Bug 1209568

Summary:	RFE: add option for leap smear
Product:	Red Hat Enterprise Linux 7	Reporter:	Miroslav Lichvar <mlichvar>
Component:	chrony	Assignee:	Miroslav Lichvar <mlichvar>
Status:	CLOSED ERRATA	QA Contact:	Jakub Prokes <jprokes>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	7.1	CC:	chorn, jprokes, jscotka, ovasik, rhack
Target Milestone:	rc	Keywords:	FutureFeature
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:	chrony-2.1-1.el7	Doc Type:	Enhancement
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2015-11-19 08:29:49 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Miroslav Lichvar 2015-04-07 16:31:26 UTC

Description of problem:
Leap smear (as originally described by Google) is useful when serving time to clients that can't apply leap second slowly by slewing or they don't apply it at at the same time, which means their clocks are not close to each other for a long time after the leap second is applied to UTC. With leap smear the leap second status is suppressed and the time is corrected slowly on the NTP server instead. The clients can track the time easily during whole correction and they stay close together.

In chrony git there is now a smoothtime directive that can be enabled to perform a leap smear. The main difference from the Google implementation is that it's applied after the leap second is inserted to UTC and it can smooth out any offset, not just leap second.

Comment 3 Miroslav Lichvar 2015-06-10 13:51:31 UTC

In chrony-2.1-pre1 a leaponly option was added to the smoothtime directive, which allows a synchronized leap smear between multiple servers. It will be included in the chrony package.

The chrony leap smearing feature is explained here:

http://developerblog.redhat.com/2015/06/01/five-different-ways-handle-leap-seconds-ntp/

Comment 6 errata-xmlrpc 2015-11-19 08:29:49 UTC

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://rhn.redhat.com/errata/RHSA-2015-2241.html