[Bug 623609] Re: grub-pc needs some help in uec instances

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** Branch linked: lp:ubuntu/lucid-proposed/grub2

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Title:
  grub-pc needs some help in uec instances

Status in “cloud-init” package in Ubuntu:
  Fix Released
Status in “grub2” package in Ubuntu:
  Fix Released
Status in “cloud-init” source package in Lucid:
  Fix Released
Status in “grub2” source package in Lucid:
  Fix Committed
Status in “cloud-init” source package in Maverick:
  Fix Released
Status in “grub2” source package in Maverick:
  Fix Released

Bug description:
  Binary package hint: grub2

  The uec images are intended to "just work" in 6 different
  environments:

  A.) ec2 with xen disk root device (/dev/sda1)
  B.) UEC with scsi root device (/dev/sda1)
   1.) Booted via floppy that multiboots to (hd0,1)/boot/grub/core.img
   2.) Booted via '-kernel <linux_kernel>'
  C.) UEC with virtio root device (/dev/vda1)
   1.) Booted via floppy that multiboots to (hd0,1)/boot/grub/core.img
   2.) Booted via '-kernel <linux_kernel>'
  D.) nocloud, with virtio or scsi root device as /dev/sda or /dev/vda
    Ie, this is booting the partition image as if it were a disk.
    Booted via grub boot floppy that just finds root and /vmlinuz,
    /initrd.img and boots them

  Currently, during our build process we trick grub-pc into installing as
  if it were writing to /dev/sda (which is correct for 'B' above).  That
  is done by providing a psuedo grub-probe and running [1] 
    grub-install --grub-setup=/bin/true /dev/sda && /usr/sbin/update-grub

  By tricking grub-install into working, we get core.img and associated
  files in /boot/grub that allow the bootloader to multiboot load and
  boot the system.  All of the A,B,C,D above boot first time correctly.

  In A, B.2, and C.2 I'd like for grub-pc to generally just not
  get in the way.  B.2 and C.2 work just as well as B.1 and C.1 do, so
  thats not too difficult.

  In B.1, C.1 above, we want grub-pc to actually maintain
  /boot/grub/core.img and other files.  The installation to the MBR is
  not necessary, It will be the floppy disk that multiboot loads
  (hd0)/boot/grub/core.img rather than grub installed on the MBR.

  My problems right now are:

  1.) Currently update-grub is not set to run in /etc/kernel-img.conf
      because if it is, kernel installation will fail in 'A' (bug 610554)
  2.) in C.1 and C2.2 above, on the first grub-pc upgrade, the user is
      prompted where to install grub to.  I'd like to seed the answer with
      /dev/vda.

  I'm fine with determining in cloud-init which of the situations is
  present, and on the first boot making it so everything appears to "just
  work".  I'm just need to figure out what correct set of actions to take
  is.

  Notes:
  - upgrade/install as mentioned above can be done with:
    'apt-get install --reinstall grub-pc'
  - On EC2, grub-pc is not needed.  grub-legacy-ec2 (from the cloud-init
    package) maintains /boot/grub/menu.lst, which is read by EC2's
    pv-grub.  grub-pc is not needed, but is present to keep a single
    image.
  - on EC2, there is no /dev/sda, only /dev/sdaX, and grub's searching
    for bios drives in grub-probe won't work, as there isn't really a bios.
    $ grep . /proc/partitions
    major minor  #blocks  name
     202        1   10485760 sda1
     202        2  156352512 sda2
     202        3     917504 sda3
    $ ls /dev/sda*
    /dev/sda1  /dev/sda2  /dev/sda3
    $ df / | grep -v Filesystem
    /dev/sda1             10321208    722144   9074788   8% /
    $ sudo grub-probe --device /dev/sda1
    grub-probe: error: cannot find a GRUB drive for /dev/sda1.  Check your
    device.map.
  - 'D' is by far the lowest concern, but it seems if I can get a fix
    for the others, I can probably manage something.

  --
  [1] http://bazaar.launchpad.net/~ubuntu-on-ec2/vmbuilder/automated-ec2-builds/annotate/head%3A/vmbuilder-uec-ec2-fixes

  ProblemType: Bug
  DistroRelease: Ubuntu 10.10
  Package: grub-pc 1.98+20100804-4ubuntu1
  ProcVersionSignature: User Name 2.6.35-17.23-virtual 2.6.35.2
  Uname: Linux 2.6.35-17-virtual i686
  Architecture: i386
  Date: Tue Aug 24 18:12:05 2010
  Ec2AMI: ami-a2d339cb
  Ec2AMIManifest: ubuntu-images-testing-us/ubuntu-maverick-daily-i386-server-20100824.manifest.xml
  Ec2AvailabilityZone: us-east-1b
  Ec2InstanceType: m1.small
  Ec2Kernel: aki-407d9529
  Ec2Ramdisk: unavailable
  ProcEnviron:
   PATH=(custom, no user)
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: grub2

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