Add free disk space check.

roles/debian_server/vars/main.yml

@@ -10,6 +10,11 @@ maintenance_tasks:
     description: Download pending APT updates for faster updates
     command: '{{ maintenance_directory }}/apt-download-updates'
     frequency: daily
+  - name: check_disk
+    description: Check for available disk space
+    # yamllint disable-line rule:line-length
+    command: mnpw --errors --warn -- /usr/lib/nagios/plugins/check_disk --warning 10% --critical 5% --include-type btrfs --include-type ext4 --include-type vfat --include-type xfs
+    frequency: daily
   - name: flatpak-update
     description: Update flatpaks
     command: '{{ maintenance_directory }}/flatpak-update'