Ansible Basics: Automation and Configuration Management

Introduction to Ansible

Ansible is an open-source automation tool that simplifies configuration management, application deployment, and task automation. Unlike other configuration management tools, Ansible uses a simple, agentless architecture powered by SSH.

What is Ansible?

Ansible is:

Configuration Management: Maintain consistent system configurations
Application Deployment: Automate application deployments
Orchestration: Coordinate multi-machine deployments
Provisioning: Set up infrastructure and services

Why Ansible?

Key Benefits:

Agentless: No agents to install on managed nodes
Simple: Uses YAML for configuration
Powerful: Complex automation with minimal code
Reliable: Idempotent operations ensure consistency
Fast: Parallel execution across multiple hosts

Installing Ansible

Installation Methods

1. pip (Python Package Manager):

bash

pip install ansible

2. Package Managers:

macOS:

bash

brew install ansible

Ubuntu/Debian:

bash

sudo apt update
sudo apt install ansible

RHEL/CentOS:

bash

sudo yum install ansible

3. pipx (Recommended for development):

bash

pipx install ansible

Verifying Installation

bash

ansible --version
ansible 2.15.0
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/home/user/.ansible/plugins/modules']
  ansible python module location = /usr/lib/python3/dist-packages/ansible
  ansible collection location = /home/user/.ansible/collections

Ansible Architecture

Control Node vs Managed Nodes

Control Node:

Runs Ansible
Manages configuration
Executes playbooks

Managed Nodes:

Systems being configured
Only require Python and SSH
No agent installation needed

Architecture Diagram

┌──────────────┐         SSH          ┌──────────────┐
│ Control Node │ ─────────────────────▶│ Managed Node │
│              │    SSH Keys/Password  │              │
│ - Ansible    │                       │ - Python     │
│ - Playbooks  │                       │ - Services   │
│ - Modules    │◀───────────────────── │              │
└──────────────┘    Connection         └──────────────┘
                       Established

Inventory

What is Inventory?

Inventory defines the hosts that Ansible manages. It's a list of target systems grouped logically.

INI Format Inventory

ini

# inventory.ini

[webservers]
web1.example.com
web2.example.com
web3.example.com

[dbservers]
db1.example.com
db2.example.com

[production]
web1.example.com
db1.example.com

[staging]
web2.example.com
db2.example.com

[all:vars]
ansible_user=ubuntu
ansible_ssh_private_key_file=~/.ssh/id_rsa

YAML Format Inventory

yaml

# inventory.yaml

all:
  children:
    webservers:
      hosts:
        web1.example.com:
        web2.example.com:
        web3.example.com:
    dbservers:
      hosts:
        db1.example.com:
        db2.example.com:
    production:
      children:
        webservers:
        dbservers:
  vars:
    ansible_user: ubuntu
    ansible_ssh_private_key_file: ~/.ssh/id_rsa

Dynamic Inventory

bash

# AWS EC2 dynamic inventory
ansible-inventory -i ec2.yaml --list

# Kubernetes dynamic inventory
ansible-inventory -i kubernetes.yaml --list

Ad-Hoc Commands

Basic Syntax

bash

ansible [pattern] -m [module] -a "[module arguments]"

Common Ad-Hoc Commands

1. Ping Check:

bash

ansible all -m ping

2. Check Uptime:

bash

ansible webservers -m command -a "uptime"

3. Install Package:

bash

ansible webservers -m apt -a "name=nginx state=present" -b

4. Start Service:

bash

ansible webservers -m service -a "name=nginx state=started" -b

5. Copy Files:

bash

ansible webservers -m copy -a "src=./index.html dest=/var/www/html/" -b

6. Gather Facts:

bash

ansible all -m setup
ansible webservers -m setup -a "filter=ansible_distribution*"

Useful Modules

Command Modules:

command: Execute commands (default)
shell: Execute shell commands with pipes/redirection
raw: Execute via SSH without Python

File Modules:

copy: Copy files to hosts
file: Set file attributes
fetch: Copy files from hosts
template: Deploy template files

Package Modules:

apt: Debian/Ubuntu packages
yum: RHEL/CentOS packages
dnf: Fedora packages
pip: Python packages

Service Modules:

service: Manage services
systemd: Manage systemd services

Modules

Understanding Modules

Modules are the building blocks of Ansible. Each module performs a specific task.

Using Modules

1. Command Module:

bash

ansible webservers -m command -a "ls -l /var/www"

2. Shell Module:

bash

ansible all -m shell -a "echo $HOME >> /tmp/test.txt"

3. Copy Module:

bash

ansible webservers -m copy -a \
  "src=/etc/hosts dest=/tmp/hosts backup=yes"

4. Template Module:

bash

ansible webservers -m template -a \
  "src=index.j2 dest=/var/www/html/index.html"

5. File Module:

bash

ansible all -m file -a \
  "path=/tmp/myfile state=touch mode=0600"

6. Service Module:

bash

ansible webservers -m service -a \
  "name=nginx state=started enabled=yes"

7. Apt Module:

bash

ansible webservers -m apt -a \
  "name=nginx state=present update_cache=yes"

8. User Module:

bash

ansible all -m user -a \
  "name=john state=present shell=/bin/bash groups=sudo"

9. Git Module:

bash

ansible webservers -m git -a \
  "repo=https://github.com/user/repo.git dest=/var/www/myapp version=main"

10. Cron Module:

bash

ansible all -m cron -a \
  "name='daily backup' job='/backup.sh' hour=2 minute=0"

Configuration

ansible.cfg

ini

# ansible.cfg

[defaults]
# Inventory location
inventory = ./inventory

# Remote user
remote_user = ubuntu

# Private key file
private_key_file = ~/.ssh/id_rsa

# Host key checking
host_key_checking = False

# Timeout
timeout = 30

# Number of parallel processes
forks = 5

# Display task timing
callback_whitelist = timer, profile_tasks

# Gather facts
gathering = smart
fact_caching = jsonfile
fact_caching_connection = /tmp/facts_cache
fact_caching_timeout = 86400

# Disable retry files
retry_files_enabled = False

# Log path
log_path = ./ansible.log

[inventory]
# Enable inventory plugins
enable_plugins = host_list, script, auto, yaml, ini, toml

[privilege_escalation]
become = True
become_method = sudo
become_user = root
become_ask_pass = False

[ssh_connection]
# SSH connection settings
pipelining = True
control_path = /tmp/ansible-ssh-%%h-%%p-%%r

Environment Variables

bash

export ANSIBLE_HOST_KEY_CHECKING=False
export ANSIBLE_INVENTORY=./inventory
export ANSIBLE_REMOTE_USER=ubuntu
export ANSIBLE_PRIVATE_KEY_FILE=~/.ssh/id_rsa

SSH Setup

SSH Key Authentication

1. Generate SSH Key:

bash

ssh-keygen -t rsa -b 4096 -C "your_email@example.com"

2. Copy Public Key to Managed Nodes:

bash

ssh-copy-id ubuntu@web1.example.com
ssh-copy-id ubuntu@web2.example.com

3. Test Connection:

bash

ssh ubuntu@web1.example.com

SSH Agent

bash

# Start SSH agent
eval "$(ssh-agent -s)"

# Add key to agent
ssh-add ~/.ssh/id_rsa

# Test with Ansible
ansible all -m ping

SSH Config

# ~/.ssh/config


Host *.example.com
  User ubuntu
  IdentityFile ~/.ssh/id_rsa
  StrictHostKeyChecking no
  UserKnownHostsFile=/dev/null

Facts Gathering

What are Facts?

Facts are system information collected by Ansible from managed nodes.

Disabling Facts

yaml

---
- name: Play without facts
  hosts: webservers
  gather_facts: no
  tasks:
    - name: Task without facts
      debug:
        msg: "Facts gathering disabled"

Gathering Specific Facts

yaml

---
- name: Play with specific facts
  hosts: webservers
  gather_facts: yes

  vars:
    ansible_facts_modules:
      - setup
      - ansible.builtin.setup

  tasks:
    - name: Use gathered facts
      debug:
        msg: "OS: {{ ansible_distribution }}"

Fact Caching

ini

# ansible.cfg
[defaults]
gathering = smart
fact_caching = jsonfile
fact_caching_connection = /tmp/facts_cache
fact_caching_timeout = 86400

Idempotency

Understanding Idempotency

Idempotency ensures that running the same task multiple times produces the same result without side effects.

Idempotent Example

yaml

- name: Ensure nginx is installed
  apt:
    name: nginx
    state: present
  become: yes

This task:

Installs nginx if not present
Does nothing if already installed
Never attempts to reinstall

Non-Idempotent Commands

Avoid:

yaml

- name: Bad example
  command: apt-get install nginx

Prefer:

yaml

- name: Good example
  apt:
    name: nginx
    state: present

Best Practices

1. Use Version Control

bash

git init
git add .
git commit -m "Initial Ansible setup"

2. Organize Playbooks

project/
├── inventory/
│   ├── production
│   └── staging
├── playbooks/
│   ├── web.yml
│   └── db.yml
├── roles/
│   ├── web/
│   └── db/
├── files/
├── templates/
└── ansible.cfg

3. Use Inventory Groups

ini

[webservers]
web1.example.com
web2.example.com

[dbservers]
db1.example.com
db2.example.com

[production:children]
webservers
dbservers

4. Enable Verbosity for Debugging

bash

ansible-playbook playbook.yml -v      # Verbose
ansible-playbook playbook.yml -vv     # More verbose
ansible-playbook playbook.yml -vvv    # Debug

5. Use Check Mode

bash

ansible-playbook playbook.yml --check

6. Run on Specific Hosts

bash

ansible-playbook playbook.yml -l webservers
ansible-playbook playbook.yml -l web1.example.com

7. Use Tags

bash

ansible-playbook playbook.yml --tags "nginx,mysql"
ansible-playbook playbook.yml --skip-tags "debug"

8. Enable Diff Output

bash

ansible-playbook playbook.yml --diff

Common Tasks

System Updates

yaml

---
- name: Update all packages
  hosts: all
  become: yes
  tasks:
    - name: Update apt cache
      apt:
        update_cache: yes
        cache_valid_time: 3600

    - name: Upgrade all packages
      apt:
        upgrade: dist

User Management

yaml

---
- name: Manage users
  hosts: all
  become: yes
  tasks:
    - name: Create user
      user:
        name: deploy
        shell: /bin/bash
        groups: sudo,docker
        append: yes

    - name: Add SSH key
      authorized_key:
        user: deploy
        key: "{{ lookup('file', '~/.ssh/id_rsa.pub') }}"

File Management

yaml

---
- name: Manage files
  hosts: all
  become: yes
  tasks:
    - name: Create directory
      file:
        path: /opt/myapp
        state: directory
        mode: '0755'

    - name: Copy configuration
      copy:
        src: config.ini
        dest: /opt/myapp/config.ini
        mode: '0644'

    - name: Create symlink
      file:
        src: /opt/myapp/config.ini
        dest: /etc/myapp.conf
        state: link

Troubleshooting

Common Issues

1. Connection Issues:

bash

# Check SSH connection
ssh ubuntu@web1.example.com

# Verbose output
ansible webservers -m ping -vvv

2. Permission Issues:

bash

# Use become for privilege escalation
ansible-playbook playbook.yml -b

# Specify sudo user
ansible-playbook playbook.yml -b --become-user=root

3. Python Issues:

bash

# Specify Python interpreter
ansible-playbook playbook.yml -e "ansible_python_interpreter=/usr/bin/python3"

Debug Mode

yaml

- name: Debug task
  debug:
    msg: "Variable value: {{ my_variable }}"
    verbosity: 1

Next Steps

Now that you understand Ansible basics, explore:

Playbooks for complex automation
Roles for reusability
Ansible Galaxy for sharing
Ansible Vault for secrets
Advanced patterns and best practices

Ansible basics provide the foundation for automating your infrastructure efficiently and reliably.

Ansible Basics: Automation and Configuration Management

Introduction to Ansible

What is Ansible?

Why Ansible?

Installing Ansible

Installation Methods

Verifying Installation

Ansible Architecture

Control Node vs Managed Nodes

Architecture Diagram

Inventory

What is Inventory?

INI Format Inventory

YAML Format Inventory

Dynamic Inventory

Ad-Hoc Commands

Basic Syntax

Common Ad-Hoc Commands

Useful Modules

Modules

Understanding Modules

Using Modules

Configuration

ansible.cfg

Environment Variables

SSH Setup

SSH Key Authentication

SSH Agent

SSH Config

Facts Gathering

What are Facts?

Disabling Facts

Gathering Specific Facts

Fact Caching

Idempotency

Understanding Idempotency

Idempotent Example

Non-Idempotent Commands

Best Practices

1. Use Version Control

2. Organize Playbooks

3. Use Inventory Groups

4. Enable Verbosity for Debugging

5. Use Check Mode

6. Run on Specific Hosts

7. Use Tags

8. Enable Diff Output

Common Tasks

System Updates

User Management

File Management

Troubleshooting

Common Issues

Debug Mode

Next Steps

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