- In this video,
I want to talk about NTP.
NTP is the network time protocol
and NTP plays an important role in Linux.
Because from NTP you will typically manage your system time.
That's a time that is maintained by your operating system
about which we have talked before.
In order to synchronize your system time,
Linux knows different NTP services.
Chrony is one of the fundamental services.
Apart from that,
there is systemd-timesyncd.
Both are fulfilling the same role,
and they get their time from the internet.
To determine the trustworthiness of a NTP time server
that they are going to synchronize with,
NTP uses the notion of stratum.
The stratum explains the reliability of an NTP time server.
And stratum goes from 1 all the way up to 16,
where 16 means do not use
and 1 means the most reliable time server.
Now what is going to happen
if your chrony is getting the time
from a time server that has stratum 1?
Well then chrony knows
that it's the highest level of reliability
and it will most likely choose
to synchronize with that specific time server.
In a time server's configuration
you typically will work with different time sources.
So you might find that chrony
is getting the time from three different time servers,
one of them having stratum 1,
the other ones having stratum 3.
So chrony definitely
is going to synchronize with the stratum 1.
And as a result,
your NTP stack on your system will get stratum 2.
And that allows you to determine
the trustworthiness of time services and time sources
in an internet environment.
The chrony utilities even allows you
to figure out which stratum currently is used,
and you'll learn about these next.