Docker in a nutshell

A Docker container image is a lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries and settings.

Why use Docker?

How we used to ship

The standardization

The present

Hello World

    docker run hello-world

    
    Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/

Args

    docker run andersbogsnes/cowsay hello world

 -------------
< hello world >
 -------------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

Starting a database

    docker run -d \
-e ACCEPT_EULA=Y \
-e MSSQL_SA_PASSWORD=Secure.Password1234 \
-p 1433:1433 \
mcr.microsoft.com/mssql/server:2019-latest

Keeping tabs

docker ps

CONTAINER ID   IMAGE                                        COMMAND                  CREATED          STATUS          PORTS                    NAMES
736c8af768c3   mcr.microsoft.com/mssql/server:2019-latest   "/opt/mssql/bin/perm…"   25 seconds ago   Up 24 seconds   0.0.0.0:1433->1433/tcp   interesting_kalam

Webserver

# Create a simple webpage
echo "
Hello world
" >> index.html

# Run an nginx container
docker run -d \
-v ${PWD}/index.html:/usr/share/nginx/html/index.html:ro \
-p 8080:80 \
nginx

Terminology

Image

A Blueprint for a docker container

Described in a Dockerfile and the result of docker build

Container

A running instance of an Image

The result of a docker run

Container Registry

A place to store Docker Images.

Default is Dockerhub - companies run their own registries such as Docker Trusted Registry aka DTR

Dockerfile

Define what the Container looks like

# The python maintainers have already defined an image
# with python installed. I want to build on top of that
FROM python:3.9-slim

# Copy files from my local filesystem into the container
COPY my_code.py my_code.py

# Run an arbitrary command
RUN echo "This is executed when building this image"

# What command should my image run by default?
CMD ["echo", "This is executed when I run the image"]

Build the image

    docker build -t test_image .

    docker images

Run the image

docker run test_image

Run the image with a given command

docker run test_image python my_code.py