Introduction
Containers are semi-isolated environments in which applications, or parts of applications, can run. Unlike VMs which run entirely separate OSes, containers directly share resources with the OS of the server that hosts the containers. This makes containers more efficient than VMs because each containerized environment does not require a complete guest OS.
Moreover, containers are isolated at the process level from other containers, as well as non-containerized processes that run on the server. This isolation makes containers more secure than multiple applications that run directly on a host server. Each container can have different environment parameters, rather than all containers sharing a common configuration.
Technology to deploy applications inside containers has existed since the introduction of the Unix chroot call in the 1970s. Containers became massively popular in the mid-2010s with the introduction of Docker and Kubernetes, which provided tooling that made it easier for developers to create and manage containerized applications.
To learn more about containers and their benefits, refer to the course content and see Containers 101 course on KubeAcademy
TASKS
In this lab, you will run your first Docker Container. For this lab, you will use a dedicated Windows 10 Desktop with all of the tools and applications needed to build run containers, and Manage a Kubernetes Environment. This Desktop can be accessed via RDP from within your VDI desktop session (There is an RDP shortcut on the VDI desktop to it). The windows 10 Desktop has Docker Desktop among other tools installed.
Docker Desktop is an easy-to-install application for your Mac or Windows environment that enables you to build and share containerized applications and microservices.
It provides a simple interface that enables you to manage your containers, applications, and images directly from your machine without having to use the CLI to perform core actions.
Docker Desktop includes:
- Docker Engine
- Docker CLI client
- Docker Compose
- Docker Content Trust
- Kubernetes
- Credential Helper
Docker Desktop works with your choice of development tools and languages and gives you access to a vast library of certified images and templates in Docker Hub. This enables development teams to extend their environment to rapidly auto-build, continuously integrate, and collaborate using a secure repository.
Note: Docker Desktop is free for small businesses, personal use, education, and non-commercial open source projects. See https://www.docker.com/blog/updating-product-subscriptions/ for more information.
- From your Laptop/desktop open a new Google Chrome Incognito window
- Type https://vdi.27virtual.net in the browser address bar
- Click the checkbox "Check here to skip this screen and always use HTML Access"
- Click VMware Horizon HTML Access
- When prompted log in as: (Get the login details from the Student Assignment Spreadsheet)
- Username: VMCExpert#-XX (where # is the Environment ID and XX is your student number)
- Password: {Password-Provided-by-Instructor}
- Select the available Desktop pool
- Once the VDI Desktop has loaded, Click on the "Tanzu Lab Desktop" RDP Shortcut
- If prompted for a password to the RDP session, type the following
- Password: {Password-Provided-by-Instructor}
NOTE: From this point on all lab steps must be performed from this RDP session not your laptop/desktop or the VDI session. The tools needed to are only installed here.
Once you've successfully logged into the Tanzu desktop, it takes a min or two for Docker Desktop to start. Please wait for Docker to start before proceeding
- Once Docker has started successfully, notice that there are currently no Containers. To confirm this, in the left pane click
- Containers
- From the Tanzu Desktop Taskbar or Start menu click Windows Terminal.
If prompted, Click Yes to process
- At the Windows Terminal Prompt Type the following to run the Docker Getting Started application as a container:
docker run -d -p 80:80 docker/getting-startedNOTE:
-d = detached mode
-p = port mapping [host port]:[container port]
docker/ = docker registry
getting-started = container name
- Once the command completes successfully, you'll notice the Docker Desktop User Interface now shows 1 container
- From the Tanzu Desktop (RDP session), Launch Firefox, Edge or Brave
- In the browser Address bar type:
- In the Docker Desktop User Interface, Select your Docker Getting Started application
- Click Stop, to stop the application
In this task, you will build your container image based on nginx and will run this image on your Tanzu Desktop. This lab uses a pre-built Dockerfile and two HTML files, both of which are found in C:\Lab_files\VCE\Containers.
A Dockerfile is a text document that contains all the commands a user could call on the command line to assemble an image. Using docker build users can create an automated build that executes several command-line instructions in succession. This page describes the commands you can use in a Dockerfile
A Docker image is a read-only template with instructions for creating a Docker container. Often, an image is based on another image, with some additional customization. For example, you may build an image that is based on the ubuntu image but installs the Apache web server and your application, as well as the configuration details needed to make your application run.
You might create your own images or you might only use those created by others and published in a registry. To build your image, you create a Dockerfile with a simple syntax for defining the steps needed to create the image and run it. Each instruction in a Dockerfile creates a layer in the image. When you change the Dockerfile and rebuild the image, only those layers which have changed are rebuilt. This is part of what makes images so lightweight, small, and fast when compared to other virtualization technologies.
- In the Tanzu RDP Session Click Lab Files on the desktop
- Click VCE, then Containers to view the Contents of C:\Lab_files\VCE\Containers
- You'll notice 2 HTML files and 1 Dockerfile
- Right-Click Index.html and Edit with Notepad ++
- In Notepad ++ Replace {VMCEPERT#-XX} with your First and Last name
- Click File --> Save Menu to save the file
- Back in windows Explorer, right-click the dockerfile and Edit with Notepad ++, to review how a container is built
Test your understanding:
- What is the base layer?
- What port will the container be available on?
- Is there any way to re-write this Dockerfile to reduce the number of layers it contains?
We will now use this dockerfile to build a new container image
- In Windows Terminal, type the following commands to change directory to the location of the dockerfile and build the image
cd c:\lab_files\vce\containers
docker build -t nginx:task2 .NOTE: Make sure to include the . (dot / point) at the end of the 2nd command
- Click the Docker Desktop User Interface, you'll notice there aren't any new containers at this time
- Select Images in the left pane
Notice you now have a new Image Names "nginx"
Now, let's run a new container from this local image just built
- In Windows Terminal, type the following command to run (deploy) a new container from an image
docker run -d -p 8080:80 nginx:task2
- Click the Docker Desktop User Interface
- Select Containers in the left pane
You'll notice you now have a 2nd Container
- Launch Firefox, Edge, or Brave
- In the browser Address bar type
- In Windows terminal type the following commands to identify your docker images, stop and delete them
docker ps -a
docker stop {container_ID}
docker rm {container_ID}
- In the docker GUI, confirm that the containers have been deleted
Conclusion
Containers require less system resources than traditional or hardware virtual machine environments because they don't include operating system images. Applications running in containers can be deployed easily to multiple different operating systems and hardware platforms.
The use of containers to increase speed of deployment and portability for modern applications is growing rapidly. Now part of the standard architecture for cloud-native businesses, Gartner predicts that, by 2025, 85 percent of organizations will run containers in production, up from less than 30 percent in 2020
The biggest advantage of using Containerization is that the applications are platform-independent. A container will already contain everything that the application needs. It will come with various configuration dependencies and files. This will allow you to run your application on any computer you wan
Docker is a software platform that allows you to build, test, and deploy applications quickly. Docker packages software into standardized units called containers that have everything the software needs to run including libraries, system tools, code, and runtime.
Docker images contain all the dependencies needed to execute code inside a container, so containers that move between Docker environments with the same OS work with no changes. Docker uses resource isolation in the OS kernel to run multiple containers on the same OS.
Docker is an open-source container technology used by developers and system admins to build, ship, and run distributed applications. Docker has been a game-changer since its release in 2013. It has become a massively popular containerization technology.
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