Bug#755722: systemd must sync systemclock to RTC on shutdown

[Michael Biebl]

Am 17.02.2015 um 00:27 schrieb Josh Triplett:
> On Mon, 16 Feb 2015 16:41:21 +0100 Martin Pitt <mpitt at debian.org> wrote:
>> For jessie+1/experimental onward, we'll fix this properly by enabling
>> timesyncd by default. It won't start if ntp or similar are installed.
>> This will make sure that the hw clock will be updated often enough,
>> and we won't poke false data into it:
>>
>>   http://anonscm.debian.org/cgit/pkg-systemd/systemd.git/commit/?h=experimental&id=929bece5326
> 
> Using ConditionFileIsExecutable on specific NTP daemons seems odd here.
> Doesn't systemd already have a mechanism for choosing from multiple
> alternative implementations of a given feature, automatically running
> only one of them?  If not, perhaps it should; that same mechanism would
> then work for display managers, web servers, etc.

Sort of. The plan here is, that the individual ntp implementations ship
a native systemd unit file, which has
Conflicts=systemd-timesyncd.service [1]

This will make sure, that if e.g. ntp is installed and enabled, ntp will
be used instead of systemd-timesyncd.

None of the ntp implementations currently ship such a native unit file
though, that's why we decided to add such a Condition to the
systemd-timesyncd.service unit file for the time being.

There were concerns that adding this Conflicts to every time
synchronization service is a questionable approach [2].

Arguably, for ntp, chrony and openntpd, we can solve this on a packaging
level, by making those packages conflict.

If we want to enable timesyncd by default and keep it as a part of the
systemd package, this approach doesn't work, and we need the Conflicts=
on the systemd unit level.

Michael


[1] http://article.gmane.org/gmane.comp.sysutils.systemd.devel/22172
[2] https://bugzilla.redhat.com/show_bug.cgi?id=1116369

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