Openstack can use cloud-config to provide arbritary scripts to instances at first boot. This can be used to customize your VM's in an automated way

Providing a script to a VM created through the horizon web-interface:

To provide a script to a VM created in the Openstack Horizon web-interface you simply need to use the "Configuration" pane in the "Create Instance" dialog. The following example shows a bash-script creating a file "/root/postinstall.txt" with the content "Postinsall virker!":

When the VM is created, we can log in and verify that the scrip indeed did run by seeing that the file /root/postinstall.txt actually exists.