libvirt/qemu-kvm failing to start interfaces wasn't the problem (though I thought it was since those interfaces weren't around when the VM wouldn't start). I eventually realized that the socket I was telling libvirt to accept on was in the ephemeral port range, and a webserver I was running on the same machine was accepting a bunch of connections at VM spin up time.
#mysterysolved Thanks! On 28 March 2015 at 14:29, Laine Stump <la...@laine.org> wrote: > On 03/27/2015 12:42 PM, Dave Sayles wrote: > > I'm running libvirt with qemu-kvm underneath. > > > > My network stack has the eth0 interface which is bridged to a br0 > interface. > > Usually, when a VM starts up, a new "vnet" interface is created as well > by > > libvirt. That vnet interface has a matching HWaddr to the VM that was > spun up > > with it, so I'm assuming they're associated somehow. > > The vnetX device is a tap device created by libvirt for use by qemu. One > end of the tap device is attached to the bridge, and the other end is a > file descriptor which the qemu process connects to the guest's emulated > network device. > > The MAC address of the tap device actually isn't identical to the MAC > address used by the guest's emluated network device - the first byte is > 0xFE, and all the other bytes match. > > > > > Sometimes, after using libvirt's "virt-install" to create a VM, I'm > unable to > > "virsh start" it. Virsh will print this out to stderr that it couldn't > start > > that VM, since the connection was "Reset by peer". > > > > I've yet to find a repro case for this issue. Eventually, I am able to > "virsh > > start" the instance, but only after several minutes. > > > > Are there any known issues with libvirt/qemu-kvm failing to instantiate > > network devices when it spins up VMs? > > What makes you think that is the problem? > > > > > This is printed to the logs as well: > > > > Mar 27 16:21:07 localhost kernel: device vnet42 entered promiscuous mode > > Mar 27 16:21:07 localhost kernel: br0: port 44(vnet42) entering > forwarding > > state > > Mar 27 16:21:07 localhost logger: KVM: 43 guests now active > > Mar 27 16:21:08 localhost kernel: br0: port 44(vnet42) entering disabled > > state > > Mar 27 16:21:08 localhost kernel: device vnet42 left promiscuous mode > > Mar 27 16:21:08 localhost kernel: br0: port 44(vnet42) entering disabled > > state > > Mar 27 16:21:08 localhost logger: KVM: 42 guests now active > > None of those are error messages. They are all indications of normal > operation. > > It you don't see any error messages attributes to libvirtd in the logs, > try looking in /var/log/libvirt/$guestname.log > -- dgs3
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