Ansible Playbookでlocalhostに接続できない問題を解決する

Ansible Playbookをlocalhostを対象に実行しようとすると、以下のエラーが発生しplaybookが実行できなかった。

$ ansible-playbook -i inventory playbook.yml

PLAY [all] ***********************************************************************************************************

TASK [Gathering Facts] ***********************************************************************************************
The authenticity of host 'localhost (127.0.0.1)' can't be established.
ECDSA key fingerprint is SHA256:(****).
Are you sure you want to continue connecting (yes/no)? yes
fatal: [localhost]: UNREACHABLE! => {"changed": false, "msg": "Failed to connect to the host via ssh: Warning: Permanently added 'localhost' (ECDSA) to the list of known hosts.\r\nroot@localhost: Permission denied (publickey,password,keyboard-interactive).", "unreachable": true}

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

調査したところlocalhostで実行するときには--connection localオプションを実行時につけると良いらしい。

$ ansible-playbook -i inventory playbook.yml --connection=local

PLAY [all] ***********************************************************************************************************

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

TASK [helloworld : Hello World!] *************************************************************************************
ok: [localhost] => {
    "msg": "Hello World!"
}

PLAY RECAP ***********************************************************************************************************
localhost                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0