[ntp:questions] "Oneshot" time sync without risk of jumping time?

Manuel Reimer Manuel.Nulldevice at nurfuerspam.de
Sun Apr 27 08:49:08 UTC 2014


Hello,

I want to keep the time updated on a small Embedded Linux device.

The clock doesn't have to be very accurate. An offset of a few seconds 
is OK.

This small device only has Internet for a few minutes a day and I have 
to pay for each byte that gets transmitted, so I want to keep the 
traffic low.

My idea to solve this was to run "ntpd -xq" as soon as I have 
established my Internet connection.

The problem with this is that the time jumps if the difference is above 
600s.

The documentation about the "-g" option says that there is a "panic 
threshold" which is 1000s "by default". What does "by default" mean? 
Does this mean that this value is configurable? If so: How?

What I want ntpd to do is to exit with error status if the time 
difference is above the 600s limit. I don't want it to set the time 
forcefully (jumping time) as this may cause trouble with cronjobs 
running on the device.

Greetings,

Manuel



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