forum/docs/build.md

# Build Options

## 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=

## Customizing the Server Name

Use the `SERVER_NAME` environment variable to define your custom server name(s).

    SERVER_NAME="app.localhost" docker compose up -d --wait

> [!TIP]
> You can define your server name variable in your `.env` file to keep it at each up

## 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.