[ntp:questions] debugging strange ntp in virtual environment

unruh unruh at invalid.ca
Thu Sep 19 00:34:08 UTC 2013


On 2013-09-18, Riccardo Castellani <ric.castellani at alice.it> wrote:
> My NTP server has strange problem and my clients cannot update their time 
> clock.
> My NTP server is Linux and NTP version is 4.2.0.a

That is really really really old.

> This NTP server is a virtual machine (by P2V) but few months ago it was 
> working fine.

Time control on a virtual machine is in general terrible. You should be
having the underlying OS running ntp and having your virtual OS getting
the time from that underlying OS.

> My clients get following msg when I run ntpd daemon: 'no server suitable for 
> synchronization found'
> In client 'A' I run this command 'ntpq -pn' :
>
>      remote           refid      st t when poll reach   delay   offset 
> disp
>==============================================================================
>  myntpserver    0.0.0.0         16 u   29   64    0     0.00    0.000 
> 16000.0
>
>
> In client 'B' I run this command 'ntpq -pn' :
>      remote           refid      st t when poll reach   delay   offset 
> disp
>==============================================================================
> myntpserver    83.84.69.80     16 u   38   64    0     2.78  -758.11 16000.0
>
> In NTP server 'ntpq -pn' shows:
>
>      remote           refid      st t when poll reach   delay   offset 
> jitter
>==============================================================================
> *193.204.114.232 .CTD.            1 u   22   64  375   20.863  -672.31 
> 232.744
> +193.204.114.233 .CTD.            1 u   22   64  377   20.846  -884.47 
> 178.639
> +193.79.237.14   .PPS.            1 u   17   64  377   26.264  -819.79 
> 181.462
> x192.93.2.20     .GPSi.           1 u   16   64  377   32.996  -1039.3 
> 262.130
> +131.188.3.221   .DCFp.           1 u   22   64  377   42.731  -818.20 
> 179.726
>
> I reset drift file, I restarted daemon but 'offset' value increases in few 
> hours until to be 800-1000.
>
> In NTP server 'ntpq -c rv' shows:
>
> assID=0 status=c6f4 sync_alarm, sync_ntp, 15 events, event_peer/strat_chg,
> version="ntpd 4.2.0a at 1.1196-r Fri May 12 09:51:35 EDT 2006 (1)"?,
> processor="i686", system="Linux/2.6.11-1.1369_FC4smp", leap=11,
> stratum=16, precision=-18, rootdelay=0.000, rootdispersion=197.910,
> peer=18845, refid=STEP,
> reftime=00000000.00000000  Thu, Feb  7 2036  7:28:16.000, poll=6,
> clock=0xd5e45b57.a691d9b1, state=2, offset=0.000, frequency=0.000,
> noise=775.898, jitter=238.455, stability=0.000
>
>
> I installed another server (this time physical server) in the same lan, 
> configured in the same way, same ntp version and it works fine!!!
> It's physical server, unique difference ! Clients can update time from 
> physical server and no update from the virtual server !

Remember that virtual servers have little control over the hardware, and
get time at the whim of the underlying OS. Thus their system clocks need
not be running at all regularly and they could have drift rates that are
way outside of ntpd's range (500PPM) in which case ntpd will just give
up. 


>
> In physical server  'ntpq -pn' shows:
>
>      remote           refid      st t when poll reach   delay   offset 
> jitter
>==============================================================================
> *193.204.114.232 .CTD.            1 u  216  512  335   22.177   -4.268 
> 0.244
> +193.204.114.233 .CTD.            1 u   98  512  331   20.756   -4.873 
> 0.351
> -131.188.3.221   .DCFp.           1 u  201  512  335   49.258  -12.984 
> 2.276
> +193.79.237.14   .PPS.            1 u  203  512  335   27.570   -5.418 
> 1.051
>
> In physical server 'ntpq -c rv' shows:
>
> assID=0 status=0644 leap_none, sync_ntp, 4 events, event_peer/strat_chg,
> version="ntpd 4.2.0a at 1.1196-r Fri May 12 09:51:35 EDT 2006 (1)"?,
> processor="i686", system="Linux/2.6.11-1.1369_FC4smp", leap=00,
> stratum=2, precision=-17, rootdelay=22.177, rootdispersion=35.682,
> peer=64524, refid=193.204.114.232,
> reftime=d5e45b36.ce35610a  Wed, Sep 18 2013 19:02:46.805, poll=9,
> clock=0xd5e45c4d.f6807bbb, state=4, offset=-4.293, frequency=8.223,
> noise=0.823, jitter=0.951, stability=40.108
>
>
> Can you help me to debug my problem 



More information about the questions mailing list