Previously we showed how to install Docker on Ubuntu. Docker is a handy tool designed to make it easier to create, deploy, and run applications by using containers. Today, let’s talk about working with Docker images, Containers, and the DockerHub.
Docker Hub, Images, and Containers
As the name indicates, DockerHub is a hosted repository service provided by the publisher for finding and sharing container images with developers/users. A Docker image has everything needed to run an application as a container. A container is a runtime instance of an image. We will show you how to work with these things with easy to follow examples.
1. Pulling the docker image and setting up a software
To pull the docker image, use the following command:
docker pull ubuntu
It should download the latest ubuntu image. If needed, you can get a specific version using tags. You can go to the docker hub and see the Ubuntu docker images.
I. Get a specific version
For example, pull Ubuntu xenial:
docker pull ubuntu:xenial
II. Listing images
Run the following command to list downloaded images
III. Running docker image
Here we run ubuntu latest image and give name called “ubuntu_apache”:
docker run -it --name="ubuntu_apache" ubuntu:latest /bin/bash
docker run:– command lets you run any Docker image as a container.
-it:– executes the container in interactive mode (not in the background).
IV. Configuring new image
Now you are inside ubuntu latest container. Here we are going to install apache and git.
Let’s update Ubuntu first:
Install apache2 and check the version.
apt-get install apache2
Now install GIT:
apt-get install git
Start apache 2:
2. Creating an account on Docker Hub
Now we are going to build a new image and push it to the docker hub. So you must create a docker hub account first.
Then go to your docker host. Exit from the docker container.
3. Building a new image
I. Commit modifications
docker commit -m="ubuntu-apache-git-image" ubuntu_apache ddarshana/ubuntuapache
-m:– Commit message.
ubuntu_apache: Name of the container that we are going to creating the image.
ddarshana/ubuntuapache: Name of the Docker Hub repository. (replace this with your docker hub name and repo name)
After you list images, you can see a new image.
Push docker image to docker hub repository:
II. Login into the docker hub repository.
III. Now we can push the image to the Docker hub repository.
docker push ddarshana/ubuntuapache
Docker PushNow, you browse a login to your docker hub account, and under repositories, you can see a new image.
IV) Removing Docker Images
Now we are going to remove the docker image (ddarshana/ubuntuapache) in our host machine. Before that, you need to list docker images. Then get an image ID to execute the following command to remove it.
docker rmi -f "Image ID"
4. Now again, we are going to pull our docker image from the docker hub.
docker pull ddarshana/ubuntuapache
I. Running the new Docker image as a container and in a background
docker run -itd -p 80:80 ddarshana/ubuntuapache
-itd:- executes the container in the background
-p 80:80:- using the -p option we’re connecting the internal port 80 of the container the external port 80. Apache uses port 80. So we can send the HTTP request to the server from our local machine by opening up URL http://IP:80.
II. Listing Docker containers
docker ps -a
III. Login to docker container
docker exec -it "container ID" /bin/bash
Before we create an image, we install git too. You can run the following command and check the git version:
IV. Checking apache service
Now you can browse apache server page using your host machine IP or hostname:
Now we will stop the container and remove it.
5. Listing containers and get the container ID
docker ps -a
I. Stoping the container
docker stop "container ID"
II. Removing container
docker rm "container ID"
That’s it for now! I hope you liked this section of working with Docker images and containers.