Bug 1209568 – RFE: add option for leap smear

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Bug 1209568 - RFE: add option for leap smear

Summary:	RFE: add option for leap smear

Status:	CLOSED ERRATA

Aliases:	None

Product:	Red Hat Enterprise Linux 7
Classification:	Red Hat
Component:	chrony (Show other bugs)
Sub Component:
Version:	7.1
Hardware:	Unspecified Unspecified

Priority	unspecified Severity unspecified
Target Milestone:	rc
Target Release:	---
Assigned To:	Miroslav Lichvar
QA Contact:	Jakub Prokes
Docs Contact:

URL:
Whiteboard:
Keywords:	FutureFeature

Depends On:
Blocks:
	Show dependency tree / graph

Reported:	2015-04-07 12:31 EDT by Miroslav Lichvar
Modified:	2015-11-19 03:29 EST (History)
CC List:	5 users (show)

See Also:
Fixed In Version:	chrony-2.1-1.el7
Doc Type:	Enhancement
Doc Text:
Story Points:	---
Clone Of:
Environment:
Last Closed:	2015-11-19 03:29:49 EST
Type:	Bug
Regression:	---
Mount Type:	---
Documentation:	---
CRM:
Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
Add an attachment (proposed patch, testcase, etc.)

External Trackers
Tracker	ID	Priority	Status	Summary	Last Updated
Red Hat Product Errata	RHSA-2015:2241	normal	SHIPPED_LIVE	Moderate: chrony security, bug fix, and enhancement update	2015-11-19 03:59:36 EST

Groups: None (edit)

Description Miroslav Lichvar 2015-04-07 12:31:26 EDT

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 09:51:31 EDT

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 03:29:49 EST

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

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