==Install NTP==

<pre>
sudo apt-get update
sudo apt-get install ntp
</pre>

==Config NTP Server==

Edit /etc/ntp.conf file, below is a real sample:

<pre>
# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for help

driftfile /var/lib/ntp/ntp.drift
logfile /var/log/ntp.log


# Enable this if you want statistics to be logged.
#statsdir /var/log/ntpstats/

statistics loopstats peerstats clockstats
filegen loopstats file loopstats type day enable
filegen peerstats file peerstats type day enable
filegen clockstats file clockstats type day enable

# Specify one or more NTP servers.

# Use servers from the NTP Pool Project. Approved by Ubuntu Technical Board
# on 2011-02-08 (LP: #104525). See http://www.pool.ntp.org/join.html for
# more information.
#server 0.ubuntu.pool.ntp.org
#server 1.ubuntu.pool.ntp.org
#server 2.ubuntu.pool.ntp.org
#server 3.ubuntu.pool.ntp.org

broadcast 224.0.1.1 minpoll 3, maxpoll 4

# Use Ubuntu's ntp server as a fallback.
#server ntp.ubuntu.com
server 127.127.1.1
fudge  127.127.1.1 stratum 10
# Access control configuration; see /usr/share/doc/ntp-doc/html/accopt.html for
# details.  The web page <http://support.ntp.org/bin/view/Support/AccessRestrictions>
# might also be helpful.
#
# Note that "restrict" applies to both servers and clients, so a configuration
# that might be intended to block requests from certain clients could also end
# up blocking replies from your own upstream servers.

# By default, exchange time with everybody, but don't allow configuration.
restrict -4 default kod notrap nomodify
restrict -6 default kod notrap nomodify

# Local users may interrogate the ntp server more closely.
restrict 127.0.0.1
restrict ::1

# Clients from this (example!) subnet have unlimited access, but only if
# cryptographically authenticated.
restrict 192.168.0.0 mask 255.255.0.0 trust

# If you want to provide time to your local subnet, change the next line.
# (Again, the address is an example only.)
# broadcast 255.255.255.255

# If you want to listen to time broadcasts on your local subnet, de-comment the
# next lines.  Please do this only if you trust everybody on the network!
disable auth
#broadcastclient
</pre>

Edit /etc/ntp.conf

Start/Stop/Restart NTP daemon
/etc/init.d/ntp start/stop/restart

<pre>/sbin/route add -net 224.0.0.0 netmask 240.0.0.0 eth0</pre>

==Config NTP Client==

Edit /etc/ntp.conf file, below is a real sample:

<pre>
#server 0.pool.ntp.org iburst
#server 1.pool.ntp.org iburst

tinker panic 0
interface listen eth0

restrict default kod nomodify notrap
restrict -6 default kod nomodify notrap

restrict 127.0.0.1
restrict -6 ::1
multicastclient 224.0.1.1
disable auth
logfile /var/log/ntp.log
</pre>

View NTP server list
<pre>
root@arm:~# ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*192.168.11.240  LOCAL(1)        11 m    4    8  376   41.552   -3.044   0.289
+192.168.101.11  LOCAL(1)        11 m    4    8  376   58.331    5.223   0.296
</pre>