Container development

A container is a portable package: code, runtime, libraries, and settings. It shares the host kernel, so it starts fast and uses fewer resources than a full VM.

Main pieces

• Image — the immutable package you build and ship.
• Runtime — starts and stops containers (e.g. Docker, containerd).
• Registry — where images are stored and pulled from.
• Orchestration — schedules many containers in production (e.g. Kubernetes).

Containers vs VMs

• Containers isolate processes; VMs isolate hardware with a guest OS.
• Containers are lighter and denser; VMs give stronger isolation.
• Containers start in seconds; VMs often take longer to boot.

Namespaces

Linux namespaces give containers their isolation: process IDs, network, mounts, users, and more. That is why the same image can run predictably on different hosts.