![Check out this sweet Dockerfile ..
FROM python:3.6.7-jessie
COPY app /app
RUN pip install Flask
EXPOSE 8000
CMD ["python", "/app/__init__.py"]](https://image.slidesharecdn.com/gettingstartedwithdockerslides-190315203728/85/Getting-Started-with-Docker-13-320.jpg)
![FROM python:3.6.7-jessie
COPY app /app
RUN pip install Flask
EXPOSE 8000
CMD ["python", "/app/__init__.py"]
Check out this sweet Dockerfile ..
FROM loads a published
image as a starting point for
your application](https://image.slidesharecdn.com/gettingstartedwithdockerslides-190315203728/85/Getting-Started-with-Docker-14-320.jpg)
![FROM python:3.6.7-jessie
COPY app /app
RUN pip install Flask
EXPOSE 8000
CMD ["python", "/app/__init__.py"]
Check out this sweet Dockerfile ..
COPY takes files in the host file system
and moves them into the image](https://image.slidesharecdn.com/gettingstartedwithdockerslides-190315203728/85/Getting-Started-with-Docker-15-320.jpg)
![FROM python:3.6.7-jessie
COPY app /app
RUN pip install Flask
EXPOSE 8000
CMD ["python", "/app/__init__.py"]
Check out this sweet Dockerfile ..
RUN allows you to execute
commands inside the image](https://image.slidesharecdn.com/gettingstartedwithdockerslides-190315203728/85/Getting-Started-with-Docker-16-320.jpg)
![EXPOSE defines a
port that can be
accessed outside of
the container
FROM python:3.6.7-jessie
COPY app /app
RUN pip install Flask
EXPOSE 8000
CMD ["python", "/app/__init__.py"]
Check out this sweet Dockerfile ..](https://image.slidesharecdn.com/gettingstartedwithdockerslides-190315203728/85/Getting-Started-with-Docker-17-320.jpg)
![FROM python:3.6.7-jessie
COPY app /app
RUN pip install Flask
EXPOSE 8000
CMD ["python", "/app/__init__.py"]
Check out this sweet Dockerfile ..
CMD defines a
default command
the container will
run](https://image.slidesharecdn.com/gettingstartedwithdockerslides-190315203728/85/Getting-Started-with-Docker-18-320.jpg)
![Vagrant + Docker provider [+Puppet]](https://cdn.slidesharecdn.com/ss_thumbnails/npoggivagrant-docker-140725100147-phpapp02-thumbnail.jpg?width=560&fit=bounds)
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Getting Started with Docker
- 2. YipitData is not endorsed by, directly affiliated with, maintained, authorized, or sponsored by Docker Inc. Disclaimer
- 4. ● Brief terminology ● Running containers ● Dockerfiles & Images ● Tips for development General Outline
- 5. ● Dockerfile: Defines the instructions to create an image ● Image: An executable package that contains the resources needed to run a container ● Container: The result (a process) of executing an image. A new container is made each time an image is executed Dockerfile, Images, Containers, .. ?
- 6. ● An easy way to create a container is by using “docker run” docker run -it --rm <IMAGE:TAG> <COMMAND> ● Example: docker run -it --rm python:3.6.5-jessie python OK, but how do I even container ?
- 7. ● An easy way to create a container is by using “docker run” docker run -it --rm <IMAGE:TAG> <COMMAND> OK, but how do I even container ? Exposes STDIN to the container and emulates a terminal session. It lets you run commands within the container
- 8. ● An easy way to create a container is by using “docker run” docker run -it --rm <IMAGE:TAG> <COMMAND> OK, but how do I even container ? Deletes the container after you exit the process, helps keep disk space under control
- 9. ● There is no concept of “SSH” in docker. But you can access a shell in a running container using docker exec: docker exec -it <CONTAINER ID> bash ● You can find the container ID by running: docker ps So what about SSH ..
- 10. Live Demo Exec into a container
- 11. ● Exec is helpful during development to debug a container’s state ● When debugging production, you should try to recreate the error using a fresh container locally ○ Exec is not supported in production ○ “Show Docker CLI” in YAWS is your friend ○ Enable logging to see more details Don’t exec unless you have to.
- 13. Check out this sweet Dockerfile .. FROM python:3.6.7-jessie COPY app /app RUN pip install Flask EXPOSE 8000 CMD ["python", "/app/__init__.py"]
- 14. FROM python:3.6.7-jessie COPY app /app RUN pip install Flask EXPOSE 8000 CMD ["python", "/app/__init__.py"] Check out this sweet Dockerfile .. FROM loads a published image as a starting point for your application
- 15. FROM python:3.6.7-jessie COPY app /app RUN pip install Flask EXPOSE 8000 CMD ["python", "/app/__init__.py"] Check out this sweet Dockerfile .. COPY takes files in the host file system and moves them into the image
- 16. FROM python:3.6.7-jessie COPY app /app RUN pip install Flask EXPOSE 8000 CMD ["python", "/app/__init__.py"] Check out this sweet Dockerfile .. RUN allows you to execute commands inside the image
- 17. EXPOSE defines a port that can be accessed outside of the container FROM python:3.6.7-jessie COPY app /app RUN pip install Flask EXPOSE 8000 CMD ["python", "/app/__init__.py"] Check out this sweet Dockerfile ..
- 18. FROM python:3.6.7-jessie COPY app /app RUN pip install Flask EXPOSE 8000 CMD ["python", "/app/__init__.py"] Check out this sweet Dockerfile .. CMD defines a default command the container will run
- 19. docker build -t <NAME>:<TAG> <PATH> “docker build” translates a Dockerfile into an image
- 20. docker build -t <NAME>:<TAG> <PATH> Important to tag a readable name for your image “docker build” translates a Dockerfile into an image
- 21. docker build -t <NAME>:<TAG> <PATH> Specifying a version will pin changes of the images you create “docker build” translates a Dockerfile into an image
- 22. docker build -t <NAME>:<TAG> <PATH> Path to your Dockerfile and application code “docker build” translates a Dockerfile into an image
- 23. ● Each instruction is a layer, a change in the image state ● Only FROM, RUN, and COPY create layers ● The R/W layer is created when running a container An image is a series of “layers”
- 24. ● Ephemeral: Containers are created / destroyed with ease, and any setup is handled by the image ● Few in Layers: More layers lead to larger image size and longer build time ● Ordered for caching: The instructions in the Dockerfile are sequenced to leverage caching. Least likely to change or longest running instructions should be higher up The best Dockerfiles are:
- 25. Live Demo Caching in action
- 26. ● Base images can have unnecessary packages installed that inflate your image size FROM python:3.6.7-slim-jessie (157 MB) FROM python:3.6.7-jessie (691 MB) ● Use a versioned base image, or your image will be built on the latest base image (unstable) Use the right base image
- 27. ● A common technique is to chain shell commands using the && operator RUN apt-get update RUN apt-get install -y cron vs. RUN apt-get update && apt-get install -y cron Combine layers as much as possible
- 28. ● Linux by default will install many “recommended” packages you do not need. You can disable this behavior: RUN apt-get update && apt-get install -y --no-install-recommends cron Install only what you need
- 29. ● Packages may have extraneous files once installed, best practice is to remove them RUN curl s3://yipit/my_pkg.deb > my_pkg.deb && dpkg -i my_pkg.deb && rm -rf my_pkg.deb Delete temporary files after installation
- 30. ● The demo images were small to begin with, production image sizes can decrease 60 - 70% Significant reductions in image size
- 31. Absolute file path in the host machine you want to mount ● Volumes mount external (host) files to a container ● You can continue to modify these files and your running container will be up to date docker run --rm -it -v <HOST PATH:CONTAINER PATH> <IMAGE:TAG> Use volumes to speed up app development
- 32. ● Volumes mount external (host) files to a container ● You can continue to modify these files and your running container will be up to date docker run --rm -it -v <HOST PATH:CONTAINER PATH> <IMAGE:TAG> Destination file path in the container for the mounted file(s) Use volumes to speed up app development
- 34. ● Two ways to set variables in the Dockerfile, ARG and ENV ● ARG defines a build-time variable that is out of scope once the image is built ○ Good for secrets only used in setup (ex: localshop) ● ENV sets an environment variable that is in scope during and after the image is built Environment variables
- 35. ● Both variables can be set via the CLI. They will override values in the Dockerfile ● ARG: docker build --build-arg <NAME=VALUE> -t <IMAGE:TAG> . ● ENV: docker run --rm -it -e <NAME=VALUE> <IMAGE:TAG> Environment variables in the CLI
- 36. ● You will want to end your Dockerfile with a CMD and/or ENTRYPOINT (or inherit from your base image) ● An ENTRYPOINT executes code right at a container’s runtime ○ Establish background processes / services ○ Wrap additional context around commands ○ A CMD is passed as an argument to the entrypoint CMD or ENTRYPOINT?
- 38. ● Docker is a large platform and there is so much more to learn ● Best ways to get started: ○ Documentation: https://docs.docker.com/ ○ Read Dockerfiles for base images (usually on github) ○ Build some images! Tip of the iceberg ..
- 39. ● Containers improves parity of local development to production ○ The image you build is the image you deploy ○ Far easier to reproduce bugs ● Increases flexibility in your application architecture ○ OS packages easier to manage (no need for brew or chef) ○ Python versioning is simplified (no virtualenv) But it pays off !
- 40. Questions?
- 41. ● Official Docker Documentation ● Best Practices for Writing Dockerfiles ● Docker Container Layers ● XKCD on Containers ● XKCD on Compiling References