[ntp:questions] Synchronizing contrived time

mike cook michael.cook at sfr.fr
Mon Mar 10 08:09:23 UTC 2014


Le 8 mars 2014 à 05:16, Amit Dor-Shifer a écrit :

> Hi.
> I'm wishing to setup some arbitrary time on host A, and have host B
> synchronize off A. I was considering ntp for that:
> 1. Set the desired time on A.
> 2. fire-up ntpd on A, but prevent it from synching against any external
> server.

 just use the local clock 127.127.1.x  for A's source. 
muon# cat /etc/ntp.conf
server 127.127.1.0 minpoll 4 maxpoll 4

  stop ntp on A
set the date manually
muon# date 8506131627
Thu Jun 13 16:27:00 CEST 1985
muon# /usr/local/bin/ntpd -c /etc/ntp.conf -p /var/run/ntpd.pid     or wherever you find it
muon# ntpq -pn
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*127.127.1.0     .LOCL.           5 l   12   16    1    0.000    0.000   0.008
muon# date
Thu Jun 13 16:32:29 CEST 1985

> 3. use an ntp client (ntpdate?) on B to sync to A's time.

> I'm stumbling on:
> a. the correct ntpd configuration on A.
> b. forcing B to sync off A: it seems the client drops the server,
> considering it as an unreliable source.

On B.

Mon Mar 10 08:51:42 CET 2014
rstop ntp if it is running on B 
Stopping NTP server: ntpd.
root at raspberrypi:/home/mike# date
Mon Mar 10 08:52:11 CET 2014
  get A's date
root at raspberrypi:/home/mike# ntpdate muon
13 Jun 16:29:10 ntpdate[20937]: step time server 192.168.1.4 offset -906917207.279748 sec
root at raspberrypi:/home/mike# date
Thu Jun 13 16:29:16 CEST 1985

  you can start ntpd on B. Just reference A in ntp.conf

root at raspberrypi:/home/mike# cat /etc/ntp.conf
server muon minpoll 4 maxpoll 4

 restart ntpd on B.

root at raspberrypi:/home/mike# /usr/bin/ntpd -c /etc/ntp.conf -p /var/run/ntpd.pid
root at raspberrypi:/home/mike# ntpq -pn
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
 192.168.1.4     LOCAL(0)         6 u    9   16    1    1.084   -4.010   0.002

 root at raspberrypi:/home/mike# date
Thu Jun 13 16:40:24 CEST 1985
root at raspberrypi:/home/mike# ntpq -pn
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*192.168.1.4     LOCAL(0)         6 u   10   16  377    1.013  -10.238   4.158

  So still running after 10 mins. 


> Guidance appreciated, tnx :)
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