Getting Started

Now that you have read the installation guide and installed Ansible on a control node, you are ready to learn how Ansible works. A basic Ansible command or playbook:

  • selects machines to execute against from inventory

  • connects to those machines (or network devices, or other managed nodes), usually over SSH

  • copies one or more modules to the remote machines and starts execution there

Ansible can do much more, but you should understand the most common use case before exploring all the powerful configuration, deployment, and orchestration features of Ansible. This page illustrates the basic process with a simple inventory and an ad hoc command. Once you understand how Ansible works, you can read more details about ad hoc commands, organize your infrastructure with inventory, and harness the full power of Ansible with playbooks.

Selecting machines from inventory

Ansible reads information about which machines you want to manage from your inventory. Although you can pass an IP address to an ad hoc command, you need inventory to take advantage of the full flexibility and repeatability of Ansible.

Action: create a basic inventory

For this basic inventory, edit (or create) /etc/ansible/hosts and add a few remote systems to it. For this example, use either IP addresses or FQDNs:

192.0.2.50
aserver.example.org
bserver.example.org

Beyond the basics

Your inventory can store much more than IPs and FQDNs. You can create aliases, set variable values for a single host with host vars, or set variable values for multiple hosts with group vars.

Connecting to remote nodes

Ansible communicates with remote machines over the SSH protocol. By default, Ansible uses native OpenSSH and connects to remote machines using your current user name, just as SSH does.

Action: check your SSH connections

Confirm that you can connect using SSH to all the nodes in your inventory using the same username. If necessary, add your public SSH key to the authorized_keys file on those systems.

Beyond the basics

You can override the default remote user name in several ways, including:

  • passing the -u parameter at the command line

  • setting user information in your inventory file

  • setting user information in your configuration file

  • setting environment variables

See Controlling how Ansible behaves: precedence rules for details on the (sometimes unintuitive) precedence of each method of passing user information. You can read more about connections in Connection methods and details.

Copying and executing modules

Once it has connected, Ansible transfers the modules required by your command or playbook to the remote machine(s) for execution.

Action: run your first Ansible commands

Use the ping module to ping all the nodes in your inventory:

$ ansible all -m ping

You should see output for each host in your inventory, similar to this:

aserver.example.org | SUCCESS => {
    "ansible_facts": {
        "discovered_interpreter_python": "/usr/bin/python"
    },
    "changed": false,
    "ping": "pong"
}

You can use -u as one way to specify the user to connect as, by default Ansible uses SSH, which defaults to the ‘current user’.

Now run a live command on all of your nodes:

$ ansible all -a "/bin/echo hello"

You should see output for each host in your inventory, similar to this:

aserver.example.org | CHANGED | rc=0 >>
hello

Action: Run your first playbook

Playbooks are used to pull together tasks into reusable units.

Ansible does not store playbooks for you; they are simply YAML documents that you store and manage, passing them to Ansible to run as needed.

In a directory of your choice you can create your first playbook in a file called mytask.yml:

---
- name: My playbook
  hosts: all
  tasks:
     - name: Leaving a mark
       command: "touch /tmp/ansible_was_here"

You can run this command as follows:

$ ansible-playbook mytask.yaml

and may see output like this:

PLAY [My playbook] **********************************************************************************************************************

TASK [Gathering Facts] ******************************************************************************************************************
ok: [aserver.example.org]
ok: [aserver.example.org]
ok: [192.0.2.50]
fatal: [192.0.2.50]: UNREACHABLE! => {"changed": false, "msg": "Failed to connect to the host via ssh: ssh: connect to host 192.0.2.50 port 22: No route to host", "unreachable": true}

TASK [Leaving a mark] *******************************************************************************************************************
[WARNING]: Consider using the file module with state=touch rather than running 'touch'.  If you need to use command because file is
insufficient you can add 'warn: false' to this command task or set 'command_warnings=False' in ansible.cfg to get rid of this message.
changed: [aserver.example.org]
changed: [bserver.example.org]

PLAY RECAP ******************************************************************************************************************************
aserver.example.org        : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
bserver.example.org        : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
192.0.2.50                 : ok=0    changed=0    unreachable=1    failed=0    skipped=0    rescued=0    ignored=0

Read on to learn more about controlling which nodes your playbooks execute on, more sophisticated tasks, and the meaning of the output.

Beyond the basics

By default Ansible uses SFTP to transfer files. If the machine or device you want to manage does not support SFTP, you can switch to SCP mode in Configuring Ansible. The files are placed in a temporary directory and executed from there.

If you need privilege escalation (sudo and similar) to run a command, pass the become flags:

# as bruce
$ ansible all -m ping -u bruce
# as bruce, sudoing to root (sudo is default method)
$ ansible all -m ping -u bruce --become
# as bruce, sudoing to batman
$ ansible all -m ping -u bruce --become --become-user batman

You can read more about privilege escalation in Understanding privilege escalation: become.

Congratulations! You have contacted your nodes using Ansible. You used a basic inventory file and an ad hoc command to direct Ansible to connect to specific remote nodes, copy a module file there and execute it, and return output. You have a fully working infrastructure.

Next steps

Next you can read about more real-world cases in Introduction to ad hoc commands, explore what you can do with different modules, or read about the Ansible Working with playbooks language. Ansible is not just about running commands, it also has powerful configuration management and deployment features.

See also

How to build your inventory

More information about inventory

Introduction to ad hoc commands

Examples of basic commands

Working with playbooks

Learning Ansible’s configuration management language

Ansible Demos

Demonstrations of different Ansible usecases

RHEL Labs

Labs to provide further knowledge on different topics

Mailing List

Questions? Help? Ideas? Stop by the list on Google Groups

Real-time chat

How to join Ansible chat channels