On Thu 27 Sep 2018 04:14:15 PM CEST, Max Reitz wrote: > On 25.09.18 16:13, Alberto Garcia wrote: >> On Thu 13 Sep 2018 08:37:05 PM CEST, Max Reitz wrote: >>> First, split .003 into the part we want to commit and the part we >>> don't want to commit. This is a bit tricky without qemu-img dd @seek >>> (or a corresponding convert parameter), so we'll have to make do with >>> backing=null so we don't copy anything into the output from img.003's >>> backing chain. >>> >>> Or, we would have to use backing=null, but for some reason that >>> doesn't work. I'll have to investigate. >>> >>> So rebase will need to do: >>> >>> $ qemu-img rebase -u -b '' img.003 >>> >>> $ qemu-img convert -O qcow2 \ >>> "json:{'driver':'raw','offset':0,'size':1048576,\ >>> 'file':{'driver':'qcow2',\ >>> 'file':{'driver':'file','filename':'img.003'}}}" \ >>> "json:{'driver':'null-co','size':2097152}" \ >>> img.003.commit.000 >> >> If you only want to copy parts of a backing file I think it's much >> simpler if you use copy-on-read: > > And you can do it at runtime!
How would you do that? As far as I'm aware HMP's qemu-io doesn't allow you to enable copy-on-read, and block-stream (which uses copy-on-read) doesn't allow you to specify a range. Berto