On 20.02.19 06:54, Richard W.M. Jones wrote: > It seems like it's not easy to write to a place in a qcow2 file using > qemu-io or qemu-img. For example suppose I want to overwrite blocks > 100 and 101 with my own data: > > $ qemu-img dd -f raw -O qcow2 bs=4096 skip=100 count=2 \ > if=/tmp/input.raw of=/tmp/disk.qcow2 > qemu-img: /tmp/input.raw: cannot skip to specified offset > > Skip is skipping the input, not the output. Turning to qemu-io, it > doesn't look like you can control the data written (only write > patterns). > > This patch looks good, but AFAICT it never went upstream: > > https://patchwork.kernel.org/patch/9273161/ > "qemu-img: add seek option to dd" > > Is there anything I'm missing? What is the status of that patch?
Eric sent another version last year: http://lists.nongnu.org/archive/html/qemu-block/2018-08/msg00513.html My main issue is that dd should be a frontend to convert, but it still isn't. On top, I don't see why we need feature parity with dd when it's also possible to use qemu-nbd and just the normal dd. (Or qemu-blkfuse for which I should sent patches one of these days...) I think it's wrong to re-implement existing tools in qemu. Instead, we should work on making it simpler for those existing tools to access qemu images. Note that while I did rant a bit about the concept of Eric's patch, I didn't object it in principle. I pointed out two technical issues, Eric talked about a v2, but that never appeared, I think. Max
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