[gentoo-user] /dev/rtc => rtc0

[gentoo-user] /dev/rtc => rtc0

[Mark Knecht]

Hi,
   I know nothing of this part of the Linux boot process. If it's
*fairly* simple can someone point me at the right stuff to understand
how Gentoo creates a link from /dev/rtc to rtc0? When in the boot
process does this link become valid?

   Is it something that's held in a file and recreated from that file
on each boot? Is it created automagically by Gentoo Angels that look
after my well being but seldom reveal themselves? Is it created by the
kernel itself when something is specifically configured to do so?
Something else?

Thanks,
Mark

lightning src # uname -a
Linux lightning 2.6.27-gentoo-r8 #6 Fri Jan 30 18:55:56 PST 2009
x86_64 AMD Athlon(tm) 64 Processor 3000+ AuthenticAMD GNU/Linux
lightning src # ls -al /dev/rtc*
lrwxrwxrwx 1 root root      4 2009-01-30 10:58 /dev/rtc -> rtc0
crw-r--r-- 1 root root 254, 0 2009-01-30 10:58 /dev/rtc0
lightning src #

Re: [gentoo-user] /dev/rtc => rtc0

[Dale]

Mark Knecht wrote:
> Hi,
>    I know nothing of this part of the Linux boot process. If it's
> *fairly* simple can someone point me at the right stuff to understand
> how Gentoo creates a link from /dev/rtc to rtc0? When in the boot
> process does this link become valid?
>
>    Is it something that's held in a file and recreated from that file
> on each boot? Is it created automagically by Gentoo Angels that look
> after my well being but seldom reveal themselves? Is it created by the
> kernel itself when something is specifically configured to do so?
> Something else?
>
> Thanks,
> Mark
>
> lightning src # uname -a
> Linux lightning 2.6.27-gentoo-r8 #6 Fri Jan 30 18:55:56 PST 2009
> x86_64 AMD Athlon(tm) 64 Processor 3000+ AuthenticAMD GNU/Linux
> lightning src # ls -al /dev/rtc*
> lrwxrwxrwx 1 root root      4 2009-01-30 10:58 /dev/rtc -> rtc0
> crw-r--r-- 1 root root 254, 0 2009-01-30 10:58 /dev/rtc0
> lightning src #
>
>
>   

From my understanding udev creates all the "stuff" in /dev.  You can
change the rules that it uses to make them tho.  I think there is
documentation on gentoo.org to help with that.  So far, mine has worked
well enough.  Lucky I guess.

That help?

Dale

:-)  :-)

Re: [gentoo-user] /dev/rtc => rtc0

[Mark Knecht]

On Sat, Jan 31, 2009 at 2:43 PM, Dale <rdalek1967@gmail.com> wrote:
> Mark Knecht wrote:
>> Hi,
>>    I know nothing of this part of the Linux boot process. If it's
>> *fairly* simple can someone point me at the right stuff to understand
>> how Gentoo creates a link from /dev/rtc to rtc0? When in the boot
>> process does this link become valid?
>>
>>    Is it something that's held in a file and recreated from that file
>> on each boot? Is it created automagically by Gentoo Angels that look
>> after my well being but seldom reveal themselves? Is it created by the
>> kernel itself when something is specifically configured to do so?
>> Something else?
>>
>> Thanks,
>> Mark
>>
>> lightning src # uname -a
>> Linux lightning 2.6.27-gentoo-r8 #6 Fri Jan 30 18:55:56 PST 2009
>> x86_64 AMD Athlon(tm) 64 Processor 3000+ AuthenticAMD GNU/Linux
>> lightning src # ls -al /dev/rtc*
>> lrwxrwxrwx 1 root root      4 2009-01-30 10:58 /dev/rtc -> rtc0
>> crw-r--r-- 1 root root 254, 0 2009-01-30 10:58 /dev/rtc0
>> lightning src #
>>
>>
>>
>
> From my understanding udev creates all the "stuff" in /dev.  You can
> change the rules that it uses to make them tho.  I think there is
> documentation on gentoo.org to help with that.  So far, mine has worked
> well enough.  Lucky I guess.
>
> That help?
>
> Dale

Hi Dale,
   While poking around in a bunch of different kernel config files -
some gentoo-sources - some not - I found there is an option in

Device Drivers -> RTC

that ONLY shows up when you tell the kernel to build the support in.
(I.e. - not off or modular) The option says

<*> Set system time from RTC on startup or resume
(rtc0) RTC used to set the system time

So, it appears it's a kernel oriented thing which allows it to get set
very early in the boot process. My problem on a kernel I built
yesterday was "File has a date in the future" sort of messages. I had
this set as modular so it couldn't load that early. The other problem
was that since it was a module and apparently I didn't load that
module the command hwclock -r failed.

I've reconfigured the kernel and will build it and test after I get
finished with an emerge -e world later today.

Thanks for the response. Hope this info helps someone else in the
future. (and me after the reboot!) ;-)

Cheers,
Mark

Re: [gentoo-user] /dev/rtc => rtc0

[Dale]

Mark Knecht wrote:
> On Sat, Jan 31, 2009 at 2:43 PM, Dale <rdalek1967@gmail.com> wrote:
>   
>> Mark Knecht wrote:
>>     
>>> Hi,
>>>    I know nothing of this part of the Linux boot process. If it's
>>> *fairly* simple can someone point me at the right stuff to understand
>>> how Gentoo creates a link from /dev/rtc to rtc0? When in the boot
>>> process does this link become valid?
>>>
>>>    Is it something that's held in a file and recreated from that file
>>> on each boot? Is it created automagically by Gentoo Angels that look
>>> after my well being but seldom reveal themselves? Is it created by the
>>> kernel itself when something is specifically configured to do so?
>>> Something else?
>>>
>>> Thanks,
>>> Mark
>>>
>>> lightning src # uname -a
>>> Linux lightning 2.6.27-gentoo-r8 #6 Fri Jan 30 18:55:56 PST 2009
>>> x86_64 AMD Athlon(tm) 64 Processor 3000+ AuthenticAMD GNU/Linux
>>> lightning src # ls -al /dev/rtc*
>>> lrwxrwxrwx 1 root root      4 2009-01-30 10:58 /dev/rtc -> rtc0
>>> crw-r--r-- 1 root root 254, 0 2009-01-30 10:58 /dev/rtc0
>>> lightning src #
>>>
>>>
>>>
>>>       
>> From my understanding udev creates all the "stuff" in /dev.  You can
>> change the rules that it uses to make them tho.  I think there is
>> documentation on gentoo.org to help with that.  So far, mine has worked
>> well enough.  Lucky I guess.
>>
>> That help?
>>
>> Dale
>>     
>
> Hi Dale,
>    While poking around in a bunch of different kernel config files -
> some gentoo-sources - some not - I found there is an option in
>
> Device Drivers -> RTC
>
> that ONLY shows up when you tell the kernel to build the support in.
> (I.e. - not off or modular) The option says
>
> <*> Set system time from RTC on startup or resume
> (rtc0) RTC used to set the system time
>
> So, it appears it's a kernel oriented thing which allows it to get set
> very early in the boot process. My problem on a kernel I built
> yesterday was "File has a date in the future" sort of messages. I had
> this set as modular so it couldn't load that early. The other problem
> was that since it was a module and apparently I didn't load that
> module the command hwclock -r failed.
>
> I've reconfigured the kernel and will build it and test after I get
> finished with an emerge -e world later today.
>
> Thanks for the response. Hope this info helps someone else in the
> future. (and me after the reboot!) ;-)
>
> Cheers,
> Mark
>
>
>   

My CMOS time chip sucks on this mobo.  Everything else rocks but that
stupid clock and yes I have checked the battery.  Anyway, I get that
error all the time.  If I just reboot it does all right but if I do a
shutdown, that error pops up.  Sometimes it may only be a few seconds
off, sometimes several hours to a day.  I have never had it hurt
anything here tho.  It just warns you I guess. 

Dale

:-)  :-)