On 09/16/2015 05:04 AM, Laszlo Ersek wrote: > On 09/16/15 12:56, Vasiliy Tolstov wrote: >> Hi, I'm need help to understand qcow2 file format, can somebody explain >> to me, for example if i need to read 1K from offset 512? >> >> As i'm understand i need to calculate offset in qcow2 file using some >> things from header, can somebody explains my how can i do that? > > All I can say is, "docs/specs/qcow2.txt".
qemu-img map file.qcow2 is a great way to learn which physical host offsets hold the data at which guest offsets. As for coding interactions with qcow2, see the source under block/qcow2.c. You may also be interested in the visual representation of qcow2 in my KVM Forum slides, part 1: http://events.linuxfoundation.org/sites/events/files/slides/2015-qcow2-expanded.pdf -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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