How To Install and Configure Ansible on Ubuntu 20.04
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Introduction

Configuration management systems are designed to streamline the process of controlling large numbers of servers, for administrators and operations teams. They allow you to control many different systems in an automated way from one central location.

While there are many popular configuration management tools available for Linux systems, such as Chef and Puppet, these are often more complex than many people want or need. Ansible is a great alternative to these options because it offers an architecture that doesn’t require special software to be installed on nodes, using SSH to execute the automation tasks and YAML files to define provisioning details.

In this guide, we’ll discuss how to install Ansible on an Ubuntu 20.04 server and go over some basics of how to use this software. For a more high-level overview of Ansible as configuration management tool, please refer to An Introduction to Configuration Management with Ansible.

Prerequisites

To follow this tutorial, you will need:

  • One Ansible Control Node: The Ansible control node is the machine we’ll use to connect to and control the Ansible hosts over SSH. Your Ansible control node can either be your local machine or a server dedicated to running Ansible, though this guide assumes your control node is an Ubuntu 20.04 system. Make sure the control node has:

    • A non-root user with sudo privileges. To set this up, you can follow Steps 2 and 3 of our Initial Server Setup Guide for Ubuntu 20.04. However, please note that if you’re using a remote server as your Ansible Control node, you should follow every step of this guide. Doing so will configure a firewall on the server with ufw and enable external access to your non-root user profile, both of which will help keep the remote server secure.
    • An SSH keypair associated with this user. To set this up, you can follow Step 1 of our guide on How to Set Up SSH Keys on Ubuntu 20.04.
  • One or more Ansible Hosts: An Ansible host is any machine that your Ansible control node is configured to automate. This guide assumes your Ansible hosts are remote Ubuntu 20.04 servers. Make sure each Ansible host has:

    • The Ansible control node’s SSH public key added to the authorized_keys of a system user. This user can be either root or a regular user with sudo privileges. To set this up, you can follow Step 2 of How to Set Up SSH Keys on Ubuntu 20.04.

Step 1 — Installing Ansible

To begin using Ansible as a means of managing your server infrastructure, you need to install the Ansible software on the machine that will serve as the Ansible control node. We’ll use the default Ubuntu repositories for that.

First, refresh your system’s package index with:

  • sudo apt update

Following this update, you can install the Ansible software with:

  • sudo apt install ansible

Press Y when prompted to confirm installation.

Your Ansible control node now has all of the software required to administer your hosts. Next, we’ll go over how to set up an inventory file, so that Ansible can communicate with your managed nodes.

Step 2 — Setting Up the Inventory File

The inventory file contains information about the hosts you’ll manage with Ansible. You can include anywhere from one to several hundred servers in your inventory file, and hosts can be organized into groups and subgroups. The inventory file is also often used to set variables that will be valid only for specific hosts or groups, in order to be used within playbooks and templates. Some variables can also affect the way a playbook is run, like the ansible_python_interpreter variable that we’ll see in a moment.

To edit the contents of your default Ansible inventory, open the /etc/ansible/hosts file using your text editor of choice, on your Ansible control node:

  • sudo nano /etc/ansible/hosts

Note: Although Ansible typically creates a default inventory file at etc/ansible/hosts, you are free to create inventory files in any location that better suits your needs. In this case, you’ll need to provide the path to your custom inventory file with the -i parameter when running Ansible commands and playbooks. Using per-project inventory files is a good practice to minimize the risk of running a playbook on the wrong group of servers.

The default inventory file provided by the Ansible installation contains a number of examples that you can use as references for setting up your inventory. The following example defines a group named [servers] with three different servers in it, each identified by a custom alias: server1, server2, and server3. Be sure to replace the highlighted IPs with the IP addresses of your Ansible hosts.

/etc/ansible/hosts
[servers]
server1 ansible_host=203.0.113.111
server2 ansible_host=203.0.113.112
server3 ansible_host=203.0.113.113

[all:vars]
ansible_python_interpreter=/usr/bin/python3

The all:vars subgroup sets the ansible_python_interpreter host parameter that will be valid for all hosts included in this inventory. This parameter makes sure the remote server uses the /usr/bin/python3 Python 3 executable instead of /usr/bin/python (Python 2.7), which is not present on recent Ubuntu versions.

When you’re finished, save and close the file by pressing CTRL+X then Y and ENTER to confirm your changes.

Whenever you want to check your inventory, you can run:

  • ansible-inventory --list -y

You’ll see output similar to this, but containing your own server infrastructure as defined in your inventory file:

Output
all: children: servers: hosts: server1: ansible_host: 203.0.113.111 ansible_python_interpreter: /usr/bin/python3 server2: ansible_host: 203.0.113.112 ansible_python_interpreter: /usr/bin/python3 server3: ansible_host: 203.0.113.113 ansible_python_interpreter: /usr/bin/python3 ungrouped: {}

Now that you’ve configured your inventory file, you have everything you need to test the connection to your Ansible hosts.

Step 3 — Testing Connection

After setting up the inventory file to include your servers, it’s time to check if Ansible is able to connect to these servers and run commands via SSH.

For this guide, we’ll be using the Ubuntu root account because that’s typically the only account available by default on newly created servers. If your Ansible hosts already have a regular sudo user created, you are encouraged to use that account instead.

You can use the -u argument to specify the remote system user. When not provided, Ansible will try to connect as your current system user on the control node.

From your local machine or Ansible control node, run:

  • ansible all -m ping -u root

This command will use Ansible’s built-in ping module to run a connectivity test on all nodes from your default inventory, connecting as root. The ping module will test:

  • if hosts are accessible;
  • if you have valid SSH credentials;
  • if hosts are able to run Ansible modules using Python.

You should get output similar to this:

Output
server1 | SUCCESS => { "changed": false, "ping": "pong" } server2 | SUCCESS => { "changed": false, "ping": "pong" } server3 | SUCCESS => { "changed": false, "ping": "pong" }

If this is the first time you’re connecting to these servers via SSH, you’ll be asked to confirm the authenticity of the hosts you’re connecting to via Ansible. When prompted, type yes and then hit ENTER to confirm.

Once you get a "pong" reply back from a host, it means you’re ready to run Ansible commands and playbooks on that server.

Note: If you are unable to get a successful response back from your servers, check our Ansible Cheat Sheet Guide for more information on how to run Ansible commands with different connection options.

Step 4 — Running Ad-Hoc Commands (Optional)

After confirming that your Ansible control node is able to communicate with your hosts, you can start running ad-hoc commands and playbooks on your servers.

Any command that you would normally execute on a remote server over SSH can be run with Ansible on the servers specified in your inventory file. As an example, you can check disk usage on all servers with:

  • ansible all -a "df -h" -u root
Output
server1 | CHANGED | rc=0 >> Filesystem Size Used Avail Use% Mounted on udev 3.9G 0 3.9G 0% /dev tmpfs 798M 624K 798M 1% /run /dev/vda1 155G 2.3G 153G 2% / tmpfs 3.9G 0 3.9G 0% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup /dev/vda15 105M 3.6M 101M 4% /boot/efi tmpfs 798M 0 798M 0% /run/user/0 server2 | CHANGED | rc=0 >> Filesystem Size Used Avail Use% Mounted on udev 2.0G 0 2.0G 0% /dev tmpfs 395M 608K 394M 1% /run /dev/vda1 78G 2.2G 76G 3% / tmpfs 2.0G 0 2.0G 0% /dev/shm tmpfs 5.0M 0 5.0M 0% /run/lock tmpfs 2.0G 0 2.0G 0% /sys/fs/cgroup /dev/vda15 105M 3.6M 101M 4% /boot/efi tmpfs 395M 0 395M 0% /run/user/0 ...

The highlighted command df -h can be replaced by any command you’d like.

You can also execute Ansible modules via ad-hoc commands, similarly to what we’ve done before with the ping module for testing connection. For example, here’s how we can use the apt module to install the latest version of vim on all the servers in your inventory:

  • ansible all -m apt -a "name=vim state=latest" -u root

You can also target individual hosts, as well as groups and subgroups, when running Ansible commands. For instance, this is how you would check the uptime of every host in the servers group:

  • ansible servers -a "uptime" -u root

We can specify multiple hosts by separating them with colons:

  • ansible server1:server2 -m ping -u root

For more information on how to use Ansible, including how to execute playbooks to automate server setup, you can check our Ansible Reference Guide.

Conclusion

In this guide, you’ve installed Ansible and set up an inventory file to execute ad-hoc commands from an Ansible Control Node.

Once you’ve confirmed you’re able to connect and control your infrastructure from a central Ansible controller machine, you can execute any command or playbook you desire on those hosts.

For more information on how to use Ansible, check out our Ansible Cheat Sheet Guide.

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