Creating and mounting data volumes
All meaningful applications consume or produce data. Yet containers are, ideally, meant to be stateless. How are we going to deal with this? One way is to use Docker volumes. Volumes allow containers to consume, produce, and modify a state. Volumes have a life cycle that goes beyond the life cycle of containers. When a container that uses a volume dies, the volume continues to exist. This is great for the durability of the state.
Modifying the container layer
Before we dive into volumes, let’s first discuss what happens if an application in a container changes something in the filesystem of the container. In this case, the changes are all happening in the writable container layer that we introduced in Chapter 4, Creating and Managing Container Images. Let’s quickly demonstrate this:
- Run a container and execute a script in it that is creating a new file, like this:
$ docker container run --name demo \ alpine...
