guestfs: add configurable VM image size with custom image resize support

Base images were using hardcoded 20G size while custom images remained
at their original download size, causing disk space issues.

This adds LIBVIRT_IMAGE_SIZE config option (default: 20G) that:
- Replaces hardcoded "20G" in base image creation
- Adds automatic resizing for custom images using qemu-img resize

Both image types now consistently use the same configurable size,
resolving "No space left on device" errors in custom image VMs.

Generated-by: Claude AI
Signed-off-by: Daniel Gomez <[email protected]>

Author: dkruces

kconfigs/Kconfig.libvirt

@@ -458,6 +458,16 @@ config LIBVIRT_MEM_MB
 	help
 	  How much MiB of RAM to use per guest.
 
+config LIBVIRT_IMAGE_SIZE
+	string "VM image size"
+	output yaml
+	default "20G"
+	depends on GUESTFS
+	help
+	  The size of the VM disk image for all libvirt images, whether they
+	  are base images (created with virt-builder) or custom images
+	  (downloaded and resized with qemu-img resize).
+
 config HAVE_LIBVIRT_PCIE_PASSTHROUGH
 	bool
 	default $(shell, scripts/check_pciepassthrough_kconfig.sh passthrough_libvirt.generated)

playbooks/roles/base_image/tasks/base-image.yml

@@ -44,7 +44,7 @@
       - "-o"
       - "{{ base_image_pathname }}"
       - "--size"
-      - "20G"
+      - "{{ libvirt_image_size }}"
       - "--format"
       - "raw"
       - "--commands-from-file"
@@ -63,7 +63,7 @@
       - "-o"
       - "{{ base_image_pathname }}"
       - "--size"
-      - "20G"
+      - "{{ libvirt_image_size }}"
       - "--format"
       - "raw"
       - "--commands-from-file"

playbooks/roles/base_image/tasks/custom-image.yml

@@ -41,10 +41,21 @@
     url: "{{ guestfs_custom_raw_image_url }}"
     dest: "{{ custom_image_dir }}"
     mode: "u=rw,g=r,o=r"
+  register: custom_image_download
   when:
     - not custom_image_stat.stat.exists
     - guestfs_has_custom_raw_image_url|bool
 
+- name: Resize custom image to match configured size
+  become: true
+  become_method: ansible.builtin.sudo
+  ansible.builtin.command:
+    cmd: "qemu-img resize {{ custom_image }} {{ libvirt_image_size }}"
+  changed_when: true
+  when:
+    - custom_image_download is changed or custom_image_stat.stat.exists
+    - guestfs_has_custom_raw_image_url|bool
+
 - name: Check if the custom image sentinel file already exists
   ansible.builtin.stat:
     path: "{{ custom_image_ok }}"