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Re: Bug#520763: hwclock: NVRAM flat battery sets date to 1904

Hi, Jörg.

On May 16 2009, Jörg Sommer wrote:
> I would much more prefer to get prompted for the correct time, because
> with a wrong time fsck fail due to the last fsck is in the future.

The basic idea is sound.

> But I don't know how to do prompting in init scripts correctly.

But the problem here is that prompting in init scripts shouldn't be
done. At least, a lot of users wouldn't like to have to attend the boot
up process. Not without a timeout in the read, at least. Controlled by
the system administrator.

And, please, do remember that while we are discussing this on
debian-powerpc, other arches suffer from the very same problem too (dead
battery/lack of power leading to clock being set waaaaay before the
current date).

> And to guess if the hardware clock is wrong I think we can look at the
> installation time of the module directory of the kernel.
> /boot/vmlinux-$(uname -r) is possible, too.

I already suggested something that is slightly more general (even though
I think that it is a hack):

* save the date on every shutdown (say, somewhere under /var or a
  similar place that is guaranteed to be there when the system
  boots---we have to be sure that the place isn't mounted readonly
  when saving the date and that it will be available for reading);

* upon boot, if any saved date is used, then use it. Otherwise, set a
  dummy date (taken, say, as the most recent from the kernel, the
  filesystem being mounted or some fixed date that is known to be
  "valid"---the date of the release of the package, perhaps).

I do think that this is a dirty hack, but it is a bit more flexible than
just asking the user.

> I propose this patch:

And this doesn't mean that the possibility of asking the user is
completely ignored. Just put a configuration variable there defaulting
to allow unattended boots to proceed, while still providing the
opportunity for the sysadmin to do what you proposed in your patch.


Rogério Brito : rbrito@{mackenzie,ime.usp}.br : GPG key 1024D/7C2CAEB8
http://www.ime.usp.br/~rbrito : http://meusite.mackenzie.com.br/rbrito
Projects: algorithms.berlios.de : lame.sf.net : vrms.alioth.debian.org

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