Sharing Local Files with Docker Containers

--- title: Sharing local files with containers weight: 4 keywords: concepts, images, container, docker desktop description: This concept page will teach you the various storage options available in Docker and their common usage. aliases: - /guides/docker-concepts/running-containers/sharing-local-files/ --- {{< youtube-embed 2dAzsVg3Dek >}} ## Explanation Each container has everything it needs to function with no reliance on any pre-installed dependencies on the host machine. Since containers run in isolation, they have minimal influence on the host and other containers. This isolation has a major benefit: containers minimize conflicts with the host system and other containers. However, this isolation also means containers can't directly access data on the host machine by default. Consider a scenario where you have a web application container that requires access to configuration settings stored in a file on your host system. This file may contain sensitive data such as database credentials or API keys. Storing such sensitive information directly within the container image poses security risks, especially during image sharing. To address this challenge, Docker offers storage options that bridge the gap between container isolation and your host machine's data. Docker offers two primary storage options for persisting data and sharing files between the host machine and containers: volumes and bind mounts. ### Volume versus bind mounts If you want to ensure that data generated or modified inside the container persists even after the container stops running, you would opt for a volume. See [Persisting container data](/get-started/docker-concepts/running-containers/persisting-container-data/) to learn more about volumes and their use cases. If you have specific files or directories on your host system that you want to directly share with your container, like configuration files or development code, then you would use a bind mount. It's like opening a direct portal between your host and container for sharing. Bind mounts are ideal for development environments where real-time file access and sharing between the host and container are crucial. ### Sharing files between a host and container Both `-v` (or `--volume`) and `--mount` flags used with the `docker run` command let you share files or directories between your local machine (host) and a Docker container. However, there are some key differences in their behavior and usage. The `-v` flag is simpler and more convenient for basic volume or bind mount operations. If the host location doesn’t exist when using `-v` or `--volume`, a directory will be automatically created. Imagine you're a developer working on a project. You have a source directory on your development machine where your code resides. When you compile or build your code, the generated artifacts (compiled code, executables, images, etc.) are saved in a separate subdirectory within your source directory. In the following examples, this subdirectory is `/HOST/PATH`. Now you want these build artifacts to be accessible within a Docker container running your application. Additionally, you want the container to automatically access the latest build artifacts whenever you rebuild your code. Here's a way to use `docker run` to start a container using a bind mount and map it to the container file location. ```console $ docker run -v /HOST/PATH:/CONTAINER/PATH -it nginx ``` The `--mount` flag offers more advanced features and granular control, making it suitable for complex mount scenarios or production deployments. If you use `--mount` to bind-mount a file or directory that doesn't yet exist on the Docker host, the `docker run` command doesn't automatically create it for you but generates an error. ```console $ docker run --mount type=bind,source=/HOST/PATH,target=/CONTAINER/PATH,readonly nginx ``` > [!NOTE] > > Docker recommends using the `--mount` syntax instead of `-v`. It provides better control over the mounting process and avoids potential issues with missing directories.

Docker containers run in isolation, which means they cannot directly access data on the host machine by default. Docker offers two primary storage options for persisting data and sharing files between the host machine and containers: volumes and bind mounts. Volumes ensure data persistence even after the container stops, while bind mounts allow direct sharing of files and directories between the host and container. The `-v` or `--volume` flag is simpler for basic operations, while the `--mount` flag offers more advanced features and granular control. Docker recommends using the `--mount` syntax instead of `-v`.