Docker

Installation

• TODO

docker without sudo

sudo groupadd docker 
sudo gpasswd -a $USER docker 
newgrp docker 

centos

sudo yum remove docker docker-engine docker.io containerd runc

sudo yum install -y yum-utils
sudo yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
sudo yum install docker-ce docker-ce-cli containerd.io

systemctl start docker
systemctl status docker
systemctl stop docker

CLI

• see the docker images

  docker images

• remove one image

  docker rmi <image-name>

• run a docker container

  docker run --name <container-name> -d <image-name>

  flag --rm is used to remove the container after it stops.

• stop a docker container forcefully

  docker kill <container-id>

• see the running container

  docker ps

• see all running and stoped containers

  docker ps -a

• remove stoped docker containers

  docker container prune

• remove all docker containers (running and stoped) forcefully

  docker rm -vf $(docker ps -aq)

• remove all docker images:

  docker rmi -f $(docker images -aq)

• transfering files between host and container (VERY PRACTICAL)

docker cp container:path/in/container host_path

docker cp host_path container:path/in/container

• remove docker cache and danglings (can be very huge sometimes)

  docker system prune

• store pulled images on your machine in file for transfering

  docker save -o <save-location>/<file-name>.tar <image-name>

• load image from file to machine

  docker load -i <image-file-path>.tar

Volumes

• always try to give name to your volumes to be easier later that you want to delete the specific volumes.

• default volumes path is /var/lib/docker/volumes

• when you specify volumes in docker-compose below form saved in default path

  volumes:
      <volumename1>:
      <volumename2>:
  

in docker volume mounting it is possible that does not work correctly and you lose your data! because default mode in docker volume plugging is :mrw that contains mknod that cause unauthorized not accessible, so you should specify :rw to remove mknod mode.

Dockerfile COPY vs Running with volume

• you can use and it is recommended to use from volume for TEST & DEVELOPMENT BUT NOT for PRODUCTION.

Dockerfile CMD vs docker-compose command:

• you can have both or just one of them
• if you have both command: overrides the CMD command

Network

Default

• docker in default running usually up to one bridge network that has from first in installation.

after installation docker your system add to a new network adapter (subnet), that you may see your ip in the hostanme -I command!

Bridge

• while container wants to talk with each other you can put them in a bridge network and for connection ip you can simply use from the docker container name!
  • consider that port is original docker container port not the port-mapping (port-mapping is used for network host mode)

Access to Host machien from Container

IN BRIDGE MODE YOU CAN ACCESS TO THE DOCKER CONTAINER FROM YOUR HOST, BUT YOU CANNOT ACCESS TO THE HOST FROM DOCKER CONTAINER, SO YOU SHOULD DO THIS

• add this to docker-compose.yaml

  extra_hosts:
      - "host.docker.internal:host-gateway"

  • or run docker by flag

    docker run --add-host host.docker.internal:host-gateway

• now you can access to host machine from container by

  ping host.docker.internal

Dockerfile

• try to always have Dockerfile in parent of all files.

• use from Dockerfile.purpose naming convention to be convenient! (ex: Dockerfile.dev)

• you cannot address the parent directory in the Dockerfile:

  COPY ../file.txt /app/file.txt # this is wrong

• comment

  # this is comment

• copy file from host to container

  COPY <host-path>  <container-path>

• base image

  FROM <image-name>:<image-version>

• set working directory of container

  WORKDIR <path-in-container>

• container os environment variable

  ENV <var-name>=<var-value>

• run shell command

  RUN <shell-command>

• run command with running container

  CMD [ '<command>', '<arg1>', '<arg2>' ]

  ENTRYPOINT [ '<command>', '<arg1>', '<arg2>' ]

docker-compose.yaml

docker compose up

when you shut down this you just stoped it for removing completely you should run below:

docker compose down

docker compose up -d

docker compose down

!!!DONT WRITE THE VOLUME AND THE DOCKERFILE CONFIGS (COPY COMMANDS) IN SAME DIRECTORY!!!

this is RIDICULOUS ALTHOUGH :)

• writing docker-compose

# this is comment
version: <version>

networks:
    <network-name>:
        driver: <network-type>

volumes:
    <volume-name>:

services:
    <service-name>:
        image: <image-address>
        depends_on: <dependencies>
        build: <dockerfile-path>
        deploy: <deploy-config>
        ports: <port-mapping>
        restart: <restart-policy>
        networks: <networks>
        environment: <environment-variables>
        volumes: <volumes-mapping>
        container_name: <container-name>

• docker-compose.yml example

# this is comment
version: '3.8'

services:
  postgres-db:
    image: postgres:15
    container_name: app-db
    restart: always
    environment:
      POSTGRES_USER: myuser
      POSTGRES_PASSWORD: mypassword
      POSTGRES_DB: mydb
    volumes:
      - db_data:/var/lib/postgresql/data
      - ./files:/files
    networks:
      - backend
    ports:
      - "5432:5432"
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U myuser"]
      interval: 5s
      timeout: 5s
      retries: 5

  webapp:
    build:
      context: ./webapp
      dockerfile: Dockerfile
    container_name: app-web
    restart: on-failure:3
    ports:
      - "3000:3000"
    environment:
      DB_HOST: db
      DB_USER: myuser
      DB_PASS: mypassword
      DB_NAME: mydb
    depends_on:
      postgres-db:
        condition: service_healthy
    networks:
      - backend
      - frontend

volumes:
  db_data:
  redis_data:

networks:
  backend:
  frontend:

Registry

• add image to registry:

  sudo docker tag <image-name> <your-registry-address>/<image-name>
  sudo docker push <your-registry-address>/<image-name>

docker swarm

• DONT USE DOCKER SWARM IF YOU CAN USE ANY OTHER APPROACHE!

• CONNECTING 2 DOCKER ON 2 SERVER IS NOT THAT MUCH SIMPLE THAT I WAS THINKING! :/
• first sync the dates!!!
• SOMETIMES YOU SHOULD REMOVE THE WHOLE SWARM TO GET RID OF SOME PROBLEMS!
• MORE THAN 2 CORE WAS REQUIRED!
• BE CAREFUL ABOUT THE /etc/docker/daemon.json
• FLAG --detach=false HELPS YOU TO SEE MORE LOGS!
• i dont know why should i run this manually!: export $(cat .env)

• initialize the first server

docker swarm init

• docker swarm join

docker swarm join --token <token> <manager-ip>:2377

• deploy a docker compose on an network!

docker stack deploy -c docker-compose.yml my-stack

• check the stack status

docker stack services my-stack

• remove the stack

docker stack rm stack_name

• remove the service

docker service rm sercie_name

• see the logs

docker service logs service_name

• SEE THE PROCESS OF SERVICE

docker service ps service_name

• check swarm status (even worker node)

docker info

• docker all services

docker service ls