Added README.md for roles

Signed-off-by: Tuan-Dat Tran <tuan-dat.tran@tudattr.dev>

roles/docker_host/README.md

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+# Ansible Role: Docker Host
+
+This role sets up a Docker host, installs Docker, and configures it according to the provided variables. It also handles user and group management, directory setup, and deployment of Docker Compose services.
+
+## Role Variables
+
+### General
+
+- `docker_host_package_common_dependencies`: A list of common packages to be installed on the host.
+  - Default: `nfs-common`, `firmware-misc-nonfree`, `linux-image-amd64`
+- `apt_lock_files`: A list of apt lock files to check.
+- `arch`: The architecture of the host.
+  - Default: `arm64` if `ansible_architecture` is `aarch64`, otherwise `amd64`.
+
+### Docker
+
+- `docker.url`: The URL for the Docker repository.
+  - Default: `https://download.docker.com/linux`
+- `docker.apt_release_channel`: The Docker apt release channel.
+  - Default: `stable`
+- `docker.directories.local`: The local directory for Docker data.
+  - Default: `/opt/local`
+- `docker.directories.config`: The directory for Docker configurations.
+  - Default: `/opt/config`
+- `docker.directories.compose`: The directory for Docker Compose files.
+  - Default: `/opt/compose`
+
+### Keycloak
+
+- `keycloak_config`: A dictionary containing the Keycloak configuration. See `templates/keycloak/realm.json.j2` for more details.
+
+### Services
+
+- `services`: A list of dictionaries, where each dictionary represents a Docker Compose service. See `templates/compose.yaml.j2` for more details.
+
+## Tasks
+
+The role performs the following tasks:
+
+1.  **Setup VM**:
+    - Includes `non-free` and `non-free-firmware` components in the apt sources.
+    - Installs common packages.
+    - Removes cloud kernel packages.
+    - Reboots the host.
+2.  **Install Docker**:
+    - Uninstalls old Docker versions.
+    - Installs dependencies for using repositories over HTTPS.
+    - Adds the Docker apt key and repository.
+    - Installs Docker Engine, containerd, and Docker Compose.
+3.  **Setup user and group for Docker**:
+    - Ensures the `docker` group exists.
+    - Adds the `ansible_user_id` to the `docker` group.
+    - Reboots the host.
+4.  **Setup directory structure for Docker**:
+    - Creates necessary directories for Docker and media.
+    - Sets ownership of the directories.
+    - Mounts NFS shares.
+5.  **Deploy configs**:
+    - Sets up Keycloak realms if the host is a Keycloak host.
+6.  **Deploy Docker Compose**:
+    - Copies the Docker Compose file to the target host.
+7.  **Publish metrics**:
+    - Copies the `daemon.json` file to `/etc/docker/daemon.json` to enable metrics.
+
+## Handlers
+
+- `Restart docker`: Restarts the Docker service.
+- `Restart compose`: Restarts the Docker Compose services.
+- `Restart host`: Reboots the host.
+
+## Usage
+
+To use this role, include it in your playbook and set the required variables.
+
+```yaml
+- hosts: docker_hosts
+  roles:
+    - role: docker_host
+      vars:
+        # Your variables here
+```
+
+## License
+
+This project is licensed under the MIT License - see the [LICENSE.md](LICENSE.md) file for details.