NTP stands for Network Time Protocol, and it is an Internet protocol used to synchronize the clocks of computers to some time reference.

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Anyone else experiencing high rates of Linux server crashes during a leap second day?

*NOTE: if your server still has issues due to confused kernels, and you can't reboot - the simplest solution proposed with gnu date installed on your system is: date -s now. This will reset the ...
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Windows Server unable to synchronize NTP time reliably

Why does Windows Server (2008, in this case, but I've seen the same problem in 2003) seem to have problem synchronizing time? I've seen this error in my System log across a variety of servers: The ...
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12answers
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Is anyone using GPS for time sync?

I've come across a handful of GPS NTP servers, as well as some inexpensive solutions using off-the-shelf receivers and software. Right now I'm just using NTP with a list of servers over the Internet. ...
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Risk of starting NTP on database server?

I've heard rumors of bad things happening to database and mail servers if you change the system time while they are running. However, I'm having a hard time finding any concrete information on actual ...
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Should servers have their timezone set to GMT/UTC? [closed]

This may not be a big deal for smaller shops that only have one or a few site, but for larger organizations this is something I'm curious about. What are the pros and cons have having all/most of ...
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Compare NTPD and ntpdate

What are the pros and cons between these two ways to synchronize your server? It seems to me that your server would probably not drift more than 1 second every day, so ntpdate on a crontab would be ...
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What is NTP dispersion and how do I control it?

We roll out Ubuntu 14.04 servers on isolated networks, running ntpd 4.2.6p5, configured to use multiple NTP servers as provided by customers (no access to pool.ntp.org). Our dumb terminal client ...
16
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3answers
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How can I compare an ntp server's time to my server's time?

I have ntpd running on a box. I want to see how the time on the box compares to the time retrieved from ntp.ubuntu.com. Is there an easy way to do this?
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questionable timeservers in pool.ntp.org?

I've noticed that, after changing the reg settings outlined in Episode 52 of the Stack Overflow podcast to pool.ntp.org, my box keeps requesting time from gordo.foofus.net. The web site hosted on that ...
13
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2answers
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Why does ntpd listen on so many ports/addresses?

I’ve noticed this for a while, and it’s never made any sense to me: Why does ntpd need to listen on so many addresses? For example, a Debian machine: $ netstat Proto Local Address Foreign Address ...
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Dealing with NTP reflection attacks in IPTables

We're dealing with an NTP reflection / amplification attack at our colocated servers. This question is specific to responding to NTP reflection attacks, and not directed at DDoS in general. Here's ...
13
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2answers
671 views

What can be done to improve time synchronization on networks with sporadic internet access?

I'm looking for advice setting up time servers for a very non-typical network. I support many closed networks that have occasional access to the internet. A network would get access most days for a ...
12
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What are the limits of running NTP servers in virtual machines?

I want to set up several Stratum 2 time servers on my local network. Virtual machines would certainly be a cheaper way to do this than buying three 1U servers. What limitations would doing so impose? ...
12
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7answers
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Why is ntpd not updating the time on my server?

I have ntpd running on my server. It's all the default settings, except I commented out its ability to be a server to other machines: # restrict -4 default kod notrap nomodify nopeer noquery ...
12
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2answers
809 views

Linux kernel detecting wrong processor frequency

After a cold boot of a 6.0.8 Debian server (HP ProLiant), ntpd played havoc with system time: offset and jitter with respect to the usual and reliable reference time servers growing without limit. (...
11
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Do I need to run a NTP server in every VM?

Couldn't the guests somehow inherit the system time of the host ? It seems kind of pointless to run the same daemon to get the same results on the same machine multiple times but I didn't find ...
10
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Replacing sick NTP server source and re-synching (with internal time currently 2 minutes late)

One of the external NTP servers (the primary one--currently) we're using as source seems to not be responding to NTP calls. Unfortunately, on our core router (Cisco 6509), the NTP functionality hasn'...
10
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Why not use vmware tools for time synchronisation?

We have two VMWare environments running a bunch of (mainly) Redhat 5.9 and 6.4 guests. We are having issues with time drift (minutes ahead per week). We use ntp, syncing to the local domain controller....
10
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NTP is running, system clock still not in time - what gives?

A Debian Stable (5.0.3) server is running ntpd, and connected to the internet. Still, the system clock is about 5 minutes wrong. $ /etc/init.d/ntp status NTP server is running.. Relevant parts (I ...
10
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2answers
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why doesn't ntp recover after an Internet-less startup?

I have a few Linux devices (without TOY chips, so they completely rely on ntp) which may boot without access to Internet (the link to the switch is up). The ntp service will start but obviously no ...
10
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2answers
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ntpdate and ntpd failing to sync clock on Linux

I have a strange problem with one of my servers. ntpd and ntpdate fail to work, but debugging shows no errors at all. At first I thought maybe a local or network firewall was blocking UDP port 123, ...
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Time drift

How do you deal with server time drift?
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What is the strategy for detecting time drift in a linux based data centre?

What is the strategy for detecting time drift in all linux based data centre? This is a more difficult problem than it seems at first. Time drift can cause serious problems for certain applications ...
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Vmware host time drift

How does one ensure that linux hosts, running on vmware infrastruction 3 or vmware 3 esxi remain in sync with the ntp server. I have found that a linux guest running under esx or esxi has a tendency ...
9
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4answers
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How to set a frequent period for NTP client to sync with the NTP server

I've setup an NTP client for my DC to sync time with time.windows.com but I want it to query the NTP server at least twice a day. I made all the changes via the registry, is there a period registry I ...
9
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ntpdate -d Server dropped Strata too high

I cannot sync with a NTP source thats coming from an internal router/firewall. Anyone help ? ntppdate -d 192.168.92.82 6 Jun 11:57:30 ntpdate[5011]: ntpdate 4.1.2@1.892 Tue Feb 24 06:32:26 EST ...
9
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Linux ntpd leap second preparation

There will be a leap second on June 30, 2015 at 23:59:60 UTC. I have a Linux based stratum 1 NTP server which uses GPS as a reference clock. The server is using the "default" ntp.org ntpd. How ...
8
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Local or public NTP servers?

For a relatively large network (thousands of hosts) - what are the arguments for and against running a locally managed (pool of) NTP server(s) (perhaps periodically set via some public NTP server) and ...
8
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Managing multi-timezone servers

What would be an ideal time and timezone setup for multi-country servers? Especially considering one central IT team managing these servers. Currently we have each server using a local timezone. e.g. ...
8
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448 views

Proper NTP configuration for a few servers

I have about 20 Linux servers in a small network and I need their clocks decently close to each other (e.g. within 20msec). I've started with every one of them synced to europe.pool.ntp.org and the ...
8
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3answers
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Is there research material on NTP accuracy available?

As far as I know, accuracy of NTP syncronization highly depends on the network. I've seen some numbers from 50 microseconds to a "below one second" over the internet. Well, this is a huge difference. ...
8
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Hyper-V Machine drifts time all over, even with NTP

Resolved The problem was Hyper-V on that machine. I removed Hyper-V, installed VMware Server, ran the same VM. Time sync issues went away (< 100ms difference after a day). My setup is like this: ...
8
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555 views

Best choice for NTP client configuration

Lets see if someone can throw a bit of light on this subject.. I'm making a server installation in the next days. My client wants to deploy a Hortonworks HDP with 2 servers as master servers and 5 ...
8
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0answers
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How come one of my switches is off by two minutes in spite of ntp?

I just noticed by pure chance that one of my Cisco 4500 switches has its clock going wrong: it is more than 2 minutes behind in spite of seemingly functional ntp. In my opinion, even a single second ...
7
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5answers
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Accurate, Unspoofable Time Source

I need an unspoofable and accurate time source. Short of setting up my own atomic clock (unless that's easier than it sounds) how could I accomplish this? It's not that I don't trust the NTP pools;...
7
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Domain Controller time is incorrect

I have a domain controller running in VM on Hyper-V, the time seems to be steadily getting faster, over the X-mas period it's 5 faster, which seems odd! I know how to change the time and I belive we ...
7
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Does NTP daemon set the host timezone?

If I am using NTP daemon or ntpdate command, do I need to worry about changing the timezone? Should I re-configure the timezone using cron job to guarantee the accuracy of the server time? I am ...
7
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4answers
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Why is NTP syncing to LOCAL rather than remote server?

So, I'm trying to debug my current NTP setup, and found that he offset from my single configured server is over 3 seconds, and not adjusting. The asterisk on the LOCAL(0) in the ntpq output seems to ...
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NTP Server with no connection to the internet

I have a small LAN that has no connection to the internet. It consists of two ubuntu servers clustered together providing NFS services to two IP cameras. I need to synchronize the time on all the ...
7
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What are the disadvantages of disabling tinker panic 0 in NTP?

We sometimes have the problem that new servers have the wrong time in the bios, so there time can be off by a month. When you suspend a VM in VMware and then unsuspend it, the time will be off too. ...
7
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1answer
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Single NTP server on isolate network

I have two linux machines (A and B) on an isolated network. They must be time-synchronized. Machine A is powered intermittently and must serve the time, as it is connected to an authoritative time ...
7
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2answers
545 views

DST Morocco, a way to trick NTP server

From several years Morocco have been using GMT without DST, in the past years, our government reactivated the use of DST. In the first years, the DST was a mess, different periods, starts, ends, so ...
7
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How to make NTP work despite a high offset?

Recently I have kickstarted some servers that had their time off by a month in the bios. The time in the bios said it was a random time/date in May, while it was June. This caused NTP not to work, ...
7
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1answer
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How well will ntpd work when the latency is highly variable?

I have an application where we are using some non-standard networking equipment (cannot be changed) that goes into a dormant state between traffic bursts. The network latency is very high for the ...
7
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1answer
2k views

Why should I care about NTP Kernel statistics?

I'ved noticed that munin graphs a few bits of information about timing/kernel statistics that I've never quite understood. Most of my servers seem to stay close to 0, which I presume is good, but one ...
7
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When should NTPd broadcast/broadcastclient be used instead of client/server or peer modes?

The NTP deamon if often used in its simplest mode, which is client/server: you specify one or more server directives in your ntp.conf and your clients will use those servers. In addition to that, ...
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Public NTP servers

Is there a list of public NTP servers on the internet I can use.
6
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How to configure ntpd to sync time more frequently?

I need to set ntpd to sync time as often as possible, how to do that? UPD I need to make ntpd adjust system clock more frequently, not poll servers. It's necessary because system clock of my virtual ...
6
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ESXi VM NTP Server

We need to setup an internal NTP server. Because this server will pretty much ONLY be a time server I was thinking of just creating a VM for it. However, Googling around it appears that there there ...
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What is a realistic average time difference between servers in the same LAN?

Until recently, we had at work a small cluster of about 20 small Windows servers (which have now all been virtualized). They were all configured to synchronize with the local time server. It was on an ...