Run Container From a Public Docker Image¶

Before we create our own Docker image, let's see how we can use publicly available Docker images to run containers.

Docker Hub is one of the public registries you can use to download the official images for many popular services such as Nginx, MySQL, MongoDB, Redis, Node.js, Java, Python, etc.. These images are created either by the companies that developed these services or by the Docker community.

List Images and Containers¶

Execute the following Docker CLI commands to view images and containers on your host.

List Docker Images:

docker images

List Docker Containers:

docker ps -a

You can also use the Docker Desktop GUI to view the images and containers on your host.

At this point, you will see that you don't have any images or containers.

Run an Nginx Container¶

You can go to Docker Hub Explore Page and search for the images that you want to use.

Execute the following command to run an Nginx container:

docker run nginx

The command above runs the container in the foreground and stream the container logs. You can press Ctrl+C to exit but the container will stop.

To avoid that, you can use --detach or -d option to run the container in the background.

docker run -d nginx

docker run -d <image-name>:<image-tag>

docker run -d --name my-nginx-container nginx:latest

List Containers¶

List only running containers:

docker ps

You can use --all or -a option to show all containers, Running or Stopped:

docker ps -a

You can use --quiet or -q option to display only the container IDs:

# List running container IDs
docker ps -q

# List all container IDs
docker ps -a -q

Stop a Container¶

# Stop container using ID
docker stop <container-id>

{OR}

# Stop container using name
docker stop <container-name>

Start a Stopped Container¶

# Start container using ID
docker start <container-id>

{OR}

# Start container using name
docker start <container-name>

Execute a Command in the Running Container¶

The docker exec command runs a new command in a running container. The command runs in the default directory of the container.

1. Execute a command in a running container without starting a shell session:

   # List files and directories
   docker exec -it <container-name/container-id> ls
   

2. Start a shell session in the container:

   docker exec -it <container-name/container-id> sh
   {OR}
   docker exec -it <container-name/container-id> bash
   

   Difference between sh and bash

   bash and sh are two different shells in the Unix operating system. bash is an extended version of sh with additional features and improved syntax.

   Once the shell session is started, you can interact with the container just like you would with your own machine. You can run shell commands like ls, pwd, or any other desired commands.

   In our case since the container is running Nginx, we can request the default nginx page as follows:

   curl localhost
   

   You can also view the nginx configuration files and default Html page that is served:

   # View nginx configuration file
   cd /etc/nginx/conf.d
   cat default.conf
   
   # View the content of the default Html page that Nginx serves
   cat /usr/share/nginx/html/index.html
   

Port Mapping¶

In the previous section we learned how to access the application from within the container. But, how do you access the application running inside the container from outside?

You can use Port Mapping to make the processes inside the container available from the outside.

docker run -d --name nginx -p 81:80 nginx:latest

In the above command, we are creating the nginx container in detached mode and using the -p option to map port 80 of the container, where Nginx is running, to port 81 on the host.

Once the container is up and running, you can open any browser on your local machine and access the Nginx application running in the container by visiting localhost:81.

View Container Logs¶

docker logs -f <container-id/container-name>

Delete a Container¶

# Delete container using ID
docker rm <container-id>

{OR}

# Delete container using name
docker rm <container-name>

Delete All Stopped Containers¶

What if you have multiple stopped containers and you want to delete all of them in a single command?

You can use the following command to delete all stopped containers:

docker container prune

Delete an Image¶

You can use the following commands to delete Docker images:

# Delete image using image ID
docker rmi <image-id>

{OR}

# Delete image using image name and tag
docker rmi <image-name>:<image-tag>

Delete All Unused Images¶

You can use the following command to remove all images on your Docker host that are not associated with a container:

docker image prune -a

Clean Up¶

You can use the following command to perform a comprehensive cleanup of your Docker system. It removes not only unused containers and images but also associated volumes:

docker system prune -a --volumes