Containerization

What Is Containerization?

An introduction to containerization as a lightweight, OS-level virtualization technique for packaging and running applications with their dependencies.

Containers vs Virtual Machines

Containers and virtual machines both isolate applications, but a container shares the host operating system’s kernel and packages only the app plus its depende…

What is Docker?

Docker is a platform that packages an application together with its dependencies, libraries, and runtime into a lightweight, portable unit called a container,…

What is a Docker Image vs a Container?

A Docker image is a read-only, layered blueprint containing the application code, dependencies, and configuration, while a container is a running, writable ins…

What is a Dockerfile?

A Dockerfile is a plain-text script of sequential instructions that tells the Docker engine exactly how to assemble a Docker image, layer by layer.

How Do Docker Image Layers and Build Caching Work?

Each instruction in a Dockerfile produces an immutable, content-addressed image layer, and Docker’s build cache reuses a previously built layer whenever the in…

What is a Docker Multi-Stage Build?

A multi-stage Docker build uses multiple FROM instructions in one Dockerfile, where each stage can compile or prepare artifacts and only the final stage copies…

How Do Docker Volumes Persist Data?

Docker volumes are storage areas managed by the Docker engine, living outside any single container’s writable layer, so data written to a volume survives conta…

How Does Docker Networking Work?

Docker networking connects containers using virtual network drivers — most commonly the bridge driver, which creates an isolated virtual network on the host wh…

What is Docker Compose and When Do You Use It?

Docker Compose is a tool for defining and running multi-container applications from a single declarative YAML file, letting you start, stop, and network an ent…

What is the Difference Between ENTRYPOINT and CMD?

ENTRYPOINT defines the fixed, always-executed command a container runs, while CMD supplies default arguments to that command (or a default full command if no E…

What is the Difference Between Docker Bind Mounts and Volumes?

A Docker volume is storage fully managed by the Docker engine in its own dedicated area on disk, while a bind mount maps an arbitrary existing path on the host…

What is the Docker Build Context and Why Does It Matter?

The Docker build context is the set of files at a specified path (or URL) that the Docker client packages up and sends to the Docker daemon before a build star…

What Are the Key Principles of Container Security?

Container security means hardening every layer of the container lifecycle — the base image, the build process, the runtime configuration, and the host kernel —…

What is an Artifact Repository?

An artifact repository is a centralized, versioned storage system for the binary outputs of a build — such as compiled packages, Docker images, JAR files, or n…

What are cgroups and namespaces, and how do they power containers?

Linux namespaces give a process its own isolated view of system resources (PIDs, network, mounts, hostname, users, IPC), while cgroups (control groups) limit a…

How do container image layers work, and why do they matter for build speed?

A container image is a stack of read-only filesystem layers, each produced by one build instruction and identified by a content hash, that a union filesystem o…

What is the OCI Image Specification, and why does it matter?

The OCI (Open Container Initiative) Image Specification is a vendor-neutral standard that defines the exact format of a container image — its manifest, config,…

What is BuildKit, and how does it improve on the classic Docker builder?

BuildKit is Docker’s modern build engine that replaces the legacy sequential builder with a concurrent, dependency-graph-based system, enabling parallel execut…

What causes cache busting in Docker builds, and how do you avoid it?

Cache busting happens when a Dockerfile instruction’s cache key changes unexpectedly — usually because an earlier layer’s content changed, the instruction itse…