[ntp:questions] How can i make sure that how much time ntp is adjusting one day

[David Woolley]

i enable the ntp, how can end of the day i can get the total time which ntp adjusted.

NTP adjusts frequency, not time. It doesn't predict what the internal
clock would show if it hadn't been adjusted

when i execute ntpstat command i can see following output
synchronised to NTP server (169.254.169.123) at stratum 4
time correct to within 9 ms
polling server every 8 s

I'm not sure what is being measured to produce the 9ms figure. It seems
suspiciously
low for a good estimate of the error bounds for a such a high stratum
client.

If you are polling the server every 8 seconds you have overridden the
default settings in a way that is not recommended, is likely to cause
sub-optimal time keeping, and is likely to get you blacklisted by many
servers.

[William Unruh]

Hi,
I am facing time drifting problem in my production env.
I install ntp on my linux server and configure that.
i enable the ntp, how can end of the day i can get the total time which ntp adjusted.
when i execute ntpstat command i can see following output
synchronised to NTP server (169.254.169.123) at stratum 4
time correct to within 9 ms
polling server every 8 s

That poll interval is really short, and if you are getting the time from a
server that you do not control, they could get really really annoyed with you
and cut you off.

That is a link local address, so I do not know what it is you are using as a
server. Could you post your ntp.conf file.

is there is anything need to do.

Use a decent server?

Please help.

[Mike Cook]

Post by William Unruh

Hi,
I am facing time drifting problem in my production env.

When face with this or any problem you should measure it BEFORE applying corrections. I have seen many admins just add NTP, only to find that the clock drift was too great to be corrected by NTP.
NTP will bail out if it finds a drift of over 500ppm.
Check the value measured before correcting and see if it is within the server manufactures clock spec. You may have a bad board or need a firmware update.
It may also depend on the hardware context. Is your prod running in a stand alone server or is it in a virtual environment (container). There are tight constraints for running time critical stuff in containers.
Maybe your server is modifying its cpu clock frequencies depending on load. You will need to check and stop that.

Post by William Unruh

I install ntp on my linux server and configure that.
i enable the ntp, how can end of the day i can get the total time which ntp adjusted.

As said by others , NTP alters the clock frequency rather than setting the clock (unless way out).
If you run « ntpq -c rv » you will see a variable labeled « frequency » which gives the clock drift that NTP is correcting for at any one time.
The best way to evaluate this over long periods this is to enable stats logging and graph the loopstats drift frequency data.

Post by William Unruh

when i execute ntpstat command i can see following output
synchronised to NTP server (169.254.169.123) at stratum 4
time correct to within 9 ms
polling server every 8 s

That poll interval is really short, and if you are getting the time from a
server that you do not control, they could get really really annoyed with you
and cut you off.
That is a link local address, so I do not know what it is you are using as a
server. Could you post your ntp.conf file.

is there is anything need to do.

Use a decent server?

Please help.

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[Jakob Bohm]

here is my ntp.conf file.
.......
and destination ip is (169.254.169.123)
I am using ntp on my aws ec2 instance.

The IP address 169.254.169.123 is an IANA reserved non-routable internal one.
Is this address one that is local to your Amazon EC2 instance region and
ntpq -c as
Does the billboard show that address as reachable?
Tom

FYI Amazon EC2 uses the non-routable network 169.254.169.0/24 for
services local to each datacenter, or even to smaller subdivisions. So
this is probably an extremely local Amazon time server.

That said, the Amazon part of the pool also contains servers not on that
subnet (I tried a DNS lookup from one of my own EC2 instances, and it
gave back routable IPs).


Enjoy

Jakob