r/netboot/basementhud: Configure NBD export

The *netboot/basementhud* Ansible role configures two network block
devices for the basement HUD machine:

* The immutable root filesystem
* An ephemeral swap device

roles/netboot/basementhud/tasks/main.yml

@@ -0,0 +1,7 @@
+- name: ensure basementhud nbd export is configured
+  template:
+    src: basementhud.ini.j2
+    dest: /etc/nbd-server/config.d/basementhud.conf
+    mode: u=rw,go=r
+  tags:
+  - nbd-config

roles/netboot/basementhud/templates/basementhud.ini.j2

@@ -0,0 +1,8 @@
+[basementhud]
+exportname = /var/lib/nbd/basementhud.squashfs
+readonly = true
+
+[basementhud-swap]
+exportname = /var/lib/nbd/
+temporary = true
+filesize = 8589934592