Docker Guide

Understanding Dockerfile, Creating Images, DockerIgnore | Docker series in Nepali | EverydayKarma

config→ image(environment or template)→ container

Sample docker config file (Dockerfile)

FROM "node:21-alpine"
WORKDIR /app
COPY . .
CMD ["npm","run","start"]

After server and .node_modules are created

FROM "node:21-alpine"
WORKDIR /app
COPY package.json .
RUN npm install //install dependencies in docker env
COPY . .
CMD ["npm","run","start"]

Build image

docker build .

List docker images

docker images or docker image ls

Get ID of docker images

docker image ls -q

Remove docker image

docker rmi <IMAGE_ID> or docker image rm <IMAGE_ID>
docker rmi -f <IMAGE_ID> //forcefully removing image as sometimes container is running using the image

//to delete all image
docker image rm 234 2342 3423
//or
docker image rm $(docker image ls -q) //get all image id and delete

Remove docker container

docker rm <CONTAINER_ID>
docker container rm <CONTAINER_ID> //same as above

//similarly to remove all containers
docker container rm $(docker container ls -a -q)

Add tag name to image

docker build . -t mynode:1.0

Run docker image (containerize)

docker run <IMAGE_ID or NAME>:<VERSION> //eg: docker run mynode:1.0
//use -d to run in detached mode
docker run -d -p 5000:4000 2344254 //runnning in detached mode with port mapping

See container list

docker container ls //show only running container
docker ps //same command as above
docker container ls -a //to see all container
docker container ls -la //last active container

Get into docker image environment (i.e. operating system where our app is running). For this run docker image in interactive mode(it). This allows to access shell (generally bash in Linux) of used OS

docker run -it <IMAGE_ID or NAME> /bin/sh

Set environment (env) variable

docker run -e <NAME>=<VALUE> <IMAGE_ID> //eg docker run -e NODE_ENV="production" 35a80
docker run -e NODE_ENV="production" -e DB_NAME="trydb" 35a80

docker run --env-file=<ENV_LOCATION> <IMAGE_ID>//eg docker run --env-file=.env 35a80

NOTE: RUN command runs during image building whereas CMD commands runs after container is created

Map port of docker to local

docker run -p <LOCAL_PORT>:<DOCKER_PORT> 23421

Stop docker container

docker stop <CONTAINER_ID> or <NAME>
docker container stop <CONTAINER_ID> or <NAME>

.dockerignore file to list the files that should not be added in the docker

Login docker

docker login

Push image to dockerHub

docker push romanpoudel/imagename

Pull image to local

docker pull romanpoudel/imagename

Name the container

docker run -p 4000:4000 --name <NAME> romanpoudel/image

Stop container running

docker stop <unique id of image>e.g docker stop 234
docker kill werewr //this is to stop forcefully immediately

to write command in multiline for readability use backslash \ and hit enter. This is the feature of shell not docker.

Ignore data from cache

docker build --no-cache . -t romanpoudel/nodejs

💡 docker run -it vs docker exec -it: run is used when we want to use interactive mode *initially* when running image but exec is used when we want to have interactive mode on the *running* container.(`docker exec -it 32412 /bin/sh`)

Docker Compose (docker-compose.yml)

docker compose comes pre-installed with docker

docker-compose --version

sample yaml file

version: "3.8" //version of dockercompose
name: "main_container_of_compose"

services:
  web:
    image: "mero_image_from_compose"
    container_name: "mero_node_container"
    build:
      dockerfile: ./Dockerfile
    ports:
      -"4000:4000"
    depends_on:
      -db

  db:
    container_name: "mero_db_container"
    image: postgres
    environment:
      POSTGRES_DB: mydatabase
      POSTGRES_USER: myuser
      POSTGRES_PASSWORD: mypassword

Docker compose CMD

docker-compose up //this creates a running container
docker-compose build //to build image
docker-compose down

Docker volume

add -v or —version to sync vscode to docker and specify location i.e. -v $(pwd):/app

If you don’t want to synchronize some file then use -v location i.e. -v /app/node_modules

You can make separate file for development and production. In that case, you change the name of the file like Dockerfile.dev and Dockerfile. In this case, you can build the image as

docker build -t mynode:v1 -f Dockerfile.dev .

In this case it searches the file in . i.e. present directory.

See docker networks

docker network ps

Inspect container

docker inspect <CONTAINER_NAME>

Create separate network

docker network create <NAME>

Assigning network while running the container

docker run -d -p 4001:4000 --name <NAME> --network <NETWORK_NAME> mynode:v1

To run docker in host network, we should not mention port as it uses computer network by default. It is not supported by Mac and Linux for security reasons.

docker run -d --name mynodeapp --network host mynode:v1

Default type network is bridge network, it uses subnet address and bridge connects all the container to computer network.

Remove unused networks

docker network prune