---
url: /en/workspaces/double-container.md
---
Cloud-native development can be launched in two modes:

* Single Container Mode: Development environment and code service (`code-server`) are in the same container
* Double Container Mode: Development environment and code service (`code-server`) are in two different containers, with the workspace (`/workspace`) directories shared between the two containers

​​**Development Environment**​​: This can be understood as a user-customized development environment container (configured via `.ide/Dockerfile` or a custom image), or the default container environment provided by CNB. It includes software installed by the user or pre-installed by default.

## Single Container Mode

Single container mode is recommended. The following methods start in single container mode:

### Starting with Default Configuration

When users haven't made any configurations (i.e., haven't configured startup pipeline and `.ide/Dockerfile`), the development environment starts with default configuration.
The default development environment has both `code-server` service and `ssh` service installed, so it will start in single container mode, supporting both WebIDE and VSCode remote development.

See [documentation](./default-dev-env.md) for details.

### Starting with Custom Configuration

When users have configured a startup pipeline or `.ide/Dockerfile`, and the custom image or `.ide/Dockerfile` has `code-server` service installed,
the development environment and `code-server` service are in the same container, which will start in single container mode.

The following three methods (all development environment images have code-server service installed) start in single container mode:

* [Specifying development environment via Docker image](./custom-dev-env.md#specifying-development-environment-via-docker-image)
* [Customizing development environment via Dockerfile](./custom-dev-env.md#customizing-development-environment-via-dockerfile)
* [Customizing both development environment and startup process](./custom-dev-env.md#customizing-both-development-environment-and-startup-process)

## Double Container Mode

When the development environment container doesn't have code-server service installed, we will start an additional `code-server` container as the code service container,
to support `WebIDE` and `VSCode` client access to the development environment, i.e., double container mode. The workspace (`/workspace`) directories of the two containers are shared.

The following two methods will start in double container mode:

### Docker Image Without code-server Installed

```yaml{14-18} title=".cnb.yml"
$:
  vscode:
    # Docker image without code-server service installed
    - docker:
        image: node:22
      services:
        - vscode
        - docker
      # Tasks to execute after the development environment starts
      stages:
        - name: ls
          script: ls -al
```

### Custom Dockerfile Without code-server Installed

```dockerfile
# .ide/Dockerfile

# You can replace node with your required base image
FROM node:20

# Install software as needed
RUN apt-get update && apt-get install -y git wget unzip openssh-server

# Specify character set to support Chinese input in command line (choose character set as needed)
ENV LANG C.UTF-8
ENV LANGUAGE C.UTF-8
```

## Double Container Mode - Cross-Container Terminal

In double container mode, when accessing WebIDE or VSCode, you're actually accessing the `code-server` container.

So how do you access the development environment container from the editor?

We've added an extra cross-container terminal in the `code-server` container. In WebIDE or VSCode client, when you open a terminal,
the default terminal is one that can access the development environment container across containers. This terminal is named `CNB`.

If the development environment container doesn't support git commands, you can switch to other terminals not named `CNB` to use the terminal built into code-server for git operations.

## Double Container Mode - Plugin Capability Limitations

In double container mode, when accessing `WebIDE` or `VSCode`, the installed VSCode plugins are in the code-server container,
which may not be able to implement capabilities like Debug that need to access the development environment container.