Docker

Video

Docker conatiner lifecycle

Core Distinctions

Pro Tip: Use docker run for new instances and docker start to resume work on an existing container to preserve file changes not saved in a volume.

When to use which?

1. run: Your "Go-To" for launching a service for the first time.
2. start: When you've previously stopped a container with docker stop and want it back.
3. restart: Best for clearing memory leaks or applying config changes.
4. unpause: Best for ultra-fast resumption without the overhead of a full boot cycle.

Run new docker image

docker run -d -p 49161:1521 -p 5000:8080 -v db-vol:/opt/oracle/oradata oracleinanutshell/oracle-xe-11g

• -d: Run images in detach mode
• -p: Port mapping from container port 8080 to client port 5000
• -v: Mount data volume

Command

Image management

docker image inspect: See image info

docker image prune: Delete unsed images

docker rmi <image_id>: Remove image from local storage

docker build -t <name> .: Create a custom image from a Dockerfile in your current directory.

Container management

docker ps -a: List all container

docker rm: Delete a stopped container

docker kill <container_id>: Force stop the container

docker stop <container_id>: Stop the container

Clean up

docker system df: Amount of storage docker used

docker system prune: Removes all stopped containers, unused networks, and dangling images.

Dockerfile

Dockerfile

Instructions for Docker to build an image

Here's a simple Dockerfile

FROM python:3.13.12-slim
 
COPY . /app
WORKDIR /app
 
 
RUN python3 -m venv /opt/venv
 
RUN /opt/venv/bin/pip install pip --upgrade && \
    /opt/venv/bin/pip install -r requirement.txt && \
    chomod +x entrypoint.sh
 
CMD ["/app/entrypoint.sh"]

Let's break down this Dockerfile

FROM: Create a new build stage from a base image

COPY: Copy files and directories

When you use ./, you are telling Docker explicitly that the destination must be a directory.

• With the slash ./: If the directory /app (your WORKDIR) somehow doesn't exist or there is an error, Docker knows you intended to put files inside a folder.

• Without the slash .: If you were copying a single file and the destination didn't exist, Docker might rename your file to the name of the destination instead of putting it inside the folder.

WORKDIR: This just changes the directory

RUN: Execute build commands.

CMD: Command to be executed when running a container from an image.

Run docker image

Run with .env file

docker run --env-file .env -p 3000:3000 your-image

Tips

• Use node:20-alpine for lightest weight and secure nodejs's dockerization

• Most instructions in a Dockerfile (RUN, COPY, ADD) create a new, immutable layer

Compose file

compose file

Used to configure your Docker application’s services, networks, volumes, and more.

docker-compose.yaml

services:
  api:
    build:
      context: .
      dockerfile: Dockerfile
    environment:
      - NODE_ENV=development
    env_file:
      - .env.local
    ports:
      - "4000:4000"
 

Run compose

docker compose up