[libvirt-users] Fwd: Re: New with Libvirt and having problems.

Kevins Thoughts thoughts at kevinsthoughts.com
Tue Aug 30 04:25:52 UTC 2011


On 8/29/2011 10:29 PM, Trey Dockendorf wrote:
> Have you looked into using virt-manager?  When I started using KVM I 
> found that new VM provisioning was much simpler with that interface.

Alas, Virtmanager doesn't seem to be a supported program under Gentoo - 
the distribution I use.  If its X-based, it wouldn't work anyhow - I'm 
strictly a command line shop.
>
> Once you've created your domain with "virt-install" you can make 
> changes using virsh.
>
> virsh -c qemu:///system edit Test
>
> That will allow you to directly edit the domain.
>
> In the virt-install line you used "bridge=br0" , maybe replace that 
> with "bridge=tap5".  If that doesn't do it, once your editing the XML 
> you can try something like the following...

I'm familiar with virsh edit and have used it to probe around a bit.  
Actually tried the "bridge=tap5" a few days ago and get the message:

/ERROR    internal error Failed to add tap interface to bridge. tap5 is 
not a bridge device/

>
> <interface type='bridge'>
> <mac address='52:54:00:4d:74:c7'/>
> <source bridge='tap5'/>
> <model type='virtio'/>
> <address type='pci' domain='0x0000' bus='0x00' slot='0x03' 
> function='0x0'/>
> </interface>
>
> That was created using virt-manager, so you probably need to use what 
> virt-install created for your mac address and address.

Gave that a shot, attempting to create a new domain with "br0" replaced 
by "tap5" and got the same error message:

/error: internal error Failed to add tap interface to bridge. tap5 is 
not a bridge device/


>
> Is your init failing on /dev/vda3 and then kernel panic?  If so it's 
> likely your guest OS doesn't have the necessary kernel modules loaded. 
>  Depending on your distro it will vary, but using CentOS 6 I've found 
> they are automatically loaded.  This is what's loaded in CentOS 6

Well, yes and no.  Its failing with a kernel panic because KVM is being 
started with if=none instead of if=virtio.  If I manually change it, it 
works fine.  Just need to know where to update that in the domain XML file.

For what its worth, the image runs 100% fine with started manually with:

/kvm -net nic,model=virtio -net tap,ifname=tap5,script=no  -drive 
file=test1.img,if=virtio,boot=on -curses -no-reboot -m 2g -smp 2/

So I know the image is good.

>
> # lsmod | grep virtio
> virtio_blk              5087  5
> virtio_pci              6733  0
> virtio_ring             7169  2 virtio_blk,virtio_pci
> virtio                  4824  2 virtio_blk,virtio_pci
>
> Try changing the disk to ide , and then verifying your system is able 
> to load the virtio modules.
>
> Also , once you have your XML the way you like, if your going to stick 
> with command line look at using virsh though I highly recommend 
> virt-manager.
>
> I'm still very new to KVM myself, so hopefully that was of some use
>
> - Trey

Thanks!

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