Docker Q&A Flashcards
What are docker images
Docker images have intermediate layers that increase reusability, decrease disk usage, and speed up docker build by allowing each step to be cached. These intermediate layers are not shown by default.
The SIZE is the cumulative space taken up by the image and all its parent images. This is also the disk space used by the contents of the Tar file created when you docker save an image.
An image will be listed more than once if it has multiple repository names or tags. This single image (identifiable by its matching IMAGE ID) uses up the SIZE listed only once.
What are docker containers
Created from Docker images and run the actual application. We create a container using docker run which we did using the busybox image that we downloaded. A list of running containers can be seen using the docker ps command.
What is a Docker daemon?
The background service running on the host that manages building, running and distributing Docker containers. The daemon is the process that runs in the operating system which clients talk to.
What is a Docker Client
The command line tool that allows the user to interact with the daemon. More generally, there can be other forms of clients too - such as Kitematic which provide a GUI to the users.
What is a Docker Hub?
A registry of Docker images. You can think of the registry as a directory of all available Docker images. If required, one can host their own Docker registries and can use them for pulling images.
what is a container runtime?
A container runtime is software that executes containers and manages container images on a node. Today, the most widely known container runtime is Docker, but there are other container runtimes in the ecosystem, such as rkt, containerd, and lxd. Docker is by far the most common container runtime used in production Kubernetes environments, but Docker’s smaller offspring, containerd, may prove to be a better option. This post describes using containerd with Kubernetes.
