[PLUG] Linux Time?
Jim Garrison
jhg at jhmg.net
Sun Oct 22 01:30:11 UTC 2017
On 10/21/2017 5:12 PM, Dave Lien - W7DAL wrote:
> TNX Larry. I discovered that NTP is already present as part of the Mint
> 18.2 default installation. Can I assume from this that is probably
> active? Is there a simple command to determine it's status? -Dave.
Both ntpq and ntpdc will display the current status. The 'pe' command
displays the status of the peers.
[jhg at janus ~]$ ntpq
ntpq> hostnames no
ntpq> pe
remote refid st t when poll reach delay offset
jitter
==============================================================================
*152.2.133.53 .PPS. 1 u 549 1024 377 95.099 -3.895
2.996
+129.6.15.28 .NIST. 1 u 722 1024 377 96.811 2.228
5.503
-72.5.72.15 162.213.2.253 2 u 402 1024 377 30.709 5.615
1.761
+52.6.160.3 209.51.161.238 2 u 583 1024 377 90.134 1.960
1.645
This tells me that I'm synced (*) to 152.2.133.53, which is a
top-level "Stratum 1" time server, probably getting its time from GPS
or another atomic clock standard. It's just a hair over 95ms away and
currently my clock is 3.895ms behind it. Other candidates (+) are
129.6.15.28 and 52.6.160.3, while the outlier is 72.5.72.15, which
will not be used.
Synchronizing time is quite a complex and arcane topic, see
http://doc.ntp.org/ for more detail than you'll ever need to know.
When there is an offset, the local ntp daemon does not step the clock,
to prevent problems with software that might have a problem with
discontinuities (especially backwards discontinuities). Instead it
slightly adjusts the clock frequency to bring it slowly into sync.
The ntpdate utility is usually run once at bootup and DOES reset the
clock in one step if necessary, but ongoing sync is accomplished by
modulating the local clock frequency.
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