Bug#747653: grub2-common: update-grub adds both devices and a line feed for BTRFS RAID 1 setup

[Andrey Borzenkov]

В Sat, 10 May 2014 20:53:34 +0200
Martin Steigerwald <Martin at Lichtvoll.de> пишет:

> Package: grub2-common
> Version: 2.02~beta2-10
> Severity: normal
> 
> Dear Maintainer,
> 
> I am booting my Debian system via a BTRFS RAID 1 which spans a logical
> volume on a Crucial MSATA and Intel SATA SSD each.
> 
> After running update-grub I am getting this in /boot/grub/grub.cfg:
> 
>                 echo    'Linux 3.15.0-rc5-tp520 wird geladen …'
>                 linux   /vmlinuz-3.15.0-rc5-tp520 root=/dev/mapper/sata-debian
>         /dev/mapper/msata-debian ro rootflags=subvol=debian  init=/bin/systemd resume=/dev/mapper/sata-swap 
>                 echo    'Initiale Ramdisk wird geladen …'
>                 initrd  /initrd.img-3.15.0-rc5-tp520
> 
> update-grub basically adds both devices of the BTRFS RAID 1 device
> separated by a line feed. For mounting BTRFS RAID 1 tough one of them
> is enough, once btrfs device scan is run, for which I currently use an
> script for initramfs-tools as a work-around as it didn´t work out of
> the box on my last tests[1].
> 
> This behaviour is due to grub-probe which is called by grub-mkconfig
> at line 139
> 
> 138 # Device containing our userland.  Typically used for root= parameter.
> 139 GRUB_DEVICE="`${grub_probe} --target=device /`"
> 140 GRUB_DEVICE_UUID="`${grub_probe} --device ${GRUB_DEVICE} --target=fs_uuid 2> /dev/null`" || true
> 
> which is called by update-grub returns both devices with a
> linefeed:
> 
> merkaba:~> grub-probe --target=device /
> /dev/mapper/sata-debian
> /dev/mapper/msata-debian
> 
> grub-probe is an ELF binary.
> 
> The following little change workarounds the issue for me:
> 
> merkaba:~> diff -u /usr/sbin/grub-mkconfig.dist /usr/sbin/grub-mkconfig     
> --- /usr/sbin/grub-mkconfig.dist        2014-05-08 14:35:25.000000000 +0200
> +++ /usr/sbin/grub-mkconfig     2014-05-10 20:46:00.380096263 +0200
> @@ -136,7 +136,7 @@
>  fi
>  
>  # Device containing our userland.  Typically used for root= parameter.
> -GRUB_DEVICE="`${grub_probe} --target=device /`"
> +GRUB_DEVICE="`${grub_probe} --target=device / | head -1`"
>  GRUB_DEVICE_UUID="`${grub_probe} --device ${GRUB_DEVICE} --target=fs_uuid 2> /dev/null`" || true
>  
>  # Device containing our /boot partition.  Usually the same as GRUB_DEVICE.
> 
> 
> But I suppose the real fix is to be made in the binary grub-probe.
> 

No, grub-probe is correct; grub needs to know all devices so it can
have full information which drivers it requires to access them.

See also
https://lists.gnu.org/archive/html/grub-devel/2014-05/msg00005.html

I suggest you discuss it with Colin, but for now I tend to think, fix
should go into 10_linux. May be always use UUID for btrfs.

But this sounds like new can of worms :(