cloud-init
cloud-init samples to launch new services on OpenStack instances
Providing User Data to Instances
$ nova boot --image myUbuntuImage --flavor myFlavorOne --user-data mydata.file
some extra info on [redhat openstack docs] (https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux_OpenStack_Platform/4/html/End_User_Guide/user-data.html)