I have a qemu qcow2 disk snapshot dev.img that is based off a backing file dev.bak.
How can I merge both into a standalone devplus.img, while leaving dev.bak as it is?
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Cristian Ciupitu
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user2512377
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2 Answers
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I got some help from the qemu mailing list: First copy the original base file to your standalone image file:
cp dev.bak devplus.img
Then "rebase" the image file that was backed off the original file so that it uses the new file:
qemu-img rebase -b devplus.img dev.img
Then you can commit the changes in the dev file back into the new base:
qemu-img commit dev.img
Now you can use devplus.img as a standalone image file and get rid of dev.img if you wish, leaving the original dev.bak intact and not corrupting any other images that were based off it.
user2512377
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qemu-img convert -O qcow2 dev.img devplus.img
This detects that dev.img is based off dev.bak and creates a standalone devplus.img.
Tigran Ghahramanyan
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1Rebasing didn't work in my case, but this did - THANK YOU! (situation was: merging a "disk" snapshot, which was a mistake to create in the first place) – Jay Taylor Sep 20 '21 at 19:58
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Much better way than via `commit`, keeps all input files intact (commit "wants" to change top layer at least), also can add `-c` to compress and get smaller size. – Martian2020 Dec 06 '22 at 13:17
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`commit` answer is when one wants to flatten only part of backing chain. I don't see this answer can do that. – Martian2020 Dec 06 '22 at 13:23
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@Martian2020 what does it mean "to flatten only part of backing chain"? Do you think it is relevant to original poster's question? – Tigran Ghahramanyan Dec 08 '22 at 07:09
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well, generally speaking, it could be, image could be not directly based, but via long chain of backing images. Why do you ask? – Martian2020 Dec 08 '22 at 07:55
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ok, now I get your point. thanks. – Tigran Ghahramanyan Dec 08 '22 at 15:42