# Custom Alpine Image

This repository contains the necessary files to build a customizable Alpine Linux Docker image. The image can be configured at runtime by providing a `sysconfig.toml` file.

## How to build the image

To build the Docker image, run the following command from the root of this repository:

```sh
docker build -t alpine-customizable .
```

## How to configure the image

You can configure the container at runtime by mounting a `sysconfig.toml` file at `/etc/sysconfig.toml`.

```sh
docker run -it --rm -v ./sysconfig.toml:/etc/sysconfig.toml alpine-customizable
```

The `sysconfig.toml` file supports the following sections for configuration:

### `[general]`

This section is used for general system-wide settings.

-   `packages`: A list of strings specifying additional Alpine packages to install using `apk add`.

    *Example:*
    ```toml
    [general]
    packages = ["openssh-server", "curl"]
    ```

### `[users]`

This section allows you to define users that will be created on the container. Each user is defined in a sub-section using the format `[users.username]`.

The following keys are supported for each user:

-   `password` (optional): A string to set the user's password.
-   `pubkeys` (optional): A list of public SSH keys (strings) to add to the user's `~/.ssh/authorized_keys` file, enabling key-based authentication.

    *Example:*
    ```toml
    [users.dmitry]
    password = "a-secure-password"
    pubkeys = [
        "ssh-rsa AAAA...",
        "ssh-ed25519 AAAA..."
    ]
    ```

### `[groups]`

This section allows you to define groups and manage their members. Each group is defined in a sub-section using the format `[groups.groupname]`.

The following keys are supported for each group:

-   `users`: A list of usernames to be added to this group. These users should typically be defined in the `[users]` section or already exist on the system.

    *Example:*
    ```toml
    [groups.sftp-users]
    users = ["dmitry"]
    ```

### `[configs]`

This section allows you to create arbitrary configuration files on the container's filesystem. Each file is defined in a sub-section where the name is the full, quoted path to the file, e.g., `[configs."/etc/motd"]`.

The following keys are supported for each file:

-   `body` (required): A string (often a multi-line string) containing the content of the file.
-   `permissions` (optional): An integer representing the file permissions in standard Linux octal notation (e.g., `644`, `755`).
-   `owner` (optional): A string in `"user:group"` format to set the file's ownership.

    *Example:*
    ```toml
    [configs."/etc/ssh/sshd_config.d/sftp.conf"]
    body = """
    Match group sftp-users
      ChrootDirectory /chroot
      ForceCommand internal-sftp
      AllowTcpForwarding no
    """
    permissions = 644
    owner = "root:root"
    ```