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+Docker for SW Development
+=========================
+
+.. post:: 31, January 2025
+   :tags: development, infrastructure, tools, lunch-n-learn 
+   :category: Projects
+   :author: len0rd
+
+This is from a lunch-n-learn I hosted which aimed to showcase the features and advantages of using
+docker during the development process. It includes with a few tutorials on how to use it.
+
+Example code is hosted on my personal git server:  https://git.lenord.me/len0rd/docker_demo
+
+What is Docker
+--------------
+
+- Framework for defining and running low overhead sand-boxed environments called 'containers' on your host
+
+- Its more than a "cheap VM"
+
+.. image:: https://iot.samteck.net/wp-content/uploads/2018/10/vm-vs-docker.jpg
+
+https://medium.com/@saschagrunert/demystifying-containers-part-i-kernel-space-2c53d6979504
+
+
+.. image:: https://cdn-images-1.medium.com/max/1600/1*bIQOZL_pZujjrfaaYlQ_gQ.png
+    :class: dark-light
+
+Why docker?
+-----------
+
+- version-controlled binary dependency management
+
+- documented and repeatable dependency installation in a living (version-controlled) file
+
+- "containerize once and run everywhere" 
+
+  - No more "it works on my machine"
+
+- Industry-standard tool for CI/CD
+
+Why docker for development?
+^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- consistent environment between developers and CI servers
+
+- Project environment isolation - useful when working multiple projects
+
+- Easy to experiment with and revert dependency changes - agile dependency management
+
+Docker and Linux
+-----------------
+
+- Docker is built atop core features of the Linux kernel (Namespaces) that are not available in Windows without WSL
+
+- Docker desktop requires a license for commercial use. Docker server/CLI does not
+
+docker image
+------------
+
+- Docker image is a snapshot of a linux rootfs
+
+- Images can be built manually or downloaded from a registry
+
+Command: ``docker image [--help]``
+
+docker registry
+---------------
+
+- Pre-built images published online you can download
+
+- Anyone can host a registry. Largest: https://hub.docker.com/search?q=
+
+Command: ``docker pull <image_name>``
+
+.. admonition:: Example
+
+    Take a look at `example 1 <https://git.lenord.me/len0rd/docker_demo/src/branch/develop/01_registry_pull>`_
+
+docker container
+----------------
+
+- Container is a spawned docker image
+
+- Container *images* become *containers* at runtime
+
+- You can spawn many containers from a single image
+
+- Containers can run one or many processes, can provide user shells
+
+Managing existing containers: ``docker container [--help]``
+
+dockerfiles
+-----------
+
+- How you define custom images
+
+- Good documentation: https://docs.docker.com/engine/reference/builder/
+
+- Dockerfiles build off images. Each step in a dockerfile is a snapshot of changes to a linux rootfs
+
+Command: ``docker build --help``
+
+.. image:: ../assets/img/writeup/docker/dockerfile_as_layers.png
+    :class: dark-light
+
+.. admonition:: Example
+
+    Take a look at `example 2 <https://git.lenord.me/len0rd/docker_demo/src/branch/develop/02_simple_dockerfile>`_
+
+Running Containers
+------------------
+
+- when a container is run you are in full control of what parts have access to the outside world
+
+  - ports forwarded from container to host
+
+  - network configuration in general
+
+  - mounting files/folders from the host within the container
+
+Running: ``docker run --help``
+
+docker cache
+------------
+
+- Every step in a dockerfile is cached. if a step in the middle of the file changes, the image is rebuilt from that point onward
+
+- https://docs.docker.com/build/cache/
+
+cache minimization
+^^^^^^^^^^^^^^^^^^
+
+- docker caches can take up a lot of space
+
+- Best practice is to combine logically linked commands into single steps to reduce the amount of cache a dockerfile build produces
+
+- clearing out old cache: ``docker builder prune``
+
+
+multi-stage builds
+------------------
+
+- newish (in the last couple years) feature, now standard is docker's BuildKit backend
+
+- allows definition of distinct stages in the dockerfile to allow parallel build and reduce unnecessary dependencies
+
+- https://docs.docker.com/build/buildkit/
+
+.. admonition:: Example
+
+    Take a look at `example 4 <https://git.lenord.me/len0rd/docker_demo/src/branch/develop/04_multistage_docker_file>`_
+
+.. image:: https://git.lenord.me/len0rd/docker_demo/raw/branch/develop/04_multistage_docker_file/stage_graph.png
+    :class: dark-light
+
+DevContainers: an additional layer on top of docker
+---------------------------------------------------
+
+- Feature first added by VSCode, eventually published as an open standard by Microsoft:
+
+  - https://containers.dev/
+
+- Now multiple IDEs (IntelliJ, Visual Studio, NeoVim) have support for the standard 
+
+.. image:: https://code.visualstudio.com/assets/docs/devcontainers/containers/architecture-containers.png
+    :class: dark-light
+
+docker-compose: container orchestration
+---------------------------------------
+
+- ``docker run`` and ``docker build`` commands can get long and tedious for more complex containers
+
+- ``docker compose`` solves this. Sits on top of docker and supports building/running multiple containers via yaml
+
+.. admonition:: Example
+
+    Take a look at `example 5 <https://git.lenord.me/len0rd/docker_demo/src/branch/develop/05_complex_run_with_compose>`_