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Volumes

By default, Docker containers don't retain any state from past containers. For example, if I:

Start a container from an image
Make some changes to the filesystem (like installing a new package) in that container
Stop the container
Start a new container from the same image
The new container does not have the changes I made in step 2.

However, if I restart the stopped container, it will have the changes I made. This is only worth mentioning because sometimes developers think that killing an old container and starting a new one is the same as restarting a process - but that's not true... it's more like resetting the state of the entire machine to the original image.

All this said, Docker does have ways to support "persistent state" through storage volumes. They're basically a filesystem that lives outside of the container, but can be accessed by the container.

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Assignment

Ghost is an open-source blogging software, kind of like WordPress. As you can imagine, blogging software that doesn't save your blog posts, would be pretty useless, so we'll install Ghost and use volumes to persist our data!

Create a new empty volume called ghost-vol:

docker volume create ghost-vol

Make sure it worked:

docker volume ls

Inspect the volume to see where it is on your local machine:

docker volume inspect ghost-vol

Run and submit the CLI tests.