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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31
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4answers
14k views

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 ...
27
votes
12answers
8k views

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. ...
17
votes
10answers
16k views

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 ...
16
votes
7answers
8k views

Should servers have their timezone set to GMT/UTC?

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 ...
13
votes
12answers
3k views

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
votes
2answers
487 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
votes
2answers
2k views

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 ...
10
votes
2answers
172 views

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
votes
2answers
247 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. ...
9
votes
9answers
5k views

Time drift

How do you deal with server time drift?
9
votes
2answers
534 views

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 ...
9
votes
10answers
3k views

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
votes
6answers
565 views

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 ...
9
votes
4answers
3k views

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? ...
9
votes
3answers
987 views

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 ...
8
votes
6answers
706 views

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 ...
8
votes
3answers
235 views

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
votes
3answers
2k views

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 ...
8
votes
4answers
13k views

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 ...
8
votes
7answers
45k views

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 ...
8
votes
2answers
4k views

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, ...
7
votes
3answers
907 views

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
votes
1answer
1k views

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 ...
6
votes
3answers
5k views

Public NTP servers

Is there a list of public NTP servers on the internet I can use.
6
votes
6answers
7k views

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 ...
6
votes
7answers
3k views

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 ...
6
votes
3answers
5k views

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 ...
6
votes
7answers
12k views

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: ...
6
votes
3answers
192 views

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, ...
5
votes
4answers
4k views

openwrt: Use rdate with NTP servers?

I've noticed that some embedded devices (such as OpenWRT, which runs on Busybox) use rdate to set the system time, instead of NTP. Rdate is an older time protocol, and I'm having trouble finding any ...
5
votes
3answers
2k views

DDOS using ntp server

I've heard about new kind of DDOS where ntp is used for reflection . My questions are really simple : Can you please give details on how they work and clarify? Since ntp is ran over UDP, I suppose ...
5
votes
2answers
1k views

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 ...
5
votes
3answers
218 views

Is an ntpdate correction atomic?

I've got the following in /var/log/syslog, from yesterday (July 30th) Dec 16 22:54:05 omap ntpdate[432]: step time server 91.189.94.4 offset 12052648.821465 sec ntpdate 91.189.94.4 "corrected" my ...
5
votes
3answers
5k views

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?
5
votes
3answers
2k views

SNTP, why do you mock me?

--- SOLVED SEE EDIT 5 --- My w2k3 pdc is configured as an authoritative time server. Other servers on the domain are able to sync with it if I manually specify it in the peer list. By if I try to ...
5
votes
1answer
607 views

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 ...
5
votes
3answers
520 views

hyper-v server time sync source - PDC / external NTP?

The environement: 10 Hyper-V hosts, all AD joined a lot of VMs AD joined and some not some AD DCs including PDC as Guests What You think is the best approach to time sync a hyper-v farm with AD ...
5
votes
3answers
8k views

Setting up a local stratum 2 NTP server

I'm trying to setup NTP on a local network that has no (and never will) internet connection. The main priority is that the machines on the network are synced with each other, even if the time they're ...
5
votes
1answer
159 views

ntp multicast address

A silly question probably, but guess I need to ask. If I've got four centos boxes that are acting as ntpd multicast servers, will the multicast address configured in each box's ntp.conf all be the ...
5
votes
3answers
1k views

NTP fudge network source stratum

Is it possible to configure ntpd to fudge the stratum level of a network source? Upon first glance, I thought the fudge directive could accomplish this, however after browsing the ntp.conf(5) man ...
4
votes
2answers
3k views

Why does Ubuntu 9.04 reset my Windows clock?

I've got a rig with 2 hard drives. I've put Ubuntu 9.04 (Jaunty) on one of the drives and Windows Vista SP2 runs on the other drive. I went with this approach rather than dual boot since I wanted to ...
4
votes
7answers
3k views

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 ...
4
votes
3answers
745 views

Using NTP to sync a group of linux servers to a common time source

I have 20 or so linux servers and I want to sync all of their clocks to a single NTP server, which is in the same rack and switch as my servers. Nothing is virtualized. Our admins are having trouble ...
4
votes
3answers
268 views

Usefulness of a new stratum-1 NTP server

A physicist I know that works in a government institution recently commented that they have a cesium clock, and they were considering the possibility of setting up a public stratum 1 NTP server ...
4
votes
1answer
591 views

How to set common NTP server for all computers in AD [duplicate]

Possible Duplicate: How to set a frequent period for NTP client to sync with the NTP server. I want to set default NTP server to pool.ntp.org to all computers joining my domain. How can I ...
4
votes
3answers
10k views

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 ...
4
votes
2answers
839 views

Active Directory Time Synchronisation - Time-Service Event ID 50

I have an Active Directory domain with two DCs. The first DC in the forest/domain is Server 2012, the second is 2008 R2. The first DC holds the PDC Emulator role. I sporadically receive a warning ...
4
votes
3answers
471 views

Is there research material on NTP accuracy available? [closed]

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. ...
4
votes
3answers
2k views

Seemingly poor quality of NTP time synchronization using a GPS clock

I have a Linux server which has its time synchronized to a GPS-based NTP appliance located close by. Ping times from the server to the appliance are circa 1ms, with very low jitter: --- x.x.x.x ping ...
4
votes
2answers
788 views

Setting up NTP servers

I have a problem setting up NTP to maintain time on a stand-alone network. This will be an island time-zone. The problem is that the time drifts apart, even after they have been initially ...