Re: [Qemu-devel] [PATCH][RFC] Add compare subcommand for qemu-img

[Eric Blake]

On 08/01/2012 04:03 AM, Miroslav Rezanina wrote:
> This patch adds compare subcommand that compares two images. Compare has 
> following criteria:
> - only data part is compared
> - unallocated sectors are not read
> - in case of different image size, exceeding part of bigger disk has to be 
> zeroed/unallocated to compare rest
> - qemu-img returns:
>    - 0 if images are identical
>    - 1 if images differ
>    - 2 on error
> 
> Signed-off-by: Miroslav Rezanina <address@hidden>
> 

> +++ b/qemu-img.c
> @@ -96,7 +96,9 @@ static void help(void)
>             "  '-a' applies a snapshot (revert disk to saved state)\n"
>             "  '-c' creates a snapshot\n"
>             "  '-d' deletes a snapshot\n"
> -           "  '-l' lists all snapshots in the given image\n";
> +           "  '-l' lists all snapshots in the given image\n"
> +           "Parameters to compare subcommand:\n"
> +           "  '-g' Second image format (in case it differs from first 
> image)\n";

As written, this sounds like:

No -f, no -g => probe both
-f, no -g => -f applies to both
no -f, -g => probe first, use -g for second
-f, -g => use given formats for both

Is that really what you meant, or do we actually get:

-f, no -g => -f applies to first, probe second

I think both interpretations could make sense, but I'd prefer having the
omission of -g imply probing the second file type regardless of the
presence or absence of -f, for consistency.

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

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