[systemd-devel] systemd 28 time handling changes "breaks" ntpdate and date ?

[Colin Guthrie]

'Twas brillig, and Kay Sievers at 27/04/12 11:03 did gyre and gimble:
> 
> On Apr 27, 2012 2:11 AM, "Colin Guthrie" <gmane at colin.guthr.ie
> <mailto:gmane at colin.guthr.ie>> wrote:
>>
>> 'Twas brillig, and Sam Morris at 25/04/12 23:41 did gyre and gimble:
>> > On Wed, 25 Apr 2012 11:28:14 -0400, Martin Langhoff wrote:
>> >
>> >> Apologies if this has been discussed -- a search through the archives
>> >> didn't find anything.
>> >>
>> >> Reading the announcement of systemd v28...
>> >>
>> >> "At shutdown we no longer invoke "hwclock --systohc", i.e. do not write
>> >> the system clock back to the RTC. Why? In general there's not really a
>> >> reason to assume that the system clock was anymore correct than the RTC
>> >> so it's probably a good idea to leave the RTC untouched."
>> >
>> > Hm, every time I reboot I'm prompted to run fsck because the last mount
>> > time is in the future. Is this the reason?
>>
>> Yes, this is the reason.
> 
> The real reason is that the extfs tools just make silly assumptions. You
> should patch it away or disable that nonsense in the extfs config file,
> which is what Fedora does.

Ahh, thanks for the hint. Are there similar tweaks in Fedora for other
fs types (xfs, reiser)?

>> But that said there should be an automatic sync if you run chrony or
>> ntpd every 12s or so at the kernel level.
> 
> Every 11 minutes. 

I was only out by bit then... :p

> The kernel writes to the rtc when ntp puts the kernel
> into that mode.
> 
> There is only one piece missing, the kernel syncs not over deltas larger
> than 15 or 30 minutes, even when ntp sets the clock to that. That can
> get into our way when daylight saving time changes and the rtc is in
> localtime. It should be fixed in the kernel, by adding a mode that says
> full-sync-if-in-11-minute mode.

Thanks, as always, for the insights.

Cheers

Col


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Colin Guthrie
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