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Questions tagged [clock-synchronization]

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How "real" is the POSIX clock in a virtual machine?

Introduction: Time is OS like Linux is typically derived from a clock chip (RTC), or maintained by software using either periodic interrupts or some hardware registers (e.g. CPU's TSC cycle counter) ...
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1 answer
72 views

Cannot change NTP Time Source on a 2012 R2 DC Server

So I have seen dozens of people with this issue on various websites and forums, but here I am asking again. No matter what I try so far, nothing has fixed the issue which I will describe below in as ...
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0 votes
2 answers
71 views

Is there a way to keep server times in sync to the millisecond, globally?

I'm working on a project where I need to keep server times in sync, to the millisecond. There are servers in the UK, US and Asia amongst other countries, and at the moment someone is manually having ...
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1 vote
1 answer
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Incorrect PTP timestamps [closed]

I have trouble syncing to Linux systems using PTP. Setup: Two PCBs with a BegleCore module and a DP83640 PHY are connected with each other over Ethernet. One board should act as the PTP master, the ...
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0 votes
1 answer
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ntpdate succeeds but ntpq fails against Windows DC

DC: Server 2019 Client: TrueNAS https://docs.microsoft.com/en-US/troubleshoot/windows-server/identity/configure-authoritative-time-server for step 3, the DC is configured to be an NTP server and is ...
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1 vote
1 answer
2k views

How to Set Up Time Synchronization with NTP on Ubuntu 20.04.1 LTS

After updating the base system with the latest available packages: apt-get update -y and root@localhost:~# timedatectl Local time: Wed 2021-01-06 08:03:11 UTC Universal time:...
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0 votes
1 answer
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DC NTP not syncing and Local CMOS Clock issue

I've configured my DC (Domain Controller; Windows 2016) as described here to get his time from my Sophos-UTM. So i configured the GPO as described there. But after that and a restart of the server i ...
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1 answer
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Problems with chronyd Centos 7 all updates applied

I have an email server running on top of CentOS7. This is a new server and has been in production for 2 days. It seems that chronyd is losing it's connection to the ntp servers that it contacts at ...
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1 vote
1 answer
744 views

Prevent VM clock running faster than it should

I have a unRAID 6.6.5 server with perfectly correct time and multiple Linux VMs which used to be perfectly synced too. I rebooted one of my VM and suddenly the clock goes twice as fast as the hwclock. ...
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3 votes
1 answer
169 views

Compute Engine VM clock runs fast and gains 15 seconds per hour (or about 1 second per each 4 minutes)

I have a 2 vm instances in GCE that do not keep correct time in spite of the server OS being set to sync with NTP every 24 hours. The OS clock gains about 1 second of time every four minutes (or ...
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8 votes
3 answers
5k views

Ntpd on local network - Preventing clock drift causing high offsets

I have a local network with a microcontroller ARM as the NTP server and I have a desktop computer running with ubuntu 16.04 LTS as a NTP client. Once I start ntpd -g -c /etc/ntp.conf with the ...
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  • 211
8 votes
1 answer
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Force chrony time check

Context: Centos 7.0 chronyc (chrony) version 3.1 (+READLINE +IPV6 +DEBUG) Issue I want to find a way to force chronyd to change the hardware clock instantly without waiting. The program chronyd is ...
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0 votes
1 answer
578 views

How to have WSL think it is in the past? [closed]

I am developing PHP/Apache/MySQL based code on my Windows 10 laptop via Windows Subsytem For Linux. I am working on some code that is time related. It has a mix of PHP date commands, and MySQL "NOW()"...
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3 votes
1 answer
725 views

AWS EC2 with huge clock drift at boot

We have an Amazon EC2 CentOS 7.5 instance whose clock, at boot, is always 35 days late. Yes, you read it correctly. That's a hell of a drift. [root@myec2 ~]# ntpd -gqn ntpd: time set +2937270.012860s ...
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3 votes
0 answers
841 views

NTP 'reach' resetting, wrong refid of remote ntp server, and high jitter

I've got a remote unmanned server that's been exhibiting some extremely strange clock/NTP behavior lately. Symptoms: Very high jitter ntpq -pn returns: A resetting 'when' count of back to 1, even ...
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-5 votes
1 answer
152 views

Time on Windows servers out and won't stay corrected

I have a bunch of windows servers that are VM's running on a group of hypervisors, all in a domain environment. Its a mix of Server 2012 R2 and Server 2016 For some reason the clock is out by about 7 ...
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6 votes
5 answers
10k views

Completely disable Date and Time sync in a Hyper-V VM

No matter what, a Hyper-V virtual machine keeps finding ways to sync time with the host. I have: Disabled the time synchronization service Disabled Windows time synchronization on the guest machine ...
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  • 189
0 votes
1 answer
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/sbin/hwclock --utc --systohc not working on AWS EC2 under Ubuntu

I'm in the process of moving some servers to AWS. One problem I'm encountering is that my script to synchronize the time using ntpdate and then write that time to the hwclock is failing. When the ...
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2 votes
0 answers
772 views

Chrony reporting system time slower than NTP and growing

I have chrony running on several of my instances. Unfortuantely, on one of them, it keeps reporting that the system time is slower than NTP time. This number of seconds keeps growing at a rate of ...
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How to read VMware interrupt backlog?

The VMware document titled "Timekeeping in VMware Virtual Machines" have the following referente to the issues with the time drift: If the virtual machine is running too slowly, perhaps as a result ...
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7 votes
3 answers
28k views

hwclock: Cannot access the Hardware Clock via any known method

On a Debian server, I'm having problem with hwclock: $ hwclock --show hwclock: Cannot access the Hardware Clock via any known method. hwclock: Use the --debug option to see the details of our search ...
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3 votes
2 answers
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FreeBSD: how to syncronize the system clock with the hardware clock in bash?

I am writing a script that synchronizes the system clock with the hardware clock (aka RTC, or CMOS clock) assuming that no Network Time Protocol (NTP) daemon is running. I am running in a virtual ...
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  • 213
2 votes
1 answer
1k views

RTC time is going totally wrong after a few minutes (Ubuntu 16.04 + Hyper-V)

My RTC time on my Ubuntu 16.04 is going crazy. After a few minutes the RTC time is going totaly wrong. The strange thing is, if I disable NTP Service (timedatectl set-ntp false and service ntp stop) ...
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0 votes
0 answers
1k views

When to change current_clocksource

I am running an Ubuntu 16.04 machine on a M4.xlarge in AWS EC2. I was reading about some of the performance tuning that Netflix did for their EC2 machines (link: http://www.brendangregg.com/blog/2015-...
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2 votes
0 answers
1k views

How to configure hwclock to UTC on Redhat Linux?

I have linux redhat machine # more /etc/redhat-release Red Hat Enterprise Linux Server release 5.11 (Tikanga) I want to change the hwclock to UTC time So I perform little test as # date -u Tue ...
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8 votes
2 answers
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Red hat Linux + TIME ZONE CONFIGURATION + details from clock file

In order to configure the Time Zone on red hat Linux machine ( version 5 and 6 ) need to configure the file: /etc/sysconfig/clock And create a symbolic link between /etc/localtime to /usr/share/...
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1 vote
0 answers
195 views

Preventing system clock from auto-updating in Windows Server 2012

I'm working on a project right now where as part of testing I have to move the system clock to far-off future dates. There are two servers involved in the project: an app server and a database server. ...
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1 vote
1 answer
894 views

NTP synchronized clock alongside the system clock

Does NTP daemon(ntpd) provide some sort of virtual clock that it disciplines and serves, but not touch the system clock? Goal: On a realtime Linux OS, have a NTP synchronized clock alongside of the ...
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1 vote
0 answers
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RTC/UTC was innacurate on MySQL (MariaDB) server. I fixed it - was that bad?

I'm pinch hitting as an admittedly green server admin. I installed a bunch of security patches on a MariaDB server that had an incorrectly configured repo (not by me) and wasn't getting patches for a ...
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5 votes
2 answers
1k views

How to fix time on NTP server with a lot of machines synchronized by it

I have one NTP server which has a wrong time setting which are 7 hours in the future (timezone was changed after machine shipment, but not the time). The server itself is not synchronized, but only ...
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2 votes
2 answers
2k views

How accurate can we get computer clocks synchronized in a local network of any number of computers?

In the past, I have seen that most of my computer on my local network don't really have the same time within up to 1 second or so. So I wanted to make sure that it would be possible for a stack of ...
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0 votes
2 answers
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NTP service stopped in centos7.1 linux machine

In our 3 linux boxes centos 7.1, we saw below messages in the logs and then ntpd service got stopped since the offset is more than 1000s. systemd: Time has been changed ntpd[2626]: 0.0.0.0 0617 07 ...
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  • 363
0 votes
1 answer
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How to synchronize the time in Debian6 server? We have 30 min delay in our VMs

I can't have the correct time in our servers. We get always the same delay in the three of them (they are VM on the same server). We use ntp to have our date always synchronized· The main server ...
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3 votes
1 answer
2k views

TSC missing from available clocksources

Not sure why TSC as a clock source is not available? cat /sys/devices/system/clocksource/clocksource0/available_clocksource hpet acpi_pm The CPU I'm using is Intel Xeon(R) X5570 @ 2.93GHz. The ...
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1 vote
1 answer
900 views

Why is clock synchronization on servers difficult?

See: Clock synchronization quality on Windows Azure? This is not meant as a rant, it is just curiosity. Is a computer really drifting more than a second in a single day? I can barely imagine that. ...
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3 votes
1 answer
575 views

system clock skewing backwards 112 seconds

I'm troubleshooting a problem on one of my NTP servers. This server seems to defy logic, and I'm at my wits end trying to troubleshoot it. Roughly every 162 seconds, the system clock reverts to (...
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  • 191
13 votes
3 answers
12k views

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 ...
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-1 votes
1 answer
106 views

ntp daemon seems useless and why my server date time is far behind my local time

I've installed ntp daemon in ubuntu to sync my date time with the network time. Now my time on the server is 11:00 while my PC date/time is 19:30. Now all my transactions date/times are logged ...
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26 votes
3 answers
47k views

How far is "too far off" for ntpd? Can it get there by a sudden jump to heavy load? Can this be overridden?

In many primers on ntpd, like this one, there's always a warning that ntpd will stop resetting the clock "[if] your clock is too far off." How far off is "too far off"? Also, if a server takes a ...
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0 votes
1 answer
777 views

Windows server and AWS clock synchronization

I have a Windows 7 computer that communicates with Amazon Web Servers (S3, SES). This server uses windows internet time for clock synchronization time.windows.com. On my linux machines I ran into ...
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2 votes
0 answers
621 views

Hardware Clock (RTC) Stuck / Will Not Increment

After we rebooted one of our servers (RHEL), we noticed that it would hang when entering GRUB. The problem was the countdown in GRUB (Booting in 5... 4......) was not counting down, and was stuck at ...
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1 vote
2 answers
578 views

Cent OS 6 clock 3 minutes 35 seconds in the future

I run Cent os 6 64 bit on linode. server (incorrect): date Thu Aug 29 11:41:00 BST 2013 client (correct): date Thu Aug 29 11:37:25 BST 2013 As you can see the server clock is in ...
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1 vote
0 answers
1k views

Update clock on virtualbox virtual machine with cent os from host

I have a virtual machine, with cent os installed, and everytime I sleep the host computer, the clock of the VM goes out of sync. I would like it to pick up the current time from virtualbox - which I ...
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-2 votes
1 answer
184 views

System Time Synchronization Procedure [closed]

I am looking for procedure which I can execute in cron to synch the system time in clustered servers. Can any of the experienced SME's please help?
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2 votes
1 answer
429 views

How to backdate a domain-connected workstation?

I need to verify some test cases by backdating my system. How to do this?
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6 votes
3 answers
3k views

Clock is 10% faster than normal

I'm having some strange problem with the clock on my server – it's about 10% faster than normal. The problem started 2 days ago and I've not done anything special with the server. I tried to turn of ...
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0 votes
3 answers
269 views

Is TimeSync still needed on Windows Server 2008?

I've always used TimeSync on my servers. With Windows' built in internet time updating, should I remove TimeSync? I've never turned off windows time updating even with TimeSync - what is the best ...
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  • 399
3 votes
2 answers
66k views

WS2008 NTP - Using time.windows.com,0x9 - Time always skewed forwards

I have a domain controller configured to use time.windows.com (with 0x09 flags set). I've noticed that frequently the systems' clock is fast - it varies from 10 minutes to even 45 minutes. I always ...
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0 votes
2 answers
605 views

Virtualizing NTP server [duplicate]

Possible Duplicate: What are the limits of running NTP servers in virtual machines? I was wondering if virtualizing NTP is okay. I have a VMware ESXi 5.0 box, and I want to virtualize my router ...
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2 votes
2 answers
632 views

SLES guest on HyperV: high CPU usage vs. accurate time keeping

Here is the issue: SLES 10 SP1 guest is running on HyperV. I need accurate timekeeping on this box, so I have applied these kernel parameters (which were proven to work on other identical SLES 10 SP1 ...
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