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Bug 1190619 - ntpd -x steps clock on leap second
ntpd -x steps clock on leap second
Status: CLOSED ERRATA
Product: Red Hat Enterprise Linux 6
Classification: Red Hat
Component: ntp (Show other bugs)
6.6
Unspecified Unspecified
urgent Severity high
: rc
: ---
Assigned To: Miroslav Lichvar
Jakub Prokes
: ZStream
Depends On:
Blocks: 1199978 1381600
  Show dependency tree / graph
 
Reported: 2015-02-09 04:49 EST by Miroslav Lichvar
Modified: 2016-10-22 13:19 EDT (History)
16 users (show)

See Also:
Fixed In Version: ntp-4.2.6p5-3.el6
Doc Type: Bug Fix
Doc Text:
Previously, when the ntpd daemon was configured with the "-x" option to adjust the system clock slowly instead of changing the time instantaneously, the system clock was incorrectly changed instantaneously when a leap second occurred. In certain applications, this could lead to a variety of system clock related problems, such as incorrect event sorting or triggering. To fix this bug, ntpd now adjusts for the leap second slowly over a long interval, which prevents the described problems.
Story Points: ---
Clone Of:
: 1191122 1196635 1199978 1381600 (view as bug list)
Environment:
Last Closed: 2015-07-22 03:00:28 EDT
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
CRM:
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

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External Trackers
Tracker ID Priority Status Summary Last Updated
Network Time Protocol 2745 None None None Never
Red Hat Knowledge Base (Solution) 1379783 None None None Never
Red Hat Product Errata RHSA-2015:1459 normal SHIPPED_LIVE Moderate: ntp security, bug fix, and enhancement update 2015-07-21 10:15:04 EDT

  None (edit)
Description Miroslav Lichvar 2015-02-09 04:49:28 EST 
Description of problem:
With older ntp versions, the -x option was sometimes used as a workaround to avoid kernel inserting/deleting leap seconds by stepping the clock and possibly upsetting running applications. That no longer works with 4.2.6 as ntpd steps the clock itself when a leap second occurs.

The fix is to treat the one second offset gained during leap second as a normal offset and check the stepping threshold (set by -x or tinker step) to decide if a step should be applied.

Version-Release number of selected component (if applicable):
ntp-4.2.6p5

How reproducible:
Always

Steps to Reproduce:
1. add -x to /etc/sysconfig/ntpd
2. wait for leap second
3. observe how was clock corrected

Actual results:
step

Expected results:
slew
Comment 1 Christian Horn 2015-02-18 03:34:00 EST 
Just so its all together:

upstream bz: http://bugs.ntp.org/show_bug.cgi?id=2745

discussion in upstream seeded by Miroslav, wether one should get the behaviour to "get leapseconds slowly" or not: 
http://lists.ntp.org/pipermail/questions/2015-February/039885.html
Comment 14 Muneaki Sugaya 2015-03-23 02:21:02 EDT 
Bug 1199978 is this clone for rhel-6.6.z and has released ntp-4.2.6p5-3.el6_6 which can be used for the following:

Red Hat Enterprise Linux Desktop (v. 6)
Red Hat Enterprise Linux HPC Node (v. 6)
Red Hat Enterprise Linux Server (v. 6)
Red Hat Enterprise Linux Server EUS (v. 6.6.z)
Red Hat Enterprise Linux Workstation (v. 6)

cf.
https://rhn.redhat.com/errata/RHBA-2015-0690.html
Comment 17 errata-xmlrpc 2015-07-22 03:00:28 EDT 
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-2015-1459.html
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