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Docker🔗

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Installation🔗

# Add Docker's official GPG key:
sudo apt update
sudo apt install ca-certificates curl
sudo install -m 0755 -d /etc/apt/keyrings
sudo curl -fsSL https://download.docker.com/linux/debian/gpg -o /etc/apt/keyrings/docker.asc
sudo chmod a+r /etc/apt/keyrings/docker.asc

# Add the repository to Apt sources:
echo \
  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/debian \
  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt update

sudo apt install docker-ce docker-ce-cli containerd.io

# managing docker as non root user
$USER=smk
sudo groupadd docker
sudo usermod -aG docker $USER
newgrp docker # refresh group

# test docker run hello-world
# NOTE : fix .docker dir due to previous root runs if you get config errors
sudo chown "$USER":"$USER" /home/"$USER"/.docker -R
sudo chmod g+rwx "$HOME/.docker" -R

Essential Commands🔗

Category Command Description
Containers docker run -d -p 80:80 ngnix Run Container in background
docker stop <container> Stop container
docker logs -f <container> Follow logs
Images docker build -t myapp:latest . Build from Dockerfile
docker pull ubuntu:22.04 Download image
docker image prune Remove unused images
System docker ps -a List all containers
docker system df Show disk usage
docker exec -it <id> bash Enter running container

Docker Compose Setup🔗

Sample docker-compose.yml

version: '3.8'  
services:  
  web:  
    image: nginx:alpine  
    ports:  
      - "80:80"  
    volumes:  
      - ./html:/usr/share/nginx/html  
  db:  
    image: postgres:15  
    environment:  
      POSTGRES_PASSWORD: example

Run with:

docker compose up -d

Cleanup🔗

docker system prune -a --volumes  # Remove all unused data

Debugging🔗

docker inspect <container>  # Show detailed config

Security🔗

docker scan nginx:alpine  # Vulnerability check

Security Best Practices🔗

  • Avoid using --privileged flag
  • Use non-root users in containers
FROM alpine
RUN adduser -D appuser && chown appuser /app
USER appuser
  • Limit Resources
docker run --memory=512m --cpus=1.5 myapp

Resources🔗

Installing Portainer🔗