Docker/Volumes

Lesson 2 of 4

Mounting Volumes

Let’s see how to actually use a volume with a container. We’ll use the official Ghost blogging software image as an example. A blogging software that doesn’t save your posts would be useless, so it’s a perfect use case for volumes!

Running a Container with a Volume

You can mount a volume to a container using the -v flag in your docker run command:

docker pull ghost

# Run Ghost with a volume mounted
docker run -d -e NODE_ENV=development -e url=http://localhost:3001 -p 3001:2368 -v my-vol:/var/lib/ghost ghost

Let’s break down these flags:

  • -d: Runs the image in detached mode.
  • -e NODE_ENV=development: Sets an environment variable within the container telling Ghost to run in “development” mode.
  • -e url=http://localhost:3001: Sets another environment variable so Ghost knows its access URL.
  • -p 3001:2368: Port forwards the container’s port 2368 to our host machine’s port 3001.
  • -v my-vol:/var/lib/ghost: Mounts the my-vol volume we created to the /var/lib/ghost path inside the container.

Ghost will now use the /var/lib/ghost directory to persist stateful data (like blog posts) between runs. If you were to navigate to http://localhost:3001/ and create a post, that data would be stored safely in my-vol.