On 30.01.2017 19:37, Eric Blake wrote: > On 01/26/2017 07:27 AM, Daniel P. Berrange wrote: >> On Thu, Jan 26, 2017 at 08:35:30PM +0800, Fam Zheng wrote: >>> On Thu, 01/26 11:04, Daniel P. Berrange wrote: >>>> The -n arg to the convert command allows use of a pre-existing image, >>>> rather than creating a new image. This adds a -n arg to the dd command >>>> to get feature parity. >>> >>> I remember there was a discussion about changing qemu-img dd's default to a >>> "conv=nocreat" semantic, if so, "-n" might not be that useful. But that part >>> hasn't made it into the tree, and I'm not sure which direction we should >>> take. >>> (Personally I think default to nocreat is a good idea). >> >> Use nocreat by default would be semantically different from real "dd" >> binary which feels undesirable if the goal is to make "qemu-img dd" >> be as consistent with "dd" as possible. >> >> It would be trivial to rewrite this patch to add support for the "conv" >> option, allowing the user to explicitly give 'qemu-img dd conv=nocreat' >> instead of my 'qemu-img dd -n' syntax, without changing default semantics. > > Adding 'conv=nocreat' (and not '-n') feels like the right way to me.
The original idea was to make conv=nocreat a mandatory option, I think. qemu-img was supposed error out if the user did not specify it. Max
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