Ntp how long

If you need highly accurate time then you probably should spend time reviewing the official documentation on ntp. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.

Create a free Team What is Teams? Learn more. Asked 8 years ago. Active 3 years, 10 months ago. Viewed 10k times. Communities: Chinese Japanese Korean. All Rights Reserved. The Cisco Learning Network. Enterprise Certifications Community.

View This Post. Edited by Admin February 16, at AM. NTP Synchronization , How long it takes? Tube Jan 7 Zip time-based-acl-startup-configs. Download Download. Show more actions. What is the RPM package and how can I get sure that the ntpdate runs before ntpd? And for testing I made just a drift of 20 min to the current time.

You don't really need ntpdate. There's the fake-hwclock package already installed as a standard part of RPi distributions to get the clock correct to a reasonable approximation prior to NTP kicking in. My fake-hwclock is really close to the real time. Because when I put on the write access the fake-hwclock is updated before the Pi shuts down. So now is approx. Sign up or log in Sign up using Google.

Sign up using Facebook. Sign up using Email and Password. Post as a guest Name. Email Required, but never shown. The Overflow Blog. Does ES6 make JavaScript frameworks obsolete? Podcast Do polyglots have an edge when it comes to mastering programming Featured on Meta. Now live: A fully responsive profile. Linked 1. Related 2. Hot Network Questions. If you have sufficiently-motivating need for even better time stability, then relying exclusivelyl on internet time servers doesn't seem Not sure what you mean?

Is it the infomality of "shove" you object to? His hypothesis is that you can only measure the time offset to within a second. No idea why. Usually you do not run into either the PPM limit or the ms jumps. However, at a restart you can, especially if, as with the older Linux kernels, the rate changes by up to PPM between separate boots. A "jump" is an infinite rate.

Thus ntp says that it will only change rates by up to PPM except when it is infinity. Is that better than say removing that PPm limit and allowing the system to correct for up to say PPM the limit of the adjtimex function under Linux. Many now use say gps which can give better time stability than that, using ntpd.

Do you want to re-do the algorithmic analysis of everything NTP does to make sure that it behaves OK in all circumstances if you bump the limit to ppm? And what about kernels that do not currently allow changes to be applied at that rate? There are also the issues of if we should prepare for the case where the rate to advance the clock is different from the rate to retard the clock. I've long wondered about this - there are known needs for many folks to have a monotonic clock.

That means that forward jumps are OK. It means that it should be possible to allow the clock to step forward but slew backwards. We don't have a mode for this right now. But I think the better solution is one I've been thinking about for a while, where we have an "augmented" timestamp that includes a few more bits of information.

I"ll be talking more about this Later. Yup, but this discussion seems to be more about sites that don't have GPS units. Bill, The bottom of that page mentions ntp versions 4. In practice, even on a portable PC running Windows over Wi-Fi ntp is usually synced to within a few milliseconds as soon as the system is booted. That may be. I have not looked at the source code in a number of years.

It is not a hypothesis. It a human scale example, representative of simple use of digital watch without interpolation etc. No it doesn't. It is basically a feedback controller. If you take a modern central heating controller, which varies the output by varying how much of a ten minute cycle the pump is running, you have something similar to version 3 ntpd, except that it used 4 seconds. The central heating controller will use the measured difference from the target temperature to adjust the on to off proportion, and also include some of the integral of that, to, eventually, remove any remaining offset.

A fitting process would be more like the controller measuring the rate of temperature change when the heat was off, and when it was on, and then calculating exactly how much on to off time to apply in one go.