On 03.07.2012 15:05, xiaw...@linux.vnet.ibm.com wrote: > From: Wenchao Xia <xiaw...@linux.vnet.ibm.com> > > 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 <xiaw...@linux.vnet.ibm.com> > --- > 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
