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Bug 1209568 - RFE: add option for leap smear
Summary: RFE: add option for leap smear
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: chrony
Version: 7.1
Hardware: Unspecified
OS: Unspecified
unspecified
unspecified
Target Milestone: rc
: ---
Assignee: Miroslav Lichvar
QA Contact: Jakub Prokes
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2015-04-07 16:31 UTC by Miroslav Lichvar
Modified: 2015-11-19 08:29 UTC (History)
5 users (show)

Fixed In Version: chrony-2.1-1.el7
Doc Type: Enhancement
Doc Text:
Clone Of:
Environment:
Last Closed: 2015-11-19 08:29:49 UTC
Target Upstream Version:
Embargoed:


Attachments (Terms of Use)


Links
System ID Private Priority Status Summary Last Updated
Red Hat Product Errata RHSA-2015:2241 0 normal SHIPPED_LIVE Moderate: chrony security, bug fix, and enhancement update 2015-11-19 08:59:36 UTC

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


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