Running playbooks locally

It is important to note that when we talk about running a playbook locally with Ansible, it is not the same as talking about running it on localhost. If we run a playbook on localhost, Ansible actually sets up an SSH connection to localhost (it doesn't differentiate its behavior or attempt to detect whether a host in the inventory is local or remote—it simply tries faithfully to connect).

Indeed, we can try creating a local inventory file with the following contents:

[local]
localhost

Now, if we attempt to run the ping module in an ad hoc command against this inventory, we see the following:

$ ansible -i localhosts -m ping all --ask-pass
The authenticity of host 'localhost (::1)' can't be established.
ECDSA key fingerprint is SHA256:DUwVxH+45432pSr9qsN8Av4l0KJJ+r5jTo123n3XGvZs.
ECDSA key fingerprint is MD5:78:d1:dc:23:cc:28:51:42...