set the vagrant box version to 0.0.0

this is especially convenient for having a stable libvirt disk file name that can be referenced in terraform projects

.gitignore

@@ -2,6 +2,7 @@
 packer_cache/
 tmp/
 *.box
+*.box.json
 *.log
 output*
 *-packages.txt

Makefile

@@ -16,17 +16,13 @@ ubuntu-${VERSION}-amd64-libvirt.box: autoinstall-cloud-init-data/* provision.sh
 	rm -f $@
 	PACKER_KEY_INTERVAL=10ms CHECKPOINT_DISABLE=1 PACKER_LOG=1 PACKER_LOG_PATH=$@.log PKR_VAR_vagrant_box=$@ \
 		packer build -only=qemu.ubuntu-amd64 -on-error=abort -timestamp-ui ubuntu.pkr.hcl
-	@echo BOX successfully built!
-	@echo to add to local vagrant install do:
-	@echo vagrant box add -f ubuntu-${VERSION}-amd64 $@
+	@./box-metadata.sh libvirt ubuntu-${VERSION}-amd64 $@
 
 ubuntu-${VERSION}-uefi-amd64-libvirt.box: tmp/libvirt-uefi-autoinstall-cloud-init-data/user-data autoinstall-cloud-init-data/* provision.sh ubuntu.pkr.hcl Vagrantfile-uefi.template
 	rm -f $@
 	PACKER_KEY_INTERVAL=10ms CHECKPOINT_DISABLE=1 PACKER_LOG=1 PACKER_LOG_PATH=$@.log PKR_VAR_vagrant_box=$@ \
 		packer build -only=qemu.ubuntu-uefi-amd64 -on-error=abort -timestamp-ui ubuntu.pkr.hcl
-	@echo BOX successfully built!
-	@echo to add to local vagrant install do:
-	@echo vagrant box add -f ubuntu-${VERSION}-uefi-amd64 $@
+	@./box-metadata.sh libvirt ubuntu-${VERSION}-uefi-amd64 $@
 
 tmp/libvirt-uefi-autoinstall-cloud-init-data/user-data: autoinstall-cloud-init-data/user-data
 	mkdir -p $(shell dirname $@)
@@ -36,17 +32,13 @@ ubuntu-${VERSION}-amd64-virtualbox.box: autoinstall-cloud-init-data/* provision.
 	rm -f $@
 	CHECKPOINT_DISABLE=1 PACKER_LOG=1 PACKER_LOG_PATH=$@.log PKR_VAR_vagrant_box=$@ \
 		packer build -only=virtualbox-iso.ubuntu-amd64 -on-error=abort -timestamp-ui ubuntu.pkr.hcl
-	@echo BOX successfully built!
-	@echo to add to local vagrant install do:
-	@echo vagrant box add -f ubuntu-${VERSION}-amd64 $@
+	@./box-metadata.sh virtualbox ubuntu-${VERSION}-amd64 $@
 
 ubuntu-${VERSION}-amd64-hyperv.box: tmp/hyperv-autoinstall-cloud-init-data/user-data autoinstall-cloud-init-data/* provision.sh ubuntu.pkr.hcl Vagrantfile.template
 	rm -f $@
 	CHECKPOINT_DISABLE=1 PACKER_LOG=1 PACKER_LOG_PATH=$@.log PKR_VAR_vagrant_box=$@ \
 		packer build -only=hyperv-iso.ubuntu-amd64 -on-error=abort -timestamp-ui ubuntu.pkr.hcl
-	@echo BOX successfully built!
-	@echo to add to local vagrant install do:
-	@echo vagrant box add -f ubuntu-${VERSION}-amd64 $@
+	@./box-metadata.sh hyperv ubuntu-${VERSION}-amd64 $@
 
 # see https://docs.microsoft.com/en-us/windows-server/virtualization/hyper-v/supported-ubuntu-virtual-machines-on-hyper-v
 tmp/hyperv-autoinstall-cloud-init-data/user-data: autoinstall-cloud-init-data/user-data

box-metadata.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+set -euo pipefail
+
+provider="$1"
+name="$2"
+path="$3"
+
+# see https://developer.hashicorp.com/vagrant/docs/boxes/format#box-metadata
+# see https://developer.hashicorp.com/vagrant/docs/boxes/format#box-file
+# see https://github.com/hashicorp/packer-plugin-vagrant/blob/v1.0.3/post-processor/vagrant/libvirt.go#L100-L105
+# see https://github.com/vagrant-libvirt/vagrant-libvirt/blob/0.11.2/spec/unit/action/handle_box_image_spec.rb#L96-L125
+# see https://github.com/vagrant-libvirt/vagrant-libvirt/blob/0.11.2/lib/vagrant-libvirt/action/handle_box_image.rb
+# see https://github.com/vagrant-libvirt/vagrant-libvirt/blob/0.11.2/docs/boxes.markdown
+cat >"$path.json" <<EOF
+{
+  "name": "$name",
+  "versions": [
+    {
+      "version": "0.0.0",
+      "providers": [
+        {
+          "name": "$provider",
+          "url": "$path"
+        }
+      ]
+    }
+  ]
+}
+EOF
+cat <<EOF
+
+Add the Vagrant Box with:
+
+vagrant box add -f $name $path.json
+EOF