Re: [Qemu-devel] [PATCH 02/15] block: Add driver-specific options for backing files

[Eric Blake <eblake@redhat.com>]

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On 04/12/2013 02:47 PM, Kevin Wolf wrote:
> Options starting in "backing." are passed to the backing file now. If
> you don't need to specify the filename for the backing file, you can add
> it on the command line instead of in the image file:
> 
> $ qemu-nbd -t /tmp/test.img
> $ qemu-img create -f qcow2 empty.qcow2 1G
> $ qemu-system-x86_64 -drive file=empty.qcow2,backing.file.driver=nbd,\
>     backing.file.host=localhost

So effectively empty.qcow2 is booted as though it had an explicit
nbd://localhost in its backing metadata?  Looks interesting!

> 
> Note that this doesn't override the backing filename from the image. If
> the image has one, this will fail because NBD doesn't want the options
> and a filename at the same time.
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block.c               | 27 +++++++++++++++++++++++----
>  block/mirror.c        |  2 +-
>  include/block/block.h |  2 +-
>  3 files changed, 25 insertions(+), 6 deletions(-)

Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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