From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59987) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZcD2Y-0000s1-3Z for qemu-devel@nongnu.org; Wed, 16 Sep 2015 09:46:27 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZcD2T-00085p-FQ for qemu-devel@nongnu.org; Wed, 16 Sep 2015 09:46:26 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56372) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZcD2T-000854-Ah for qemu-devel@nongnu.org; Wed, 16 Sep 2015 09:46:21 -0400 References: <55F94CC1.5050401@redhat.com> From: Eric Blake Message-ID: <55F972A6.50906@redhat.com> Date: Wed, 16 Sep 2015 07:46:14 -0600 MIME-Version: 1.0 In-Reply-To: <55F94CC1.5050401@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="1FTxIpux7S9gO4bTv870n0Gmhox54JcF3" Subject: Re: [Qemu-devel] help with understanding qcow2 file format List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laszlo Ersek , Vasiliy Tolstov Cc: qemu-devel This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --1FTxIpux7S9gO4bTv870n0Gmhox54JcF3 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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 explai= n >> 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? >=20 > 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= =2E 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-ex= panded.pdf --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --1FTxIpux7S9gO4bTv870n0Gmhox54JcF3 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJV+XKnAAoJEKeha0olJ0NqYOAH/AoVO8n7ZXwAXjIIxmqnQt9s M8Kj5XhZgPgYUYOMncPAXuDLOhRnC0eG4lfsjLvoBA9XjEn/0CVjwannxuav24Fo KqWS8NYfohbKY6Vrz243LurcYJ1Ci8vQAn3TO1sIthiGBFx1rMqJMRX2jn0JhCxr l9EBfyDevV2RtdwskMNpNttYQfVgSYM3ZTvDHeDR74+m9h9yhiA/MslJnrXx+Ee9 m3qZMde1/Cc7Piij4CACdBU6eOy34AJdRshHFoq7Upwo8TUJzyHazB8KYSQv2fFL 426sQ8D1dddVmGyR8ZLrdHO+d2sE1+A41M6Fp/u+2xANpFwpgEpv2YgoWfQKn8g= =83Zq -----END PGP SIGNATURE----- --1FTxIpux7S9gO4bTv870n0Gmhox54JcF3--