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Running Containers (Hands-on Basics)

This article is hands-on. You will pull images and run containers. No Dockerfile yet.

Step 1: Confirm Docker works​

docker version

What you see:

  • Client section
  • Server section

If Server is missing, Docker Engine is not running.

Step 2: Pull an image​

docker pull hello-world

What you see (sample):

Using default tag: latest
latest: Pulling from library/hello-world
Digest: sha256:...
Status: Downloaded newer image for hello-world:latest

What this means:

  • Docker downloaded the image locally
  • Image is now available to run

Step 3: Run a container​

docker run hello-world

What you see:

  • a message printed by the container
  • then it exits

Important:

  • A container is a process.
  • This process finished, so the container stopped.

Step 4: List running containers​

docker ps

What you see:

  • probably nothing (hello-world already exited)

Step 5: List all containers (including stopped)​

docker ps -a

What you see (sample):

CONTAINER ID   IMAGE         COMMAND    STATUS                     NAMES
a1b2c3d4e5f6   hello-world   "/hello"   Exited (0) 10 seconds ago   gifted_panini

What this means:

  • The container exists (metadata)
  • It is not running

Step 6: Run an interactive container​

docker run -it alpine:latest sh

What you see:

  • you get a shell prompt inside the container

Try:

uname -a
cat /etc/os-release
ls -la

Exit:

exit

What happens:

  • container stops when the main process ends

Step 7: Run in detached mode​

docker run -d --name web nginx:alpine

What you see:

  • a long container id

Check it is running:

docker ps

Sample output:

CONTAINER ID   IMAGE         STATUS          NAMES
8f1c...        nginx:alpine  Up 10 seconds   web

Step 8: View logs​

docker logs web

What you see:

  • nginx startup logs

Logs come from stdout/stderr of the container process.

Step 9: Execute a command inside a running container​

docker exec -it web sh

Try:

nginx -v
ls -la /usr/share/nginx/html
exit

Step 10: Stop and remove containers​

Stop:

docker stop web

Remove:

docker rm web

Verify:

docker ps -a

Step 11: Clean up stopped containers (optional)​

docker container prune

What you see:

  • a list of removed containers
  • reclaimed space

Step 12: Images on your machine​

docker images

Sample output:

REPOSITORY    TAG      IMAGE ID       SIZE
nginx         alpine   123456789abc   20MB
alpine        latest   987654321def   7MB
hello-world   latest   111111111111   13kB

Remove an image (only if no containers depend on it):

docker rmi hello-world

Quick mental model​

  • docker pull downloads an image
  • docker run creates + starts a container
  • docker ps shows running containers
  • docker ps -a shows all containers
  • docker logs shows output
  • docker exec runs commands in a running container
  • docker stop stops a container process
  • docker rm removes container metadata