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Questions tagged [clock-synchronization]

58 questions
27
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3 answers

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 sudden jump to heavy load, for example from total…
user144330
14
votes
3 answers

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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9
votes
1 answer

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 currently running on my machine : [root@localhost…
Orelsanpls
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8
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3 answers

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 following ntp config file server 192.168.0.11 minpoll 4…
Daniel R.
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8
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2 answers

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/zoneinfo/America/New_York but /etc/sysconfig/clock…
dandan
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8
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6 answers

What consequences / implications can arise from a wrong system clock?

What issues can you think of that may arise from a wrong system clock setting ? Primarily interested in potential problems affecting servers and Linux or UNIX-like systems in particular. And how severe are these consequences, depending on how much…
Arc
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7
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3 answers

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 for an access method. System runs on backports…
Tombart
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6
votes
5 answers

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 mapped time.windows.com to 127.0.0.1 on the hosts…
resle
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6
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3 answers

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 the ntp update by stopping the ntpd daemon. It…
Linus Oleander
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5
votes
2 answers

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 has its local clock. On this server >10 clients…
Rick-Rainer Ludwig
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5
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3 answers

Clock synchronisation on kvm guests

I'm having trouble keeping the system clocks sync'd on a number of kvm guests. I've googled a fair bit, and found a lot of different options, many of which I've tried, to no avail. So here I am. ntpd is out of the question (the host system runs it…
DictatorBob
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5
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3 answers

System clock drifting out of sync with hwclock and ntpd

My current system drifts from the hwclock and ntpd dramatically. I've looked at many forums and posts online and on SF, but haven't found a suitable solution. Here is my ntpq -pn output: remote refid st t when poll reach delay …
samxli
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4
votes
1 answer

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 motherboard is Supermicro X8DTU-F. Running CentOS 6.3…
sudoer
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4
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2 answers

Synchronize time on a private network that must not connect to the Internet

For HIPAA compliance, this network can not be connected to the Internet or to any other network or computer which connects to the Internet. I've got a small private network comprised entirely of Macs running Mac OS X 10.6. The computers share files…
Justin Force
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3
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1 answer

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 about 15 seconds each hour). One vm instance machine…
Ricky
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