From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49289) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZC1mt-0007Uy-AQ for qemu-devel@nongnu.org; Mon, 06 Jul 2015 04:30:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZC1mp-0001vG-W8 for qemu-devel@nongnu.org; Mon, 06 Jul 2015 04:30:03 -0400 Received: from smtp.sangfor.com.cn ([222.126.229.182]:49646 helo=mail.sangfor.com.cn) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZC1mp-0001jA-9V for qemu-devel@nongnu.org; Mon, 06 Jul 2015 04:29:59 -0400 Date: Mon, 6 Jul 2015 16:20:58 +0800 From: vt Mime-Version: 1.0 Message-ID: <201507061620581832887@sangfor.com.cn> Content-Type: multipart/alternative; boundary="----=_001_NextPart261041472731_=----" Subject: [Qemu-devel] Can the backing file of qcow2 points to a snapshot of base file? Reply-To: vt List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel , kwolf , stefanha This is a multi-part message in MIME format. ------=_001_NextPart261041472731_=---- Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: base64 DQpIaS4NCg0KSWYgYSBiYXNlIHFjb3cyIGltYWdlIHNuYXBzaG90IGNoYWluIGxpa2UgdGhpczoN Cg0KYmFzZS5xY293MjogW0FdIC0+IFtCXSAtPiBbQ10NCg0KW0NdIGlzIHRoZSBjdXJyZW50IGlt YWdlIHdoZXJlIGd1ZXN0IHJlYWQvd3JpdGUgdG8sdXN1YWxseSB3ZSBjcmVhdGUgYSBuZXcgaW1h Z2UgYmFzZSBvbiB0aGUgYmFzZS5xY293MiBsaWtlIHRoaXMNCg0KcWVtdS1pbWcgY3JlYXRlIC1m IHFjb3cyIC1vIGJhY2tpbmdfZmlsZT0vcGF0aC9iYXNlLnFjb3cyIG5ldy5xY293Mg0KDQpzbyB0 aGUgZGF0YSBvZiBuZXcucWNvdzIgaXMgZnJvbSBbQ10gb2YgYmFzZS5xY293MiwgYXNzdW1pbmcg dGhlIG5ldy5xY293MiBoYXMgbm90IGJlZW4gd3JpdGUgdG8gc2luY2UgY3JlYXRlZC4NCg0KV2hh dCBJIHdhbnQgaXMgdGhhdCB0aGUgZGF0YSBvZiBuZXcucWNvdzIgaXMgZnJvbSBbQl0gb2YgYmFz ZS5xY293MiwgbGlrZSB0aGlzOg0KDQpxZW11LWltZyBjcmVhdGUgLWYgcWNvdzIgLW8gYmFja2lu Z19maWxlPS9wYXRoL2Jhc2UucWNvdzIsYmFja2luZ19zbmFwc2hvdD1CICBuZXcucWNvdzINCg0K Q2FuIHRoZSBxZW11IHN1cHBvcnQgaXQgbm93Pw0KDQpUaGFua3MNCg0KDQoNCnZ0 ------=_001_NextPart261041472731_=---- Content-Type: text/html; charset="gb2312" Content-Transfer-Encoding: quoted-printable

Hi.

If a base qcow2 image snapshot chain like this:

base.qcow2: [A] -> [B] -> [C]

[C] is the current image where guest read/write to,usually we cr= eate a=20 new image base on the base.qcow2 like this

qemu-img create -f qcow2 -o backing_file=3D/path/base.qcow2 new.qcow2=

so the data of new.qcow2 is from [C] of base.qcow2, assuming the= =20 new.qcow2 has not been write to since created.

What I want is that the data of new.qcow2 is from [B] of base.qcow2, = like=20 this:

qemu-img create -f qcow2 -o=20 backing_file=3D/path/base.qcow2,backing_snapshot=3DB new.qcow2

Can the qemu support it now?

Thanks

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