The other fixes I wanted to bundle turned out to have a too low rate of
response and some show issues on testing. To not postpone this fix any
longer (which it already had it share of) I un-bundled this fix and
moved it into xenial-proposed now.
It is now in the SRU review queue and given that the SRU Team acks it
should show up here soon for final proposed verification.
** Changed in: qemu (Ubuntu Xenial)
Status: In Progress => Fix Committed
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https://bugs.launchpad.net/bugs/1490611
Title:
Using qemu >=2.2.1 to convert raw->VHD (fixed) adds extra padding to
the result file, which Microsoft Azure rejects as invalid
Status in QEMU:
Fix Released
Status in qemu package in Ubuntu:
Fix Released
Status in qemu source package in Xenial:
Fix Committed
Bug description:
[Impact]
* Starting with a raw disk image, using "qemu-img convert" to convert
from raw to VHD results in the output VHD file's virtual size being
aligned to the nearest 516096 bytes (16 heads x 63 sectors per head x
512 bytes per sector), instead of preserving the input file's size as
the output VHD's virtual disk size.
* Microsoft Azure requires that disk images (VHDs) submitted for
upload have virtual sizes aligned to a megabyte boundary. (Ex. 4096MB,
4097MB, 4098MB, etc. are OK, 4096.5MB is rejected with an error.) This
is reflected in Microsoft's documentation: https://azure.microsoft.com
/en-us/documentation/articles/virtual-machines-linux-create-upload-
vhd-generic/
* The fix for this bug is a backport from upstream.
http://git.qemu.org/?p=qemu.git;a=commitdiff;h=fb9245c2610932d33ce14
[Test Case]
* This is reproducible with the following set of commands (including
the Azure command line tools from https://github.com/Azure/azure-
xplat-cli). For the following example, I used qemu version 2.2.1:
$ dd if=/dev/zero of=source-disk.img bs=1M count=4096
$ stat source-disk.img
File: ‘source-disk.img’
Size: 4294967296 Blocks: 798656 IO Block: 4096 regular file
Device: fc01h/64513d Inode: 13247963 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 1000/ smkent) Gid: ( 1000/ smkent)
Access: 2015-08-18 09:48:02.613988480 -0700
Modify: 2015-08-18 09:48:02.825985646 -0700
Change: 2015-08-18 09:48:02.825985646 -0700
Birth: -
$ qemu-img convert -f raw -o subformat=fixed -O vpc source-disk.img
dest-disk.vhd
$ stat dest-disk.vhd
File: ‘dest-disk.vhd’
Size: 4296499712 Blocks: 535216 IO Block: 4096 regular file
Device: fc01h/64513d Inode: 13247964 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 1000/ smkent) Gid: ( 1000/ smkent)
Access: 2015-08-18 09:50:22.252077624 -0700
Modify: 2015-08-18 09:49:24.424868868 -0700
Change: 2015-08-18 09:49:24.424868868 -0700
Birth: -
$ azure vm image create testimage1 dest-disk.vhd -o linux -l "West US"
info: Executing command vm image create
+ Retrieving storage accounts
info: VHD size : 4097 MB
info: Uploading 4195800.5 KB
Requested:100.0% Completed:100.0% Running: 0 Time: 1m 0s Speed: 6744 KB/s
info: https://[redacted].blob.core.windows.net/vm-images/dest-disk.vhd was
uploaded successfully
error: The VHD
https://[redacted].blob.core.windows.net/vm-images/dest-disk.vhd has an
unsupported virtual size of 4296499200 bytes. The size must be a whole number
(in MBs).
info: Error information has been recorded to /home/smkent/.azure/azure.err
error: vm image create command failed
* A fixed qemu-img will not result in an error during azure image
creation. It will require passing -o force_size, which will leverage
the backported functionality.
[Regression Potential]
* The upstream fix introduces a qemu-img option (-o force_size) which
is unset by default. The regression potential is very low, as a
result.
...
I also ran the above commands using qemu 2.4.0, which resulted in the
same error as the conversion behavior is the same.
However, qemu 2.1.1 and earlier (including qemu 2.0.0 installed by
Ubuntu 14.04) does not pad the virtual disk size during conversion.
Using qemu-img convert from qemu versions <=2.1.1 results in a VHD
that is exactly the size of the raw input file plus 512 bytes (for the
VHD footer). Those qemu versions do not attempt to realign the disk.
As a result, Azure accepts VHD files created using those versions of
qemu-img convert for upload.
Is there a reason why newer qemu realigns the converted VHD file? It
would be useful if an option were added to disable this feature, as
current versions of qemu cannot be used to create VHD files for Azure
using Microsoft's official instructions.
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