How to run an Ansible playbook locally

ansible_local_playbooks.md

• using Ansible command line:

ansible-playbook --connection=local 127.0.0.1 playbook.yml

• using inventory:

127.0.0.1 ansible_connection=local

• using Ansible configuration file:

[defaults]
transport = local

• using playbook header:

- hosts: 127.0.0.1
  connection: local

which is recommended or best practice?

I don't know anything about official best practices, but by myself most often use the last variant (i.e., playbook header).

But if I have'nt understood this badly (https://docs.ansible.com/ansible/latest/inventory/implicit_localhost.html), it isn't necessary to indicate explicitely the connection type: just writing "localhost" as target will make Ansible to infer it has to make a "local" connection, isn't?

I'm not sure it worked this way in all versions of Ansible I'd previously coded for, so I used to always add connection: local just to make sure that the connection will not go through SSL.

ansible-playbook -c local -i localhost, ini.yaml

ubuntu@ip-172-31-28-5:$ ansible-playbook -c local -i localhost, sample-play.yaml
ERROR! the playbook: sample-play.yaml could not be found
ubuntu@ip-172-31-28-5:$ ansible-playbook -c local -i localhost, sample-play.yml
ERROR! the playbook: sample-play.yml could not be found
ubuntu@ip-172-31-28-5:$ vi sample-play.yml
ubuntu@ip-172-31-28-5:$ ansible-playbook -c local -i localhost, sample-play.yml
[WARNING]: Could not match supplied host pattern, ignoring: host1

PLAY [Installing apache2 on host1] *********************************************************************************************************************************************
skipping: no hosts matched
[WARNING]: Could not match supplied host pattern, ignoring: host2

PLAY [Installing nginx on host2] ***********************************************************************************************************************************************
skipping: no hosts matched

PLAY RECAP *********************************************************************************************************************************************************************

Thanks a lot, this is so annoying to figure out!