dracut waiting for background mdadm reconstruction to complete

Sam Varshavchik mrsam at courier-mta.com
Thu Dec 1 22:17:10 UTC 2011

Daniel Drake writes:

> On Wed, Nov 30, 2011 at 5:15 PM, Sam Varshavchik <mrsam at courier-mta.com>  
> wrote:
> > Daniel Drake writes:
> >
> >> My understanding is that this reconstruction is a background task, is
> >> there really a need for this to hold up boot?
> >>
> >> This behaviour comes from
> >> 0064-90mdraid-wait-for-md-devices-to-become-clean.patch in the
> >> dracut-013-19.fc16 package.
> >
> >
> > What part dracut runs during boot?
> Not sure if I understand the question.
> Dracut runs "mdadm -W" for each mdraid device during every boot when
> the mdraid module is included in the initramfs. This is illustrated
> clearly in the patch in question:

Ok, so it's not dracut itself that runs, it's what it puts into the  
initramfs. That's what confused me.

> http://pkgs.fedoraproject.org/gitweb/?p=dracut.git;a=blob;f=0064-90mdraid- 
> wait-for-md-devices-to-become- 
> clean.patch;h=58c786cc5ca0b94fd138674c54417w29c38befc0;hb=refs/heads/f16
> -W is documented to behave as follows:
>        -W, --wait
>               For each md device given, wait  for  any  resync,  recovery,   
> or
>               reshape  activity to finish before returning.  mdadm will  
> return
>               with success if it actually waited for every device listed,  
> oth‐
>               erwise it will return failure.

Not sure I understand the need for that at boot, myself.

mdraid does seem to have become a little bit of a fustercluck, recently. I  
now know more about raid than I ever wanted to know. And this one should  
make installing Fedora on a large mdraid box even more fun. Anaconda will  
happily create mdraid partitions for you, if you ask, and then proceed to  
install everything; but I'm sure it won't wait for the just-assembled arrays  
to sync up, so the first boot after a Fedora install will now halt – likely  
with nary a clue what's going on.
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