If you’re a systems administrator, there’s a good chance you’ve heard of Ansible. But if you’re not familiar with the tool or just getting started with it, there are some key terms and concepts you need to know.
Here we will give you an overview of Ansible, from its origins to the latest features. We’ll also cover some of the key terminology associated with Ansible so you can start using it effectively immediately.
How Does Ansible Work?
Ansible is a configuration management tool that automates the provisioning and deployment of applications and infrastructure. It is designed to be simple to use and easy to extend, making it an ideal tool for managing complex deployments.
Ansible works by connecting to your servers via SSH and then executing tasks on those servers.
You can think of Ansible as a remote execution tool, like SSH, but with some important differences.
- First, Ansible is designed to be idempotent, meaning that if a task is run more than once, it will have the same result each time.
- Second, Ansible is agentless, meaning that it does not require any software to be installed on the servers that it manages.
- Third, Ansible is designed to be easily extensible. There is a wide range of community-developed modules that can be used to add support for new technologies and systems.
Key Ansible Terms
Let’s go through some of the key Ansible terminologies:
- Playbooks: A Playbook is an expression of Ansible’s configuration, deployment, and orchestration language. They can describe a policy you want your remote systems to enforce or a set of steps in a general IT process.
- Server: Remote servers that you manage with Ansible are called Managed Hosts. Once you install Ansible on a management machine, you will use SSH to connect to remote servers.
- Target Machine: The machine where Ansible is run is called the Control Node. The target machines can be virtualized or physical systems.
- Task: A task is a unit of work Ansible performs. Tasks are organized into plays, which are then executed on target machines.
- Machine: A machine is a physical or virtual server that Ansible can manage.
- Modules: Modules are small codes Ansible uses to perform tasks on target machines.
- Roles: Roles are collections of related tasks and supporting files that can be used to easily provision complex environments.
- Variables: Variables are used to store values that can be referenced in plays and tasks. Variables can be defined in playbooks, inventory files, and variable files.
Ansible Playbooks are a set of instructions that define what actions should be taken on a remote server or group of servers. They can configure, deploy, and manage systems and applications. Playbooks are written in YAML format and are very easy to read and understand.
Playbooks can be used to perform various tasks, such as installing software, configuring services, or even rolling out entire application stacks. Playbooks are typically run from the command line using the ansible-playbook command.
Ansible playbooks are very flexible and can be used to automate many different types of tasks. Here are five main use cases for Ansible playbooks:
- Configuration Management
- Software Deployment
- Continuous Integration and Delivery
- Application Orchestration
- Security and Compliance
Ansible machines are essentially software-defined machines that can be used to manage and automate tasks across your infrastructure. Ansible machines are built on top of existing physical or virtual machines, providing a consistent and repeatable way to manage your infrastructure.
Ansible machines are typically used to manage server deployments, provisioning, and configurations. They can also be used to automate application deployment and orchestration. Ansible machines are often used with other DevOps tools, such as Puppet, Chef, and SaltStack.
How Do You Set Up an Ansible Machine?
If you want to set up an Ansible machine, there are a few things you need to do.
- First, you need to install the Ansible software on your machine. This can be done using a package manager like apt or yum.
- Once Ansible is installed, you need to create an inventory file. This file will list all of the machines that Ansible should manage.
- Next, you need to create a playbook. This is a YAML file that contains a list of tasks that Ansible should run.
- Finally, you need to run the ansible-playbook command to execute the playbook.
Types of Ansible Machines
Ansible machines are classified into several types depending on their functionality. The most common types are Control, Remote, and Target machines.
- Control machine: A control machine is the central node in an Ansible infrastructure. It is used to manage all the other machines in the network. The control machine must have a copy of the Ansible project code and playbooks.
- Remote machine: A remote machine is any machine that is not the control machine. Remote machines are managed by the control machine using SSH.
- Target machine: A target machine is a remote machine being provisioned or configured by Ansible. Target machines can be of any type, including physical servers, virtual machines, containers, etc.
Ansible tasks are small pieces of code that can be used to automate workflows and processes. There are three types of tasks: simple, complex, and conditional.
- A simple task is a single line of code that performs a specific action.
- A complex task is a multi-line task that can perform multiple actions.
- A conditional task is a task that only runs if certain conditions are met.
A handler is an Ansible keyword that triggers a particular action on a remote server. Handlers are usually associated with notify directives, which tell Ansible to run a handler when a task changes state.
For example, if you have a task that restarts a service, you may want to use a handler to restart the service only if the task has changed state. This way, you can avoid unnecessary restarts and keep your remote servers running smoothly.
To create a handler, you need to use the Ansible handler module. This module allows you to specify the name of the handler, the action to be taken, and the remote server on which the handler should run.
Ansible commands are the basic building blocks for automating infrastructure management with Ansible. By running simple Ansible commands or playbooks (YAML files that define groups of hosts and tasks to be run), entire server deployments can be set up or torn down in moments.
How you could use Ansible commands for some common tasks.
Task 1: Start and Stop a Service
If you need to start or stop a service on a remote server, you can use the following command:
$ ansible -m service -a “name= state=”
For example, if you need to start the Apache service on a remote server, you would use the following command:
$ ansible server1 -m service -a “name=httpd state=started”
Task 2: Install a Package
If you need to install a package on a remote server, you can use the following command:
$ ansible -m yum -a “name= state=present”
For example, if you need to install the Apache HTTP Server on a remote server, you would use the following command:
$ ansible server1 -m yum -a “name=httpd state=present”
Ansible commands are very powerful and can help you automate many tasks. Below we will discuss the most commonly used Ansible commands.
- ansible-playbook: This is the most important Ansible command used to run playbooks. Playbooks are a set of instructions or tasks that need to be performed on a remote host or a group of hosts.
- ansible-doc: This command is used to view documentation for Ansible modules.
- ansible-galaxy: This command is used to install roles from Galaxy, a repository of community-contributed roles.
- ansible-vault: This command is used to encrypt and decrypt sensitive data.
- ansible-console: This command is used to launch an interactive Ansible session.
- ansible-pull: This command is used to pull playbooks from a remote Git repository.
- ansible-inventory: This command is used to generate an inventory file.
Ansible variables help you define values that you can reference in your playbooks. Variables can be used to store values that you want to reuse throughout your playbooks, and they can be used in conditionals and loops to dynamically change the behavior of your playbooks.
In Ansible, there are two types of variables: facts and vars. Facts are variables automatically populated by Ansible from the information it gathers about the managed system. Vars are user-defined variables that can be used to store any value, including strings, numbers, lists, and dictionaries.
YAML is a human-readable data serialization format often used for configuration files. It is easy to learn and understand and can be used in conjunction with other languages, such as JSON or XML. Ansible uses YAML because it is easy to read and write, and computers can easily parse it.
YAML tags are a powerful tool for Ansible that allows you to specify the type of data stored in a variable. This is especially useful when working with complex data structures like lists or dictionaries. By tagging the data, you can ensure that Ansible knows how to interpret it properly.
If you want to learn more about Ansible playbooks, tasks, handlers, or variables, check the official documentation. And if you have any questions or run into any problems while trying to set up your own Ansible machine, don’t hesitate to reach out for help.