--- title: "Discovering the Ansible Hosts File" description: "Discover and learn best practices for managing inventory with the Ansible Hosts File in this tutorial from ATA Learning." canonical: "https://adamtheautomator.com/ansible-hosts-file/" --- # Discovering the Ansible Hosts File > Discover and learn best practices for managing inventory with the Ansible Hosts File in this tutorial from ATA Learning. Source: https://adamtheautomator.com/ansible-hosts-file/ --- ATA Learning Tap to hide [ ATA Learning ](/) * [Home](/) * [Tutorials](/tutorials/) * [Instructors](/author/) * [Advertising](/advertising/) * [Recommended Resources](/resources/) * [About Adam](/about-adam/) Search for: * [](https://twitter.com/adbertram) * [](https://github.com/Adam-the-Automator) * [](https://www.linkedin.com/company/adam-the-automator-llc) * [](/feed/) ![Discovering the Ansible Hosts File](https://adamtheautomator.com/wp-content/uploads/2022/05/Discovering-the-Ansible-Hosts-File.jpg) # Discovering the Ansible Hosts File [![](https://secure.gravatar.com/avatar/2788bb1a3f735603f81eca51d68daec56a9d97e805a10268fb2c20afcc76b81b?s=192&d=mm&r=g)Nicholas Xuan Nguyen](https://adamtheautomator.com/author/nicholas-xuan-nguyen/)18 May 202210 min. read Categories: [IT Ops](/category/it-ops/) Tags:[Ansible](/tag/ansible/) Table of Contents * [Prerequisites](#prerequisites) * [Setting up a Custom Inventory File](#setting-up-a-custom-inventory-file) * [Testing the Custom Inventory File](#testing-the-custom-inventory-file) * [Organizing Servers Into Groups](#organizing-servers-into-groups) * [Working with Dynamic Inventory](#working-with-dynamic-inventory) * [Securing Sensitive Data in Inventory File](#securing-sensitive-data-in-inventory-file) * [Conclusion](#conclusion) As a system admin, you might have come across a situation where you need to manage multiple servers. This situation can be daunting unless you consider discovering the Ansible hosts file. Ansible hosts file or inventory is an important file that tells Ansible about the hosts to manage. Ansible hosts file helps you to automate all these tasks. And in this tutorial, you’ll learn how to set up Ansible inventories from scratch. Read on and never be timid managing multiple servers simultaneously! ## Prerequisites This tutorial will be a hands-on demonstration. If you’d like to follow along, be sure you have the following. * Ansible control nodes, which can be your local machine – This tutorial uses Ubuntu 20.04 and AWS EC2 instances. Related:[How to Install Ubuntu 20.04 \[Step-by-Step\]](https://adamtheautomator.com/install-ubuntu/) * A few servers that Ansible can manage (Ansible Hosts) – This tutorial uses Ubuntu and AWS EC2 host nodes. [SSH keys](https://www.digitalocean.com/community/tutorials/how-to-set-up-ssh-keys-on-ubuntu-20-04) and a user account that can access each node with [sudo](https://phoenixnap.com/kb/how-to-create-sudo-user-on-ubuntu) privileges are required. * [Ansible](https://adamtheautomator.com/install-ansible/) and [Python](https://phoenixnap.com/kb/how-to-install-python-3-ubuntu) installed on all the nodes (control nodes and host nodes). Ansible modules and commands require Python libraries. Related:[Guide: How to Setup Ansible (Ubuntu, RHEL, CentOS, macOS)](https://adamtheautomator.com/install-ansible/) * An [AWS user with programmatic access](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_users_create.html) (AWS Access Key and Secret Access Key) – This user must have permissions to create, manage AWS resources, and make API calls. ## Setting up a Custom Inventory File Now that you have all the prerequisites in place, it’s time to start configuring Ansible by setting up a custom inventory file. But first, you’ll have to check if both Ansible and Python are correctly installed. 1\. Run the command below to verify Ansible and Python versions installed on each node. ```powershell ansible --version python3 -version ``` You’ll see the Ansible and Python version numbers, as shown below. ![Checking Ansible and Python version](https://adamtheautomator.com/wp-content/uploads/2022/05/image-103.png) Checking Ansible and Python version 2\. Open the default _hosts_ file (_/etc/ansible/hosts_) using your favorite text editor to see what an Ansible _hosts_ file looks like. By default, Ansible looks for the hosts in the _/etc/ansible/hosts_ file. The default inventory file contains different examples you can use as references while setting up your inventory. Below, you can see the _hosts_ file’s content is divided into many sections with examples: * The **\[webservers\]** section is commented out, which is where you declare the hosts that will be used as web servers. * The **\[dbservers\]** section is also commented out, where you declare hosts that will be used as database servers and so on. The brackets \[\] are used to group hosts together to be targeted as a group in playbooks. Related:[How to Build (And Actually Understand) a Solid Ansible Playbook](https://adamtheautomator.com/ansible-playbook-example/) You can put one hostname or IP address in each group. For example, one server could be both a webserver and a dbserver. In that case, note that Ansible [variables](https://docs.ansible.com/ansible/latest/user_guide/playbooks_variables.html) will come from all of the groups they are members of. ![Viewing the /etc/ansible/hosts File](https://adamtheautomator.com/wp-content/uploads/2022/05/image-104.png) Viewing the /etc/ansible/hosts File > _Depending on your needs, you can have as many groups as you want in your inventory file. For example, if you manage an extensive infrastructure, you might need different groups for each environment, such as dev, test, and production._ 3\. Run the below command to create a new directory (mkdir) named ansible in your home directory. The _ansible_ directory stores all the files related to your Ansible project. ```bash cd && mkdir ansible ``` > _You can use the default inventory file without problems. But having your custom inventory file for each project you work on is good practice. How? First, using per-project inventory files helps you avoid running a playbook on the wrong group of servers. Second, you can share your inventory file with others who use Ansible._ 4\. Now, run the below commands to move into the newly-created directory (_ansible_), create and open a new inventory file named inventory. ```bash cd ansible && nano inventory ``` 5\. Add your Ansible hosts ungrouped inside the inventory file, then save the changes and close the file. Note that only one entry per line is allowed, as shown below. > _If you put more than one host on the same line, they will be considered one host. As a result, you’ll get an error when you try to run the playbook._ At this point, you have a basic but functional Ansible inventory file. ![Declaring Hosts](https://adamtheautomator.com/wp-content/uploads/2022/05/image-105.png) Declaring Hosts 6\. Lastly, run the below [ansible-inventory](https://docs.ansible.com/ansible/latest/cli/ansible-inventory.html) command to –list all the hosts and groups in your inventory file (-i inventory). You must use the -i option, or else, Ansible will look for the default hosts file instead. ```bash ansible-inventory -i inventory --list ``` Even though you only have three ungrouped servers listed in your inventory file, Ansible automatically infers two distinct groups, as follows: * **all** – Contains all the servers from your inventory file, no matter how they are organized. * **ungrouped** – Contains all the servers that don’t belong to any group. ![Listing Ansible Hosts](https://adamtheautomator.com/wp-content/uploads/2022/05/image-106.png) Listing Ansible Hosts ## Testing the **Custom Inventory File** Now that you have a custom inventory file, you need to tell Ansible to use that file in your playbooks. But first, be sure to test the connectivity between your Ansible control server and the hosts in your inventory file. Run the below command to `ping` `all` servers in your inventory file (`-i inventory`) from your Ansible control server. ```bash ansible -i inventory all -m ping ``` This command tests Ansible control servers, the hosts in your inventory file’s connectivity, and provides output as follows: * **SUCCESS –** Verifies you can reach all servers listed in your inventory file from the Ansible control server. * **“discovered\_interpreter\_python”** – The Python interpreter used on your remote servers. In this case, Python 3. * “**changed**“: **false –** Indicates the ping module didn’t make any changes on your servers. The **ping** module is one of the few modules that doesn’t make any changes on your servers but simply returns information. * “**ping**“: “**pong**“: This line indicates that the ping module was executed successfully. Your control node sends a ping request to all servers listed in your inventory file, and all servers respond pong. ![Testing Ansible Node Connectivity](https://adamtheautomator.com/wp-content/uploads/2022/05/image-107.png) Testing Ansible Node Connectivity Now, run the following command to verify the connectivity of a specific server. Replace `159.65.197.8` with the actual name of your remote server. ```bash ansible -i inventory 159.65.197.8 -m ping ``` The output below verifies connecting to a server with the IP address **159.65.197.8** is a **SUCCESS**. ![Verifying Connectivity of a Specific Server](https://adamtheautomator.com/wp-content/uploads/2022/05/image-108.png) Verifying Connectivity of a Specific Server ## **Organizing Servers Into Groups** You’ve just created a basic inventory file with ungrouped hosts, and it works. So why group your servers? When you organize your servers into groups, they become more manageable. At the same time, you can apply a set of configurations or run a playbook on a specific group of servers instead of running it on all servers. To organize your servers into their respective groups: 1\. Open your custom _inventory_ file in a text editor. 2\. Add your servers into their groups, as shown below. This tutorial organizes servers into three groups (webserver, dbservers, and production), as shown below. Save and close the inventory file when you are finished. ![Adding Servers Into Groups](https://adamtheautomator.com/wp-content/uploads/2022/05/image-109.png) Adding Servers Into Groups 3\. Now, run the below command to –list all hosts and groups in your inventory file (-i inventory). ```bash ansible-inventory -i inventory --list ``` The output below shows that the servers are grouped into webservers, dbservers, and production. Notice all servers still belong to all group, and any servers that don’t belong to any groups are placed in the ungrouped group. At this point, you already have a basic inventory file with a few servers organized into groups. ![Viewing Ansible Groups](https://adamtheautomator.com/wp-content/uploads/2022/05/image-110.png) Viewing Ansible Groups 4\. Run the following apt command to install the NGINX package on all servers in the webservers group. Ansible has a built-in apt module (ansible.builtin.apt) you can use to install packages on your remote Ubuntu servers. ```bash ansible -i inventory -m ansible.builtin.apt -a "name=nginx state=present" webservers ``` ![Installing the NGINX Package on all Servers in the webservers Group](https://adamtheautomator.com/wp-content/uploads/2022/05/image-111.png) Installing the NGINX Package on all Servers in the webservers Group Related:[Learning Ubuntu Apt Get Through Examples](https://adamtheautomator.com/ubuntu-apt-get/) 5\. Lastly, run the below command to verify the status of the NGINX service that it’s running on all servers in the webservers group. ```bash ansible -i inventory -m shell -a "systemctl status nginx" webservers ``` The output below indicates the NGINX service is running on all servers in the webservers group and are now ready to serve web traffic! Similarly, you can perform other tasks not limited to the ones below: * Install the MariaDB package on all servers in the **dbservers** group. * Apply a set of configurations to all servers in the production group. ![Checking the NGINX Status on Remote Servers](https://adamtheautomator.com/wp-content/uploads/2022/05/image-112.png) Checking the NGINX Status on Remote Servers Related:[Correct Way of Using Ubuntu systemctl to Control Systemd](https://adamtheautomator.com/ubuntu-systemctl/) ## Working with Dynamic Inventory So far, you’ve worked with Ansible playbooks and static and custom inventory files. But in the real world, you’ll work with cloud environments, such as AWS, Google Cloud, Azure, and so on. These platforms have their own APIs to manage infrastructure and services. You may need to scale servers in and out frequently, in which a static inventory file will not work well. Infrastructures are constantly changing, and you’ll have to update the inventory file frequently. Luckily, Ansible provides a way to work with cloud environments and external inventory called dynamic inventory. And in this tutorial, you’ll touch on the basic concepts of dynamic inventory in a short demo for AWS. 1\. Run the below command to install the boto3 library. Ansible uses this library to query for information about hosts in AWS EC2. ```bash pip3 install boto3 ``` ![Installing boto3 Library](https://adamtheautomator.com/wp-content/uploads/2022/05/image-113.png) Installing boto3 Library 2\. Next, run the below command to create a new directory (mkdir) called /opt/ansible/inventory and navigate to that directory (cd). ```bash mkdir -p /opt/ansible/inventory && cd /opt/ansible/inventory ``` 3\. Configure AWS EC2 dynamic inventory with the following: * Create a new file called _aws\_ec2.yaml_ in your text editor, and populate the file with the below content. The _aws\_ec2.yaml_ file is the configuration file for the AWS EC2 dynamic inventory. * Replace and with your own AWS access and secret key. * Save and close the _aws\_ec2.yaml_ file. ```bash --- plugin: aws_ec2 aws_access_key: aws_secret_key: keyed_groups: - key: tags prefix: tag ``` > _Note that you must include the — at the beginning of the file for YAML syntax. This symbol is not a typo but is required for Ansible to parse the file correctly._ 4\. Open the /_etc/ansible/ansible.cfg_ file in a text editor and enable the aws\_ec2 inventory plugin with the following: * Uncomment the **enable\_plugins** directive by removing the **#** symbol at the beginning. This directive enables the aws\_ec2 inventory plugin. Ansible uses this plugin to interact with AWS EC2. * Set enable\_plugins directive’s value to aws\_ec2, as shown below. * Save the changes and close the _ansible.cfg_ file. You’ve now successfully configured Ansible to use the AWS EC2 dynamic inventory. ![Enabling the aws\_ec2 Inventory Plugin](https://adamtheautomator.com/wp-content/uploads/2022/05/image-114.png) Enabling the aws\_ec2 Inventory Plugin 5\. Finally, run the below command to verify that Ansible can connect to AWS and pull information about the hosts. ```bash ansible-inventory -i aws_ec2.yaml --graph ``` In the output below, Ansible successfully pulled information about the two hosts in your AWS EC2 account. Each time you terminate or create an instance in AWS, the inventory updates automatically. Now, group the servers by region or any other criteria (dbserver, webservers…). You can then install software on those servers using Ansible playbooks. For example, you may want to group the servers by webservers and install NGINX on all the servers in that group just like you would for a static inventory. ![Viewing the EC2 Ansible Groups](https://adamtheautomator.com/wp-content/uploads/2022/05/image-115.png) Viewing the EC2 Ansible Groups ## Securing Sensitive Data in Inventory File As you’ve noticed, the inventory file (_aws\_ec2.yaml_) contains sensitive data, such as your AWS access key and secret key. Storing these keys in clear text in the inventory file is risky. Fortunately, Ansible provides you with a way to encrypt your inventory files using ansible-vault. To encrypt your inventory files, you’ll first need to set the `$EDITOR` variable’s value in your shell. This variable tells Ansible which text editor (i.e., nano, vim…) to use when editing a file using ansible-vault. 1\. Open the _~/.bashrc_ file in your editor and add the export EDITOR=nano line to the end of the _~/.bashrc_ file. Be sure to replace nano with your preferred text editor, save the changes and close the editor. The _~/.bashrc_ file is a shell script that Bash runs whenever the Bash shell starts up. This file is where you set environment variables, start background processes, and set the current user’s alias. ![Setting the Default Text Editor](https://adamtheautomator.com/wp-content/uploads/2022/05/image-116.png) Setting the Default Text Editor 2\. Next, run the following commands to source the script, apply the changes and verify that the EDITOR variable is set correctly. ```bash # Source the script, and apply the changes . ~/.bashrc # Print the $EDITOR variable's value echo $EDITOR ``` You’ll see the name of your text editor printed out on the terminal, as shown below. ![Verifying the Default Editor](https://adamtheautomator.com/wp-content/uploads/2022/05/image-117.png) Verifying the Default Editor 3\. Run the ansible-vault create command below to create a new encrypted inventory file to store your AWS access key and secret key. You can name the file as you like, but the file is named encrypted\_inventory in this tutorial. ```bash ansible-vault create encrypted_inventory ``` You’ll be prompted to set and confirm a password to encrypt and decrypt the _encrypted\_inventory_ file. A new _encrypted\_inventory_ file will be created and opened automatically in your default editor (nano), as you set in the $EDITOR variable. > _The password should be more than eight characters, a mix of uppercase and lowercase letters, and at least one number or special character._ ![Creating an Encrypted Inventory File](https://adamtheautomator.com/wp-content/uploads/2022/05/image-118.png) Creating an Encrypted Inventory File 4\. Add the inventory data to the _encrypted\_inventory_ file, save and close the file when you’re happy with the changes. At this point, you’ve created an encrypted inventory file that can be used with the ansible-playbook command. ![Adding Data in the Encrypted Inventory File](https://adamtheautomator.com/wp-content/uploads/2022/05/image-119.png) Adding Data in the Encrypted Inventory File 5\. Run the cat command below to verify that the file is encrypted. ```bash cat encrypted_inventory.yml ``` You’ll see an output similar to the one below if the _encrypted\_inventory_ file is encrypted. The $ANSIBLE\_VAULT;1.1;AES256 string indicates that the file is encrypted using Ansible Vault with the AES256 cipher. The encrypted data is the random string of characters below the $ANSIBLE\_VAULT string. No one can read your AWS access and secret keys without the correct password. ![Viewing the Encrypted Inventory File Content](https://adamtheautomator.com/wp-content/uploads/2022/05/image-120.png) Viewing the Encrypted Inventory File Content 6\. Finally, run the ansible-vault view command to decrypt and view the contents of the _encrypted\_inventory.yml_ file. Provide the password you set for encrypting and decrypting the file in step three. ```bash ansible-vault view encrypted_inventory.yml ``` As you can see below, Ansible decrypts the _encrypted\_inventory.yml_ file and displays its contents after verifying the password. ![Decrypting the encrypted\_inventory.yml File](https://adamtheautomator.com/wp-content/uploads/2022/05/image-121.png) Decrypting the _encrypted\_inventory.yml_ File ## Conclusion This tutorial walked you through setting up and configuring Ansible inventories on your Ubuntu 20.04 server. You’ve created a custom Ansible inventory file/Ansible hosts file and organized servers into groups. You can now effectively manage multiple servers, like installing packages on all servers in a group simultaneously. At this point, you can start using the Ansible _hosts_ file to automate your server configuration and management tasks. There’s a lot more to learn about Ansible. Why not start learning how to [assign an inventory group alias to a variable](https://www.linuxtechi.com/use-variables-in-ansible-playbook/)? It’s time to make your playbooks more readable and easier to maintain. Share this article [Share on X](https://twitter.com/intent/tweet?url=https%3A%2F%2Fadamtheautomator.com%2Fansible-hosts-file%2F&text=Discovering%20the%20Ansible%20Hosts%20File)[Share on Facebook](https://www.facebook.com/sharer/sharer.php?u=https%3A%2F%2Fadamtheautomator.com%2Fansible-hosts-file%2F)[Share on LinkedIn](https://www.linkedin.com/sharing/share-offsite/?url=https%3A%2F%2Fadamtheautomator.com%2Fansible-hosts-file%2F) ## Related Posts ![](https://adamtheautomator.com/wp-content/uploads/2022/05/Manage-Playbooks-and-Inventories-Easily-with-Ansible-Tower.jpg) ### [Ansible Tower Basics for Easy Playbook and Inventory Management](/ansible-tower/) Master Ansible Tower for effortless playbook and inventory management, elevating your automation skills to the next level with practical, user-friendly strategies. ![](https://adamtheautomator.com/wp-content/uploads/2022/08/How-to-Manage-Services-With-the-Ansible-Service-Module.jpg) ### [How to Manage Services With the Ansible Service Module](/ansible-service/) Learn how to manage, control, and integrate OS services with the Ansible Service module in this ATA Learning tutorial! ![](https://adamtheautomator.com/wp-content/uploads/2022/05/Secure-Your-Secrets-With-Ansible-Vault.jpg) ### [Secure Your Secrets With Ansible Vault](/ansible-vault/) Make sure your playbook and environment secrets are secure with the Ansible Vault and level up your playbooks in this ATA Learning tutorial! ## Categories * [IT Ops](/category/it-ops/) * [Cloud](/category/cloud/) * [DevOps](/category/devops/) * [Home Ops](/category/home-ops/) * [Information Security](/category/infosec/) * [Software Development](/category/software-development/) ## Site * [Home](/) * [Tutorials](/tutorials/) * [Instructors](/author/) * [Advertising](/advertising/) * [Recommended Resources](/resources/) * [About Adam](/about-adam/) Copyright 2026© ATA Learning | [Privacy Policy](/privacy/)