Re: multipath device issue

[Harald Hoyer <harald-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

Am 03.08.2012 07:36, schrieb Dave Young:
> Hi, harald
> 
> It has nothing to do with the udev rules.
> 
> There's two issues:
> 1) 90multipath install multipath.sh to pre-trigger hook, but seems
> /dev/mapper/mpathX depends on /dev/dm-* population which will be created
> after udev trigger.
> 
> 2) fstab-sys call wait_for_dev /dev/mapper/mpathb in initqueue,
> /dev/mapper/mpathb does not geting change to create, so dracut drop to
> emergency shell.
> 
> I'm not sure what's the right way to resolve this, move multipath.sh to
> pre-mount hook looks resolve the issue 1), how to resolve the issue 2)?
> comment out it works, but it looks not a right fix.
> 
> I'm not familiar with multipath, please correct me for anything wrong.
> 

I think it _has_ to do with the udev rules.

1. the multipathd daemon has to be started before udevd is started.
2. when udev is triggered, 62-multipath.rules should kick in and call
"multipath" for every disk, which adds disks to the daemon, if they fit.
3. of course /etc/multipath.conf has to be configured correctly.

So, if you see /dev/mapper/mpathb be correctly created, when you start multpathd
after all devices exist in /dev, then the 62-multipath.rules
mechanism does not seem to work,

With the next systemd release "rd.udev.log-priority=debug" does work again and
we might be able to debug this issue.