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Questions tagged [ntp]

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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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 Program name udp 0.0.0.0:123 0.0.0.0:* …
Abraham Vegh
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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 the traffic: It's churning a bit of CPU on our…
Jeff Atwood
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ntp.conf pool vs server directives

I came across an ntp.conf file that specifies pool directives: # Use servers from the NTP Pool Project. Approved by Ubuntu Technical Board # on 2011-02-08 (LP: #104525). See http://www.pool.ntp.org/join.html for # more information. pool…
user3141592
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Wrong time on my Ubuntu Amazon EC2 instances

I have three Ubuntu EC2 instances on Amazon AWS (EU/Ireland), all set up as web server. I noticed the system date/time is incorrect in two of them (timezone is always set to UTC for my choice). Here is the output of date -R for my PC (EU/Italy, 2…
lorenzo-s
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What are the limits of running NTP servers in virtual machines? (2010)

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? That is, to what degree will accuracy be…
James A. Rosen
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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. (Note that a twin identical server had no problem at…
Stefano M
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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 and often, even though NTP is installed, it's…
Stuart Woodward
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Synchronize clock with NTP while online, and with RTC while offline?

Is there a existing mechanism that synchronizes a linux system with NTP while online, and with a predictably drifting RTC while offline? We operate remote "collectors": embedded Linux systems that collect and timestamp sensor data. We need their…
Nils Toedtmann
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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 few hours, but would frequently go 1-3 weeks…
anregen
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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, but that is not the case- this server can talk…
Crash Override
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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 2004…
AndyM
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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 using ubuntu server.
Khaled
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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 can amend and how?
stead1984
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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. This recommendation by VMWare specifically says…
Josh Smeaton
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How to change time source from "Local CMOS Clock" to "DC"

In a domain, I want to set DC as time server. To do that I use this command: w32tm /config /manualpeerlist:europe.pool.ntp.org /syncfromflags:manual /reliable:yes /update and w32tm /resync /rediscover In the client servers I use net time…
Barny
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