Ansible playbooks automate complex IT tasks, but even simple automation can encounter unexpected issues. Handling errors and debugging effectively is essential to ensure that your automation runs reliably and produces predictable results. Without proper error management, a small misconfiguration or typo can cause tasks to fail silently or produce confusing results, making troubleshooting difficult—especially if you are new to Ansible.

Common Errors in Ansible

When starting with Ansible, you may encounter several frequent issues. Understanding these common errors helps you troubleshoot efficiently and avoid unnecessary frustration.

Syntax Errors

• Occur if your YAML files contain incorrect indentation or invalid characters;
• Result in Ansible failing to parse your playbooks, often producing messages like mapping values are not allowed here;
• Can be minimized by using a text editor with YAML support.

Connection Issues

• Happen when Ansible cannot reach the target hosts due to network problems or incorrect SSH credentials;
• Typically produce errors such as UNREACHABLE! or Permission denied (publickey);
• Are often resolved by verifying your host inventory, network connectivity, and SSH keys.

Missing Packages

• Arise when a playbook tries to use a module or software that is not installed on the managed node;
• May cause module failures or tasks to report FAILED! => {"msg": "...not found"};
• Can be prevented by ensuring all required packages are installed before running your playbooks.

Recognizing these errors and their causes prepares you to resolve issues quickly and continue automating with confidence.

Error Handling Techniques in Ansible

Ansible provides several methods to control and manage errors during playbook execution. Applying these techniques helps you build robust automation that can handle unexpected issues gracefully.

Using ignore_errors

The ignore_errors directive allows a task to continue playbook execution even if it fails. This is useful when a failure is non-critical.

- name: Try to restart a service
  ansible.builtin.service:
    name: nginx
    state: restarted
  ignore_errors: yes

• The playbook will not stop if the nginx service fails to restart;
• Subsequent tasks will continue to run.

Using failed_when

The failed_when directive lets you define custom failure conditions for a task. This is helpful when the default failure detection does not fit your requirements.

- name: Check disk space
  ansible.builtin.shell: df -h /
  register: disk_output
  failed_when: "'100%' in disk_output.stdout"

• The task only fails if the output contains '100%', indicating the disk is full;
• You can tailor failure logic to your specific needs.

Using block and rescue

The block and rescue keywords enable you to group tasks and specify actions to take if any task in the block fails.

- block:
    - name: Install package
      ansible.builtin.yum:
        name: mypackage
        state: present
    - name: Start service
      ansible.builtin.service:
        name: myservice
        state: started
  rescue:
    - name: Send failure notification
      ansible.builtin.debug:
        msg: 'Installation or service start failed.'

• All tasks inside the block are attempted;
• If any task fails, tasks in the rescue section are executed;
• This approach allows you to handle errors and implement fallback logic.

Applying these error handling techniques ensures your Ansible playbooks are resilient and easier to debug during automation workflows.

Debugging with ansible.builtin.debug

The ansible.builtin.debug module helps you display custom messages, variable values, and task outputs during playbook execution. Use this module to gain insight into what your playbook is doing at each step.

Example: Printing a variable value

tasks:
  - name: Show the value of the variable
    ansible.builtin.debug:
      msg: "The server name is {{ inventory_hostname }}"

Example: Displaying structured data

tasks:
  - name: Show all facts collected
    ansible.builtin.debug:
      var: ansible_facts

Using Verbose Output with -vvv

The -vvv command line option increases the verbosity of Ansible's output, showing more detailed information about task execution, variable resolution, and errors. This helps you trace problems and understand playbook behavior.

Example: Running a playbook with high verbosity

ansible-playbook site.yml -vvv

Key points when using -vvv:

• Reveals detailed task execution steps;
• Shows variable values and resolved templates;
• Displays module arguments and responses;
• Helps pinpoint the source of errors.

Use both the ansible.builtin.debug module and the -vvv option together for effective troubleshooting and to accelerate playbook development.