<a id="ansible-prepare"></a>

# Prepare Ansible Inventory File to Install Confluent Platform

Before running the Ansible playbooks, you need to generate an inventory file.
The inventory file specifies the hosts in which to provision Confluent Platform
components. For more information about the Ansible inventory file, see
[Ansible Inventory Basics](https://docs.ansible.com/ansible/latest/user_guide/intro_inventory.html#inventory-basics-hosts-and-groups).

## Generate an inventory file

To generate an inventory file, gather all of the Fully Qualified Domain Names
(FQDNs) of your hosts and create a file called `hosts.yml` on your Ansible
control node, setting each hostname under the desired groups as shown below.

The built-in `inventory_hostname` variable of each host is set to the hostname
of the host. The hostname can be internal or external addresses that can be
reachable from the control node.

#### NOTE
You cannot co-locate Control Center on the same host as KRaft because of the port
collision on `9093`.

An example inventory file snippet, when using KRaft on IPv4 network:

```yaml
kafka_controller:
  hosts:
    ip-172-31-34-246.us-east-2.compute.internal:
    ip-172-31-37-15.us-east-2.compute.internal:
    ip-172-31-34-231.us-east-2.compute.internal:

kafka_broker:
  hosts:
    ip-172-31-34-246.us-east-2.compute.internal:
    ip-172-31-34-247.us-east-2.compute.internal:
    ip-172-31-34-248.us-east-2.compute.internal:

schema_registry:
  hosts:
    ip-172-31-34-246.us-east-2.compute.internal:

kafka_rest:
  hosts:
    ip-172-31-34-246.us-east-2.compute.internal:

ksql:
  hosts:
    ip-172-31-37-15.us-east-2.compute.internal:
    ip-172-31-37-16.us-east-2.compute.internal:

kafka_connect:
  hosts:
    ip-172-31-34-246.us-east-2.compute.internal:

control_center_next_gen:
  hosts:
    ip-172-31-34-247.us-east-2.compute.internal:
```

An example inventory file snippet, when deploying Confluent Platform with KRaft on IPv6
network:

```yaml
kafka_controller:
  hosts:
    2600:1f14:1a1d:6904:5b64:5d77:4417:370b:

kafka_broker:
  hosts:
    2600:1f14:1a1d:6904:5b64:5d77:4417:370b:
```

### Use `ansible_host` for SSH connections

When your `inventory_hostname` does not work with SSH, you can specify one
additional hostname for SSH connection using the `ansible_host` variable.

In the following example, `ip-172-31-40-189.us-west-2.compute.internal` is the
`inventory_hostname`, and `ec2-34-217-174-252.us-west-2.compute.amazonaws.com` is used for SSH.

```yaml
kafka_broker:
  hosts:
    ip-172-31-40-189.us-west-2.compute.internal:
      ansible_host: ec2-34-217-174-252.us-west-2.compute.amazonaws.com
```

## Verify connection to Confluent Platform hosts

After generating an inventory file, set connection variables so that the Ansible
control node can connect to each Confluent Platform host.

Most commonly, Ansible uses SSH for its connections. For more information about
setting up connection variables, see [Connecting to hosts: behavioral inventory
parameters](https://docs.ansible.com/ansible/latest/user_guide/intro_inventory.html#connecting-to-hosts-behavioral-inventory-parameters).

Add the following section to `hosts.yml`:

```none
all:
  vars:
    ansible_connection: ssh
    ansible_user: ec2-user
    ansible_become: true
    ansible_ssh_private_key_file: /tmp/certs/ssh_priv.pem
```

Use the following command to verify that Ansible can connect over SSH:

```none
ansible -i /path/to/hosts.yml all -m ping
```

The above command validates that a Python Interpreter is available for use on
all the hosts, and it returns `pong` on success.

If you cannot reach the host even after providing the SSH private key path in
the `hosts.yml` file for Ansible, the SSH private key file might have
incorrect permissions.

Use the `chmod` command to update the permissions of the SSH private key file
to read-only for the owner.

```bash
chmod 400 <ansible_ssh_private_key_file>
```

It is recommended that you store your inventory file in its own Git repository.
You may have a Git repo with an inventory file for each of your deployments.

## Next steps

[Configure Ansible Playbooks for Confluent Platform](ansible-configure.md#ansible-configure).