Oracle/OVM–OVM Server UUID Challenges

 

While installation of the Oracle OVM server, it automatically selects a “random” number to setup a “UUID” – a unique ID number for itself. It is THIS UUID that the OVM Manager detects and registers within itself for all further communication between the OVM Manager and the OVM Server.

 

Having said that, did you land yourself into a situation wherein:

a.       The OVM server refuses to boot successfully?

b.      The OVM server does boot, but the VMs doesn’t appear?

c.       The OVM manager is unable to communicate with the OVM server?

 

What had happened just before you land up in the above scenarios?

1.       Motherboard of the OVM Server was replaced?

2.       NIC of the OVM server was replaced?

 

Any of the above two scenarios can land you up in to the above 3 situations J

Fear not, below is the reason why and how to get out of it. J

 

Every OVM Server receives a unique ID (also called UUID) when the agent starts. Without this ID, a server can’t join a cluster and the manager can’t dispatch commands to the agent.

 

But the million Dollar Question: “How does this UUID get set in the first place? From where does the OVM Server decides where to pick up the UUID from?

 

What I discovered is this:

 

The ovs-agent will do the following:

 

1.       Ask SMBIOS for an id and if it’s valid use it.

2.       If not valid or no ID then, Get the MAC address of physical Ethernet devices on the system and concatenate in an UUID

 

This poses a great risk because if for some reason you change the motherboard (other SMBIOS) or 1 of the network devices on the system (other MAC), you’ll have a new UUID.

 

Now, how do we detect a changed UUID?

 

The following errors points to a changed UUID:

 

1.       Unable to join cluster after reboot

2.       “Unable to send notification” messages on the console

3.       The OVM Manager fails to rediscover the server after reboot (tries 5 times and gives up)

4.       The OVM Server in OVM Manager will become in ERROR state with an error that looks like: “The server has changed IP or is unreachable”

 

 

Solution?? – Fake it…. I mean, FakeUUID it!!!

In order to solve this issue, the agent has an ini parameter you can set to ensure the same UUID all the time. You can find it in the file /etc/ovs-agent/agent.ini. Get the server UUID from OVM Manager and set it in this parameter.

 

[Server]
fakeuuid=34:45:4c:4c:5a:00:10:20:80:59:b5:c0:4a:42:35:45

 

I personally set this on every OVM installation that I do to ensure there are no issues with this ID changing.