Container states (created, running, paused, stopped) in Docker - Commands & Configuration

Introduction

Containers are like small packages that hold your app and everything it needs. They can be in different states like created, running, paused, or stopped, which tells you what the container is doing right now.

When you want to start an app inside a container and check if it is running properly

When you need to pause a container temporarily without stopping it completely

When you want to stop a container to save resources but keep its data intact

When you create a container but want to start it later

When you want to see the current status of your containers to manage them

Commands

This command creates a container named 'example-container' from the nginx image but does not start it yet. It is in the 'created' state.

Terminal

docker create --name example-container nginx

Expected Output

a1b2c3d4e5f6g7h8i9j0k1l2m3n4o5p6q7r8s9t0u1v2w3x4y5z6

→

--name - Assigns a custom name to the container for easy reference

This command starts the container named 'example-container', changing its state from 'created' to 'running'.

Terminal

docker start example-container

Expected Output

example-container

This command pauses the running container, freezing its processes temporarily without stopping it.

Terminal

docker pause example-container

Expected Output

No output (command runs silently)

This command resumes a paused container, returning it to the 'running' state.

Terminal

docker unpause example-container

Expected Output

No output (command runs silently)

This command stops the running container, changing its state to 'exited'. The container is not removed and can be started again.

Terminal

docker stop example-container

Expected Output

example-container

This command lists all containers including stopped ones, filtering by name 'example-container' and showing their current status.

Terminal

docker ps -a --filter "name=example-container" --format "{{.Names}} {{.Status}}"

Expected Output

example-container Exited (0) 5 seconds ago

→

-a - Show all containers, including stopped ones

→

--filter - Filter containers by name

→

--format - Customize the output format

Key Concept

If you remember nothing else from this pattern, remember: container states tell you exactly what your container is doing and help you control its lifecycle.

Common Mistakes

Trying to start a container that is already running

Docker will return an error because the container is already in the running state

Check the container state with 'docker ps' before starting it

Pausing a container that is not running

You can only pause containers that are running; otherwise, Docker will error

Ensure the container is running before pausing it

Stopping a container that is already stopped

Docker will return an error or no effect because the container is not running

Use 'docker ps -a' to check container status before stopping

Summary

Create a container with 'docker create' to prepare it without running.

Start the container with 'docker start' to run your app inside it.

Pause and unpause containers to temporarily freeze and resume processes.

Stop containers with 'docker stop' to end their running state but keep them for later use.

Use 'docker ps -a' with filters to check container states anytime.