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Ansible

Ansible​

  • Ansible is an open source engine that automates application deployment, orchestration, cloud provisioning etc.
  • It uses human readable YAML syntax for Ansible Playbooks to describe automation jobs.
  • Ansible is agent-less and designed for multi-tier deployment. Connects nodes via ssh by pushing "Ansible modules" which is removed after its execution.

Environment Setup​

Types of machines:​

  • Control machine − a system on which Ansible is installed which manages other machines by executing playbook.
  • Remote machine − a remote system managed by control machine.

Installation​

apt update
apt upgrade -y

apt install ansible -y

Ansible project hierarchy​

ansible-project/
├── ansible.cfg                # Project-specific config (overrides /etc/ansible/ansible.cfg)
├── inventory.ini              # List of managed nodes, groups, and variables
├── site.yml                   # Master playbook; imports other playbooks (entry point)
├── webservers.yml             # Tier-specific playbook (e.g., handles web stack)
├── group_vars/                # Variables applied to specific inventory groups
│   ├── all.yml                # Variables for every host in the inventory
│   └── webservers.yml         # Variables only for hosts in [webservers] group
├── host_vars/                 # Variables for unique individual hosts
│   └── db-server-01.yml       # Custom settings for one specific database node
├── library/                   # Optional: Custom Ansible modules written in Python
├── filter_plugins/            # Optional: Custom Jinja2 filters for data manipulation
└── roles/                     # Modular, reusable units of automation
    └── common/                # A role for base configuration (NTP, Users, etc.)
        ├── tasks/             # Execution logic
        │   └── main.yml       # e.g., - name: install git | apt: name=git state=present
        ├── handlers/          # Service triggers
        │   └── main.yml       # e.g., - name: restart ntp | service: name=ntp state=restarted
        ├── templates/         # Jinja2 configuration files
        │   └── ntp.conf.j2    # e.g., server {{ ntp_server }} iburst
        ├── files/             # Static files to be copied to nodes
        │   └── motd           # e.g., "Welcome to this Managed Server"
        ├── vars/              # High-priority role-specific variables
        │   └── main.yml       # e.g., pkg_name: apache2
        ├── defaults/          # Low-priority default variables (easily overridden)
        │   └── main.yml       # e.g., port: 80
        └── meta/              # Role dependencies and author info
            └── main.yml       # e.g., dependencies: [ { role: firewall } ]

Ansible configuration​

ansible.cfg​

[default]
inventory = nameOfInventoryFile
private_key_file = ~/.ssh/nameOfSSHKey

Ad-hoc commands​

Playbook​

Ansible commands​

ansible all --key-file ~/.ssh/nameOfSSHKey -i inventory -m ping

ansible all --list-hosts

ansible all -m gather_facts
ansible all -m gather_facts --limit ip.address.of.single.host

# sudo apt update to update package index
ansible all -i hosts -m apt -a update_cache=true --become --ask-become-pass

# install tmux
ansible all -i hosts -m apt -a name=tmux --become --ask-become-pass
ansible all -i hosts -m apt -a "name=tmux state=latest" --become --ask-become-pass

# sudo apt dist-upgrade
ansible all -i hosts -m apt -a upgrade=dist --become --ask-become-pass

ansible-playbook --ask-become-pass playbookFileName.yml

# List tags of a playbook
ansible-playbook -i nameOfInventory --list-tags playbookFileName.yml
ansible-playbook -i nameOfInventory --tags "tag1,tag2,tag3" --ask-become-pass playbookFileName.yml

# Syntax check
ansible-playbook --syntax-check <YAML>

# Ansoble Vaults
ansible-vault create secret.yml
ansible-vault edit secret.yml

# Ansoble Galaxy
ansible-galaxy install -r requirements.yml

Playbook snippets​

Ansible Inventory​

A list of managed nodes that are logically organized. You create an inventory on the control node to describe host deployments to Ansible.

WSL Playbook​

See https://github.com/m19v/dotfiles/blob/main/README.md

Roles​

Variables​

Advanced execution​

Troubleshooting​

SSH Overview​

SSH Key-Based Authentication​

  • Install OpenSSH on server
# Ubuntu
sudo apt install openssh-server
  • Create an SSH key pair (with a passphrase) for your normal user account and copy it to target server

# -t ed25519        type of algorith
# -C                comment to ssh key
ssh-keygen -t ed25519 -C "ansible tutorial key"

# following command will copy the public key to the host under the folder 
# .ssh/authorized_keys
ssh-copy-id -i ~/.ssh/id_ed25519.pub 1p.address.of.host
  • Create a specific SSH key for Ansible Control Node (without passphrase as ansible can not enter passphrase everytime connecting target servers) and copy it to target server
# with different name e.g. /home/username/.ssh/ansible
ssh-keygen -t ed25519 -C "ansible control node"

Adding SSH Key to SSH Agent​

# Check if ssh-agent is running
eval "$(ssh-agent -s)"        
# Add ssh key to ssh-agent
ssh-add ~/.ssh/nameOfSSHKey
# Verify Key is added to ssh-agent
ssh-add -l

References​