Re: Simple way of putting a VM on a LAN

[Bill Davidsen <davidsen@tmr.com>]

Chris Lalancette wrote:
> Mike Snitzer wrote:
>> I've taken to using a bridge (or in virt-manager speak "shared
>> physical device").  The 'network-bridge' script (and supporting
>> xen-network-common.sh and xen-script-common.sh) that are provided with
>> xen rpms (e.g. xen-3.1.0-13.fc8.x86_64.rpm) make this relatively
>> painless.
>>
>> The overall solution is not what I'd call "simple" but once I've
>> started the bridge I just defer to libvirtd to abstract away the
>> complexity associated with exposing each kvm guest to the physical
>> network.
> 
> Yep, exactly.  Actually, generally your distribution of choice provides nice
> startup scripts to such things; in Fedora, you create an
> /etc/sysconfig/network-scripts/ifcfg-eth0 that has a BRIDGE=br0, and an
> /etc/sysconfig/network-scripts/ifcfg-br0 that defines the actual bridge with
> TYPE=Bridge, and the system will bring up the bridge at bootup and plug your
> eth0 into it.  I'm sure the other distributions have similar mechanisms.
> 
A bit of the original problem seems to have been clipped before you read 
it, or I stated it poorly.
- the problems are immediate, not permanent hosting. So startup 
anythings are out, I'd have to put in scripts for every machine I might 
ever want to host on every machine capable of hosting.
- I need to bind an IP, unless you can point me to a different bridge 
package. If eth0 is x.y.z.10 and I put x.y.z.20 on eth0:1
     ifconfig eth0:1 x.y.z.20 up
adding eth0:1 moves the whole NIC to the bridge, and the normal 
functions of the machine come to a halt. I'm probably doing something 
wrong, currently I'm getting this done by ugly iptables abuse.

I am missing some piece on doing this quickly and selectively, for the 
case of "dns02 just dropped a cooling fan, we need another server, run 
it on your {whatever} machine for a few minutes." These are immediate 
and short term, but often done on machines in burn-in state, someone's 
desktop, etc. Little load, but the service must be running.

Does that clarify?

-- 
Bill Davidsen <davidsen@tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot