Notes on “Docker Mastery: …”

Reference to the course: Docker Mastery: with Kubernetes +Swarm from a Docker Captain

I will update this post while continuing advance through the course.
Last updated: 25 February 2023.

Image vs Container

An Image is the application we want to run.
A Container is an instance of that image running as a process.

We can have many containers running off the same image.

Containers

Run a container

docker container run --publish 80:80 --name my_server nginx

--publish (short -p): Publish port 80 on local machines, and sends all traffic from it, to program running in container on port 80.
--name: Set a name for the container; if not specificed a random name is generated and used.

Run a container detached mode

docker container run --p 80:80 --detach nginx

--detach (short -d): Run detached from CLI.

List all containers

docker container ls -a

Check logs for running container

docker container logs <container name>

Run command from within container

docker container exec -it <container name> <command>

You can use docker container run if you need to startup the container.

Stop running container

docker container stop <container id>

Delete container

docker container rm <container id> -f

-f: Needed to delete a running container.

Docker Networks

Relevant lectures:

docker network create my_net

Create a new Docker network with the default bridge driver.

Images

It’s the application binaries and dependencies for your app and the metadata on how to run it.

Inside the image, there’s not actually a complete OS. There’s no kernel. There’s no kernel modules like drivers. That’s one of the distinct characteristics around containers that makes it different from a virtual machine; it’s not booting up a full operating system.

Pushing an Image to Docker Hub

Image don’t have a name.

docker login
docker image push <image>:<tag>

Dockerfile Basics

Dockerfile reference

docker image build --tag <name>:<tag> .

--tag (short -t): Name and optionally a tag in the ’name:tag’ format

Volumes & Bind Mounts

Containers are usually immutable and ephemeral. Docker has two solutions to persist data, known as data volumes and bind mounts.

Data Volumes are a configuration option for a container that creates a special location outside of that container’s union file system to store unique data. This preserves it across container removals and allows us to attach it to whatever container we want. The container just sees it like a local file path.
Bind Mounts allows sharing or mounting a host directory, or file, into a container. Again, it will just look like a local file path, or a directory path, to the container.

Data Volumes

VOLUME in Dockerfile.

VOLUME /var/lib/mysql

Any data we put here from the container, will outlive the container.

Create named volume

docker container run -d --name mysql --volume my_db:/var/lib/mysql mysql

--volume (short -v): Bind mount a named volume, at given location.

View existing volumes

docker volume ls

Bind Mounts

We can still use -v to create Bind Mounts, altough --mounts option exists (see differences).

docker container run -d --name ngnix -p 80:80 -v $(pwd):/usr/share/nginx/html nginx

We can use Bind Mounts to quickly edit code running in a container.

Docker Compose

Allow to save Docker container run settings in a file, docker-compose.yml.

# same as
# docker container run -p 80:4000 -v $(pwd):/site bretfisher/jekyll-serve

services:
    jekyll:
        image: bretfisher/jekyll-serve
    volumes:
        - .:/site
    ports:
        - "80:4000"

Run with: docker compose up.

Build image

Compose can also build custom images.

services:
  proxy:
    build:
      context: .
      dockerfile: nginx.Dockerfile
    image: my_nginx
    ports:
      - '80:80'
  web:
    image: httpd
    volumes:
      - ./html:/usr/local/apache2/htdocs/