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:

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.

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:
```
[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:
```
[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:
```
[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:

[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"