The -v flag in Docker is used to specify a volume to mount into a Docker container. A volume in Docker is a way to share data between a container and the host machine, or between containers. This allows you to persist data, share files, or communicate between containers.

The basic syntax for using the -v flag is:

docker run -v <host_path>:<container_path> ...
  • <host_path> is the path to the directory or file on the host machine that you want to make available inside the container.
  • <container_path> is the path inside the container where you want to mount the volume.

Here’s an example:

Let’s say you have a simple Node.js application in a directory on your host machine, and you want to run it in a Docker container. You can use the -v flag to mount your local directory into the container, so any changes you make on your host will be reflected in the container, and vice versa.

docker run -v /path/to/your/app:/app my-node-app

In this example:

  • /path/to/your/app is the path on your host machine where your Node.js application code resides.
  • /app is the path inside the container where you want to mount the volume.
  • my-node-app is the name of the Docker image you want to run.

Now, any changes you make to the code in /path/to/your/app on your host machine will be immediately visible inside the running Docker container at /app. This is useful for development and debugging purposes.

You can also use named volumes for more advanced use cases and data persistence in Docker. The -v flag is a powerful feature that enables data sharing and persistence between containers and the host.

By admin