CentOS virt - Nov 2009 - CentOS-5.4, KVM, QEMU, Virt-Manager and kvm-qemu-img

What is the correct combination of packages to configure and manage
VMs via virt-manager undet CentOS-5.4?  If I use qemu then while
virt-manager works I obtain SELinux alerts with respect to the
real-time clock.  If instead of qemu I use kvm-qemu-img then
virt-manager simply does not work.  It starts but it does not find
any form of qemu and the selection boxes are all greyed out.

Further, do I need tun/tap to host VMs that themselves support
virtual ips? The module for tun I found as part of the base install.
 But I cannot locate the module for ethertap and yum does not tell
me where it is found.

Lastly, why is qemu 4.5M but kvm-qemu-img is only 125K?

Regards,

-- 
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James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
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Hamilton, Ontario             fax: +1 905 561 0757
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James B. Byrne wrote on Mon, 9 Nov 2009 16:23:55 -0500 (EST):
> Lastly, why is qemu 4.5M but kvm-qemu-img is only 125K?
I would assume it's just the module that works on image files. AFAIK, you 
don't need qemu if you have KVM. The same way you don't need KVM if you 
use Xen ...

Kai

-- 
Kai Sch?tzl, Berlin, Germany
Get your web at Conactive Internet Services: http://www.conactive.com

2009/11/9 James B. Byrne <byrnejb at
harte-lyne.ca>:
> Further, do I need tun/tap to host VMs that themselves support
> virtual ips? The module for tun I found as part of the base install.
> ?But I cannot locate the module for ethertap and yum does not tell
> me where it is found.
Yep, you do want tun/tap. But if you create a regular bridge and tells
virt-manager or libvirt to use this for your virtual machines,
virt-manager/libvirt will take care of the tun/tap setup.
>From your virtual machines point of view, tun/tap will get you the
same connectivity as if you plugged a ethernet cable from your network
into it, without any restrictions.

Best Regards
Kenni

On Tue, November 10, 2009 05:34, Kenni Lund wrote:
>
> Yep, you do want tun/tap. But if you create a regular bridge and
> tells virt-manager or libvirt to use this for your virtual
> machines, virt-manager/libvirt will take care of the tun/tap setup.
>
This is what I have done.  One of difficulties I still have is
discovering where I set the IP addresses for the virtual machines. 
It seems that I get some variant of 192.168.122.x where I need an
actual routable address in the 216.185.71.0/24 space.


ifcfg-br0

# kvm virtual host bridged network connection
DEVICE=br0
TYPE=Bridge
BOOTPROTO=static
BROADCAST=216.185.71.255
#HWADDR=xx:xx:xx:xx:xx:xx
IPADDR=216.185.71.22
#IPV6INIT=yes
#IPV6_AUTOCONF=yes
NETMASK=255.255.255.0
NETWORK=216.185.71.0
ONBOOT=yes

ifcfg-eth0

# Bridged ethernet for KVM virtual hosts
# Intel Corporation 82566DC Gigabit Network Connection
DEVICE=eth0
#BOOTPROTO=static
#BROADCAST=216.185.71.255
HWADDR=xx:xx:xx:xx:xx:xx
#IPADDR=216.185.71.22
#IPV6INIT=yes
#IPV6_AUTOCONF=yes
#NETMASK=255.255.255.0
#NETWORK=216.185.71.0
ONBOOT=yes
BRIDGE=br0


-- 
***          E-Mail is NOT a SECURE channel          ***
James B. Byrne                mailto:ByrneJB at Harte-Lyne.ca
Harte & Lyne Limited          http://www.harte-lyne.ca
9 Brockley Drive              vox: +1 905 561 1241
Hamilton, Ontario             fax: +1 905 561 0757
Canada  L8E 3C3

On Tue, 2009-11-10 at 15:07 -0500, James B. Byrne wrote:
> On Tue, November 10, 2009 11:55, Kenni Lund wrote:
> 
> >
> > Hmm, try to have a look at this:
> > http://www.linux-kvm.com/content/using-bridged-networking-virt-manager
> >
> 
> Got it. Thanks. I will give this a read tonight while I am relaxing
> with the "Red Hat Virtualization" guide.
James,

Sometimes it helps to read an explanation from two sources.

At libvirt.org, the bridged networking (shared physical device) writeup
gives similar info to the above link and can be found here:

http://wiki.libvirt.org/page/Networking#Creating_network_initscripts

Once you define the bridge in /etc/sysconfig/network-scripts/, modify
the host ifcfg-eth0 to include the BRIDGE= statement (and remove the
normal BOOTPROTO= statement) and either disable netfilter on the bridge
or add the physdev --physdev-is-bridged iptables rule, then you are
basically done.

Restart the network/iptables/libvirtd and you are good to go.  Takes
maybe 5 min. to set up and does not require any knowledge of brctl.


Steve