Why does Ansible show "ERROR! no action detected in task" error?

Reason #1

You are using an older version of Ansible which did not have the module you try to run.

How to check it?

Open the list of modules module documentation and find the documentation page for your module.
Read the header at the top of the page - it usually shows the Ansible version in which the module was introduced. For example:

New in version 2.2.
Ensure you are running the specified version of Ansible or later. Run:
```
ansible-playbook --version
```
And check the output. It should show something like:

ansible-playbook 2.4.1.0

Reason #2

You tried to write a role and put a playbook in my_role/tasks/main.yml.

The tasks/main.yml file should contain only a list of tasks. If you specified:

---
- name: Configure servers
  hosts: my_hosts
  tasks:
    - name: My first task
      my_module:
        parameter1: value1

Ansible tries to find an action module named hosts and an action module named tasks. It doesn't, so it throws an error.

Solution: specify only a list of tasks in the tasks/main.yml file:

---
- name: My first task
  my_module:
    parameter1: value1

Reason #3

The action module name is misspelled.

This is pretty obvious, but overlooked. If you use incorrect module name, for example users instead of user, Ansible will report "no action detected in task".

Ansible was designed as a highly extensible system. It does not have a limited set of modules which you can run and it cannot check "in advance" the spelling of each action module.

In fact you can write and then specify your own module named qLQn1BHxzirz and Ansible has to respect that. As it is an interpreted language, it "discovers" the error only when trying to execute the task.

Reason #4

You are trying to execute a module not distributed with Ansible.

The action module name is correct, but it is not a standard module distributed with Ansible.

If you are using a module provided by a third party - a vendor of software/hardware or another module shared publicly, you must first download the module and place it in appropriate directory.

You can place it either in modules subdirectory of the playbook or in a common path.

Ansible looks ANSIBLE_LIBRARY or the --module-path command line argument.

To check what paths are valid, run:

ansible-playbook --version

and check the value of:

configured module search path =

Ansible version 2.4 and later should provide a list of paths.

Reason #5

You really don't have any action inside the task.

The task must have some action module defined. The following example is not valid:

- name: My task
  become: true

I can't really improve upon @techraf answer https://stackoverflow.com/a/47159200/619760. I wanted to add reason #6 my special case

Reason #6

Incorrectly using roles: to import/include roles as a subtask.

This does not work, you can not include roles in this way as subtasks in a play.

---
- hosts: somehosts
  tasks:

  - name: include somerole
    roles:
      - somerole

Use include_role

According to the documentation

you can now use roles inline with any other tasks using import_role or include_role:

- hosts: webservers
  tasks:
  - debug:
      msg: "before we run our role"
  - import_role:
      name: example
  - include_role:
      name: example
  - debug:
      msg: "after we ran our role"

Put the roles at the right place inline with hosts

Include the roles at the top

---
- hosts: somehosts
  roles:
    - somerole
  tasks:   
    - name: some static task
      import_role:
        name: somerole
      hosts: some host
    - include_role:
        name: example

You need to understand the difference between import/include static/dynamic

Explanation of the error :

No tasks to execute means it can not do the action that was described in your playbook

Root cause:

the installed version of Ansible doesn't support it

How to check :

ansible --version

Solution:

upgrade Ansible to a version which supports the feature you are trying to use

How to upgrade Ansible:

https://docs.ansible.com/ansible/latest/installation_guide/intro_installation.html#selecting-an-ansible-version-to-install

Quick instruction for Ubuntu :

sudo apt update
sudo apt install software-properties-common
sudo apt-add-repository --yes --update ppa:ansible/ansible
sudo apt install ansible

P.S: followed this path and upgraded from version 2.0.2 to 2.9 After upgrade, same playbook worked like a charm

I got this error when I referenced the debug task as ansible.builtin.debug

Causes a syntax failure in CI (but worked locally):

- name: "Echo the jenkins job template"
  ansible.builtin.debug:
    var: template_xml
    verbosity: 1

Works locally and in CI:

- name: "Echo the jenkins job template"
  debug:
    var: template_xml
    verbosity: 1

I believe - but have not confirmed - that the differences in local vs CI was ansible versions.

Local : 2.10
CI : 2.7

For me the problem occurred with "systemd" module. Turned out that my ansible --version was 2.0.0.2 and module was first introduced in version 2.2. Updating my ansible to latest version fixed the problem.

playbook.yaml

- name: "Enable and start docker service and ensure it's not masked"
  systemd:
    name: docker
    state: started
    enabled: yes
    masked: no

Error

ERROR! no action detected in task
etc..   
etc..
etc..

- name: "Enable and start docker service and ensure it's not masked"
  ^ here