CentOS  RHEL 7  Chrony Vs NTP (Differences Between ntpd and chronyd)

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CentOS / RHEL 7 : Chrony V/s NTP (Differences Between ntpd and chronyd)

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Chosing between Chrony and NTP

– In RHEL 7 ntpd is replaced by chronyd as the default network time protocol daemon.
– Basic configuration for synchronize time and date is stored in the file /etc/chrony.conf.
– ntpd is still included in yum repository for customers who need to run an NTP service.
– Chrony is a different implementation of the network time protocol (NTP) than the network time protocol daemon (ntpd)
   that is able to synchronize the system clock faster and with better accuracy than ntpd.

--//在RHEL7中，ntpd被chronyd替换为默认的网络时间协议守护进程。
--//同步时间和日期的基本配置存储在文件/etc/chrony.conf中。
--//对于需要运行NTP服务的客户，ntpd仍然包含在Yum存储库中。
--//chrony是网络时间协议(NTP)与网络时间协议守护进程(ntpd)的一种不同的实现，它能够比ntpd更快、更准确地同步系统时钟。   

Benefits of Chrony include:

1. Faster synchronization requiring only minutes instead of hours to minimize the time and frequency error, which is
   useful on desktops or systems not running 24 hours a day.
--//1.更快的同步只需要几分钟而不是几个小时，以尽量减少时间和频率误差，这在台式机或系统上是有用的，而不是每天24小时运行。

2. Better response to rapid changes in the clock frequency, which is useful for virtual machines that have unstable
   clocks or for power-saving technologies that don't keep the clock frequency constant.
--//2.更好地响应时钟频率的快速变化，这对于具有不稳定时钟的虚拟机或不保持时钟频率恒定的节电技术是有用的。

3. After the initial synchronization, it never steps the clock so as not to affect applications needing system time to
   be monotonic.
--//3. 在初始同步之后，它从不步进时钟，以免影响需要系统时间单调的应用程序。   

4. Better stability when dealing with temporary asymmetric delays, for example when the link is saturated by a large
   download.
--//4. 在处理临时不对称延迟时，例如当链接被大量下载饱和时，稳定性更好。   

5. Periodic polling of servers is not required, so systems with intermittent network connections can still quickly
   synchronize clocks.
--//5. 不需要定期轮询服务器，因此具有间歇性网络连接的系统仍然可以快速同步时钟。   

When to use chrony

Chrony would be considered a best match for the systems which are frequently suspended or otherwise intermittently
disconnected from a network (mobile and virtual servers etc).

--//对于经常被挂起或以其他方式间歇性地与网络(移动和虚拟服务器等)断开连接的系统，时间安排将被视为最佳匹配)。

When to use NTP

The NTP daemon (ntpd) should be considered for systems which are normally kept permanently on. Systems which are
required to use broadcast or multicast IP, or to perform authentication of packets with the Autokey protocol, should
consider using ntpd.

--//对于通常被永久保存的系统，应该考虑NTP守护进程(ntpd。 需要使用广播或多播IP或使用Autokey协议执行数据包身份验证的系统，
--//应考虑使用ntpd。

Filed Under: CentOS/RHEL 7