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i've a problem with time syncronization of a CentOS 7 host with a Windows 2008 R2 Domain controller. If I use the command ntpdate -u host.domain the synchronization is ok. But using ntpd the time is always the same, here the result of the command ntpq -p:

 10.10.10.221    .LOCL.           1 u   65   64  377    1.740  965414.   4.054
 10.10.10.220    10.10.10.221     2 u   62   64  377    1.912  965408.  12.899

and the ntp.conf is the following:

driftfile /var/lib/ntp/drift
restrict default nomodify notrap nopeer noquery
restrict 127.0.0.1
restrict ::1
server 10.10.10.221 iburst prefer
server 10.10.10.220 iburst
includefile /etc/ntp/crypto/pw
keys /etc/ntp/keys
disable monitor
logfile /var/log/ntp.log
Bartok
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2 Answers2

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I managed to find the solution after digging in more to a very similar issue on my end (different OS but same problem).

Windows NTP Servers (at times for various reaons), will report a large root dispersion. This in turn causes chronyd/ntpd to ignore the ntp server fpr inaccurate data.

In order to resolve I needed to add:

tos maxdist 16

to my /etc/ntp.conf. After restarting the service everything began working.

This article helped gave a simple explanation.

https://access.redhat.com/solutions/4652771

I also stumbled upon this post regarding inadequate times which further helped troubleshoot and identify the issue.

Why is NTP considering my server inadequate?

IT_User
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Centos 7 use systemd. I suggest you use it.

Use the command timedatectl

Enable network time synchronization:

timedatectl set-ntp True

Create a conf file:

vi /etc/systemd/timesyncd.conf

with content like this:

[Time] NTP= yourserver.org

Start systemd-timedated service:

systemctl start systemd-timedated
Esa Jokinen
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Andrés Sánchez García
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    Umm, I don't believe `centos` chose to include `systemd-timesyncd` and so manufacturing a `/etc/systemd/timesyncd.conf` would have no effect. I'm willing to be corrected but `systemd-timedated` does not read this file. See https://unix.stackexchange.com/a/312716/80414 – shalomb Jul 09 '18 at 22:03