NTP Commands

ntp_commands

# Install NTP from ubuntu repository
>> sudo apt-get install ntp

# View all the NTP master and their offset recieved
>> ./ntpd -p

# Exactly like the above command but with no ip address rather then name
>> ./ntpd -n

# Query a NTP master server
# This makes 4 request to the server before 
# calculating and updating the system clock.
>> ./ntpdate -q boss.isi.deterlab.net
   server 192.168.252.1, stratum 2, offset 0.000148, delay 0.02594
   8 Nov 11:15:49 ntpdate[30431]: adjust time serve

>> sudo tcpdump -i eth0 port 123
   11:15:43.555820 IP pc52.isi.deterlab.net.37713 > boss.isi.deterlab.net.ntp: NTPv4, Client, length 48
   11:15:43.556260 IP boss.isi.deterlab.net.ntp > pc52.isi.deterlab.net.37713: NTPv4, Server, length 48
   11:15:45.555797 IP pc52.isi.deterlab.net.37713 > boss.isi.deterlab.net.ntp: NTPv4, Client, length 48
   11:15:45.556166 IP boss.isi.deterlab.net.ntp > pc52.isi.deterlab.net.37713: NTPv4, Server, length 48
   11:15:47.555793 IP pc52.isi.deterlab.net.37713 > boss.isi.deterlab.net.ntp: NTPv4, Client, length 48
   11:15:47.556152 IP boss.isi.deterlab.net.ntp > pc52.isi.deterlab.net.37713: NTPv4, Server, length 48
   11:15:49.555797 IP pc52.isi.deterlab.net.37713 > boss.isi.deterlab.net.ntp: NTPv4, Client, length 48
   11:15:49.556205 IP boss.isi.deterlab.net.ntp > pc52.isi.deterlab.net.37713: NTPv4, Server, length 48