My context is that I'd like to run some assertions against a VM and the test framework I'm using runs all assertions from within the VM itself. So If i wanted to assert that the host running my VM is "x.foo.com" I'd have to be able to retrieve that from within the VM. I can do that via the REST API but that requires me to get a REST user/pass inside the vm and feels hacky. The common way of doing this at openstack/aws is to curl the metadata service which replies with information only relevant to the machine asking.