hwclock

Bruce Dubbs bruce.dubbs at gmail.com
Thu Jun 25 11:54:47 PDT 2009


Bryan Kadzban wrote:
> Bruce Dubbs wrote:

>> I don't know if this is worth spending a lot of time, but I'd like to
>> see a system that can have / mounted read only.
> 
> Then you're going to *NEED* the adjtime file somewhere other than the
> rootfs...  :-)

Right.

>> The problem areas during boot are /etc/mtab, /etc/blkid.tab, and
>> /etc/adjtime.  With the move of libblkid and libuuid to
>> util-linux-ng, the first two are being addressed in the relatively 
>> near future,
> 
> Mmm?  Did mount stop writing to /etc/mtab or something?  That needs to
> be writable no matter which blkid / uuid library you use.  Unless you
> don't mind having "-o user" broken (I don't, but others probably do);
> then you can symlink it to /proc/mounts.

Not yet, but Karel Zak, th emaintainer wrote: "My plan is to support systems 
without /etc/mtab and use /proc/self/mountinfo in util-linux-ng 2.{17,18} 
(September/October 2009 or so...)."

I'm not sure when mountinfo went into the kernel.  2.6.26.4 has it, but 2.2.22.5 
does not.

> blkid.tab may not be required anymore, though.  I don't know the status
> of that.

I don't either.  It's just an issue that needs to be addressed for a read only 
rootfs.  It's a chicken/egg type of thing, somewhat like the issue of log 
entries before syslogd is started up.

>> but we should get adjtime right for any reasonable configuration.
> 
> A warning in the book regarding /var might be in order.  Mentioning that
> NTP probably doesn't require the adjtime file at all (depending on
> whether the user wants a more-accurate clock before NTP starts) may be a
> good idea as well.

Yes.  That may be our best option for now.

   -- Bruce



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