[Bug 1217933] Re: update-grub fails to detect other md OS

[Paul Crawford]

This is still broken with 14.04 and the same patch seems to work:

$ lsb_release -rd
Description:	Ubuntu 14.04.2 LTS
Release:	14.04

$ apt-cache policy grub2
grub2:
  Installed: (none)
  Candidate: 2.02~beta2-9ubuntu1
  Version table:
     2.02~beta2-9ubuntu1 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty-updates/universe amd64 Packages
     2.02~beta2-9 0
        500 http://gb.archive.ubuntu.com/ubuntu/ trusty/universe amd64 Packages

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Title:
  update-grub fails to detect other md OS

Status in grub2 package in Ubuntu:
  New
Status in os-prober package in Ubuntu:
  New

Bug description:
  I have a system with two main HDD configured as several md RAID-1 devices and I installed the 32-bit version of 12.04.2 on to one of these partitions (using the "alternate installer" ISO), with most of the others being user data (e.g. one for /home, another for virtual machines, etc). I had one md partition free and then installed the 64-bit version (12.04.3) on to that, again using the alternate installer.
  However, after the installation it is unaware of the 1st system, so running update-grub fails to add that to the boot menu and I am not able to dual-boot 32 & 64 bit systems. This worked OK previously with a hardware RAID card, but that was true hardware RAID and presented the disks as a single SCSI device.

  $ lsb_release -rd
  Description:	Ubuntu 12.04.3 LTS
  Release:	12.04

  $ apt-cache policy multipath-tools
  multipath-tools:
    Installed: (none)
    Candidate: 0.4.9-3ubuntu5
    Version table:
       0.4.9-3ubuntu5 0
          500 http://gb.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages

  I expect the OS probing to detect other operating systems, in
  particular to detect another instance of Ubuntu.

  Additional information:
  $ more /proc/mdstat 
  Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] 
  md1 : active raid1 sda3[0] sdb3[1]
        72427392 blocks super 1.2 [2/2] [UU]
        
  md2 : active raid1 sda6[0] sdb6[1]
        51167104 blocks super 1.2 [2/2] [UU]
        
  md0 : active raid1 sda1[0] sdb1[1]
        2046912 blocks super 1.2 [2/2] [UU]
        
  md4 : active raid1 sda8[0] sdb8[2]
        307068736 blocks super 1.2 [2/2] [UU]
        
  md3 : active raid1 sda7[0] sdb7[1]
        1023868736 blocks super 1.2 [2/2] [UU]

  $ mount | grep '^/dev/' | sort
  /dev/md1 on / type ext4 (rw,errors=remount-ro)
  /dev/md3 on /home type ext4 (rw)
  /dev/md4 on /vm type ext4 (rw,nobarrier)
  /dev/sdc5 on /scratch type ext4 (rw,nobarrier)

  NOTE: sda & sdb form the md devices but sdc is not part of any RAID,
  md0 is unused (was planned for /boot but not used), and md2 has the
  32-bit '/' partition which can still be mounted and accessed.

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