[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Qemu-devel] [Qemu-block] Can I only commit from active image to cor

From: Eric Blake
Subject: Re: [Qemu-devel] [Qemu-block] Can I only commit from active image to corresponding range of its backing file by qemu cmd?
Date: Tue, 25 Sep 2018 10:47:31 -0500
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0

On 9/25/18 9:13 AM, Alberto Garcia wrote:

If you only want to copy parts of a backing file I think it's much
simpler if you use copy-on-read:

qemu-io -C -c 'read 0 1M' img.003.commit.000

Oh, slick.

$ qemu-img convert -O qcow2 \
     "json:{'driver':'null-co','size':1048576}" \
                    'file':{'driver':'file','filename':'img.003'}}}" \

qemu-io -C -c 'read 1M 1M' img.003.nocommit

So use copy-on-read to extract the portions you care about into temporary files, then commit those temporary files into the target.

Beats my hacks using 'qemu-nbd -c /dev/nbdN' and then several dd processes as directed by 'qemu-img map --output=json' output.

Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

reply via email to

[Prev in Thread] Current Thread [Next in Thread]