How to start a stopped Docker container?

Introduction

Docker containers have become an essential part of modern software development and deployment. In this tutorial, we will guide you through the process of restarting a stopped Docker container, ensuring your applications remain available and responsive.

Skills Graph

Introduction to Docker Containers

Docker is a powerful open-source platform that enables developers to build, deploy, and run applications in a containerized environment. Containers are lightweight, standalone, and executable software packages that include everything needed to run an application, including the code, runtime, system tools, and libraries.

Docker containers provide a consistent and predictable environment for applications, ensuring that they will run the same way regardless of the underlying infrastructure. This makes it easier to develop, test, and deploy applications, as well as to scale them up or down as needed.

To get started with Docker, you first need to install the Docker engine on your system. This can be done by following the official installation guide for your operating system, such as Ubuntu 22.04. Once installed, you can use the docker command-line tool to manage your containers.

Here's an example of how to create and run a simple Docker container using the docker run command:

$ docker run -it ubuntu:22.04 /bin/bash

This command will pull the Ubuntu 22.04 image from the Docker Hub registry, create a new container based on that image, and start a Bash shell inside the container. You can then use the Bash shell to interact with the container and run your application.

Overall, Docker containers provide a powerful and flexible way to develop, deploy, and manage applications, making it easier to ensure consistent and reliable environments across different systems and platforms.

Stopping and Restarting Docker Containers

Stopping Docker Containers

To stop a running Docker container, you can use the docker stop command followed by the container's ID or name. For example:

$ docker stop my-container

This will gracefully stop the container, allowing it to perform any necessary cleanup tasks before shutting down.

If you need to force a container to stop immediately, you can use the docker kill command instead:

$ docker kill my-container

This will immediately terminate the container's main process, without allowing it to perform any cleanup.

Restarting Docker Containers

To restart a stopped Docker container, you can use the docker start command followed by the container's ID or name. For example:

$ docker start my-container

This will start the container using the same configuration and state it had when it was stopped.

If you need to restart a running container, you can use the docker restart command:

$ docker restart my-container

This will stop the container and then start it again.

You can also use the docker run command to create and start a new container. If the container you're trying to start already exists, Docker will start the existing container instead of creating a new one.

By understanding how to stop and restart Docker containers, you can effectively manage the lifecycle of your applications and ensure they are running as expected.

Hands-on: Restarting a Stopped Docker Container

In this section, we'll walk through the steps to restart a stopped Docker container.

Step 1: Create a Docker container

First, let's create a new Docker container based on the Ubuntu 22.04 image:

$ docker run -d --name my-container ubuntu:22.04 /bin/bash -c "while true; do echo 'LabEx is awesome!'; sleep 5; done"

This command will create a new container named my-container and run a simple script that prints "LabEx is awesome!" every 5 seconds.

Step 2: Stop the container

Now, let's stop the running container:

$ docker stop my-container

Step 3: Restart the container

To restart the stopped container, use the docker start command:

$ docker start my-container

This will start the container again, and you should see the "LabEx is awesome!" message being printed to the console.

Verifying the container status

You can use the docker ps command to list all running containers, and the docker ps -a command to list all containers, including stopped ones.

$ docker ps -a
CONTAINER ID   IMAGE         COMMAND                  CREATED         STATUS                     PORTS     NAMES
9e5a4d9a1a2f   ubuntu:22.04  "/bin/bash -c 'while t…"  2 minutes ago   Up 9 seconds                         my-container

As you can see, the my-container is now in the "Up" status, indicating that it has been successfully restarted.

By following these steps, you have learned how to restart a stopped Docker container. This knowledge will be useful when managing the lifecycle of your Docker-based applications.

Summary

By following the steps outlined in this tutorial, you will learn how to easily start a stopped Docker container and resume your application's operations. This knowledge will help you effectively manage your Docker-based infrastructure and maintain the reliability of your deployments.