Building and Running Containers

Once you've written a Dockerfile, the next step is building an image and running a container from it.

Build an Image

Use the following command:

docker build -t my-app:v1 .

Explanation:

Option	Description
build	Build an image
-t	Assign a tag
.	Current directory

Verify the image exists:

docker images

Example output:

REPOSITORY   TAG   IMAGE ID
my-app       v1    abc123

Run a Container

Launch a container:

docker run my-app:v1

Docker creates a new container from the image.

Port Mapping

Most web applications require port forwarding.

Example:

docker run -p 8080:3000 my-app:v1

This maps:

Host Port      Container Port
8080     ->    3000

You can now access the application at:

http://localhost:8080

Detached Mode

Run containers in the background:

docker run -d my-app:v1

Docker returns a container ID.

View running containers:

docker ps

Naming Containers

Assign a friendly name:

docker run --name web-app my-app:v1

Instead of using container IDs, you can reference the container by name.

Stopping Containers

Stop a running container:

docker stop web-app

Removing Containers

Delete a container:

docker rm web-app

Remove all stopped containers:

docker container prune

Viewing Logs

Display container output:

docker logs web-app

Follow logs in real time:

docker logs -f web-app

Executing Commands Inside Containers

Open a shell:

docker exec -it web-app sh

Or:

docker exec -it web-app bash

depending on the image.

Summary

Building images and running containers are the two most common Docker operations. Mastering these commands forms the foundation of daily Docker usage.