make packer extra build directly configurable

Author: sjpb

docs/image-build.md

@@ -51,20 +51,21 @@ Ansible in the appliance. This allows adding additional functionality into site-
 
 To configure an "extra" image build, prepare a Packer variable definition file as described above but also including:
 
-- `extra_image_name`: A string to add into the final image name.
-- `source_image` (or `source_image_name`): The UUID or name of the fat image to start from (which must already be present in OpenStack).
-- `groups`: A mapping with a key "openhpc-extra" (i.e. the name of this Packer build) with a list of Ansible inventory groups to put the build VM into.
-  This defines the roles/functionality which are added to the image.
+- `extra_build_image_name`: A string to add into the final image name.
+- `source_image` or `source_image_name`: The UUID or name of the fat image to start from (which must already be present in OpenStack).
+- `extra_build_groups`: A list of Ansible inventory groups to put the build VM into, in addition to the `builder` group. This defines the roles/functionality
+  which are added to the image.
+- `extra_build_volume_size`: A number giving the size in GB of the volume for the build VM's root disk and therefore the resulting image size.
+  Note this assumes the default of `use_blockstorage_volume = true`.
 
 E.g. to add the lustre client to an RockyLinux 9 image:
 
     # environments/site/lustre.pkvars.hcl
 
-    extra_image_name = "lustre" # output image name will be like "openhpc-lustre-RL9-$timestamp-$commit"
+    extra_build_image_name = "lustre" # output image name will be like "openhpc-lustre-RL9-$timestamp-$commit"
     source_image_name = "openhpc-ofed-RL9-240906-1041-32568dbb" # e.g. current StackHPC RL9 image
-    groups = {
-      openhpc-extra = ["lustre"] # only run lustre role during this extra build
-    }
+    extra_build_groups = ["lustre"] # only run lustre role during this extra build
+    extra_build_volume_size = 15 # default non-CUDA build image size has enough free space
 
     # ... define flavor, network, etc as normal
 

packer/openstack.pkr.hcl

@@ -48,6 +48,7 @@ variable "os_version" {
 # Must supply either source_image_name or source_image_id
 variable "source_image_name" {
   type = string
+  default = null
   description = "name of source image"
 }
 
@@ -132,6 +133,10 @@ variable "volume_size" {
   }
 }
 
+variable "extra_build_volume_size" {
+  type = number
+}
+
 variable "image_disk_format" {
   type = string
   default = "qcow2"
@@ -154,7 +159,12 @@ variable "groups" {
   }
 }
 
-variable "extra_image_name" {
+variable "extra_build_groups" {
+  type = list(string)
+  default = []
+}
+
+variable "extra_build_image_name" {
   type = string
   description = "Infix for 'extra' build image name"
   default = "extra"
@@ -165,7 +175,7 @@ source "openstack" "openhpc" {
   flavor = var.flavor
   use_blockstorage_volume = var.use_blockstorage_volume
   volume_type = var.volume_type
-  volume_size = var.volume_size[source.name]
+  volume_size = lookup(var.volume_size, source.name, var.extra_build_volume_size)
   metadata = var.metadata
   instance_metadata = {ansible_init_disable = "true"}
   networks = var.networks
@@ -220,12 +230,12 @@ build {
   # Extended site-specific image, built on fat image:
   source "source.openstack.openhpc" {
     name = "openhpc-extra"
-    image_name = "openhpc-${var.extra_image_name}-${var.os_version}-${local.timestamp}-${substr(local.git_commit, 0, 8)}"
+    image_name = "openhpc-${var.extra_build_image_name}-${var.os_version}-${local.timestamp}-${substr(local.git_commit, 0, 8)}"
   }
 
   provisioner "ansible" {
     playbook_file = "${var.repo_root}/ansible/fatimage.yml"
-    groups = concat(["builder"], var.groups[source.name])
+    groups = concat(["builder"], lookup(var.groups, source.name, var.extra_build_groups))
     keep_inventory_file = true # for debugging
     use_proxy = false # see https://www.packer.io/docs/provisioners/ansible#troubleshooting
     extra_arguments = [