Docker Fundamentals

Docker Process

1. Developer writes code locally and shares their work as a Docker Image. 2. Docker pushes applications to a test environment for automated and/or manual testing. 3. Bugs can be fixed in development environment and redeployed in test environment for re-testing and validation. 4. When testing is done then developers push the updated image to the production environment.

Production Environments

1. Local data center 2. Cloud provider 3. hybrid

Docker benefits

1. Responsive deployment(Docker image flexibility) 2.Scalable 3. Lightweight and fast 4. NOT a virtual machine

Virtual Machine

A VM runs a full blown guest OS with virtual access to host resources through a hypervisor. VM's incur a lot of overhead.

What is Docker?

A containerization application that provides the ability to run one or more applications in an isolated environment called a Container. Does not use a hypervisor and can be run on a single computer.

Docker Platform

A platform to manage the entire lifecycle of containters: 1. Develop app with docker components 2.Container is used to support testing. 3. Deploy into production environment as Container. 4. Process works for all production environments.

Docker Architecture

Docker uses client-server architecture. Docker client talks to Docker Daemon which builds, runs, and distributes Containers. Docker client and daemon communicate with a REST API.

Docker Engine

The docker engine is a client server application with three components: 1. A server, contains daemon also called dokerd. 2.Docker REST API, communicates to daemon 3. A command line interface(CLI)

Docker Container

This is created from a docker image when you use a docker run command. It is a runnable instance of an image with encapsulation features applied to keep it isolated from host. It interacts with its own private file system. Manages with docker CLI

docker compose

Tool for defining and running multi-container Docker applications. Uses a YAML file to configure an application's services.

Dockerfile

a text document that contains all the commands a user would call on the command line to assemble an image.

docker build -t myimage .

build an image called myimage from a dockerfile at "."

docker attach <containername>

connect to a running container

docker create myimage

creates a container from an image but does not start it

Docker Daemon

creates and manages Docker objects such as images, containers, networks, and volumes

docker rm <containername>

delete a stopped container

docker ps -a

list all containers, running or stopped

docker ps

list all running containers

docker image ls

list images on machine

docker container <command>

manage containers

docker push username/reponame:<tagname>

push an image to a repo in the docker registry

docker run <containername>

re-run a container

Docker Image

standalone executable package that is read only and includes all of the instructions needed to run an application and create a container: code, runtime, system tools and libraries, and settings. Images can be based on other images.

docker start <containername>

starts a container

docker stop <containername>

stops a running container

Docker registries

stores Docker images and can be interacted with from CLI with docker pull, docker run, and docker push.