Bug 119909 - /etc/init.d/boot.clock: --systohc without ntp breaks adjtime
Summary: /etc/init.d/boot.clock: --systohc without ntp breaks adjtime
Status: RESOLVED WORKSFORME
Alias: None
Product: SUSE LINUX 10.0
Classification: openSUSE
Component: Basesystem (show other bugs)
Version: Final
Hardware: Other All
: P5 - None : Normal
Target Milestone: ---
Assignee: Ruediger Oertel
QA Contact: E-mail List
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Reported: 2005-10-03 16:52 UTC by Stanislav Brabec
Modified: 2006-02-09 16:55 UTC (History)
1 user (show)

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Found By: Other
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Marketing QA Status: ---
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Description Stanislav Brabec 2005-10-03 16:52:25 UTC 
If machine is not running NTP, using --systohc in init script breaks adjtime
logic and causes random fluctuation of clock.

Fix:

If NTP is/was not running on the machine in last minutes before terminating
boot.clock, dont use --systohc.

Technical description:

Suppose standalone machine without NTP running. During 12 hours of uptime it
looses few interrupts, which causes 1 sec delay of system clock. Systohc thinks,
that hwclock is preceding by 1 sec/12 hours, sets 2 sec daily adjtime. Next
time, the correction will be in opposite direction. The result can be for
example 15 minutes of delay in two months.

Related: http://bugs.gentoo.org/show_bug.cgi?id=15834
Comment 1 Ruediger Oertel 2006-02-09 15:22:19 UTC 
edit etc/sysconfig/clock and set SYSTOHC to no if you want that.
Comment 2 Stanislav Brabec 2006-02-09 16:47:32 UTC 
Is it possible to set it to no if NTP is not installed and for install CD and live CD? It can make ugly shifts which will invalidate adjtime.

Thanks for implementation. In 10.0 it was not implemented yet.
Comment 3 Dr. Werner Fink 2006-02-09 16:55:06 UTC 
SYSTOHC set to no will break all my test systems not using NTP.