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[Launchpad Bug Tracker <1603222@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package cloud-init - 0.7.5-0ubuntu1.21

---------------
cloud-init (0.7.5-0ubuntu1.21) trusty; urgency=medium

  * Microsoft Azure:
    - Install udev rules to create /dev/disk/cloud entries for Azure ephemeral
      disk.
    - debian/patches/lp-1603222-fix-ephemeral-disk-fstab.patch:
      - Use /dev/disk/cloud entries for ephemeral disk (LP: #1603222)

 -- Daniel Watkins <daniel.watkins@xxxxxxxxxxxxx>  Fri, 25 Nov 2016
10:12:20 +0000

** Changed in: cloud-init (Ubuntu Trusty)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1603222

Title:
  Azure: incorrect entry in fstab for ephemeral disk

Status in cloud-init:
  Fix Committed
Status in cloud-init package in Ubuntu:
  Fix Released
Status in cloud-init source package in Precise:
  Confirmed
Status in cloud-init source package in Trusty:
  Fix Released
Status in cloud-init source package in Xenial:
  Invalid
Status in cloud-init source package in Yakkety:
  Invalid

Bug description:
  [Impact]
  There is a chance that Azure users' ephemeral disks will not be mounted properly if the device names change after a reboot.

  [Test Case]

  1) Provision an Ubuntu VM on Azure (I tested with 14.04.4)
  2) The fstab entry for the ephemeral disk (/mnt) correctly points to /dev/disk/cloud/azure_resource
  3) Reboot the VM (sudo reboot)
  4) The fstab entry still points to /dev/disk/cloud/azure_resource (and not /dev/sdb)

  [Regression Potential]

  This introduces new udev rules to the cloud-init package.  These will
  only cause entries to appear on Azure.  It also makes a minor change
  to how cloud-init will write to /etc/fstab on Azure.

  Both of these changes will have no impact outside of Azure, and are
  the intended behaviour on Azure.

  [Original Bug Report]

  During provisioning cloud-init adds an entry for the ephemeral disk in
  /etc/fstab. After provisioning this entry is correct and points to
  "/dev/disk/azure/resource-part1". This symlink is created dynamically
  by 66-azure-storage.rules.

  For some reason after the first reboot cloud-init overwrites the fstab
  entry and changes the "/dev/disk/azure/resource-part1" to the device
  name that it points to, i.e. /dev/sdb1.  However, this is incorrect
  since /dev/sd* device names are not persistent.

  Repro:

  1) Provision an Ubuntu VM on Azure (I tested with 14.04.4)
  2) The fstab entry for the ephemeral disk (/mnt) correctly points to "/dev/disk/azure/resource-part1".
  3) Reboot the VM (sudo reboot)
  4) The fstab entry now incorrectly points to /dev/sdb1 instead of the symlink.

  Impact:
  There is a chance that the customer's ephemeral disk will not be mounted properly if the device names change after a reboot.

  Related bugs:
   * bug 1611074: Reformatting of ephemeral drive fails on resize of Azure VM

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