# Ansible Configuration Guide

Ansible is a powerful automation tool used to manage and configure servers. This guide provides examples of how to structure your inventory files, which are essential for defining the servers and groups that Ansible will manage. Additionally, it covers common Ansible commands for interacting with your servers.

## Inventory File Examples

### INI Format

The INI format is one of the simplest ways to define your inventory. Below are two examples showcasing different use cases.

#### Example 1: Single Group Inventory

In this example, all servers are grouped under a single `[all]` group. Each server is defined with specific connection details:

```ini
[all]
<server-name> ansible_host=<server-ip> ansible_ssh_pass=<password> ansible_port=<ssh-port> ansible_connection=<connection-type>
```

- **`<server-name>`**: A label or hostname for your server.
- **`<server-ip>`**: The IP address of the server.
- **`ansible_ssh_pass`**: The SSH password for connecting to the server.
- **`ansible_port`**: The port used for SSH connections.
- **`ansible_connection`**: The connection type (e.g., ssh, winrm).

#### Example 2: Grouped Inventory with Variables

This example demonstrates grouping servers by roles (e.g., `web`, `db`, `bk`). Group-specific variables are defined under `[all:vars]`:

```ini
[all]
<server1-name> ansible_host=<server1-ip>
<server2-name> ansible_host=<server2-ip>
<server3-name> ansible_host=<server3-ip>

[web]
<server1-name>

[db]
<server2-name>

[bk]
<server3-name>

[all:vars]
ansible_user=<username>
ansible_port=<ssh-port>
```

- **Groups**: Servers are organized into different groups (`web`, `db`, `bk`).
- **`[all:vars]`**: Common variables for all groups.

### YAML Format

The YAML format provides a more structured and readable way to define your inventory, especially useful for larger or more complex environments.

#### Example: Grouped Inventory with Host-Specific Variables

This example illustrates how to define an inventory with nested groups and host-specific variables:

```yaml
all:
  children:
    webservers:
      hosts:
        192.168.1.100:
          ansible_port: 22
        192.168.1.110:
          ansible_port: 1357
      vars:
        http_port: 8080
    dbserver:
      hosts:
        db.main.local:
          db_user: admin
          db_pass: secret
```

- **`children`**: Groups within the `all` group, such as `webservers` and `dbserver`.
- **`hosts`**: List of servers under each group, with their specific variables.
- **`vars`**: Group-specific variables, such as `http_port` for `webservers`.

## Common Ansible Commands

Here are some frequently used Ansible commands for managing your servers:

### Listing Hosts

List all hosts defined in the inventory file:

```bash
ansible --list-hosts all -i servers.ini
# or for YAML format
ansible --list-hosts all -i servers.yaml
```

### Ping All Servers

Check the connectivity of all servers:

```bash
ansible -m ping all -i server.ini
```

### Execute Commands

Run a command (e.g., `uptime`) on all servers:

```bash
ansible -m command -a "uptime" all -i server.ini
```

### Copy Files to Servers

Copy a file from the Ansible server to all target servers:

```bash
ansible -m copy -a "src=<file-location-on-ansiblesv> dest=<destination-location-on-server>" all -i server.ini
```

### Run Commands with Sudo

Execute a command with elevated privileges (sudo) as the root user:

```bash
ansible -m command -a "uptime" all -i server.ini --become --become-user root --become-method sudo 
```

### Install a Package

Install the `nginx` package on all servers:

```bash
ansible -m apt -a "name=nginx state=present" --become --become-user root --become-method sudo
```

### Uninstall a Package

Remove the `nginx` package from all servers:

```bash
ansible -m apt -a "name=nginx state=absent" --become --become-user root --become-method sudo
```

### Update and Upgrade Packages

Update the package list and upgrade all packages:

```bash
ansible -m apt -a "upgrade=yes update_cache=yes" --become --become-user root --become-method sudo
```

## Notes

- **Module Limitations**: The `command` module does not support special characters or shell features. For commands that require shell features (like pipes or redirection), use the `shell` module.
- **Raw Module**: Use the `raw` module for devices that do not have Python installed. It allows you to execute raw SSH commands directly.