"clock skew" , openrc cache file, and boot time

[ranran]

Hello,


Whenever I disconnect RTC battry I get several warnings about "Clock skew":

[Naib]

Have a read of this thread: https://forums.gentoo.org/viewtopic-t-1073968-postdays-0-postorder-asc-start-0.html?sid=b9e55fa2af27b5f5b8d6b15a68a2ec24

its either a locale issue (bios saved time and the local OS time) or something else.
Try going through this thread to at least rule out a mismatch in locale
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[ranran]

Thanks.
The warning is reasonable(, I don't use ntp or ethernet) so I do not think the local will help, Right?
The issue is that this messages or something related that is done in openrc when it has clock skew results in 6 seconds in boot.
I wanted to avoid it if possible.

[krinn]

openrc generate a cache file for its deptree structure, allowing openrc to just open the file and reuse the stored structure.
with clock skew the comparaison done by openrc on that file date/time with current time is no more reliable, and you have delay while openrc generate the file content to know the tree service dependency.

I wonder (for curisosity) why you do that, i mean what is the reason you disconnect your rtc battery? (as the only "valid" reason i have in mind is forcing a bios reset, but nearly all m/b have a switch to clear it)

[Super tux]

To fix clockskew issue
$ cd /
$ touch currtime
$ find . -cnewer /currtime -exec touch {} \;

If you want to read what it does http://www.cydeweys.com/blog/2007/08/27/fixing-clock-skew-problems-in-gnulinux/
You can set date then $ hwclock --systohc
To sync the sytem clock to bios.

[Anon-E-moose]

Does the /etc/adjtime file have a skew adjustment in it?

Are you saving system time to hwclock when you shutdown?
_________________
PRIME x570-pro, 3700x, 6.1 zen kernel
gcc 13, profile 17.0 (custom bare multilib), openrc, wayland

[Super tux]

I think it sets it, and does not change value, beside counting seconds.

[ranran]

Hi,

As long as the battery is connected, than there is no issue.
The "clock skew" happens in case I disconnect the battery,
I use the hwclock in openrc (not in kernel).
I left the configuration as-is (default), hwclock is in openrc "boot" , and as I understand the default openrc configuration (I did not make any changes in config file) take care that system clock is saved into hwclock in sutdown and viceversa in boot.
It seems that all this works perfect. But in case of disconnecting battery there is "clock skew" issue.

I would not mind about these warnings, the only thing is that it "eats" 5 seconds in boot for some reason.
It happens only in first boot (after rtc disconnection and connection), so we might ignore it. Yet, I wander if it is possible to fix that too .

Thanks

[khayyam]

[Anon-E-moose]

I didn't pay attention to the fact that he was removing the cmos battery.

Why would anyone do that, well other than to put a new one in.
If doing it repeatedly, then why start a thread about "the problem"?

Reminds me of the old joke, "doctor, doctor, it hurts when I do this"
_________________
PRIME x570-pro, 3700x, 6.1 zen kernel
gcc 13, profile 17.0 (custom bare multilib), openrc, wayland

[ranran]

Hi,

Sorry for the confusion. I changed the subject to make it clearer.
Thanks for all comments , and the jokes

Ranran

[ranran]

Thanks, I got it now. somehow I missed krin explanation above...
"
openrc generate a cache file for its deptree structure, allowing openrc to just open the file and reuse the stored structure.
with clock skew the comparaison done by openrc on that file date/time with current time is no more reliable, and you have delay while openrc generate the file content to know the tree service dependency. "

And it's not avoidable.


Got it!

[khayyam]

[ranran]

Hi,

One more and final on this...

I've found out that in our final board there will be no battery,
We update rtc only after startup (using gps).

Now, I understand from this thread, that we can't overcome the cache files, and the higher boot time in such case.

Thank you all again.
Ranran

[Hu]

You can overcome the issue if you arrange for the clock to be right before you start openrc. What are you doing that you are embedding a general purpose Linux on such a stripped down motherboard?

[ranran]

Hi

Sort of mobile handler.
We use the same linux for both operation and development.
I dont think I can update rtc right at the start of linux because application need to start, read gps, and only then can update rtc.
Thanks

[Ant P.]

If you have a standard GPS device connected over serial you could use the PPS time signal to set the clock in early inittab. But this is all speculative.