+HOSTNAME = opt['hostname_prefix'] || "vm-2p8g.#{ENV['USER']}"
Don't use USER here. Only my-qemu uses USER. Append host system's hostname instead.
+QUEUES = opt['queues'] || "vm-2p8g.#{RUBY_PLATFORM.split('-')[0]}"
vm-2p8g => should base on HOSTNAME instead.
Thanks, Fengguang