Docker Deep Dive: Zero to Docker in a single book

by Nigel Poulton

Press Ctrl-PQ to exit the container without terminating it.

You can attach your shell to the terminal of a running container with the docker container exec command.

images are considered build-time constructs, whereas containers are run-time constructs.

and you cannot delete the image until the last container using it has been stopped and destroyed.

Docker images are stored in image registries.

Image registries contain multiple image repositories. In turn, image repositories can contain multiple images.

Filtering

At a high level, we can say that hypervisors perform hardware virtualization — they carve up physical hardware resources into virtual versions. On the other hand, containers perform OS virtualization — they carve up OS resources into virtual versions.

the way you write your Dockerfiles has a huge impact on the size of your images. A common example is that every RUN instruction adds a new layer. As a result, it’s usually considered a best practice to include multiple commands as part of a single RUN instruction - all glued together with double-ampersands (&&) and backslash (\) line-breaks.

Try and build them in a way that places any instructions that are likely to change towards the end of the file.

Docker Compose lets you describe an entire app in a single declarative configuration file. You then deploy it with a single command. Once the app is deployed, you can manage its entire lifecycle with a simple set of commands.

Nodes are configured as managers or workers. Managers look after the control plane of the cluster, meaning things like the state of the cluster and dispatching tasks to workers. Workers accept tasks from managers and execute them.

swarm managers also act as workers.