Docker Run

When executing the docker run command

• You can run a container from a locally stored Docker image

  • If the image does not exist on the system, it is pulled from an online registry

image pull

• When an image is pulled, the layers are stored independently

• When running a container, these layers are stacked in order and mounted at a specific location

• By default, the layers belonging to the image are read-only and never change

• On top of them, a final container-specific writable layer is added, and all changes that occur in the container are saved to this layer

Running a container

• When running a container, a clean layer is placed on top of the image's topmost layer

• No matter how many containers are running, they do not affect each other because the layer where actual writes occur is separated

  • In other words, every container has its own unique writable area, which becomes the topmost layer and does not affect any of the lower layers