d023975 / dockerTemplate

dockerTemplate

Docker cli, server, registry

• https://docs.docker.com/install/
• server dockerd
• cli docker
• docker registry to hold images
  • https://docs.docker.com/registry/
    • docker run -d -p 5000:5000 --restart=always --name registry registry:2
  • https://docs.docker.com/registry/introduction/
  • docker pull, docker push
  • The Registry is open-source, under the permissive Apache license.
  • docker pull ubuntu instructs docker to pull an image named ubuntu from the official Docker Hub. This is simply a shortcut for the longer docker pull docker.io/library/ubuntu command
  • https://docs.docker.com/registry/deploying/

Docker registries

• Docker Hub is a public registry that anyone can use, and Docker is configured to look for images on Docker Hub by default

Use Case

Running your own Registry is a great solution to integrate with and complement your CI/CD system. In a typical workflow, a commit to your source revision control system would trigger a build on your CI system, which would then push a new image to your Registry if the build is successful. A notification from the Registry would then trigger a deployment on a staging environment, or notify other systems that a new image is available.

Dockerfiles

• ADD - copies the files from a source on the host into the container's own filesystem at the set destination
• CMD - can be used for executing a specific command within the container
• ENTRYPOINT - sets a default application to be used every time a container is created with the image
• ENV - sets environment variables
• EXPOSE - associates a specific port to enable networking between the container and the outside world
• FROM - defines the base image used to start the build process
• MAINTAINER - defines a full name and email address of the image creator
• RUN - central executing directive for Dockerfiles
• USER - sets the UID (or username) which is to run the container
• VOLUME - is used to enable access from the container to a directory on the host machine
• WORKDIR - sets the path where the command, defined with CMD, is to be executed

Create a .dockerignore file in the same directory as your Dockerfile. This will prevent your local modules and debug logs from being copied onto your Docker image.

Build images from Dockerfile

• docker build -t "NAME:Dockerfile" .
• docker build -t "webdev:Dockerfile" .
• docker build -t "appdev:Dockerfile" .
• docker build -t "secdev:Dockerfile" .
• docker images - list all docker immages

Containers

• A container is a runnable instance of an image

Services

• Scale containers
• Create replicas
• Swarm mode

Docker Compose https://docs.docker.com/compose/

• File format: https://docs.docker.com/compose/compose-file/

1. Define your app’s environment with a Dockerfile so it can be reproduced anywhere.

2. Define the services that make up your app in docker-compose.yml so they can be run together in an isolated environment.

3. Run docker-compose up and Compose starts and runs your entire app.

• You can set a custom project name by using the -p command line option or the COMPOSE_PROJECT_NAME environment variable.

Integrate Dockerfile into docker-compose.yml

• see docker-compose.yml
• docker-compose up/down/restart
• you could also define everything within the docker-compose.yml file, but making use of both Dockerfile and docker-compose.yml makes for a much more flexible and efficient system

Dockerizing a nodejs web app

• https://nodejs.org/de/docs/guides/nodejs-docker-webapp/
• create Dockerfile
• docker build -t <your username>/node-web-app
• docker run -p 49160:8080 -d /node-web-app
• If you need to go inside the container you can use the exec command:
  • docker exec -it <container id> /bin/bash