Card 05/ 05
Recap: What a Container Is
One shared kernel, a read-only image, and a writable layer per container, with where each was.
What a container is comes down to the four ideas below, each listed with the card that covers it.
| The idea | Where |
|---|---|
| A container is a process on the host's kernel, with its own view of files, processes and network | Containers and the Host Kernel |
| Nothing boots, so a container starts in milliseconds and a virtual machine in tens of seconds | Containers vs Virtual Machines |
| An image is a read-only stack of layers; a container adds a writable layer and a process | Images and Containers: What Each One Holds |
| Each container has its own writable layer, so containers from one image share nothing they write | Images and Containers Example: One Image, Three Containers |
Most of what follows in Docker builds on the last two ideas: because a container is cheap to start and to remove, you treat it as disposable, and you keep anything that matters in the image or outside the container.
← → move through sections and cards