docs: add the most popular example for container group

containergroup/README.md

@@ -3,6 +3,175 @@
 
 You can customize the specification of the Pod of the Execution Environment using **Container Group**.
 
+<!-- omit in toc -->
+## Table of Contents
+
+- [Case 1: Read and write files on K3s host during Jobs](#case-1-read-and-write-files-on-k3s-host-during-jobs)
+  - [Prepare host and Kubernetes](#prepare-host-and-kubernetes)
+  - [Create Container Group](#create-container-group)
+  - [Quick testing](#quick-testing)
+- [Case 2: Achieve complex requirements](#case-2-achieve-complex-requirements)
+  - [Prepare host and Kubernetes](#prepare-host-and-kubernetes-1)
+  - [Create Container Group](#create-container-group-1)
+  - [Quick testing](#quick-testing-1)
+
+## Case 1: Read and write files on K3s host during Jobs
+
+One typical use case to use Container Group is to read or write files on K3s host during Jobs.
+
+In this example, we make Container Group that works with the Pod with following specification.
+
+- Mount PVC as `/data/work` that is the exact `/data/work` on the K3s host
+
+By using this Container Group, you can read and write any files under `/data/work` on the K3s host during Jobs. Of course, these files are persisted since they are on the host file system, so you can read and write the same files in any Jobs.
+
+> [!NOTE]
+> Almost the same thing can be achieved by enabling `Expose host paths for Container Groups` and adding `"/data/work:/data/work:O"` to `Paths to expose to isolated jobs` on `Administration` > `Settings` > `Jobs settings`, but using Container Group is more flexible and recommended.
+> The configuration `Paths to expose to isolated jobs` is a global setting and all Jobs mount the host file system even if it's not required. Whereas, any number of container groups can be created, with different settings for each job template.
+
+### Prepare host and Kubernetes
+
+Prepare directories for Persistent Volumes defined in `containergroup/case1/pv.yaml`.
+
+```bash
+sudo mkdir -p /data/work
+sudo chmod 755 /data/work
+sudo chown 1000:0 /data/work
+```
+
+Create PV and PVC.
+
+```bash
+kubectl apply -k containergroup/case1
+```
+
+### Create Container Group
+
+You can create new Container Group by `Administration` > `Instance Group` > `Add` > `Add container group`.
+
+Enable `Customize pod specification` and define specification as following.
+
+```yaml
+apiVersion: v1
+kind: Pod
+metadata:
+  namespace: awx
+spec:
+  serviceAccountName: default
+  automountServiceAccountToken: false
+  containers:
+    - image: quay.io/ansible/awx-ee:latest
+      name: worker
+      args:
+        - ansible-runner
+        - worker
+        - '--private-data-dir=/runner'
+      resources:
+        requests:
+          cpu: 250m
+          memory: 100Mi
+      volumeMounts:
+        - name: awx-work-volume
+          mountPath: /data/work
+  volumes:
+    - name: awx-work-volume
+      persistentVolumeClaim:
+        claimName: awx-work-claim
+```
+
+This is the customized manifest to achieve mounting PVC as `/data/work` that is the exact `/data/work` on the K3s host.
+
+### Quick testing
+
+The Container Group that to be used can be specified as `Instance Groups` in the Job Template.
+
+Before proceeding the testing, create new file under `/data/work` on the K3s host.
+
+```bash
+$ echo "This file is written from K3s host." | sudo tee /data/work/demo_from_host.txt
+This file is written from K3s host.
+
+$ ls -l /data/work
+total 4
+-rw-r--r--. 1 root root 36 Feb 25 14:09 demo_from_host.txt
+```
+
+Then by running any playbooks on AWX that includes following tasks for example, you can confirm that the files under `/data/work` on the K3s host are readable and writable. Note some tasks that read or write files should be delegated to `localhost` (with `delegate_to: localhost`) if your playbook is not for `localhost`.
+
+```yaml
+---
+- hosts: localhost
+  gather_facts: false
+
+  tasks:
+    - name: Gather files under /data/work
+      ansible.builtin.find:
+        paths: /data/work
+      register: existing_files
+
+    - name: List files under /data/work
+      ansible.builtin.debug:
+        var: existing_files.files
+
+    - name: Read a file under /data/work
+      ansible.builtin.debug:
+        var: lookup("ansible.builtin.file", "/data/work/demo_from_host.txt")
+
+    - name: Write a file under /data/work
+      ansible.builtin.copy:
+        content: "This file is written during the task in the Job.\n"
+        dest: /data/work/demo_from_job.txt
+
+    - name: Read a file under /data/work
+      ansible.builtin.debug:
+        var: lookup("ansible.builtin.file", "/data/work/demo_from_job.txt")
+```
+
+This is the example output of the Job. You can see that the file written from the K3s host is readable in the Job, and writing a file in the Job is completed successfully.
+
+```bash
+TASK [Gather files under /data/work] *******************************************
+ok: [localhost]
+
+TASK [List files under /data/work] *********************************************
+ok: [localhost] => {
+    "existing_files.files": [
+        {
+            ...
+            "path": "/data/work/demo_from_host.txt",
+            ...
+        }
+    ]
+}
+
+TASK [Read a file under /data/work] ********************************************
+ok: [localhost] => {
+    "lookup('ansible.builtin.file', '/data/work/demo_from_host.txt')": "This file is written from K3s host."
+}
+
+TASK [Write a file under /data/work] *******************************************
+changed: [localhost]
+
+TASK [Read a file under /data/work] ********************************************
+ok: [localhost] => {
+    "lookup('ansible.builtin.file', '/data/work/demo_from_job.txt')": "This file is written during the task in the Job."
+}
+```
+
+You can also see that the file written in the task is actually available on the K3s host.
+
+```bash
+$ ls -l /data/work
+total 8
+-rw-r--r--. 1 root root 36 Feb 25 14:09 demo_from_host.txt
+-rw-r--r--. 1 1000 root 49 Feb 25 14:13 demo_from_job.txt
+
+$ cat /data/work/demo_from_job.txt
+This file is written during the task in the Job.
+```
+
+## Case 2: Achieve complex requirements
+
 In this example, we make the Execution Environment to work with the Pod with following specification.
 
 - Run in a different namespace `ee-demo` instead of default one
@@ -13,28 +182,20 @@ In this example, we make the Execution Environment to work with the Pod with fol
 - Have custom environment variable `MY_CUSTOM_ENV`
 - Use custom DNS server `192.168.0.219` in addition to the default DNS servers
 
-<!-- omit in toc -->
+### Prepare host and Kubernetes
-## Table of Contents
 
-- [Procedure](#procedure)
+Prepare directories for Persistent Volumes defined in `containergroup/case2/pv.yaml`.
-  - [Prepare host and kubernetes](#prepare-host-and-kubernetes)
-  - [Create Container Group](#create-container-group)
-- [Quick Testing](#quick-testing)
-
-## Procedure
-
-### Prepare host and kubernetes
-
-Prepare directories for Persistent Volumes defined in `containergroup/pv.yaml`.
 
 ```bash
 sudo mkdir -p /data/demo
+sudo chmod 755 /data/demo
+sudo chown 1000:0 /data/demo
 ```
 
 Create Namespace, PV, and PVC.
 
 ```bash
-kubectl apply -k containergroup
+kubectl apply -k containergroup/case2
 ```
 
 Add label to the node.
@@ -132,7 +293,7 @@ This is the customized manifest to achieve;
 
 You can also change `image`, but it will be overridden by specifying Execution Environment for the Job Template, Project Default, or Global Default.
 
-## Quick Testing
+### Quick testing
 
 The Container Group that to be used can be specified as `Instance Groups` in the Job Template. After specifying and running the Job, you can see the result as follows.
 

containergroup/case1/kustomization.yaml

@@ -0,0 +1,8 @@
+---
+apiVersion: kustomize.config.k8s.io/v1beta1
+kind: Kustomization
+namespace: awx
+
+resources:
+  - pv.yaml
+  - pvc.yaml

containergroup/case1/pv.yaml

@@ -0,0 +1,14 @@
+---
+apiVersion: v1
+kind: PersistentVolume
+metadata:
+  name: awx-work-volume
+spec:
+  accessModes:
+    - ReadWriteOnce
+  persistentVolumeReclaimPolicy: Retain
+  capacity:
+    storage: 4Gi
+  storageClassName: awx-work-volume
+  hostPath:
+    path: /data/work

containergroup/case1/pvc.yaml

@@ -0,0 +1,13 @@
+---
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: awx-work-claim
+spec:
+  accessModes:
+    - ReadWriteOnce
+  volumeMode: Filesystem
+  resources:
+    requests:
+      storage: 4Gi
+  storageClassName: awx-work-volume