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Docker slides
- 1. Getting Started With Docker
- 2. Why Containers? ● Isolation ○ Host OS ○ Other containers ● Resource limits ● Deployment ○ Container orchestration ○ Dependency management ● Portability
- 3. VMs vs Docker Containers Host OS Virtual Machine Monitor VM Guest OS ... VM Guest OS Base OS ... Base OS Host OS
- 6. Docker Image Layers Layer Layer Layer Layer Manifest ● Layer IDs ● Size ● Digest
- 7. Docker Registry ● Image storage, delivery service ○ Local or remote ○ Repository ■ named images ■ (version) tags ○ default: hub.docker.com
- 8. Docker Registry ● docker pull registry[:port]/repository[:tag] ● docker push registry[:port]/repository[:tag]
- 10. ● docker container run --interactive --tty python:3.6 ○ Dockerfile command: CMD ["python3"] Run Container (interactive)
- 13. ● docker image build --tag name[:tag] PATH | URL ○ Dockerfile with custom name (--file) ○ Build context (PATH | URL) ■ Build source, Dockerfile location ■ Get files from context ■ Size matters! (.dockerignore) Build Image
- 14. ● Build image from Python 3.6 parent simple_python_docker
- 15. ● docker image build --tag python3 . ○ builds python3:latest image ● docker container run python3:latest simple_python_docker
- 16. ● docker image history python3:latest Image History
- 17. ● docker image save --output python3_latest.tar python3:latest Image Save, Load ● docker image load -input python3_latest.tar python3:latest
- 18. ● ENTRYPOINT ○ Run specific executable ○ docker container run --entrypoint … ● CMD ○ Set default parameters, flags ○ docker container run python3:latest python –c “print(‘hello universe’)” ENTRYPOINT vs CMD
- 20. ● Images, containers stateless ○ ephemeral filesystem storage ● Volume or bind mounting from host OS ○ persistent storage ○ separate stateless code from stateful data Docker State
- 21. ● docker image build --tag app:1.0 . flask_docker_logs ● docker volume create my_vol
- 22. ● docker image ls List Images, Volumes ● docker volume ls
- 23. ● docker container run --name my_app --publish 5000:5000 --rm --detach --mount source=my_vol,destination=/usr/app/logs app:1.0 flask_docker_logs
- 24. ● docker container run --name my_app --publish 5000:5000 --rm --detach --volume my_vol:/usr/app/logs app:1.0 Volume mount shorthand
- 25. ● docker container run --name my_app --publish 5000:5000 --rm --detach --cpus 1 --memory 250m --mount source=my_vol,destination=/usr/app/logs app:1.0 Limit Resources
- 26. ● docker container run --name my_app_bind_mount --publish 5001:5000 --rm --detach --volume $PWD/logs:/usr/app/logs app:1.0 Bind mount
- 27. ● docker container ls (or docker container ps) ● docker container ls --all ○ Includes exited containers List Running Containers
- 28. ● docker container exec my_app ls –la /usr/app/logs Docker Container Exec
- 29. ● docker container exec --interactive --tty my_app python Docker Container Exec
- 30. ● docker image inspect app:1.0 Docker Image Inspect
- 31. ● docker container inspect my_app Docker Container Inspect
- 32. ● docker volume inspect my_vol Docker Volume Inspect
- 33. ● docker system info System Information
- 34. ● docker system df Docker System Disk Usage ● docker system df –verbose ● Disk usage by container, image, volume, caches
- 35. ● docker container stop my_app ○ Graceful exit with SIGTERM ○ SIGKILL after grace period ● docker container kill my_app ○ SIGKILL ● docker container rm my_app ● docker volume rm my_vol Stop, Remove Containers, Volumes
- 36. ● docker image rm app:1.0 python3:latest ● docker container prune ○ Remove stopped containers ● docker volume prune ○ Remove unused volumes ● docker system prune ○ Remove stopped containers, unused networks, dangling images, caches Docker Cleanup
- 37. ● Exit container interactive shell ○ detach: CTRL-P, CTRL-Q ○ re-attach: ■ docker container attach my_app ○ stop: CTRL-D or CTRL-C or exit Stop, Exit Containers
- 38. ● Docker command line reference: https://dockr.ly/2DzkgBk ● Run as non-root user: https://bit.ly/2DpSyJw ● Multistage Dockerfile reference: https://dockr.ly/2Mmy7Qt ● Play with Docker: https://bit.ly/2AXqewB ● Docker Deep Dive (Pluralsight): https://bit.ly/2khWfqt More About Docker
Editor's Notes
- Container: software tool for OS to run isolated processes with limits on resources processes can use Abstracts away the machine running software Container processes isolated from host OS processes Containers from same image also isolated from each other – independent! Declare and isolate dependencies Also set up dev environments quickly with containers (add databases, other services) Focus on Docker because most popular container standard IDEs offer live debugging in Docker (VS Code, PyCharm Pro etc.)
- VMM: create and run VMs with separate OS Divide host CPU, RAM, disk, total isolation! Docker engine layer allows container base OS to share host OS resources – lighter, much less overhead! Docker engine on MacOS and Windows uses virtualization system Also, docker on Mac and Windows (except on Windows Server 2016+) only as local dev environments! NOT FOR PRODUCTION!
- Build existing image (OS, other official Docker certified images!) pulled from local or known remote registry From scratch (special keyword) Image built to local registry Also upload to remote registry
- First part of lifecycle Dockerfile describes how the image is built Image is read-only, blueprint for creating the container at run time Image gets unique ID (SHA256 cryptographic hash) optionally name and tag (version etc)
- Image built from a stack of layers generated from Dockerfile commands (RUN, COPY, ADD which add or change files, env vars, CMD) and a manifest Layers are independent files, can be caches, each has ID (hash) Order matters!!! Digest is hash to verify image from registry (like checking MD5 sum) Caching layers matters!!! Viewing manifest is still experimental, won’t really talk about this...
- Registry contains repositories Docker Hub is default (no registry URL needed in default config), can set up registries in Google cloud, AWS etc. Repository example: collection of python images on DockerHub stored in python repo tagged by release numbers
- Can pull images from public or private registries Can push images to public or private registries Other commands can pull images (run!)
- Container is run-time instance of image Runs base OS with a command or executable set up in Dockerfile or set up command with Docker run
- Running official Python 3.6 docker image from Docker Hub If Python 3.6 image not local, pulls from Docker Hub Setting up a ”terminal” to interact with running container: flags typically used together to ensure IO attached Most flags have short form too! Command in image runs Python REPL with default settings
- See image layers pulled from registry Reports digest Work with interactive shell in container
- TODO: Slides linked in talk desc! Assume that the docker build context is the subdirectory containing code for the example!
- Tag flag is optional, can use image ID hash in run command too PATH is local dir URL can be Git repo, tar archive or plain text file see Docker docs for more info, not covering URL here dockerignore similar to git ignore, avoid bloat!
- 1st example! Docker has 2 ways of copying data into image: COPY best for local files, directories ADD best if remote URL or tar archive
- Default tag: latest, can use whatever Container run runs command in Dockerfile Not interactive this time!
- History of image we just built Missing image layer IDs from base python 3.6 image pulled from Docker Hub #nop: docker internal command (vs bash)
- Can export image and load elsewhere bypassing registry Also used for backups Best for dev and testing
- ENTRYPOINT and CMD set up docker container run something in container ENTRYPOINT is usually a single command, executable or script (bash scripts are common) In next example CMD is easier to override, can override without changing ENTRYPOINT Overriding our Dockerfile here Python parent image has null ENTRYPOINT
- Second example! Build super-simple Flask app that writes logs Binds to port 5000 in container Example of ENTRYPOINT and CMD together!
- Stateless unless connected persistent storage! Writing container data to a database or object store like S3 also works Better not to put too much data in image Bind mounts mount local filesystem files, directories Just covering volume mounts here
- Build: set tag version! Create volume to persist logs! Containers can share volumes!
- List local images Use image ID instead of name and tag! List running containers with name, command etc. Container ls alias = ps
- Use --publish to expose port to host (left is host, right is container always!), --rm to remove container on exit, --detach to run in background Without --mount, logs written only in running container and will disappear when container is removed mounted volume can be read-only --name: run container with alias, otherwise hash ID
- Shorthand with volume flag
- More memory and CPU limits in run CLI options Min memory is 4MB Container orchestration frameworks (Kubernetes) also do this
- Bind mount: mount local directory Doesn’t have to exist in either container or host Can also be read-only Note: new name, new host port
- List local images Use image ID instead of name and tag! List running containers with name, command etc. Container ls alias = ps Note random name for stopped python app
- Run one-off command in running container
- Interactive session in running container using same --interactive and --tty flags as run command Debugging!
- All the build-time data about the app:1.0 image Can also use Golang formatters to select output from inspect commands
- All the runtime data about the my_app container
- Shows mountpoint on local filesystem On Macs, need to access the VM Docker is running in Possible, but out of scope
- Overview of state of docker system about engine, running containers etc.
- Full information about disk usage by running and stopped containers Keeps info cached until system cache is pruned Note: Docker assigned random name to Python 3.6 container run earlier
- SIGTERM aka soft kill, can set timeout docker kill CLI can send signal other than SIGKILL (works like unix kill command) --signal flag
- Remove images -q: only image ids Can remove images by name
- CTRL-P, CTRL-Q leaves container running, can attach again Interactive: also use exit commands to stop container
- Play with Docker: Linux VM for experimenting with Docker containers