grub2-install: Couldn't find physical volume ‘(null)’. (fwd)

[Sam Varshavchik]

Andrei Borzenkov writes:

> 11.04.2016 20:21, Sam Varshavchik пишет:
> > Andrei Borzenkov writes:
> >
> >> On Mon, Apr 11, 2016 at 1:56 PM, Sam Varshavchik
> >> <address@hidden> wrote:
> >> >> > address@hidden ~]# /sbin/grub2-install /dev/sdb
> >> >> > Installing for i386-pc platform.
> >> >> > /sbin/grub2-install: warning: Couldn't find physical volume
> >> ‘(null)’.
> >> >> > Some modules may be missing from core image..
> >> >> > /sbin/grub2-install: warning: Couldn't find physical volume
> >> ‘(null)’.
> >> >> > Some modules may be missing from core image..
> >> >> > Installation finished. No error reported.
> >> >> >
> >> >> > Now, anyone have any idea what's up with these warnings?
> >> >> >
> >> ...
> >> >
> >> > Googling around finds some references of this warning coming out
> >> while the
> >> > md-raid volumes are being synced. This warning still comes out after
> >> > everything is fully synced up.
> >> >
> >>
> >> I think I know what happens. Did you reboot after MD was resynced? If
> >> not, please try
> >>
> >> blockdev --flushbufs /dev/sda
> >> blockdev --flushbufs /dev/sdb
> >>
> >> and try grub2-install once again.
> >
> > I did not reboot, but this did not make any difference.
> >
> > address@hidden ~]# blockdev --flushbufs /dev/sda
> > address@hidden ~]# blockdev --flushbufs /dev/sdb
> > address@hidden ~]# /sbin/grub2-install /dev/sdb
> > Installing for i386-pc platform.
> > /sbin/grub2-install: warning: Couldn't find physical volume ‘(null)’.
> > Some modules may be missing from core image..
> > /sbin/grub2-install: warning: Couldn't find physical volume ‘(null)’.
> > Some modules may be missing from core image..
> > Installation finished. No error reported.
> >
>
>
> OK, so please, do the same for partitions that are part of MD device
> where /boot is located and try once more.
>
> blockdev --flushbufs /dev/sdaX
> blockdev --flushbufs /dev/sdbX
>
> You did not answer which MD array is /boot so I cannot tell which ones.

The /boot was on /dev/md0, which was /dev/sda1 and /dev/sdb1. And that did  
it, thanks:

# mount /boot
mount: /dev/md0 is already mounted or /boot busy
      /dev/md0 is already mounted on /boot
address@hidden ~]# blockdev --flushbufs /dev/sdb1
address@hidden ~]# blockdev --flushbufs /dev/sda1
address@hidden ~]# /sbin/grub2-install /dev/sdb
Installing for i386-pc platform.
Installation finished. No error reported.

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