In this lecture, Harkirat covers several key concepts and features of Docker that are essential for building and managing containerized applications. Through the lecture he explains layers
for efficient image storage and caching, networks
for secure container communication, volumes
for data persistence.
In Docker, layers are a fundamental part of the image architecture. A Docker image is essentially built up from a series of layers, each representing a set of differences from the previous layer. These layers are stacked on top of each other, forming the complete image.
RUN
, COPY
, ENV
, and others, which modify the filesystem by installing packages, copying files from the host to the container, setting environment variables, or making other changes. Each of these modifications creates a new layer on top of the previous layer.Here's an example of how layers are created in a Dockerfile:
# Base layer
FROM ubuntu:20.04
# Instruction layer 1
RUN apt-get update && apt-get install -y python3
# Instruction layer 2
COPY . /app
# Instruction layer 3
RUN pip3 install -r /app/requirements.txt
In this example, each RUN
and COPY
instruction creates a new layer on top of the previous one.
The layered architecture of Docker images provides several benefits: