Ansible Local Action Module

Introduction

Welcome to the Ansible Local Action Module Lab! In this lab, you will dive into the usage of the Ansible Local Action module. The Local Action module allows you to run tasks on the control machine where Ansible is being executed. This is useful when you need to perform operations locally, such as executing shell commands or running scripts.

Let's get started!

Skills Graph

Executing a Simple Command Locally

In this step, you will learn how to use the Ansible Local Action module to execute a simple command on the control machine. This will help you understand the basic usage and syntax of the module.

First, complete /home/labex/project/execute_local_command.yml file.
Add the following content to the playbook file:

- name: Executing a Simple Command Locally
  gather_facts: false
  hosts: localhost

  tasks:
    - name: Print a message locally
      local_action:
        module: command
        cmd: echo "Hello, World!"
      register: result

    - name: Debug the output
      debug:
        var: result.stdout

• gather_facts: This specifies whether Ansible should gather facts about the target hosts. In this case, it's set to false, meaning facts won't be gathered.
• hosts: This specifies the target host on which to run the playbook. In this case, the playbook will run on the local host because the target host is localhost.
• tasks: This is a list of tasks to be executed.
• local_action: This indicates that the action should be performed locally on the control machine where Ansible is being run.
• module: This specifies the Ansible module to use for the action. In this case, it's the command module.
• cmd: This is the actual command to be executed. In this case, it's the shell command echo "Hello, World!", which will print the message "Hello, World!" to the console.
• register: This registers the output of the command in the result variable for later use in the playbook.
• debug: This is the Ansible module used to print debugging information.
• var: This is a parameter for the debug module that specifies the variable to be debugged. In this case, it's result.stdout, which contains the standard output of the command executed in the previous task.

In summary, this playbook executes a simple command echo "Hello, World!" locally on the control machine, registers the output, and then prints the output using the debug module.

Then, display the output of the command in the Ansible playbook.

ansible-playbook /home/labex/project/execute_local_command.yml

Example output:

[WARNING]: No inventory was parsed, only implicit localhost is available
[WARNING]: provided hosts list is empty, only localhost is available. Note that
the implicit localhost does not match 'all'

PLAY [Local Action Module Challenge] *******************************************

TASK [Print a message locally] *************************************************
changed: [localhost]

TASK [Debug the output] ********************************************************
ok: [localhost] => {
    "result.stdout": "Hello, World!"
}

PLAY RECAP *********************************************************************
localhost                  : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Here "result.stdout": "Hello, World!" is the output of echo "Hello, World!" command.

Executing a Command with Variable Substitution

In this step, you will enhance your understanding of the Local Action module by incorporating variable substitution. This will allow you to dynamically change the command being executed based on variables defined in your playbook.

First, complete /home/labex/project/execute_command_with_variable_substitution.yml file.
Add the following content to the playbook file:

- name: Executing a Command with Variable Substitution
  gather_facts: false
  hosts: localhost
  vars:
    message: "Hello, Ansible!"

  tasks:
    - name: Print a message with variable substitution
      local_action:
        module: command
        cmd: echo "{{ message }}"
      register: result

    - name: Debug the output
      debug:
        var: result.stdout

• vars: This section is used to define variables. In this playbook, it defines a variable named message with the value "Hello, Ansible!".
• local_action: This indicates that the action should be performed locally on the control machine where Ansible is being run.
• module: This specifies the Ansible module to use for the action. In this case, it's the command module.
• cmd: This is the actual command to be executed. In this case, it's the shell command echo "{{ message }}", where {{ message }} is replaced with the value of the message variable defined earlier.
• register: This registers the output of the command in the result variable for later use in the playbook.
• debug: This is the Ansible module used to print debugging information.
• var: This is a parameter for the debug module that specifies the variable to be debugged. In this case, it's result.stdout, which contains the standard output of the command executed in the previous task.

In summary, this playbook executes the command echo "{{ message }}" locally on the control machine, where {{ message }} is replaced with the value of the message variable defined in the vars section. It registers the output of the command and then prints the output using the debug module.

Then, display the output of the command in the Ansible playbook.

ansible-playbook /home/labex/project/execute_command_with_variable_substitution.yml

Example output:

[WARNING]: No inventory was parsed, only implicit localhost is available
[WARNING]: provided hosts list is empty, only localhost is available. Note that
the implicit localhost does not match 'all'

PLAY [Local Action Module Challenge] *******************************************

TASK [Print a message with variable substitution] ******************************
changed: [localhost]

TASK [Debug the output] ********************************************************
ok: [localhost] => {
    "result.stdout": "Hello, Ansible!"
}

PLAY RECAP *********************************************************************
localhost                  : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Here "result.stdout": "Hello, Ansible!" is the output of echo "{{ message }}" command.

Executing a Complex Local Action

In this step, you will explore a more complex usage of the Ansible Local Action module. You will execute a shell script locally and pass arguments to the script.

First, complete /home/labex/project/execute_complex_local_action.yml file.
Add the following content to the playbook file:

- name: Executing a Complex Local Action
  gather_facts: false
  hosts: localhost

  tasks:
    - name: Execute a shell script with arguments
      local_action:
        module: shell
        cmd: ./script.sh 5 7
      register: result

    - name: Debug the output
      debug:
        var: result.stdout

• local_action: This indicates that the action should be performed locally on the control machine where Ansible is being run.
• module: This specifies the Ansible module to use for the action. In this case, it's the shell module.
• cmd: This is the actual shell command to be executed. In this case, it's ./script.sh 5 7, which executes a shell script named script.sh with arguments 5 and 7.
• register: This registers the output of the command in the result variable for later use in the playbook.
• debug: This is the Ansible module used to print debugging information.
• var: This is a parameter for the debug module that specifies the variable to be debugged. In this case, it's result.stdout, which contains the standard output of the command executed in the previous task.

In summary, this playbook executes a shell script script.sh with arguments 5 and 7 locally on the control machine. It registers the output of the script and then prints the output using the debug module.

Tips: We have prepared this shell script for you, it is in the /home/labex/project/ directory and is called script.sh. The function of this script is to calculate the sum of two parameters.

Then, display the output of the command in the Ansible playbook.

ansible-playbook /home/labex/project/execute_complex_local_action.yml

Example output:

[WARNING]: No inventory was parsed, only implicit localhost is available
[WARNING]: provided hosts list is empty, only localhost is available. Note that
the implicit localhost does not match 'all'

PLAY [Local Action Module Challenge] *******************************************

TASK [Execute a shell script with arguments] ***********************************
changed: [localhost]

TASK [Debug the output] ********************************************************
ok: [localhost] => {
    "result.stdout": "The sum of 5 and 7 is 12."
}

PLAY RECAP *********************************************************************
localhost                  : ok=2    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Here "result.stdout": "The sum of 5 and 7 is 12." is the output of ./script.sh 5 7 script.

Summary

Congratulations on completing the Ansible Local Action Module Lab! In this lab, you learned how to use the Ansible Local Action module to execute commands and scripts locally. Starting with simple command execution, you progressed to incorporating variable substitution and executing complex shell scripts with arguments.

By completing this lab, you have gained valuable experience in leveraging the Local Action module for tasks that need to be performed on the control machine. Keep exploring Ansible and its modules to further enhance your automation capabilities.

Happy automating!