NTP Server on Centos 6
1. Host Details :-
NTP server :- ntp.momagic.com 192.168.1.10
NTP client :- client.example.com 192.168.1.11
Note :- Both machine add ip and hostname in /etc/hosts file :-
# vim /etc/hosts
192.168.1.10 ntp.momagic.com
192.168.1.11 client.example.com
Note :- both machine Iptable and Selinux service is disabled.
2. Install NTP in both machine
:-
# yum install ntp
3. NTP Server side :-
# cp –rf /etc/ntp.conf
/etc/ntp.conf.bkp
# vim /etc/ntp.conf
i)
The drift file is used to store the
frequency offset between the system clock running at its nominal frequency.
driftfile
/var/lib/ntp/drif
restrict default kod nomodify
notrap nopeer noquery
restrict -6 default kod nomodify
notrap nopeer noquery
§ noquery :- prevents
dumping status data from ntpd.
§ notrap :- prevents control message trap service.
§ nomodify :- prevents
all ntpq queries that attempts to modify the server.
§ nopeer :- prevents
all packets that attempts to establish a peer association.
§ Kod :- Kiss-o-death packet is to be sent to reduce
unwanted queries
§ The value -6 in the second line allows
forces the DNS resolution to the IPV6 address resolution.
ii)
If the localhost needs to have the full access
to query or modify.
restrict 127.0.0.1
restrict -6 ::1
iii)
Only allow machines on your own network to
synchronize with your NTP server.
restrict 192.168.1.0 mask 255.255.255.0
nomodify notrap
iv)
NTP
Server synchronize below server with internet.
server 0.asia.pool.ntp.org iburst
server 1.asia.pool.ntp.org iburst
server 2.asia.pool.ntp.org iburst
server 3.asia.pool.ntp.org iburst
v)
if
the NTP server is disconnected from the internet, NTP server provides time from
its local system clock.
server
127.127.1.0
fudge 127.127.1.0 stratum 10
server
192.168.1.10 iburst
includefile
/etc/ntp/crypto/pw
keys
/etc/ntp/keys
logfile
/var/log/ntp.log
# service ntpd start
# chkconfig ntpd
on
# ntpq -p
4.
Client
side :-
# vim /etc/ntp.conf
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
server
192.168.1.10 prefer
includefile
/etc/ntp/crypto/pw
keys /etc/ntp/keys
logfile
/var/log/ntp.log
# service ntpd start
# chkconfig ntpd on
# ntpq –p
# ntpdate –u 192.168.1.10
5.
Add
Cron job :-
*/5 * * * * /usr/sbin/ntpdate
-u 192.168.1.10
