The inventory file

We do not need Ansible if we have no remote target to manage, correct? Everything starts from the fact that we need to manage some task on a remote host. The way we specify the potential remote target is with a host file. We can either have this file specifying the remote host either in /etc/ansible/hosts or use the -i option to specify the location of the file. Personally, I prefer to have this file in the same directory where my playbook is.

Technically, this file can be named anything as long as it is in a valid format. However, you can potentially save yourself and your colleagues some headaches in the future by following this convention.

The inventory file is a simple, plain text INI-style file that states your target. By default, this can either be a DNS FQDN or an IP address:

$ cat hosts
192.168.199.170

We can now use the command-line option to test Ansible and the host file:

$ ansible -i hosts 192.168.199.170 -m ping
192.168.199.170 | SUCCESS => {
 "changed": false,
 "ping": "pong"
}

By default, Ansible assumes that the same user executing the playbook exists on the remote host. For example, I am executing the playbook as echou locally; the same user also exist on my remote host. If you want to execute as a different user, you can use the -u option when executing, that is -u REMOTE_USER.

The previous line reads that we will use the host file as the inventory file, and execute the ping module on the host called 192.168.199.170. Ping (http://docs.ansible.com/ansible/ping_module.html) is a trivial test module that connects to the remote host, verifies a usable Python installation, and return the output pong upon success.

You may take a look at all the ever expanding module list (http://docs.ansible.com/ansible/list_of_all_modules.html) if you have any questions about the usage of existing modules that were shipped with Ansible.

If you get a host key error, it is typically because the host key is not in the known_hosts file, and is typically under ~/.ssh/known_hosts. You can either ssh to the host and answer yes at adding the host, or you can disable this checking on /etc/ansible/ansible.cfg or ~/.ansible.cfg with the following code:

[defaults]
host_key_checking = False

Now that we have a valid inventory file, we can make our first playbook.

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Table of Contents for
The inventory file