Ansible Basics
Installing Ansible
Enable Required Repositories
Ansible is available via the EPEL (Extra Packages for Enterprise Linux) or the official Red Hat repositories.
Add Required Repositories
For RHEL systems, install the EPEL repository:
sudo dnf update sudo dnf install epel-release
For Ubuntu/Debian based systems:
sudo apt update sudo apt install software-properties-common sudo add-apt-repository --yes --update ppa:ansible/ansible
Install Ansible
Once the repository is enabled, install Ansible using the package manager:
RHEL Systems
sudo dnf install ansible
Ubuntu/Debian Systems
sudo apt install ansible
Verify the Installation
After installation, verify Ansible is installed correctly:
ansible --version
You should see output similar to:
ansible [core 2.x.x] config file = /etc/ansible/ansible.cfg python version = 3.x.x
Troubleshooting
- If epel-release is not found, try enabling the codeready-builder repo or check for typos.
Creating an Ansible Inventory File
An inventory file for Ansible is a file that has a list of the hosts Ansible will interact with, their hostnames, IP addresses, and other relevant information. Typically these are .ini files. i.e.:
INVENTORY.ini / ANSIBLE_HOSTS.ini / SERVER_LIST.ini
An example inventory file might look like:
[web-server] (this is the host group) web-server-01 ansible_host=1.2.3.4 (each entry is a single host, with arguments/options beside) web-server-02 ansible_host=WEBSERVER_HOSTNAME
You can also format the inventory file, to manage entire host groups collectively, like this:
[file-server] file01 ansible_host=1.2.3.4 file02 ansible_host=5.6.7.8 file03 ansible_host=9.10.11.12 [file-server:vars] ansible_user=USER ansible_port=PORT# ansible_become=[true/false] (whether or not Ansible will become 'root' user) ansible_become_user=[true/false] (whether or not Ansible will become the current user) ansible_ssh_private_key=/PATH/TO/IDENTITY/FILE
Creating an Ansible Playbook (Basics)
An Ansible playbook is the instruction set that Ansible will follow to enforce the changes/configurations/etc across the specified hosts in the playbook file. Typically these files are .yml files. i.e.:
PLAYBOOK.yml / initial_setup.yml / web_server.yml
Generic Playbook Syntax
An example playbook may look like this:
- name: Basic Setup (Description of what this playbook does)
hosts: all (You can also specify a specific host group, like "file-server" or "web-server" or "prod")
become: true
tasks:
- name: Set Hostname (Description of what this specific task does)
hostname:
name: DESIRED_CUSTOM_HOSTNAME_OF_TARGET_NODE or "{{ inventory_hostname }}" (can use this option if the target's IP is included in the inventory file, Ansible will have the target set its hostname to the target's corresponding IP address)
- name: DESCRIPTION OF WHAT THIS TASK WILL DO
dnf: (calls the Ansible module for dnf, there are other modules outlined below)
name: PACKAGE (specifies the package to pass to dnf)
state: STATE (see below for available STATES)
Example Playbook
An example playbook (with some notations) to perform specific tasks may look like this:
- name: Hostname and Repo Config Playbook
hosts: all
become: true
tasks:
- name: Set Hostname
hostname:
name: DESIRED_CUSTOM_HOSTNAME_OF_TARGET_NODE or "{{ inventory_hostname }}" (can use this option if the target's IP is included in the inventory file, Ansible will have the target set its hostname to the target's corresponding IP address)
- name: Ensure epel-release repository is installed
dnf:
name: epel-release
state: present
-name: Reboot if hostname changes
reboot:
msg: "Rebooting after hostname change"
connect_timeout: 5
reboot_timeout: 300
when: ansible_hostname != inventory_hostname (this task will only be run when this condition is met, when the device's hostname does NOT match the hostname specified in the inventory file passed to Ansible)
Ansible Playback Modules
Some other modules that can be called in an Ansible Playbook include:
Package Modules (apt, yum, dnf, etc.)
State - Description present - Ensures the package is installed. latest - Installs or upgrades the package to the latest version. absent - Removes the package if it is installed. installed - Alias for present. removed - Alias for absent.
Service Modules (service, systemd)
State - Description started - Ensures the service is running. stopped - Ensures the service is stopped. restarted - Stops and starts the service again. reloaded - Reloads the service (useful for configs). enabled (with enabled: true) - Ensures service starts at boot. disabled - Prevents service from starting at boot.
File and Directory Modules (file, copy, template)
State - Description touch - Creates an empty file if it doesn’t exist. absent - Deletes the file or directory. directory - Ensures a directory exists. file - Ensures it’s a regular file (can also adjust permissions). link - Ensures a symbolic link exists. hard - Ensures a hard link exists.
User & Group Modules (user, group)
State - Description present - Ensures the user or group exists. absent - Ensures the user or group is removed.
Network Resources / Repos
For repositories (like yum_repository, apt_repository):
State - Description present - Repo is configured and available. absent - Repo is removed.
For firewall rules, cloud resources, etc., modules usually support:
State - Description present - Create or apply the configuration. absent - Remove or undo the configuration. enabled - Turn on or activate the resource. disabled - Turn off or deactivate it.
Running an Ansible Playbook
The basic syntax for running an Ansible playbook command looks like:
ansible-playbook -i INVENTORY_FILE PLAYBOOK_FILE
If your playbook will require Ansible to perform operations as a superuser (i.e. will require 'sudo') you can pass the 'sudo' password like this:
ansible-playbook -i INVENTORY_FILE PLAYBOOK_FILE --ask-become-pass