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DevOps Day 84: Copy Data to App Servers using Ansible

This document outlines the solution for DevOps Day 84, where the objective was to distribute a specific file from the jump host to all application servers in the Stratos Datacenter using Ansible automation.

Table of Contents

Task Overview

Objective: The Nautilus DevOps team requires a file (index.html) located at /usr/src/data/ on the jump host to be copied to the /opt/data/ directory on all three application servers (stapp01, stapp02, stapp03).

Requirements: 1. Inventory Creation: Create /home/thor/ansible/inventory listing all app servers. 2. Playbook Creation: Create /home/thor/ansible/playbook.yml to perform the copy operation. 3. Source: /usr/src/data/index.html (Local on Jump Host). 4. Destination: /opt/data/index.html (Remote on App Servers). 5. Validation: Execute with ansible-playbook -i inventory playbook.yml.

Step-by-Step Solution

1. Create the Inventory File

We need to define a group of servers (which I named [app]) containing all three application nodes. We also need to define the specific connection credentials for each user (tony, steve, banner).

Command: 

cd /home/thor/ansible/
vi inventory

Content: 

[app]
stapp01 ansible_user=tony ansible_ssh_pass=Ir0nM@n
stapp02 ansible_user=steve ansible_ssh_pass=Am3ric@
stapp03 ansible_user=banner ansible_ssh_pass=BigGr33n

[all:vars]
ansible_ssh_common_args='-o StrictHostKeyChecking=no'
Note: The [all:vars] section is a best practice in these lab environments to avoid SSH "host key verification" failures.

2. Create the Playbook

We need a YAML file to describe the task. We will use the copy module.

Command: 

vi playbook.yml

Content: 

---
- name: copy data to application server
  hosts: app
  become: yes  # Required because /opt/data usually requires root/sudo permissions to write
  tasks:
    - name: copy index.html to /opt/data
      copy:
        src: /usr/src/data/index.html
        dest: /opt/data/
        mode: '0644'

3. Execution and Validation

Run the playbook against the inventory.

Command: 

ansible-playbook -i inventory playbook.yml

Output Analysis: 

PLAY [copy data to application server] **********************************************

TASK [Gathering Facts] **************************************************************
ok: [stapp02]
ok: [stapp01]
ok: [stapp03]

TASK [copy index.html to /opt/data] *************************************************
changed: [stapp03]
changed: [stapp02]
changed: [stapp01]

PLAY RECAP **************************************************************************
stapp01 : ok=2    changed=1    unreachable=0    failed=0 ...
stapp02 : ok=2    changed=1    unreachable=0    failed=0 ...
stapp03 : ok=2    changed=1    unreachable=0    failed=0 ...
* ok=2: Means both "Gathering Facts" and "Copy" succeeded. * changed=1: Means the file was successfully copied (it wasn't there before, or it was different).

Deep Dive: Ansible Concepts Used

Inventory Groups

Instead of listing every server under [all], we created a group called [app]. This allows us to target all three servers simultaneously in the playbook by simply setting hosts: app.

The copy Module

The copy module copies a file from the local or remote machine to a location on the remote machine. * src: The path to the file on the control node (jump host). * dest: The destination path on the remote host (app servers). * mode: (Optional but recommended) Sets the file permissions (e.g., 0644 for read/write owner, read others).

Troubleshooting

Issue: "Permission Denied" on Destination * Cause: The destination directory /opt/data is often owned by root. The user (e.g., tony) cannot write to it directly. * Fix: Ensure you include become: yes in your playbook. This tells Ansible to use sudo to execute the task.

Issue: "Authentication Failed" * Cause: Incorrect password in the inventory file. * Fix: Double-check the passwords for each user: * tony: Ir0nM@n * steve: Am3ric@ * banner: BigGr33n * Note: Ensure no trailing spaces are pasted into the inventory file.

Issue: "Destination directory does not exist" * Cause: The folder /opt/data might not exist on the app servers. * Fix: While the copy module can create the file, it usually expects the parent directory to exist. If it fails, add a task before the copy task using the file module with state: directory to ensure /opt/data exists.