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Pulling and running a container from Docker Hub

After installing Docker, you can verify your installation by running a container from Docker Hub. Docker Hub is service that allows you to store and share containers. When building your own container, you will usually start from a a pre-existing container. For example, the Ubuntu Docker page on Docker Hub hosts official Ubuntu operating system containers. These are minimal installations of Ubuntu you can customize to build a new container, without installing an operating system.

Tip

Docker Hub hosts Official Images, which are generally more secure than unverified images (anyone with a Docker Hub account can host and image). Official images are also more likely to be configured correctly.

We will test your installation by pulling and running the “Hello World” image:

  1. Run the following command:
docker run hello-world

You will get the following output if Docker is installed and configured successfully:

Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
1b930d010525: Pull complete
Digest: sha256:5f179596a7335398b805f036f7e8561b6f0e32cd30a32f5e19d17a3cda6cc33d
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (amd64)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/
  1. As suggested, we can run an instance of Ubuntu using the following command. Notice, we explicitly retrieve the container, use the -it (interactive) option and start the bash shell within the container:
docker run -it ubuntu bash

Try a few commands; you can use the exit command to exit the container.

  1. You can see a list of container images you have downloaded to your computer using the info command:
docker images
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
ubuntu              latest              d131e0fa2585        2 weeks ago         102MB
hello-world         latest              fce289e99eb9        4 months ago        1.84kB
  1. You can see the status of your containers using the using the ps command:
docker ps

CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

In this case, no containers are running.

  1. Let’s try a more complex container - using this command we will pull a container running RStudio

    docker run -e PASSWORD=<YOUR_PASS> -p 8787:8787 rocker/rstudio
    
    # -e passes an environment variable - change <YOUR_PASS>, e.g. 12345
    # -p maps a port inside the docker container to one on the host machine
    
You will now have an RStudio instance running at port 8787 of your computer. To access open a web browser and go to your machine’s IP address + “:8787” (this will generally be 127.0.0.1:8787). Username will be “rstudio” and password will be whatever you chose in the command above

Tip

A full list of Docker commands and their explanation can be found here: Docker child commands.


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