docs: add 100 Days of DevOps challenge notes

100 - days of devops/devops-83.md

@@ -0,0 +1,147 @@
+# Assignment
+
+An Ansible playbook needs completion on the jump host, where a team member left off. Below are the details:
+
+
+
+The inventory file /home/thor/ansible/inventory requires adjustments. The playbook must run on App Server 3 in Stratos DC. Update the inventory accordingly.
+
+
+Create a playbook /home/thor/ansible/playbook.yml. Include a task to create an empty file /tmp/file.txt on App Server 3.
+
+
+Note: Validation will run the playbook using the command ansible-playbook -i inventory playbook.yml. Ensure the playbook works without any additional arguments.
+
+# Solution
+
+# Ansible Inventory + Playbook — create `/tmp/file.txt` on App Server 3
+
+Complete the setup on the jump host so `ansible-playbook -i inventory playbook.yml` runs against
+`stapp03` and creates an empty file — with **no extra arguments**.
+
+> Note: this is an Ansible task, not Kubernetes — no manifests to pipe into `kubectl`. The heredocs
+> below write the two files.
+
+## Step 0 — See what's already there
+
+The inventory "requires adjustments," so inspect it before overwriting:
+
+```bash
+cat /home/thor/ansible/inventory
+```
+
+Note any existing hostnames/groups — if the playbook or validation expects a particular group name,
+keep it. Otherwise the version below replaces it cleanly.
+
+## Step 1 — Inventory
+
+```bash
+cat > /home/thor/ansible/inventory <<'EOF'
+[app_servers]
+stapp03 ansible_user=banner ansible_ssh_pass=BigGr33n ansible_connection=ssh
+EOF
+```
+
+## Step 2 — Playbook
+
+```bash
+cat > /home/thor/ansible/playbook.yml <<'EOF'
+---
+- name: Create an empty file on App Server 3
+  hosts: all
+  tasks:
+    - name: Create /tmp/file.txt
+      ansible.builtin.file:
+        path: /tmp/file.txt
+        state: touch
+        mode: '0644'
+EOF
+```
+
+## How it works
+
+### The inventory
+
+- **Hostname `stapp03`** — App Server 3's server name per the wiki. It's resolvable from the jump
+  host, so the inventory name doubles as the connection target; **no `ansible_host` is needed**.
+  Confirm with `getent hosts stapp03` if you want to be sure.
+- **`ansible_user` / `ansible_ssh_pass`** — the SSH credentials. These servers use password auth, so
+  both are required. **Verify the values against your lab's wiki** — the ones shown follow the
+  common Stratos DC pattern but should be confirmed, not assumed.
+- **`ansible_connection=ssh`** — the transport plugin; the default for remote hosts, stated
+  explicitly.
+
+Because validation runs the bare command (no `-u`, `-k`, or `--private-key`), **every** connection
+detail must live in the inventory file itself.
+
+### The playbook
+
+- **`hosts: all`** — deliberately chosen over `hosts: stapp03`. Since the inventory contains only
+  App Server 3, `all` targets exactly that host, and it stays correct regardless of what the group is
+  named. Using a specific name risks a "no hosts matched" skip if the inventory group and the
+  playbook's `hosts:` value ever drift apart.
+- **`ansible.builtin.file` with `state: touch`** — creates the file if absent, leaving it empty.
+  This is the right module for "create an empty file"; `copy` with empty `content` would also work
+  but `file`/`touch` expresses the intent directly.
+- **`mode: '0644'`** — standard read/write-owner, read-others permissions. Quoted so YAML treats it
+  as a string, not an octal-looking integer (a classic gotcha: unquoted `0644` can be misparsed).
+- **No `become`** — `/tmp` is world-writable, so the SSH user can create the file without
+  privilege escalation. Adding `become: yes` would invite a sudo-password prompt and could break the
+  no-extra-arguments requirement.
+
+### A note on idempotency
+
+`state: touch` updates the file's timestamps on every run, so Ansible reports **changed** each
+time rather than **ok**. That's fine for this task. If you want true idempotency:
+
+```yaml
+    - name: Create /tmp/file.txt
+      ansible.builtin.file:
+        path: /tmp/file.txt
+        state: touch
+        mode: '0644'
+        modification_time: preserve
+        access_time: preserve
+```
+
+This leaves timestamps alone when the file already exists, so re-runs report `ok`.
+
+### Host key checking
+
+A first-time SSH connection can fail on host-key verification. The safest fix — because it needs no
+extra command-line arguments during validation — is an `ansible.cfg` beside the playbook:
+
+```bash
+cat > /home/thor/ansible/ansible.cfg <<'EOF'
+[defaults]
+host_key_checking = False
+EOF
+```
+
+`sshpass` must also be present on the jump host for `ansible_ssh_pass` to work. It's usually
+pre-installed; if not, Ansible's error names it explicitly.
+
+## Verify
+
+```bash
+cd /home/thor/ansible
+
+# Inventory parses
+ansible-inventory -i inventory --list
+
+# Connectivity + credentials in one shot
+ansible -i inventory all -m ping
+
+# The actual validation command
+ansible-playbook -i inventory playbook.yml
+
+# Confirm the file exists on the target
+ansible -i inventory all -m command -a "ls -l /tmp/file.txt"
+```
+
+Expected — ping returns `"ping": "pong"` with `SUCCESS`, the playbook completes with
+`ok=2 changed=1` and no failures, and the final check lists `/tmp/file.txt` on stapp03.
+
+> `UNREACHABLE` means the hostname didn't resolve or the credentials don't match the wiki. A
+> `PLAY RECAP` showing `skipped` or "no hosts matched" means the playbook's `hosts:` value doesn't
+> align with the inventory — `hosts: all` avoids that class of failure.