[ntp:questions] ntpd -q and driftfile

Steve Kostecke kostecke at ntp.org
Wed Mar 23 11:51:36 UTC 2011

On 2011-03-22, bombjack <bombjack99 at gmail.com> wrote:

> I am fully aware fo how ntpd should be used, i.e. 24/7/365, but that
> is not what I am asking for. As I stated above, I need to make sure
> the system clock is roughly (your wrist watch would do) the correct
> time ASAP during boot as other systems will use this time and can't
> easily be changed later if time deviates too much when ntpd (later)
> has initial sync.

Then you really want to set the clock correctly the first time.

> I presume you are aware of that ntpd will take some samples/time
> before syncing and that is not good enough. therefore, I still wonder
> if ntpd -q could be used in favour of rdate?

My tests of 'ntpd -gq' (using 4.2.5*, IIRC) showed that under optimal
conditions* initial clock syncronization can be achieved in ~ 11 seconds.

* LAN time server, local DNS, "good" value in the drift file,
  warm restart of ntpd

If you just start ntpd with '-g' _and_ use 'iburst' on your server lines
_and_ have a "good" value in your drift file you should see initial
clock synchronization in ~ 20 seconds.

Is that not good enough?

Steve Kostecke <kostecke at ntp.org>
NTP Public Services Project - http://support.ntp.org/

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