Printing and PDF export are disabled for this content. View it online at Full Stack Learning Simplified.

Docker Images and Containers🌱 Beginner

The two core objects: you pull images from a registry and run them as containers. One image is a template; a container is a live, isolated instance of it.

Pull and run

bash

docker pull nginx              # download the image
docker run -d --name web -p 8080:80 nginx   # run as a background container
docker ps                      # list running containers

-d runs it detached (in the background), --name gives it a friendly name, and -p publishes a port. docker ps -a also shows stopped containers.

Image vs container

	Image	Container
Is	a read-only template	a running instance
Analogy	a class / blueprint	an object / running process
Count	one image	→ many containers
State	immutable	has a writable layer, can change

The container lifecycle

bash

docker run nginx        # create + start
docker stop web         # stop (still exists)
docker start web        # start it again
docker rm web           # remove it permanently

A stopped container still exists (and keeps its writable layer) until you rm it. Restarting resumes from where it was.

Layers

Images are built from stacked, cached layers. Multiple images sharing a base layer store it once, and pulling only downloads layers you don't already have — saving space and time.

Warning: Anything a container writes to its own filesystem is lost when it's removed. For data that must survive (databases, uploads), use a volume (its own chapter) — don't store important data inside the container.

Tip: Think of containers as disposable: destroy and recreate them freely from the image. This “cattle, not pets” mindset is central to Docker — keep state in volumes and configuration in environment variables, not baked into a running container.

Docker Container Takeaway: Volumes persist data outside the container filesystem lifecycle, preventing data loss when container instances restart.

Free preview. Sign in and subscribe to unlock all 982 lessons across 31 courses.

Printing and PDF export are disabled for this content. View it online at Full Stack Learning Simplified.

DockerDocker 29 Pro

Docker Images and Containers🌱 Beginner

The two core objects: you pull images from a registry and run them as containers. One image is a template; a container is a live, isolated instance of it.

Pull and run

bash

docker pull nginx              # download the image
docker run -d --name web -p 8080:80 nginx   # run as a background container
docker ps                      # list running containers

-d runs it detached (in the background), --name gives it a friendly name, and -p publishes a port. docker ps -a also shows stopped containers.

Image vs container

	Image	Container
Is	a read-only template	a running instance
Analogy	a class / blueprint	an object / running process
Count	one image	→ many containers
State	immutable	has a writable layer, can change

The container lifecycle

bash

docker run nginx        # create + start
docker stop web         # stop (still exists)
docker start web        # start it again
docker rm web           # remove it permanently

A stopped container still exists (and keeps its writable layer) until you rm it. Restarting resumes from where it was.

Layers

Images are built from stacked, cached layers. Multiple images sharing a base layer store it once, and pulling only downloads layers you don't already have — saving space and time.

Docker Container Takeaway: Volumes persist data outside the container filesystem lifecycle, preventing data loss when container instances restart.

Free preview. Sign in and subscribe to unlock all 982 lessons across 31 courses.