Ansible Cheat Sheet for Sysadmins

Ansible Cheat Sheet for Sysadmins

A complete reference for Ansible automation, including commands, playbooks, modules, inventory management, vaults, and expert tips.

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🔹 Ansible Basics

• Check Ansible Version:

  ansible --version
  

• Test Connectivity (Ping Module):

  ansible all -m ping -i inventory
  

  • Replace inventory with the path to your inventory file.*
• Run a Simple Command on Hosts:

  ansible webservers -a "uptime" -i inventory
  

  • Replace webservers with the group name defined in your inventory.*
• Ad-hoc Command with Become:

  ansible dbservers -m shell -a "systemctl restart mysql" -b -i inventory
  

  • Use -b to execute commands with elevated privileges.*

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🔹 Inventory

• Static Inventory Example (hosts.ini):

  [webservers]
  web01.example.com
  web02.example.com
  
  [dbservers]
  db01.example.com
  
  [all:vars]
  ansible_user=admin
  ansible_ssh_private_key_file=~/.ssh/id_rsa
  

• Dynamic Inventory: Use AWS, GCP, OpenStack via scripts or --inventory-plugin.
• Check which hosts are reachable:

  ansible all -m ping
  

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🔹 Modules (Most Used)

• Package Management:

  # Debian/Ubuntu
  ansible web -m apt -a "name=nginx state=latest" -b
  # RHEL/CentOS
  ansible db -m yum -a "name=mariadb-server state=present" -b
  

• Service Management:

  ansible web -m service -a "name=nginx state=restarted" -b
  

• File & Directory:

  ansible all -m file -a "path=/tmp/testfile state=touch mode=0644" -b
  

• Copy / Template:

  ansible all -m copy -a "src=nginx.conf dest=/etc/nginx/nginx.conf" -b
  ansible all -m template -a "src=app.j2 dest=/etc/app/config.conf" -b
  

  • Use template for Jinja2 templating and dynamic configurations.*
• Command & Shell:

  ansible all -m command -a "uptime"
  ansible all -m shell -a "echo $HOSTNAME > /tmp/hostname.txt" -b
  

  • Prefer command over shell for idempotency.*

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🔹 Playbooks

• Basic Playbook Structure: ```yaml —
  • name: Install and configure webserver hosts: webservers become: true vars: http_port: 80 tasks:
    • name: Install Nginx apt: name: nginx state: latest
    • name: Copy nginx config template: src: nginx.conf.j2 dest: /etc/nginx/nginx.conf
    • name: Ensure nginx is running service: name: nginx state: started enabled: true ```
• Run Playbook:

  ansible-playbook -i hosts.ini site.yml
  

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🔹 Roles

• Directory Structure:

  roles/
    common/
      tasks/
      handlers/
      templates/
      files/
      vars/
      defaults/
      meta/
  

• Include a Role in Playbook: ```yaml roles:
  • common
  • webserver ```

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🔹 Variables & Facts

• Declare Variables:

  vars:
    app_port: 8080
    db_name: prod_db
  

• Host-specific Variables: host_vars/hostname.yml
• Group-specific Variables: group_vars/webservers.yml
• Gather Facts: ```yaml tasks:
  • debug: var: ansible_distribution ```
• Use Variables: ```yaml
  • name: Create folder file: path: “/opt/” state: directory ```

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🔹 Handlers

• Notify a Handler: ```yaml tasks:
  • name: Copy nginx config template: src: nginx.conf.j2 dest: /etc/nginx/nginx.conf notify: Restart nginx

  handlers:

  • name: Restart nginx service: name: nginx state: restarted ```

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🔹 Vault (Secrets Management)

• Create Encrypted File:

  ansible-vault create secrets.yml
  

• Edit Encrypted File:

  ansible-vault edit secrets.yml
  

• Run Playbook with Vault:

  ansible-playbook site.yml --ask-vault-pass
  

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🔹 Tips & Tricks

• Preview Changes Before Applying:

  ansible-playbook site.yml --check --diff
  

• Use Tags to Limit Tasks:

  ansible-playbook site.yml --tags "nginx,config"
  

• Lint Your Playbooks:

  ansible-lint site.yml
  

• Debugging: ```yaml
  • debug: msg: “Current app_port is “ ```
• Run Long Tasks Asynchronously: ```yaml
  • name: Run long task asynchronously shell: /usr/local/bin/backup.sh async: 1800 poll: 0 ```

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🔹 Common Commands

• List All Hosts:

  ansible all --list-hosts -i hosts.ini
  

• Ping All Hosts:

  ansible all -m ping
  

• Show Variables:

  ansible all -m setup | grep ansible_distribution
  

• Limit Playbook to Certain Hosts:

  ansible-playbook site.yml -l web01
  

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🔹 Best Practices

• Always use modules over raw shell commands.
• Maintain idempotent playbooks for reliable automation.
• Use separate environments: dev, staging, production inventories.
• Keep sensitive data encrypted with Vault.
• Test playbooks with --check and --diff before applying.
• Use roles for modular, reusable code.
• Version control everything.
• Document dependencies, required variables, and vault secrets.