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Wesley Dupler
Containerization has brought in strategically sound optimizations through a few crucial and well-defined rationalizations and the insightful sharing of compute resources. Some of the innate and hitherto underutilized capabilities of the Linux kernel have been rediscovered. A few additional capabilities too are being embedded to strengthen the process and applicability of containerization. These capabilities have been praised for bringing in the much-wanted automation and acceleration, which will enable the fledgling containerization idea to reach greater heights in the days ahead. The noteworthy business and technical advantages of containerization include bare metal-scale performance, real-time scalability, higher availability, IT DevOps, software portability, and so on. All the unwanted bulges and flabs are being sagaciously eliminated to speed up the roll-out of hundreds of application containers in seconds. The following diagram on the left-hand side depicts the virtualization aspect, whereas the diagram on the right-hand side vividly illustrates the simplifications that are being achieved in containers:
The second one is the Type 2 virtualization, wherein the hypervisor runs on the host OS as shown in the preceding figure. This additional layer impacts the system performance and hence generally Type 2 virtualization is being used for development, testing, and staging environments. The Type 2 virtualization greatly slows down the performance because of the involvement of multiple modules during execution. Here, the arrival of Docker-enabled containerization brings forth a huge boost to the system performance.
Docker and Microsoft have entered into a long-lasting partnership to bring the much-needed agility, portability, and security benefits of the Docker platform to every edition of Windows Server 2016. Organizations that upgrade their servers to this new OS will then be able to use containers right from the development to the production environments. Windows uses namespace isolation, resource control, and process-isolation mechanisms to restrict the files, network ports, and running processes that each container can access. This isolation ensures applications running in containers can't interact with or see other applications running on the host OS or in other containers. Microsoft includes two different types of container. The first type is based on the Windows Server core image and is called a Windows Server container. The second one is called a Hyper-V container and is based on the Windows Nano Server image.
It is important to understand the Docker components and their versions, storage, and the execution drivers, the file locations, and so on. Incidentally, the quest for understanding the Docker setup will also reveal whether the installation was successful or not. You can accomplish this using two Docker subcommands: docker version and docker info.
If we dissect the internals of the docker version subcommand, then it will first list the client-related information that is stored locally. Subsequently, it will make a REST API call to the server over HTTP to obtain server-related details.
As you can see, in the output of a freshly installed Docker Engine, the number of Containers and Images is invariably nil. The Storage Driver has been set up as aufs, and the directory has been given the /var/lib/docker/aufs location. The runtime has been set to runc. This command also lists details, such as Logging Driver, Cgroups Driver, Kernel Version, Operating System, CPUs, and Total Memory.
On Linux installations, Docker is usually programmed to carry out the server-client communication using the Unix socket (/var/run/docker.sock). Docker also has an IANA-registered port, which is 2375. However, for security reasons, this port is not enabled by default.
Having installed the Docker Engine successfully, the next logical step is to download the images from the Docker Registry. The Docker Registry is an application repository that hosts various applications, ranging from basic Linux images to advanced applications. The docker pull subcommand is used to download any number of images from the registry. In this section, we will download a sample hello-world image using the following command:
The second edition, much like the first edition, targets people who are new to containerization and want a guided approach to containerizing their application. I start with setting up a Python telegram bot, building and running it as a program, and then continue containerizing the same bot, starting with steps to build the Dockerfile, adding volumes for persisting the data, setting up Docker networks for container networking, and finally multi-container orchestration with Docker Compose.
I hope the second edition is a value add and you like it as much as I enjoyed writing it. Feedback, of course, is always welcome. My Twitter DMs are always open, or you can reach out to me on the channels mentioned in the contact page.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: Let's start our Docker journey with the docker version subcommand, as shown here:
This command fetches the log of a container without logging in to the container. It batch-retrieves logs present at the time of execution. These logs are the output of stdout and stderr. The general usage is shown in docker logs [OPTIONS] CONTAINER.
The second edition of Docker on Windows takes you on the same journey as the previous edition, starting with the 101 of Windows containers, through packaging .NET Core and .NET Framework apps with Docker, to transforming monolithic apps into modern distributed architectures. And it takes in security, production readiness and CI/CD on the way.
Kubernetes is a whole different learning curve, but it will become increasingly important as more providers support Windows nodes in their Kubernetes offerings. You'll be able to capture your whole application definition in a set of Kube manifests and deploy the same app without any changes on any platform from Docker Enterprise on-prem, to AKS or any other cloud service.
As in-demand as it may be, getting started can seem a bit intimidating at first. So in this book, we'll be learning everything from the basics to a more intermediate level of containerization. After going through the entire book, you should be able to:
Now, open up Ubuntu or whatever distribution you've installed from Microsoft Store. Execute the docker --version and docker-compose --version commands to make sure that the installation was successful.
In the output, a container named exciting_chebyshev was run with the container id of 128ec8ceab71 using the hello-world image. It has Exited (0) 13 seconds ago where the (0) exit code means no error was produced during the runtime of the container.
Okay, enough talking. Now it's time for you to understand how all these pieces of the puzzle you just learned about work in harmony. Before I dive into the explanation of what really happens when you run the docker run hello-world command, let me show you a little diagram I've made:
In this section, you'll be learning about container manipulation in a lot more detail. Container manipulation is one of the most common task you'll be performing every single day, so having a proper understanding of the various commands is crucial.
The CONTAINER ID is 9f21cb777058 which is the first 12 characters of the full container ID. The full container ID is 9f21cb77705810797c4b847dbd330d9c732ffddba14fb435470567a7a3f46cdc which is 64 characters long. This full container ID was printed as the output of the docker container run command in the previous section.
As you can see, the second container in the list reverent_torvalds was created earlier and has exited with the status code 0, which indicates that no error was produced during the runtime of the container.
I hope that you remember the container you started in the previous section. It's still running in the background. Get the identifier for that container using docker container ls (I'll be using hello-dock-container container for this demo). Now execute the following command to stop the container:
As an example, if you run a container using the ubuntu image by executing docker container run ubuntu you'll see nothing happens. But if you execute the same command with the -it option, you should land directly on bash inside the Ubuntu container.
So in the end the docker container run --rm -v $(pwd):/zone fhsinchy/rmbyext pdf command translates to rmbyext pdf inside the container. Executable images are not that common in the wild but can be very useful in certain cases.
Take the official mysql image, for example. If you want to run a container using a specific version of MySQL, like 5.7, you can execute docker container run mysql:5.7 where mysql is the image repository and 5.7 is the tag.
Well, Docker has a similar concept. The .dockerignore file contains a list of files and directories to be excluded from image builds. You can find a pre-created .dockerignore file in the hello-dock directory.
This .dockerignore file has to be in the build context. Files and directories mentioned here will be ignored by the COPY instruction. But if you do a bind mount, the .dockerignore file will have no effect. I've added .dockerignore files where necessary in the project repository.
The second solution you may think of is finding the exact IP address of the postgres container using the container inspect command and using that with the port. Assuming the name of the postgres container is notes-api-db-server you can easily get the IP address by executing the following command:
This is a multi-staged build. The first stage is used for building and installing the dependencies using node-gyp and the second stage is for running the application. I'll go through the steps briefly:
Before you execute the command, though, make sure you've opened your terminal in the same directory where the docker-compose.yaml file is. This is very important for every docker-compose command you execute.
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