Docker Container Operations: Creating, Starting, Stopping, and Managing Containers

Docker containers are lightweight, isolated environments that run applications and their runtime dependencies, distinct from full virtual machines. Managing containers involves creating, starting, stopping, and removing them using Docker commands.

Starting Containers

To launch a new container, use docker run with the desired image, for example:

$ docker run ubuntu:14.04 /bin/echo 'Hello world'

To start an existing stopped container, run docker container start <container_name>.

Background Execution

Running a container in the background (detached mode) is achieved with the -d flag:

$ docker run -d ubuntu:17.10 /bin/sh -c "while true; do echo hello world; sleep 1; done"

Output from a detached container is not shown on the host terminal; it can be retrieved later with docker container logs <id_or_name>.

Interacting with Running Containers

The docker attach command re‑attaches to a container’s primary process, but exiting the attached shell will stop the container. Instead, the recommended approach is docker exec, which runs a new command inside a running container without affecting its lifecycle. Example:

$ docker exec -it 1f1b0 bash
root@1f1b0:/# ps
root@1f1b0:/# exit

Viewing Logs

Container output can be inspected with:

$ docker container logs <container_id_or_name>

Exporting and Importing Containers

Export a container’s filesystem to a tar archive:

$ docker export <container_id> > ubuntu.tar

Import the tar file as a new image:

$ cat ubuntu.tar | docker import - test/ubuntu:latest

Removing Containers

Delete a stopped container with docker container rm <name>. To force‑remove a running container, add -f. All stopped containers can be cleaned up using: $ docker container prune The guide concludes with references and author contact information.