If this is your first time here, you might find the previous tutorials quite useful, here are the links below:
How To Install and Use Docker on Ubuntu 16.04
How To Install and Use Docker on Ubuntu 16.04 – Part 2 and 3
Step 4 — Working with Docker Images
Docker containers are run from Docker images. By default, it pulls these images from Docker Hub, a Docker registry managed by Docker, the company behind the Docker project. Anybody can build and host their Docker images on Docker Hub, so most applications and Linux distributions you’ll need to run Docker containers have images that are hosted on Docker Hub.
To check whether you can access and download images from Docker Hub, type:
docker run hello-world
The output, which should include the following, should indicate that Docker in working correctly:
Hello from Docker. This message shows that your installation appears to be working correctly. ...
You can search for images available on Docker Hub by using the
docker command with the
search subcommand. For example, to search for the Ubuntu image, type:
docker search ubuntu
The script will crawl Docker Hub and return a listing of all images whose name match the search string. In this case, the output will be similar to this:
NAME DESCRIPTION STARS OFFICIAL AUTOMATED ubuntu Ubuntu is a Debian-based Linux operating s... 3808 [OK] ubuntu-upstart Upstart is an event-based replacement for ... 61 [OK] torusware/speedus-ubuntu Always updated official Ubuntu docker imag... 25 [OK] rastasheep/ubuntu-sshd Dockerized SSH service, built on top of of... 24 [OK] ubuntu-debootstrap debootstrap --variant=minbase --components... 23 [OK] nickistre/ubuntu-lamp LAMP server on Ubuntu 6 [OK] nickistre/ubuntu-lamp-wordpress LAMP on Ubuntu with wp-cli installed 5 [OK] nuagebec/ubuntu Simple always updated Ubuntu docker images... 4 [OK] nimmis/ubuntu This is a docker images different LTS vers... 4 [OK] maxexcloo/ubuntu Docker base image built on Ubuntu with Sup... 2 [OK] admiringworm/ubuntu Base ubuntu images based on the official u... 1 [OK] ...
In the OFFICIAL column, OK indicates an image built and supported by the company behind the project. Once you’ve identified the image that you would like to use, you can download it to your computer using the
pull subcommand, like so:
docker pull ubuntu
After an image has been downloaded, you may then run a container using the downloaded image with the
run subcommand. If an image has not been downloaded when
docker is executed with the
run subcommand, the Docker client will first download the image, then run a container using it:
docker run ubuntu
To see the images that have been downloaded to your computer, type:
The output should look similar to the following:
REPOSITORY TAG IMAGE ID CREATED SIZE ubuntu latest c5f1cf30c96b 7 days ago 120.8 MB hello-world latest 94df4f0ce8a4 2 weeks ago 967 B
As you’ll see later in this tutorial, images that you use to run containers can be modified and used to generate new images, which may then be uploaded (pushed is the technical term) to Docker Hub or other Docker registries.
Step 5 — Running a Docker Container
hello-world container you ran in the previous is an example of a container that runs and exits, after emitting a test message. Containers, however, can be much more useful than that, and they can be interactive. After all, they are similar to virtual machines, only more resource-friendly.
As an example, let’s run a container using the latest image of Ubuntu. The combination of the -i and -t switches gives you interactive shell access into the container:
docker run -it ubuntu
Your command prompt should change to reflect the fact that you’re now working inside the container and should take this form:
Important: Note the container id in the command prompt. In the above example, it is
Now you may run any command inside the container. For example, let’s update the package database inside the container. No need to prefix any command with
sudo, because you’re operating inside the container with root privileges:
Then install any application in it. Let’s install NodeJS, for example.
apt-get install -y nodejs
Hope you found these docker tutorials useful and thanks to Digital Ocean community for the resources.