[Bug 1336855] Re: [SRU] non-interactive grub updates for 12.04 break on AWS

[Ben Howard]

Attached debdiff against trusty-proposed. Tested and confirmed it works.

** Description changed:

  [SRU JUSTIFICATION]
  
  [IMPACT] Cloud-init, as part of the first boot configures grub-pc to set
  the device that grub should install to. However, in the case of HVM
  instances, /dev/xvda and /dev/xvda1 are not considered (only sda, sda1,
  vda and vda1). Since AWS HVM instances and Xen use /dev/xvdX devices,
  this means that any Grub update with an ABI change will break the
  instances, rendering them unable to boot.
  
  [FIX] Cloud-init has been patched to understand /dev/xvda devices and
  set the correct grub-pc/install_device. Further, cloud-init's postinst
  has been patched to fix people who might be affected by this bug.
  
  [Test Case 1]
  1. Boot HVM instance store AMI ami-90b156f8 (us-east-1)
  2. Update grub
  3. Update cloud-init from -proposed
  4. Reboot instance
  5. instance should come back up
  
- [Test Case 2]
+ [Test Case 2 -- 12.04 Only]
  1. Boot HVM instance store AMI ami-90b156f8 (us-east-1)
  2. run "cloud-init-cfg grub_dpkg  --freqenucy always"
  3. run "debconf-show grub-pc", confirm that  grub-pc/install_devices is /dev/xvda
  4. update grub
  5. Reboot
  6. instance should come back up
+ 
+ [Test Case 3 -- 14.04 Only]
+ 1. Boot HVM instance store AMI ami-1f958c76 (us-east-1)
+ 2. run "cloud-init single grub_dpkg  --freqenucy always"
+ 3. run "debconf-show grub-pc", confirm that  grub-pc/install_devices is /dev/xvda
+ 4. update grub
+ 5. Reboot
+ 6. instance should come back up
+ 
+ [Test Case 4]
+ 1. Install from -proposed
+ 2. Simulate a first-run:
+    echo "grub-pc grub-pc/install_devices select /dev/sda" | debconf-set-selections
+ 3. Run: cloud-init single --name=grub-dpkg --frequency=always
+ 4. Run: debconf-show grub-pc
+ 5. confirm that /dev/xvda is shown as the install device
  
  
  ----ORIGINAL report----
  
  It looks like a recent update to grub or the kernel on 12.04 is breaking
  unattended installs on EC2 for HVM instances.
  
  You can reproduce the problem by doing the following:
  
  region: us-east-1
  virtualization type: HVM (e.g. r3.xlarge)
  AMI ID: ami-7a916212
  
  dpkg --configure –a
  apt-get update
  apt-get install -y ruby ruby-dev libicu-dev libssl-dev libxslt-dev
  libxml2-dev monit
  apt-get dist-upgrade –y

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Title:
  [SRU] non-interactive grub updates for 12.04 break on AWS

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