[ovirt-users] Discovering oVirt/RHEV Engine from a VM guest

[Itamar Heim]

On 09/25/2014 10:13 AM, Vinzenz Feenstra wrote:
> On 09/25/2014 06:41 AM, Shawn Starr wrote:
>> Hello everyone,
>>
>> I wonder if you can tell me how I can do this. I'm creating a VM image
>> that
>> needs to discover it's hostname, IP address information so I can
>> configure
>> /etc/sysconfig/network,
>> /etc/sysconfig/network-scripts/ifcfg-[interface] and
>> other things.
> That sounds to me like a use case for cloud-init.
>>
>> If I know the oVirt/RHEV engine to connect to, I can get this information
>> successfully.
>>
>> However, when creating a dummy 'gold' VM image and having oVirt clone
>> it. I
>> have no 'key' to tell me what engine to connect to, other than trying
>> them all
>> and hoping for best.
>>
>> I've written some code with the oVirt SDK that needs to know the URL:
>>
>> from ovirtsdk.api import API
>> import platform
>> import yaml
>> import sys
>>
>>     api =  API(url="https://HOW_TO_DISCOVER_THIS/api",
>>            username="USER at internal",
>>            password="PASSWORD",
>>            insecure=True)
>>
>> ...
>>
>> Is there a way to know the engine to connect to when VM has booted up?
>>
>> I tried poking around ovirt/rhev-agent and noticed this:
>>
>> in /usr/share/rhev-agent/vdsAgentLogic.py:
>>          self.vio.write('host-name', { 'name' :
>> self.dr.getMachineName() })
> This is a pretty ancient version of the guest agent. Nevertheless the
> machine name is retrieved from the system, there's no magic happening by
> talking to the engine or anything like that. If the system does not have
> a configured FQDN or hostname it will just simply get what the system
> has set. That might be even 'localhost at localdomain'
>>
>> It *looks* like I could get the host name from what oVirt has
>> configured w/o
>> knowing the engine to connect to? But I cannot open /dev/virtio-
>> ports/com.redhat.rhevm.vdsm (since rhev-agentd) has it opened 'too
>> many files
>> open' error.
>>
>> When using OpenNebula in past, they mounted a ISO CD image that
>> contained the
>> VM's metadata you could read in as configuration and having also used
>> AWS EC2
>> You can connect to localhost to the VM itself to get metadata to get
>> this sort
>> of information.
> That's what cloudinit is doing. :-)
>  From my knowledge however there is no metadata available to be received
> within the guest without using cloudinit.

cloud-init uses "metadata" approach. you can pass 'userdata' of your own 
on top of what the engine generates.