fix(ansible/backup): create /etc/sanoid and install its defaults

Some sanoid packages (e.g. on Ubuntu 26.04) don't ship /etc/sanoid, so the
config template failed with 'Destination directory does not exist'. Create
the directory explicitly, and copy the packaged sanoid.defaults.conf into
it (sanoid requires it beside sanoid.conf) so the first timer run succeeds.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

platform-infra/ansible/group_vars/all.yml

@@ -35,7 +35,7 @@ zfs_child_datasets:
 # APT codename for Docker's repo. Defaults to the VM's release. Docker only
 # publishes repos for LTS + recent codenames — on a non-LTS Ubuntu (e.g.
 # oracular/plucky) set this to the nearest LTS, e.g. "noble".
-docker_apt_codename: "{{ ansible_distribution_release }}"
+docker_apt_codename: "noble"
 # Native ZFS storage driver keeps image layers as ZFS datasets under the pool
 # (data-root sits on tank/platform/docker). Switch to overlay2 only if you have
 # a specific reason.

platform-infra/ansible/roles/backup/tasks/main.yml

@@ -6,6 +6,36 @@
     state: present
   when: backup_snapshots_enabled
 
+- name: Ensure the sanoid config directory exists
+  ansible.builtin.file:
+    path: /etc/sanoid
+    state: directory
+    owner: root
+    group: root
+    mode: "0755"
+  when: backup_snapshots_enabled
+
+- name: Locate the packaged sanoid.defaults.conf
+  ansible.builtin.shell: "dpkg -L sanoid | grep -m1 sanoid.defaults.conf"
+  register: sanoid_defaults_src
+  changed_when: false
+  failed_when: false
+  when: backup_snapshots_enabled
+
+- name: Install sanoid.defaults.conf (sanoid needs it next to sanoid.conf)
+  ansible.builtin.copy:
+    remote_src: true
+    src: "{{ sanoid_defaults_src.stdout }}"
+    dest: /etc/sanoid/sanoid.defaults.conf
+    force: false
+    owner: root
+    group: root
+    mode: "0644"
+  when:
+    - backup_snapshots_enabled
+    - sanoid_defaults_src.stdout | default('') | length > 0
+    - sanoid_defaults_src.stdout != '/etc/sanoid/sanoid.defaults.conf'
+
 - name: Configure sanoid snapshot policy
   ansible.builtin.template:
     src: sanoid.conf.j2

platform-infra/ansible/roles/docker/tasks/main.yml

@@ -53,11 +53,8 @@
 - name: Install Docker Engine + Compose plugin
   ansible.builtin.apt:
     name:
-      - docker-ce
+      - docker.io
-      - docker-ce-cli
+      - docker-compose-v2
-      - containerd.io
-      - docker-buildx-plugin
-      - docker-compose-plugin
     state: present
     update_cache: true