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Ansible Level 03 Day 04: Ansible Lineinfile Module

This document outlines the solution for Ansible Level 03 Day 04. The objective was to create a comprehensive Ansible playbook to deploy an httpd web server, create an initial web page, and then modify that page's content dynamically using the lineinfile module.

Table of Contents

  1. Task Overview
  2. Step-by-Step Solution
  3. Deep Dive: Ansible Concepts Used

Task Overview

Objective: Install and configure httpd on all app servers, deploy an index.html with initial text, and insert a new welcome message at the top of the file.

Requirements: 1. Playbook: Create /home/thor/ansible/playbook.yml. 2. Web Server: Install httpd and ensure the service is running. 3. Initial Content: Create /var/www/html/index.html containing "This is a Nautilus sample file, created using Ansible!". 4. Modify Content: Insert "Welcome to xFusionCorp Industries!" at the top of the file using lineinfile. 5. Permissions: File owner/group: apache, Mode: 0655. 6. Constraint: Must run cleanly using ansible-playbook -i inventory playbook.yml.

Step-by-Step Solution

1. Verify the Environment

Before creating the playbook, verify the pre-existing inventory file to ensure the target hosts are ready.

Command: 

cd /home/thor/ansible
cat inventory

2. Create the Playbook

Create a multi-task YAML playbook to handle the package installation, service management, file creation, and file modification. We need become: yes because we are installing packages and writing to /var/www/html.

Command: 

vi playbook.yml

Content: 

---
- name: Deploy and Configure Web Server
  hosts: all
  become: yes
  tasks:
    - name: Install httpd package
      yum:
        name: httpd
        state: present

    - name: Start and enable httpd service
      service:
        name: httpd
        state: started
        enabled: yes

    - name: Create index.html with initial content
      copy:
        dest: /var/www/html/index.html
        content: "This is a Nautilus sample file, created using Ansible!\n"
        force: yes

    - name: Add welcome message to the top of index.html
      lineinfile:
        path: /var/www/html/index.html
        line: "Welcome to xFusionCorp Industries!"
        insertbefore: BOF
        state: present

    - name: Set ownership and permission for index.html
      file: 
        path: /var/www/html/index.html
        owner: apache
        group: apache
        mode: '0655'

3. Execute and Validate

Run the playbook from the /home/thor/ansible/ directory.

Execution Command: 

ansible-playbook -i inventory playbook.yml

Expected Output: 

PLAY [Deploy and Configure Web Server] **********************************************

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

TASK [Install httpd package] ********************************************************
changed: [stapp01]
changed: [stapp02]
changed: [stapp03]

TASK [Start and enable httpd service] ***********************************************
changed: [stapp01]
changed: [stapp02]
changed: [stapp03]

TASK [Create index.html with initial content] ***************************************
changed: [stapp01]
changed: [stapp02]
changed: [stapp03]

TASK [Add welcome message to the top of index.html] *********************************
changed: [stapp01]
changed: [stapp02]
changed: [stapp03]

TASK [Set ownership and permission for index.html] **********************************
changed: [stapp01]
changed: [stapp02]
changed: [stapp03]

PLAY RECAP **************************************************************************
stapp01                    : ok=6    changed=5    unreachable=0    failed=0    ...
stapp02                    : ok=6    changed=5    unreachable=0    failed=0    ...
stapp03                    : ok=6    changed=5    unreachable=0    failed=0    ...

Manual Verification (Optional): To independently verify the content and permissions on the remote servers, use an ad-hoc command: 

ansible all -i inventory -m command -a "cat /var/www/html/index.html"
ansible all -i inventory -m command -a "ls -l /var/www/html/index.html"

Deep Dive: Ansible Concepts Used

The lineinfile Module

This module ensures a particular line is in a file, or replaces an existing line using a regular expression. It's highly effective for editing configuration files or appending specific data. * path: The file to modify. * line: The exact line content to insert or ensure exists. * state: present: Ensures the line is added if missing.

The insertbefore Parameter

The task requirement specified adding the line at the top of the file. * insertbefore: BOF: BOF is a special alias standing for Beginning Of File. It directs Ansible to insert the line before the very first line of the file. If omitted (or if insertafter: EOF is used), the line defaults to being appended to the end of the file.

Execution Order matters: The copy task must precede the lineinfile task to ensure the file exists and has the base content before Ansible attempts to inject the new line at the top. Furthermore, the yum task must run first so the /var/www/html directory structure exists.