From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55187) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cYGpm-0004of-1l for qemu-devel@nongnu.org; Mon, 30 Jan 2017 13:37:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cYGph-000091-He for qemu-devel@nongnu.org; Mon, 30 Jan 2017 13:37:46 -0500 References: <20170126110435.2777-1-berrange@redhat.com> <20170126110435.2777-4-berrange@redhat.com> <20170126123530.GB23095@lemon.Home> <20170126132708.GB29127@redhat.com> From: Eric Blake Message-ID: <6a9aeec8-d4ee-a0aa-7e04-0ee4295fef80@redhat.com> Date: Mon, 30 Jan 2017 12:37:28 -0600 MIME-Version: 1.0 In-Reply-To: <20170126132708.GB29127@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="nGkThvJuioVSUQdDaQCFVOBUo4jTm2GgA" Subject: Re: [Qemu-devel] [PATCH v1 3/6] qemu-img: add support for -n arg to dd command List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" , Fam Zheng Cc: Kevin Wolf , qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --nGkThvJuioVSUQdDaQCFVOBUo4jTm2GgA From: Eric Blake To: "Daniel P. Berrange" , Fam Zheng Cc: Kevin Wolf , qemu-devel@nongnu.org, qemu-block@nongnu.org, Max Reitz Message-ID: <6a9aeec8-d4ee-a0aa-7e04-0ee4295fef80@redhat.com> Subject: Re: [Qemu-devel] [PATCH v1 3/6] qemu-img: add support for -n arg to dd command References: <20170126110435.2777-1-berrange@redhat.com> <20170126110435.2777-4-berrange@redhat.com> <20170126123530.GB23095@lemon.Home> <20170126132708.GB29127@redhat.com> In-Reply-To: <20170126132708.GB29127@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 01/26/2017 07:27 AM, Daniel P. Berrange wrote: > On Thu, Jan 26, 2017 at 08:35:30PM +0800, Fam Zheng wrote: >> On Thu, 01/26 11:04, Daniel P. Berrange wrote: >>> The -n arg to the convert command allows use of a pre-existing image,= >>> rather than creating a new image. This adds a -n arg to the dd comman= d >>> to get feature parity. >> >> I remember there was a discussion about changing qemu-img dd's default= to a >> "conv=3Dnocreat" semantic, if so, "-n" might not be that useful. But t= hat part >> hasn't made it into the tree, and I'm not sure which direction we shou= ld take. >> (Personally I think default to nocreat is a good idea). >=20 > Use nocreat by default would be semantically different from real "dd" > binary which feels undesirable if the goal is to make "qemu-img dd" > be as consistent with "dd" as possible. >=20 > It would be trivial to rewrite this patch to add support for the "conv"= > option, allowing the user to explicitly give 'qemu-img dd conv=3Dnocrea= t' > instead of my 'qemu-img dd -n' syntax, without changing default semanti= cs. Adding 'conv=3Dnocreat' (and not '-n') feels like the right way to me. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --nGkThvJuioVSUQdDaQCFVOBUo4jTm2GgA 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/ iQEcBAEBCAAGBQJYj4foAAoJEKeha0olJ0NqnY8H/R7d2XM8l8Z85eaTg7J8z6dh bz85W+8eJJOhntUPjOGlqnI2F4qCq3hCOMikDYO9gxsjSzptsZcoCgArB/9fTW0M JvM4N28jF8r+L1ucpkVnf8KHiZhj/Y9xBe3+69mx5J4yNYb+whqA7Mlah0JBigSG qO2F2YVtBa/ko4aLTFZ2v5LpYKRySGTUxM+7wev7UEvY9MqlqFE+Xxvpb22kSFBB hAZgB/VZ+00rF9qc98YI0yKNOI9cMcjTFypR4inEfIrGUwLcFiMRo/BSbwz5/5/1 FAadOqVWgXRe/i/85Fo1ZTA3ZFFTLa3n+5hkF2nDlT8/jrNybNR42zyEmNiHcew= =gHCe -----END PGP SIGNATURE----- --nGkThvJuioVSUQdDaQCFVOBUo4jTm2GgA--