How to run a basic Ansible playbook locally

 

Here is an example of the simplest Ansible playbook:

hello_world.yaml:

---
- name: Run Ansible playbook locally
  hosts: localhost
  gather_facts: no

  tasks:
    - ansible.builtin.debug:
        msg: Hello, world!

 

ansible-playbook

 

We can run it with ansible-playbook which executes tasks from playbook on a defined hosts. This tool is installed within Ansible (core) installation:

 

$ which ansible-playbook
/usr/bin/ansible-playbook

 

To run the playbook:

$ ansible-playbook hello_world.yaml
[WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'

PLAY [Run Ansible playbook locally] *********************************************************************************************************************************

TASK [ansible.builtin.debug] ****************************************************************************************************************************************
ok: [localhost] => {
    "changed": false,
    "msg": "Hello, world!"
}

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

To see the changes made during execution of the playbook we can use --diff option:

$ ansible-playbook hello_world.yaml --diff

From $ ansible-playbook --help:

-D, --diff: when changing (small) files and templates, show the differences in those files; works great with --check

To dry run the playbook we need to use check mode (--check or -C):

$ ansible-playbook hello_world.yaml --check

From $ ansible-playbook --help:

-C, --check: don't make any changes; instead, try to predict some of the changes that may occur

Playbook is run in read-only mode, Ansible still connects to the hosts and checks their state.

If someone manually made changes on the host, Ansible detects that but with --check option it will not revert that state to the one defined in playbook. But we'll be able to see what has been changed:

TASK [task_name]

changed: [node1]

To see changes that would be made should the playbook be executed we can combine --diff and --check options:

$ ansible-playbook hello_world.yaml --diff --check

Example:

- name: Create directory and a file in it
  hosts: localhost
  tasks:
    - name: Create directory
      ansible.builtin.file:
          path: ./temp
          state: directory
          mode: '0755'

    - name: Create a file, using symbolic modes to set the permissions (equivalent to 0644)
      ansible.builtin.file:
        path: ./temp/foo.txt
        state: touch
        mode: u=rw,g=r,o=r

Dry run and diff output:

$ ansible-playbook multiple_plays.yaml --check --diff
[WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'

PLAY [Create directory and a file in it] ****************************************************************************************************************************

TASK [Gathering Facts] **********************************************************************************************************************************************
ok: [localhost]

TASK [Create directory] *********************************************************************************************************************************************
--- before
+++ after
@@ -1,4 +1,4 @@
 {
     "path": "./temp",
-    "state": "absent"
+    "state": "directory"
 }

changed: [localhost]

TASK [Create a file, using symbolic modes to set the permissions (equivalent to 0644)] ******************************************************************************
ok: [localhost]

PLAY RECAP **********************************************************************************************************************************************************
localhost                  : ok=3    changed=1    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0 

 

Validating tasks: check mode and diff mode — Ansible Documentation

 

ansible-navigator 

 

Ansible playbooks can also be run by ansible-navigator:

$ ansible-navigator run hello_world.yaml 

This will not print the output in terminal but we can find it in stdout value in JSON file (that gets created next to the YAML source file):

hello_world-artifact-2022-07-07T10:06:23.959652+00:00.json

To get the output in stdout, we can use --mode:

$ ansible-navigator run ./run_locally/hello_world.yaml --mode stdout
[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 [Run Ansible playbook locally] ********************************************

TASK [Print debug message] *****************************************************
ok: [localhost] => {
    "msg": "Hello, world!"
}

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

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