #server 2.rhel.pool.ntp.org iburst #server 3.rhel.pool.ntp.org iburst ## add the following special IP for the local clock on the local machine server 127.127.1.0 ## restart ntpd service and open firewall ports [root@rhel7server1 ~]# systemctl restart ntpd [root@rhel7server1 ~]# firewall-cmd --permanent --add-service=ntp success [root@rhel7server1 ~]# firewall-cmd --reload success [root@rhel7server1 ~]# ntpq -p remote refid st t when poll reach delay offset jitter ============================================================================== *LOCAL(0) .LOCL. 5 l 37 64 1 0.000 0.000 0.000 ## the server is now ready to provide NTP service to clients

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Synchronize Time Using Other NTP Peers - Peer with New time server



                         ## install the required packages

            

            [root@rhel7client1 ~]# yum install -y ntp

            

            

            ## edit /etc/ntp.conf, comment out the default NTP servers, add our NTP server

            

            #server 0.rhel.pool.ntp.org iburst

            #server 1.rhel.pool.ntp.org iburst

            #server 2.rhel.pool.ntp.org iburst

            #server 3.rhel.pool.ntp.org iburst

            server rhel7server1.myexample.com iburst

            

            

            ## enable and start ntpd service and open firewall ports

            

            [root@rhel7client1 ~]# systemctl enable ntpd

            Created symlink from /etc/systemd/system/multi-user.target.wants/ntpd.service to /usr/lib/systemd/system/ntpd.service.

            

            [root@rhel7client1 ~]# systemctl start ntpd

            

            [root@rhel7client1 ~]# firewall-cmd --permanent --add-service=ntp

            success

            

            [root@rhel7client1 ~]# firewall-cmd --reload

            success

            

            

            ## check NTP peer status

            

            [root@rhel7client1 ~]# ntpq -p

            

                 remote           refid      st t when poll reach   delay   offset  jitter

            ==============================================================================

             rhel7server1.my LOCAL(0)         6 u    1   64    1    0.407    0.011   0.013

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