From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:49631) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Sm92F-0000ZB-7q for qemu-devel@nongnu.org; Tue, 03 Jul 2012 15:45:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Sm929-0005bp-NV for qemu-devel@nongnu.org; Tue, 03 Jul 2012 15:45:18 -0400 Received: from isrv.corpit.ru ([86.62.121.231]:37285) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Sm929-0005RN-Ft for qemu-devel@nongnu.org; Tue, 03 Jul 2012 15:45:13 -0400 Message-ID: <4FF34BBD.2050101@msgid.tls.msk.ru> Date: Tue, 03 Jul 2012 23:45:01 +0400 From: Michael Tokarev MIME-Version: 1.0 References: <1341313544-6256-1-git-send-email-xiawenc@linux.vnet.ibm.com> In-Reply-To: <1341313544-6256-1-git-send-email-xiawenc@linux.vnet.ibm.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] add text about how to use qemu-nbd with qemu List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: xiawenc@linux.vnet.ibm.com Cc: pbonzini@redhat.com, qemu-devel@nongnu.org, anthony@codemonkey.ws, stefanha@linux.vnet.ibm.com On 03.07.2012 15:05, xiawenc@linux.vnet.ibm.com wrote: > From: Wenchao Xia > > Qemu system emulator reports only fails that make people confused > about why, when it is invoked with nbd block device tring to connect > qemu-nbd server. In fact qemu will try connect server for several > times but server only accept one connect by default. > I paid some times to find out why it fails. This patch add special > text to explain how to use it in such case. > > Signed-off-by: Wenchao Xia > --- > qemu-nbd.texi | 6 ++++++ > 1 files changed, 6 insertions(+), 0 deletions(-) > > diff --git a/qemu-nbd.texi b/qemu-nbd.texi > index 6955d90..014040a 100644 > --- a/qemu-nbd.texi > +++ b/qemu-nbd.texi > @@ -44,6 +44,12 @@ Export QEMU disk image using NBD protocol. > display this help and exit > @item -V, --version > output version information and exit > + > + Note: When qemu-nbd was used to export a disk that would be used by QEMU > +block device, -t or --persistent must be set for that QEMU nbd client would try > +connect more than one time. For eg: > + qemu-nbd ./simple.img -p 10809 -t > + qemu -hdb nbd:127.0.0.1:10809 It is not accurate. qemu connect to nbd server not "several" but exactly two times by default. The first connection it does (it need not be a separate connection actually, and this, I'd say, a bug in qemu) in order to guess the format of the internal structure inside - be it raw, or qcow, or anything else. So, if you specify the format of the device explicitly, by using format=raw, only single connection will be made. /mjt