ansible/pxe-server: Simplify Debian version check

Simplify the rules that define whether download the Debian installer and
extract it.

Instead of getting the version of the installer via the `version.info`
file and comparing it with the user defined one, hash the downloaded
tarball, if present, and compare it before downloading it using
Ansible's builtin modules.

Extract it only if the file `version.info` is not present, since this is
the last file that gets extracted from the package. This way, if the
extraction process terminates unsuccessfully, the script remains
idempotent.

Signed-off-by: Dimitris Poulopoulos <[email protected]>

ansible/roles/pxe-server/tasks/main.yaml

@@ -18,38 +18,28 @@
     state: directory
     mode: 0755
 
-- name: Check if the a Debian version file already exists in the `tftp` directory
-  ansible.builtin.stat:
-    path: /srv/tftp/version.info
-  register: version_file_exists
-
-- name: Read the Debian version already present in the `tftp` directory
-  block:
-  - name: Slurp hosts file
-    ansible.builtin.slurp:
-      src: /srv/tftp/version.info
-    register: slurpfile
-  - name: Extract Debian major and minor version numbers
-    set_fact:
-      major_version: "{{ slurpfile['content'] | b64decode | regex_search('.*\\s*\\d+.*\\+deb(\\d+)u\\d+', '\\1') }}"
-      minor_version: "{{ slurpfile['content'] | b64decode | regex_search('.*\\s*\\d+.*\\+deb\\d+u(\\d+)', '\\1') }}"
-  - name: Combine major and minor version numbers to format `x.x`
-    set_fact:
-      formatted_version: "{{ major_version[0] }}.{{ minor_version[0] }}"
-  when: version_file_exists.stat.exists
-
 - name: Structure the `tftp` directory
   block:
   - name: Download the network installer for Debian 12 (Bookworm)
     ansible.builtin.get_url:
       url: "https://deb.debian.org/debian/dists/Debian{{ debian_version }}/main/installer-amd64/current/images/netboot/netboot.tar.gz"
-      dest: /tmp/netboot.tar.gz
+      dest: /srv/tftp/netboot.tar.gz
       mode: 0644
+      checksum: sha256:9ae301b2f6b31d6c94ca0a46b6428b550bd84416113e34054cd9167033e2c18b
+  # The `version.info` file is the last file that is extracted when we extract
+  # the network installer. We can use this file to check if the network
+  # installer has already been extracted.
+  - name: Check that the `version.info` exists
+    stat:
+      path: /srv/tftp/version.info
+    register: stat_version_info
   - name: Extract the network installer to the `tftp` directory
     ansible.builtin.unarchive:
-      src: /tmp/netboot.tar.gz
+      src: /srv/tftp/netboot.tar.gz
       dest: /srv/tftp
       remote_src: yes
+    # Only when `version.info` is not present in the `tftp` directory.
+    when: not stat_version_info.stat.exists
   - name: Remove any unnecessary files
     ansible.builtin.file:
       path: "{{ item.path }}"
@@ -78,7 +68,6 @@
       src: preseed.cfg.j2
       dest: /srv/tftp/preseed.cfg
       mode: 0644
-  when: (formatted_version is undefined) or (formatted_version | trim  != debian_version | trim)
 
 - name: Create the dnsmasq configuration file
   ansible.builtin.template: