[Libvir] Why QEMU?

Richard W.M. Jones rjones at redhat.com
Fri Feb 22 11:13:56 UTC 2008


On Fri, Feb 22, 2008 at 01:47:44PM +0300, Anton Protopopov wrote:
> When I executing virsh to connect to openvz I get the following:
> [root at localhost ~]# virsh -c openvz:///system
> libvir: QEMU error : cannot create bridge 'virbr0' : File exists
> Failed to autostart network 'default': cannot create bridge 'virbr0' :
> File existsWelcome to virsh, the virtualization interactive terminal.
> Type: 'help' for help with commands
> 'quit' to quit
> virsh #
> ...
> But I didn't want to connect to QEMU...

For reasons of history the qemu driver contains the network driver.

When libvirt connects to the hypervisor it actually makes two
connections -- one (which may be local, not an actual socket) to the
hypervisor you requested, and another (usually over a Unix socket) to
libvirtd for virNetwork* operations.

The network connection is entirely optional[1], which is why you get
the error above but your connection succeeds.

Rich.

[1] Optional unless you want to make virNetwork* calls of course.

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