Re: [libvirt] how do I stop libvirt futzing with my network configuration?

On 26 Nov 2009, Daniel P. Berrange spake thusly: > On Thu, Nov 26, 2009 at 06:25:07PM +0000, Nix wrote: >> However, there appears to be no way to say 'this is what the network is >> already like'. That network is considered 'inactive' and can't be used by >> any guests, and if I try to make it active, I get this: >> >> virsh # net-start default >> error: Failed to start network default >> error: cannot create bridge 'vm-net': File exists >> >> Of course it bloody can't create that bridge: it's already there, has an >> IP address on the host, and has the host routing packets to it. There >> appears to be no option to allow libvirt to assign IPs on the host... >> >> ... should I fix that, 'net-start' tries to update iptables rules! >> How should I put this: I do not *not not* want libvirt pissing with the >> firewall in any way at all. If I want firewall rules, I'll create them. >> But there's no way to tell it 'hands off! This network is already active, >> don't try to *make* it active!' > > If you don't want libvirt to create the bridge + setup IPtables rules > then don't use the net-XXX commands / XML. That functionality is > not there for pointing libvirt to existing bridge devices. > > If you already have a bridge configured, then just point the guest > directly at that bridge by name. OK, I still can't make this work: it worked briefly but then stopped. As far as I can tell tools like virt-manager are unwilling to *let* you connect to a network considered 'inactive', and networks are only considered active if they have a configuration file under /var/run/libvirt/network. These files are only created if libvirt has created the bridge itself as well. If no networks are considerd active, virt-manager won't let you create a guest at all: it insists on trying to start the sodding network, and when that fails doesn't let you get any further.

So as far as I can tell, if you don't want libvirt creating all your bridges for you, you may as well give up hope of using virt-manager, or start hacking all this stuff out of the source.