[systemd-devel] use RTC date/time to set system date time

[Michał Zegan]

W dniu 01.03.2021 o 17:19, Lennart Poettering pisze:
> On Mo, 01.03.21 17:09, Michał Zegan (webczat_200 at poczta.onet.pl) wrote:
> 
>>>> There are problems with log timestamps when you do that, and it is
>>>> probably why it was not done.
>>>> I am wondering if the only correct way isn't to do it in initramfs (if
>>>> it's systemd) before starting the journald, so that first saved logs
>>>> have correct timestamps?
>>>
>>> The earlier you have a "correct" clock the better.
>>>
>>> But I mean, journald won't lie to you: the log messages are associated
>>> with the timestamps that were accurate at the moment they are
>>> generated. But of course, if your clock sucks then they'll look
>>> differently than you might expect.
>> However the initial log entries in journald are taken from dmesg and
>> dmesg timestamps are relative, so setting the clock before journald
>> first starts should make journal times correct.
>> Or I am wrong?
> 
> kmsg comes with monotonic timestamps only. journald stores that away
> but generally uses its own acquired timestamps, since it needs to
> guarantee monotonicity and things.
> 
> But do note that journald typically runs in the initrd already.
Yes, my idea was to wait for time *in initramfs* before journald. Like
force the rtc driver to land in initramfs, then just load it, set time
if kernel doesn't, and then start journald.
> 
> Lennart
> 
> --
> Lennart Poettering, Berlin
> 

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