Make create_vm work on all OS versions in use

Makes it work with the same cloudinit code on Ubuntu 20.04 by mounting
it from a custom ISO as CD-ROM

site-cookbooks/kosmos_kvm/recipes/host.rb

@@ -5,6 +5,11 @@
 
 package %w(virtinst libvirt-daemon-system libvirt-clients)
 
+# Required on legacy hosts (Ubuntu 20.04) to build the NoCloud seed ISO
+# via cloud-localds. Modern virt-install (>= 4.0.0, Ubuntu >= 22.04)
+# handles cloud-init natively via --cloud-init and does not need it.
+package "cloud-image-utils" if node["platform_version"].to_f < 22.04
+
 directory "/var/lib/libvirt/images/base" do
   recursive true
   owner "libvirt-qemu"
@@ -24,7 +29,10 @@ end
 template "/usr/local/sbin/create_vm" do
   source "create_vm.erb"
   mode "0750"
-  variables base_image_path: node["kosmos_kvm"]["host"]["qemu_base_image"]["path"]
+  variables(
+    base_image_path: node["kosmos_kvm"]["host"]["qemu_base_image"]["path"],
+    modern_virt_install: node["platform_version"].to_f >= 22.04
+  )
 end
 
 firewall_rule 'ssh-alt-port' do

site-cookbooks/kosmos_kvm/templates/create_vm.erb

@@ -64,6 +64,7 @@ EOS
   popd
 fi
 
+<% if @modern_virt_install -%>
 virt-install \
   --name "$VMNAME" \
   --ram "$RAM" \
@@ -83,3 +84,30 @@ virt-install \
   --autostart \
   --import \
   --cloud-init root-password-generate=off,disable=on,meta-data=$CIDATA_PATH/meta-data,user-data=$CIDATA_PATH/user-data
+<% else -%>
+# Legacy path for hosts running virt-install < 4.0.0 (e.g. Ubuntu 20.04,
+# virt-install 2.2.x). These versions predate the --osinfo/--cloud-init
+# options, so we build a NoCloud seed ISO from the same user-data and
+# meta-data files and attach it as a cdrom. The guest receives the
+# exact same cloud-init configuration as on modern hosts.
+cloud-localds "$CIDATA_PATH/seed.iso" "$CIDATA_PATH/user-data" "$CIDATA_PATH/meta-data"
+
+virt-install \
+  --name "$VMNAME" \
+  --ram "$RAM" \
+  --vcpus "$CPUS" \
+  --cpu host \
+  --arch x86_64 \
+  --hvm \
+  --virt-type kvm \
+  --disk "$IMAGE_PATH" \
+  --disk "$CIDATA_PATH/seed.iso,device=cdrom" \
+  --boot hd \
+  --network=bridge=virbr0,model=virtio \
+  --graphics none \
+  --serial pty \
+  --console pty \
+  --channel unix,mode=bind,path=/var/lib/libvirt/qemu/$VMNAME.guest_agent.0,target_type=virtio,name=org.qemu.guest_agent.0 \
+  --autostart \
+  --import
+<% end -%>