State of the microserver HOWTO

Gary E. Miller gem at
Tue Jun 7 21:52:27 UTC 2016

Yo Frank!

Good input, net ntp.conf below.

On Tue, 7 Jun 2016 17:04:21 -0400
Frank Nicholas <frank at> wrote:

> > On Jun 7, 2016, at 4:52 PM, Gary E. Miller <gem at> wrote:
> > 
> > peer maxpoll 5 # catbert
> > peer maxpoll 5 # pi2
> > #peer maxpoll 5 # pi3
> > peer maxpoll 5 # kong
> > peer maxpoll 5
> > peer [2001:470:e815::8] maxpoll 5 # spider  
> You are using IP addresses, instead of names resolved by DNS.

I never use DNS in the ntp.conf file.  Well, maybe in the case
I try out the pool.  Since I use DNSSEC on my DNS, there is sortof
a chicken and egg problem.

> This
> might confuse some.

Clearly, the second complaint today on this list.

I really want to include some local peers to demonstrate the ARP

>  Maybe either explain the logic or change the
> conf file to use DNS resolved names.  Most of the How To users will
> not/should not be using IP addresses - they won’t know what ones to
> use or why and won’t have other “local” sources to use.

I just added a section on the pool.

But remember, Eric asked for MY config, not what I think others should be
using.  I would hope we get a collection of slightly different ntp.conf
that are optimimized for different purposes, or levels of paranoia.

Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
	gem at  Tel:+1 541 382 8588

# My RasPi 2/Adafruit HAT config.
# contributor: Gary E. Miller <gem at
# date: 7 June 2016

# /etc/ntp.conf, configuration for ntpd; see ntp.conf(5) for more help

# This configuration uses the shared-memory refclock (28), which is
# assumed to have gpsd on the other end.  Unit 0 is the in-band data,
# Unit 1 the PPS.

# I have a number of other GPS based chimers on my local network.  This
# configuration peers with them so I can compare their performace.

# for best performance, start ntpd last.  First start gpsd, and confirm 
# you have a good GPS # lock, Then confirm gpsd is supplying time to the 
# SHM interface.  Then you can start ntpd.

# I start gpsd this way:
#       # gpsd -n /dev/ttyAMA0
# check for GPS 3D fix this way:
#       # cgps
# check the SHM for good time:
#       # ntpshmmon
# Then start NTP
#       # ntpd -N -g

# save the clock drift when shutting down ntpd.
# this allows for faster NTP reconvergence after a restart
driftfile /var/lib/ntp/ntp.drift

# You want some logging, it will be useful later.
# If you add the logging now, then you have the data when you figure
# out you want it.  If you wait until you want it then it is too late.  

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

logfile /var/log/ntpd.log  
logconfig =syncall +clockall +peerall +sysall

# we want some security
# do not let random people remotely modify your ntpd server
restrict default nomodify notrap nopeer noquery
restrict -6 default nomodify notrap nopeer noquery
# allow access from localhost, IPv4 and IPv6
restrict mask
restrict -6 ::1
# replace this with your local IPv4 network
restrict mask
# replace this with your local IPv6 network
restrict -6 [2001:470:e815::]/64

# The order of servers and peers in ntp.conf matters.
# On startup ntpd will take the first time it gets to set the system
# clock. If this first time is an imprecise clock, say derived from
# NMEA, then ntpd may takes days to restabilize.
# The first time ntpd acquires will tend to be the ones higher up in
# the file with the lowest maxpoll.
# So to work around this ntpd glitch put your best time sources high
# in the ntp.conf file, with your shortest maxpoll and your worst one
# at the bottom with higher maxpolls.
# A bug is open for this behavior:

# PPS is first, it is the most precise.
# SHM for PPS and gpsd
server prefer minpoll 4 maxpoll 4
fudge refid PPS

# My other local chimers, just in case the GPS loses signal, and
# for comparison

# If you do not have any other chimers on your local network then you
# can skip this section on local peers.  Proceed to the section on 
# using the pool

# The default APR timeout on Cisco switch gear may be as long as
# 4 hours.  On windows and Linux it may be as short as 60 seconds.
# If the polling interval for a chimer is greater than 60 seconds (maxpoll 6+)
# then when ntpd sends a time request to a remote ntpd daemon the OS may
# be adding an ARP roundtrip to the process, delaying the return
# by that much extra time.  This convinces ntpd that the remote ntpd
# is further away, and has more jitter, than it actually does.
# To prevent this glitch in ntpd behavior, be sure to use 'maxpoll 4' or
# 'maxpoll 5' on servers and peers on the local network.
# Maybe ntpd should fix maxpoll at 4 or 5 for local peers?

# Notice that I do not use DNS names for my local chimers, only IP numbers.
# I do not want my NTP dependent on DNS.  DNS requires a network
# connection and I do not want my NTP down during network outages, or
# because of any DNS failure. 
# I also use DNSSEC which requires accurate time. If my NTP depends on
# DNS, and my DNS depends on NTP that can cause problems.

peer maxpoll 5 # catbert
peer maxpoll 5 # pi2
#peer maxpoll 5 # pi3
peer maxpoll 5 # kong
peer maxpoll 5
peer [2001:470:e815::8] maxpoll 5 # spidey

# end of local peers

# if you have no other local chimers to help NTP perform sanity checks
# then you can use some public chimers from the NTP public pool:

# To use the pool servers uncomment the last four lines in this section.
# The iburst option tells ntpd to query the pool serers with bursts instead
# of single requests.  This can yield better results to remote servers.
# Notice I use the 'us' country code servers, otherwise I might get one
# pool server from Ukraine and another from Singapore.  If you are
# not in the USA, then change the 'us' to your two letter country code.
#  server iburst
#  server iburst
#  server iburst
#  server iburst

# NMEA is last, it is the least precise
# SHM for gpsd
server minpoll 4 maxpoll 4
fudge time1 0.450  refid GPS

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