# Docker Build Options You can customize the docker build process using these environment variables. > [!NOTE] > All Symfony-specific environment variables are used only if no `composer.json` file is found in the project directory. ## Selecting a Specific Symfony Version Use the `SYMFONY_VERSION` environment variable to select a specific Symfony version. For instance, use the following command to install Symfony 6.4: On Linux: SYMFONY_VERSION=6.4.* docker compose up -d --wait On Windows: set SYMFONY_VERSION=6.4.* && docker compose up -d --wait&set SYMFONY_VERSION= ## Installing Development Versions of Symfony To install a non-stable version of Symfony, use the `STABILITY` environment variable during the build. The value must be [a valid Composer stability option](https://getcomposer.org/doc/04-schema.md#minimum-stability). For instance, use the following command to use the development branch of Symfony: On Linux: STABILITY=dev docker compose up -d --wait On Windows: set STABILITY=dev && docker compose up -d --wait&set STABILITY= ## Using custom HTTP ports Use the environment variables `HTTP_PORT`, `HTTPS_PORT` and/or `HTTP3_PORT` to adjust the ports to your needs, e.g. HTTP_PORT=8000 HTTPS_PORT=4443 HTTP3_PORT=4443 docker compose up -d --wait to access your application on [https://localhost:4443](https://localhost:4443). > [!NOTE] > Let's Encrypt only supports the standard HTTP and HTTPS ports. Creating a Let's Encrypt certificate for another port will not work, you have to use the standard ports or to configure Caddy to use another provider. ## Caddyfile Options You can also customize the `Caddyfile` by using the following environment variables to inject options block, directive or configuration. > [!TIP] > All the following environment variables can be defined in your `.env` file at the root of the project to keep them persistent at each startup | Environment variable | Description | Default value | |---------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---------------------------| | `CADDY_GLOBAL_OPTIONS` | the [global options block](https://caddyserver.com/docs/caddyfile/options#global-options), one per line | | | `CADDY_EXTRA_CONFIG` | the [snippet](https://caddyserver.com/docs/caddyfile/concepts#snippets) or the [named-routes](https://caddyserver.com/docs/caddyfile/concepts#named-routes) options block, one per line | | | `CADDY_SERVER_EXTRA_DIRECTIVES` | the [`Caddyfile` directives](https://caddyserver.com/docs/caddyfile/concepts#directives) | | | `SERVER_NAME` | the server name or address | `localhost` | | `FRANKENPHP_CONFIG` | a list of extra [FrankenPHP directives](https://frankenphp.dev/docs/config/#caddyfile-config), one per line | `import worker.Caddyfile` | | `MERCURE_TRANSPORT_URL` | the value passed to the `transport_url` directive | `bolt://mercure.db` | | `MERCURE_PUBLISHER_JWT_KEY` | the JWT key to use for publishers | | | `MERCURE_PUBLISHER_JWT_ALG` | the JWT algorithm to use for publishers | `HS256` | | `MERCURE_SUBSCRIBER_JWT_KEY` | the JWT key to use for subscribers | | | `MERCURE_SUBSCRIBER_JWT_ALG` | the JWT algorithm to use for subscribers | `HS256` | | `MERCURE_EXTRA_DIRECTIVES` | a list of extra [Mercure directives](https://mercure.rocks/docs/hub/config), one per line | | ### Example of server name customize: SERVER_NAME="app.localhost" docker compose up -d --wait