Docker Essentials
Introduction to Docker Containers
Docker is a powerful containerization technology that revolutionizes application deployment and management. Container technology enables developers to package applications with all their dependencies, ensuring consistent performance across different computing environments.
Core Concepts of Docker
Docker containers are lightweight, standalone, executable packages that include everything needed to run an application. They provide several key advantages:
Feature |
Description |
Isolation |
Containers run independently from host systems |
Portability |
Applications can be moved between different environments |
Efficiency |
Minimal resource consumption compared to traditional virtual machines |
Docker Architecture
graph TD
A[Docker Client] --> B[Docker Daemon]
B --> C[Container Runtime]
B --> D[Image Repository]
C --> E[Docker Containers]
Installation on Ubuntu 22.04
## Update package index
sudo apt update
## Install dependencies
sudo apt install apt-transport-https ca-certificates curl software-properties-common
## Add Docker's official GPG key
curl -fsSL | sudo gpg --dearmor -o /usr/share/keyrings/docker-archive-keyring.gpg
## Set up stable repository
echo "deb [arch=amd64 signed-by=/usr/share/keyrings/docker-archive-keyring.gpg] $(lsb_release -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
## Install Docker Engine
sudo apt update
sudo apt install docker-ce docker-ce-cli containerd.io
Basic Docker Commands
## Pull an image
docker pull ubuntu:latest
## List images
docker images
## Run a container
docker run -it ubuntu:latest /bin/bash
## List running containers
docker ps
## Stop a container
docker stop container_id
Creating a Simple Dockerfile
## Use official Ubuntu base image
FROM ubuntu:22.04
## Set working directory
WORKDIR /app
## Install Python
RUN apt-get update && apt-get install -y python3
## Copy application files
COPY . /app
## Define default command
CMD ["python3", "app.py"]
Container Networking
Docker provides multiple networking modes for containers, allowing flexible communication between containers and external networks. Developers can choose bridge, host, or custom network configurations based on specific requirements.
Docker containers offer efficient resource utilization by sharing the host system's kernel and requiring minimal overhead. They consume significantly less memory and startup time compared to traditional virtual machines.