[Bug 508901] Re: update-grub sets wrong root argument

[Peter Passchier]

The problem with this solution is, it is discarding most of the
information of os-prober, and instead is just enumerating the kernels &
initrds that are listed in /lib/modules. Now I haven't checked with many
distributions, but I know Ubuntu, Debian, OpenSUSE and RedHat is using
this same location. But you could build boot entries for any kernel you
can find anywhere. It's just that you couldn't build initrds for those
other kernels because update-initramfs will not run (I don't know about
dracut).

I have reported a related problem in these forums, but got a Won't Fix.
I'm now maintaining my own patches for my own needs, and anybody is
welcome to them.

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Title:
  update-grub sets wrong root argument

Status in grub2 package in Ubuntu:
  Confirmed

Bug description:
  Binary package hint: grub2

  I've made a backup of my system with dd and then changed the UUID and
  label of the drive.  I would like to be able to boot from either the
  main system or the backup, ideally regardless of whether the backup is
  in a USB enclosure or mounted internally.

  When I run update-grub, even though it correctly finds the backup and
  uses its UUID as a parameter for the search command, it still sets the
  root= argument of the linux command to the main system.  This makes
  the backup unusable.

  So in my setup, the original drive is
  7f0e857e-6118-4696-bdc6-7c51b31e1002, and the backup is 9de2fc84-1128
  -41eb-9c1b-a444d070d415.  Each one has its fstab set up to mount
  itself as root.  The generated boot options look like this:

  ### BEGIN /etc/grub.d/10_linux ###
  menuentry "Ubuntu, Linux 2.6.31-17-generic" {
          recordfail=1
          if [ -n ${have_grubenv} ]; then save_env recordfail; fi
  	set quiet=1
  	insmod ext2
  	set root=(hd0,1)
  	search --no-floppy --fs-uuid --set 7f0e857e-6118-4696-bdc6-7c51b31e1002
  	linux	/boot/vmlinuz-2.6.31-17-generic root=/dev/sda1 ro   quiet splash
  	initrd	/boot/initrd.img-2.6.31-17-generic
  }
  ...
  ### BEGIN /etc/grub.d/30_os-prober ###
  menuentry "Ubuntu, Linux 2.6.31-17-generic (on /dev/sdb1)" {
  	insmod ext2
  	set root=(hd1,1)
  	search --no-floppy --fs-uuid --set 9de2fc84-1128-41eb-9c1b-a444d070d415
  	linux /boot/vmlinuz-2.6.31-17-generic root=UUID=7f0e857e-6118-4696-bdc6-7c51b31e1002 ro quiet splash
  	initrd /boot/initrd.img-2.6.31-17-generic
  }

  I tried uncommenting the GRUB_DISABLE_LINUX_UUID=true" line in
  /etc/default/grub, but it only affects the output of 10_linux, not
  30_os-prober.

  ProblemType: Bug
  Architecture: i386
  Date: Sun Jan 17 21:07:18 2010
  DistroRelease: Ubuntu 9.10
  Package: grub2 1.97~beta4-1ubuntu4.1
  ProcEnviron:
   LANGUAGE=en_GB.UTF-8
   PATH=(custom, user)
   LANG=en_GB.UTF-8
   SHELL=/bin/bash
  ProcVersionSignature: Ubuntu 2.6.31-17.54-generic
  SourcePackage: grub2
  Uname: Linux 2.6.31-17-generic i686

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