Ever noticed how a clock may not have the exact right time? Like it’s close, but not there? The same thing can happen with a computer. It relies upon its internal clock, but that can be almost, but not quite, right. Luckily, there’s a protocol to fix that (the unofficial motto of the Internet) called Network Time Protocol.

This lets you automatically make sure the clock on your computer is set to the right time. This is really important if you have many computers working together. Kind of like Tony Stark’s drones in the Age of Ultron movie. Suppose he sent them after Ultron but the clocks are all just a little bit off. Instead of blasting Ultron all at once, you’d get one shot, a few minutes later another, and then another, and.. see? that’s not a good thing. You want one BLAST to take Ultron (and HIS drones) out.

So, how does it work? To begin with, you have a really accurate clock, something like an Atomic Clock. That has an awesome name, right? Sounds like something used in a Doomsday weapon to make sure that no one can stop it, except maybe Super Man. It’s one of the most accurate clocks known, so that’s a good thing to ask.

There’s computers that synchronize directly to the clocks, so those are a good thing to ask too. Generally, there’s a list of servers on your system that your system will synchronize to. Network Time Protocol is designed to use the list and say ‘yo, other computer, tell me what time it is’ and then adjust your computer if it’s off.

The list of servers is kept in the file ntp.conf which is generally located at /etc/ntp.conf. Let’s look at it:

# /etc/ntp.conf, configuration for ntpd

driftfile /var/lib/ntp/ntp.drift
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


# You do need to talk to an NTP server or two (or three).
#server ntp.your-provider.example

# pool.ntp.org maps to more than 300 low-stratum NTP servers.
# Your server will pick a different set every time it starts up.
#  *** Please consider joining the pool! ***
#  *** <http://www.pool.ntp.org/join.html> ***
server 0.debian.pool.ntp.org iburst
server 1.debian.pool.ntp.org iburst
server 2.debian.pool.ntp.org iburst
server 3.debian.pool.ntp.org iburst

There’s lots of information in there. The important part is the names after that word server. This computer uses servers by the name of 0.debian.pool.ntp.org 1.debian.pool.ntp.org, 2.debian.pool.ntp.org and 3.debian.pool.ntp.org to keep the time straight. This means that if one of those isn’t available, the Network Time Protocol will ask one of the other ones.
One of the interesting facts about the Network Time Protocol is that it’s one of the oldest protocols on the Internet. People have been trying to keep the times synchronized on their computers as long as they’ve been able to talk to other computers.