Ansible use ssh to setup softwares to remote hosts.
If there are some fresh machines just been installed, run Ansible playbook from one host will not connect them because of no authorized_keys on remote hosts.
If copy the Ansible host's pub key to those target hosts like:
$ ssh user@server "echo \"`cat .ssh/id_rsa.pub`\" >> .ssh/authorized_keys"
First should ssh login and make file on every remote host:
$ mkdir .ssh
$ touch .ssh/authorized_keys
Is this the common way to run Ansible playbook to remote servers? Is there a better way exist?