[ntp:questions] rdate vs ntpd -q

unruh unruh at wormhole.physics.ubc.ca
Tue Mar 22 17:42:04 UTC 2011

On 2011-03-22, bombjack <bombjack99 at gmail.com> wrote:
> Hi,
> I am currently working on a commercial system which uses rdate for
> roughly setting time when booting/restarting. Later ntpd is started
> and used to keep time accurate. My question: Is it possible to get rid
> of rdate in favour of "ntpd -q"? Any risks involved? ntpd starting
> later and/or needs more time to sync than rdate etc?

??? why would you use rdate? Yes, ntp -q would do all rdate does and
with greater accuracy. rdate does not sync. ntpd -q does not sync. Both
determine the time from elsewhere and set the system clock to that time. 
Boom. But you can also start up ntpd and ask it to set the system time
immediately. It may then go on a big wander (10s of ms) while it hunts
for the right drift rate compensation. 
ntpd -q and rdate will both do absolutely nothing about the drift rate.
ntpd -g and the normal operation of ntp ( it steps the clock if it is
more than 128ms off) should do what you want anyway. 

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