TSYSGroupHandbook/SourceMaterial/engineering/beginners-guide/notes/docker.md

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Docker Nomenclature and Notes

• Docker Image - the actual package, artifact which can be shared with others, docker images are built in layers via Dockerfile
• Docker Container - a running instance of a docker image, file system is virtual, contains a port for communication
• Docker run - command which executes pull and start (only pulls images we do not have locally)
• Docker vs Virtual Machine
  • Operating System = Hardware > OS Kernel (layer 1) > Applications (layer 2)
  • Docker = Virtualization of applications (layer 2)
  • Virtual Image = Virtualization of OS (layer 1)
  • Benefits of Docker = images are much smaller, runs faster
  • Benefits of VM = you can run different OS (Windows on Linux) since it has it's own OS Kernel
• Docker Port vs Host Port
  • Multiple containers may use the same port
  • Bind host port to docker port, i.e. host 3000 -> docker 3000, host 3001 -> docker 3000
• Docker Compose
  • Configuration file specifying docker commands to make it easier to work with
  • Automatically handles creating a common docker network
  • Docker compose is usually installed with docker so you already have it
• Docker Volumes
  • Provides data persistence between host machine and docker containers
  • The data between volumes is replicated between the host and docker container volumes
  • 3 docker volume types: specified, anonymous, and named volumes, named volumes on the host are managed by docker
  • Production should use named volumes
  • Container Mongodb = /data/db
  • Container MySQL = /var/lib/myself
  • Container Postgres = /var/lib/postgres/data
  • Host Windows = C:\ProgramData\docker\volumes
  • Host Linux = /var/lib/docker/volumes/[hash]/_data
  • Host Mac = /var/lib/docker/volumes/[hash]/_data
    • screen ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty add access linux VM on mac where data is stored, ctrl + a + k to exit screen session

Basic commands

• docker pull downloads a docker image locally
• docker images shows a list of local docker images and their sizes
• docker run run a docker container, it's two commands in one docker pull and docker start
• docker run -d runs the docker container in detach mode
• docker run -p binds the container to host port i.e. -p6000:6370, -p [host]:[container]
• docker run --name give the container a name so that you do not need to use the SHA
• docker run -d -it python runs python images in interactive terminal mode
• docker run -e runs an image with an environment variable
• docker run -net specify a docker network to run within
• docker start start a container, retains the settings from the run command
• docker stop - stops a container
• docker ps shows running containers
• docker ps -a shows running and not-running containers
• docker logs shows the standard output of the running container
• docker logs -f follow the standard output, similar to tail -f
• docker exec -it runs the container with interactive terminal
• docker network ls shows a list of the internal docker network
• docker network create create a docker network
• docker build -t my-app:1.0 . builds an image from a Dockerfile in the current directory
• docker rm removes a docker container which you need to do before docker rmi
• docker rmi removes a docker image, i.e. docker rmi my-app:1.0
• docker run -v mounts host filesystem to docker container filesystem

Docker Compose

• docker-compose -f mongo.yaml up pulls, starts, and creates container network
• docker-compose -f mongo.yaml up -d runs containers in detached mode
• docker-compose -f mongo.yaml down stops container, removes container, and stops container network

First Dockerfile

FROM python:3.9-alpine3.13

RUN apk add bash nodejs

COPY hello.* /

CMD ["bash"]

First commands

• docker build . builds the container
• docker run --name [name] [sha] installs the container
• docker run -it --name [name] [sha] installs the container and starts in interactive mode
• docker ps shows all the running containers
• docker ps -a shows all the running and exited containers
• docker stop [name] stop container
• docker start -ai [name] start container interactively
• docker rm [name] removes container

Resources

• Creating your first Dockerfile, image and container great place to start
• Docker Tutorial for Beginners [FULL COURSE in 3 Hours] most helpful
• Docker For Beginners: From Docker Desktop to Deployment

Related Resources

• Kubernetes Tutorial for Beginners FULL COURSE in 4 Hours To manage distribution of contains across many servers

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