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