Re: [Qemu-devel] [PATCH v3] qemu-img: Implement 'diff' operation.

[Eric Blake]

On 05/17/2012 09:34 AM, Richard W.M. Jones wrote:
> From: "Richard W.M. Jones" <address@hidden>
> 
> This produces a qcow2 file which is the difference between
> two disk images.  ie, if:
> 
>   base.img     - is a disk image (in any format)
>   modified.img - is base.img, copied and modified
> 
> then:
> 
>   qemu-img diff -b base.img modified.img diff.qcow2
> 
> creates 'diff.qcow2' which contains the differences between 'base.img'
> and 'modified.img'.  Note that 'diff.qcow2' has 'base.img' as its
> backing file.
> 
> Signed-off-by: Richard W.M. Jones <address@hidden>
> Cc: Matthew Booth <address@hidden>
> Cc: Pablo Iranzo Gómez <address@hidden>
> Cc: Tomas Von Veschler <address@hidden>

Regarding the documentation and command overview:

Reviewed-by: Eric Blake <address@hidden>

Regarding the actual logic used in computing the diff, I did not closely
look at that, and you would be wise to get a review from someone more
familiar with block dev operations.

-- 
Eric Blake   address@hidden    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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