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[Dan Watkins <daniel.watkins@xxxxxxxxxxxxx>]

** Changed in: cloud-init
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1490796

Title:
  [SRU] cloud-init must check/format Azure ephemeral disks each boot

Status in cloud-init:
  Fix Released
Status in cloud-init package in Ubuntu:
  Fix Released
Status in cloud-init source package in Precise:
  Fix Released
Status in cloud-init source package in Trusty:
  Fix Released
Status in cloud-init source package in Vivid:
  Fix Released

Bug description:
  
  [Impact]
  Sometimes when rebooting an instance in Azure, a different ephemeral disk will be presented. Azure ephemeral disks are presented as NTFS disks, but we reformat them to ext4.  With the last cloud-init upload, we shifted to using /dev/disk symlinks to mount these disks (in case they are not presented as the same physical device).  Unfortunately, the code that determines if we have a new ephemeral disk was not updated to handle symlinks, so never detects a new disk.

  [Test Case]
  1) Boot an Azure instance and install the new cloud-init.
  2) Change the size of the instance using the Azure web interface (as this near-guarantees that the ephemeral disk will be replaced with a new one). This will reboot the instance.
  3) Once the instance is rebooted, SSH in and confirm that:
   a) An ext4 ephemeral disk is mounted at /mnt, and
   b) cloud-init.log indicates that a fabric formatted ephemeral disk was found on this boot.

  [Regression Potential]
  Limited; two LOCs change, to dereference symlinks instead of using paths verbatim.

  [Original Report]
  Ubuntu 14.04.3 (20150805) on Azure with cloud-init package 0.7.5-0ubuntu1.8.

  On Azure cloud-init prepares the ephemeral device as ext4 for the
  first boot.  However, if the VM is ever moved to another Host for any
  reason, then a new ephemeral disk might be provided to the VM.  This
  ephemeral disk is NTFS formatted, so for subsequent reboots cloud-init
  must detect and reformat the new disk as ext4.  However, with cloud-
  init 0.7.5-0ubuntu1.8 subsequent boots may result in fuse mounted NTFS
  file system.

  This issue occurred in earlier versions of cloud-init, but was fixed
  with bug 1292648 (https://bugs.launchpad.net/ubuntu/+source/cloud-
  init/+bug/1292648).  So this appears to be a regression.

  Repro:
    - Create an Ubuntu 14.04.3 VM on Azure
    - Resize the VM to a larger size (this typically moves the VM)
    - Log in and run 'blkid' to show an ntfs formatted ephemeral disk:

      # blkid
      /dev/sdb1: LABEL="Temporary Storage" UUID="A43C43DD3C43A95E" TYPE="ntfs"

  Expected results:
    - After resizing the ephemeral disk should be formatted as ext4.

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