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How Leap Second Affects The OS Clock on Linux and Oracle VM (Doc ID 1453523.1)

Last updated on MAY 11, 2023

Applies to:

Oracle VM - Version 2.1 and later
Linux OS - Version Oracle Linux 4.8 and later
Oracle WebCenter Content - Version 11.1.1.6.0 to 11.1.1.6.0 [Release 11g]
Oracle Cloud Infrastructure - Version N/A and later
Linux x86
Linux x86-64

Purpose

This document describes what the leap second is, and how it affects to the OS clock on Linux and Oracle VM. Linux OS works fine even with the leap second(if there are no bugs), however applications on the OS may be affected especially when the OS clock is backward adjusted. Please contact application vendors to clarify whether the application is affected by the leap second.

In general, the OS clock which has the leap second is:

time environment

 

Arch

without ntpdwith ntpd(with default zoneinfo)
with old/default zoneinfowith right zoneinfontpd >= 4.2.2p1-9ntpd < 4.2.2p1-9
leap=01leap=10
Physical (baremetal) ServerOL4/OL5/OL6/UEK1/UEK2
x86/x86_64
not adjusted (differs 1sec, not backward) adjusted as per leap second (with out backward, but with inserting ##:##:60 or removing ##:##:59) adjusted gradually taking for a long time (not backward) adjusted with 1 sec backward adjusted with skipping 1 sec (not backward)
Xen or Oracle VMDom0 paused for 1 sec immediately before leap second (not backward)
DomU(PVM) Linux PVM kernel(kernel-xen)
DomU(HVM) depend on HVM kernel

Details

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In this Document
Purpose
Details
 What is the "leap second"?
 What might be a problem with leap second?
 How about Linux without ntp?
 How about Linux with ntp?
 How about other Operating Systems?
References

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