Add sample custom play (#232)

Signed-off-by: Christian Berendt <[email protected]>

docs/guides/operations-guide/index.md

@@ -38,3 +38,28 @@ osism noset bootstrap NODE
 
 * Ansible fact: `ansible_local.osism.bootstrap`
 * State file: `/etc/osism/bootstrap`
+
+## Custom plays
+
+Custom Plays can be used in all environments in the configuration repository.
+
+For example, this is a play to prepare all devices to be used for Ceph on a Ceph
+resource node. It is saved in the configuration repository in the file
+`environments/ceph/playbook-wipe-partitions.yml`. It is run with
+`osism apply -e ceph wipe-parititons`.
+
+```yaml title="environments/ceph/playbook-wipe-partitions.yml
+---
+- name: Wipe partitions
+  hosts: ceph-resource
+  gather_facts: false
+
+  tasks:
+    - name: Wipe partitions
+      become: true
+      ansible.builtin.shell: |
+        wipefs --all "{{ item }}"
+        dd if=/dev/zero of="{{ item }}" bs=1 count=4096
+      changed_when: false
+      with_items: "{{ devices }}"
+```