Add auto-detection feature for RAID array creation

This commit introduces an auto-detection mechanism that automatically
identifies unused disks and creates RAID arrays without manual configuration.

Changes:
- Add detect_unused_disks.yml task to identify available disks
- Update main.yml to integrate auto-detection workflow
- Add auto-detection configuration options in defaults/main.yml
- Update README.md with auto-detection usage examples

The feature detects disks that are not mounted, not in RAID, not in LVM,
and not formatted, then uses them to create RAID arrays based on the
configured template.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: rguichard

README.md

@@ -17,15 +17,41 @@ None
 
 ## Example Playbook
 
+### Manual configuration
 ```yaml
 - hosts: all
   become: true
   vars:
+    mdadm_arrays:
+      - name: md200
+        devices:
+          - /dev/nvme0n1
+          - /dev/nvme1n1
+        filesystem: lvm
+        level: 5
+        state: present
   roles:
     - role: ansible-mdadm
-  tasks:
 ```
 
+### Auto-detection mode
+```yaml
+- hosts: all
+  become: true
+  vars:
+    mdadm_auto_detect_arrays: true
+    mdadm_auto_detect_config:
+      - name: md200
+        filesystem: lvm
+        level: 5
+        state: present
+        min_disks: 3
+  roles:
+    - role: ansible-mdadm
+```
+
+Note: Auto-detection will automatically use all unused disks (not mounted, not in RAID, not in LVM, not formatted) if `mdadm_arrays` is empty and `mdadm_auto_detect_arrays` is true.
+
 ## License
 
 BSD

defaults/main.yml

@@ -35,3 +35,14 @@
 #   mountpoint: '/mnt/md0'
 #   state: 'present'
 mdadm_arrays: []
+
+# Auto-detection settings
+mdadm_auto_detect_arrays: false
+mdadm_auto_detect_config:
+  # Default configuration for auto-detected arrays
+  - name: md200
+    filesystem: lvm
+    level: 5
+    state: present
+    # Minimum number of disks required for auto-detection
+    min_disks: 3

tasks/detect_unused_disks.yml

@@ -0,0 +1,48 @@
+---
+# Detect unused disks that can be used for RAID arrays
+# This task will identify disks that are:
+# - Not mounted
+# - Not part of existing RAID arrays
+# - Not used in LVM
+# - Not formatted with a filesystem
+
+- name: detect_unused_disks | Get all block devices
+  shell: lsblk -ln -o NAME,TYPE,MOUNTPOINT,FSTYPE | grep -E '^[a-z]+[0-9]*\s+disk\s*$' | awk '{print "/dev/" $1}'
+  register: all_disks
+  changed_when: false
+
+- name: detect_unused_disks | Get mounted devices
+  shell: mount | awk '{print $1}' | grep '^/dev/' | sort | uniq
+  register: mounted_devices
+  changed_when: false
+
+- name: detect_unused_disks | Get devices used in existing RAID arrays
+  shell: cat /proc/mdstat | grep -oE 'sd[a-z]+[0-9]*|nvme[0-9]+n[0-9]+' | sed 's|^|/dev/|' | sort | uniq
+  register: raid_devices
+  changed_when: false
+  failed_when: false
+
+- name: detect_unused_disks | Get devices used in LVM
+  shell: pvs --noheadings -o pv_name 2>/dev/null | tr -d ' ' | sort | uniq
+  register: lvm_devices
+  changed_when: false
+  failed_when: false
+
+- name: detect_unused_disks | Get devices with filesystem
+  shell: blkid | cut -d: -f1 | sort | uniq
+  register: formatted_devices
+  changed_when: false
+  failed_when: false
+
+- name: detect_unused_disks | Filter unused disks
+  set_fact:
+    unused_disks: "{{ all_disks.stdout_lines | 
+      difference(mounted_devices.stdout_lines | default([])) |
+      difference(raid_devices.stdout_lines | default([])) |
+      difference(lvm_devices.stdout_lines | default([])) |
+      difference(formatted_devices.stdout_lines | default([])) }}"
+
+- name: detect_unused_disks | Debug unused disks found
+  debug:
+    msg: "Unused disks detected: {{ unused_disks }}"
+  when: unused_disks | length > 0

tasks/main.yml

@@ -12,4 +12,18 @@
   when: >
         mdadm_force_wipe is defined and
         mdadm_force_wipe
+
+- include_tasks: detect_unused_disks.yml
+  when: >
+        mdadm_auto_detect_arrays and
+        (mdadm_arrays | length == 0)
+
+- name: main | Set auto-detected arrays
+  set_fact:
+    mdadm_arrays: "{{ mdadm_auto_detect_config | map('combine', {'devices': unused_disks}) | list }}"
+  when: >
+        mdadm_auto_detect_arrays and
+        (mdadm_arrays | length == 0) and
+        (unused_disks | length >= mdadm_auto_detect_config[0].min_disks)
+
 - include_tasks: arrays.yml