Category: docker

Docker – Private Registries You might have the need to have your own private repositories. You may not want to host the repositories on Docker Hub. For this, there is a repository container itself from Docker. Let’s see how we can download and use the container for registry. Step 1 − Use the Docker run command to download the private registry. This can be done using the following command. sudo docker run –d –p 5000:5000 –-name registry registry:2 The following points need to be noted about the above command − Registry is the container managed by Docker which can be used to host private repositories. The port number exposed by the container is 5000. Hence with the –p command, we are mapping the same port number to the 5000 port number on our localhost. We are just tagging the registry container as “2”, to differentiate it on the Docker host. The –d option is used to run the container in detached mode. This is so that the container can run in the background Step 2 − Let’s do a docker ps to see that the registry container is indeed running. We have now confirmed that the registry container is indeed running. Step 3 − Now let’s tag one of our existing images so that we can push it to our local repository. In our example, since we have the centos image available locally, we are going to tag it to our private repository and add a tag name of centos. sudo docker tag 67591570dd29 localhost:5000/centos The following points need to be noted about the above command − 67591570dd29 refers to the Image ID for the centos image. localhost:5000 is the location of our private repository. We are tagging the repository name as centos in our private repository. Step 4 − Now let’s use the Docker push command to push the repository to our private repository. sudo docker push localhost:5000/centos Here, we are pushing the centos image to the private repository hosted at localhost:5000. Step 5 − Now let’s delete the local images we have for centos using the docker rmi commands. We can then download the required centos image from our private repository. sudo docker rmi centos:latest sudo docker rmi 67591570dd29 Step 6 − Now that we don’t have any centos images on our local machine, we can now use the following Docker pull command to pull the centos image from our private repository. sudo docker pull localhost:5000/centos Here, we are pulling the centos image to the private repository hosted at localhost:5000. If you now see the images on your system, you will see the centos image as well.

Docker – Installation Let’s go through the installation of each product. Docker for Windows Once the installer has been downloaded, double-click it to start the installer and then follow the steps given below. Step 1 − Click on the Agreement terms and then the Install button to proceed ahead with the installation. Step 2 − Once complete, click the Finish button to complete the installation. Docker ToolBox Once the installer has been downloaded, double-click it to start the installer and then follow the steps given below. Step 1 − Click the Next button on the start screen. Step 2 − Keep the default location on the next screen and click the Next button. Step 3 − Keep the default components and click the Next button to proceed. Step 4 − Keep the Additional Tasks as they are and then click the Next button. Step 5 − On the final screen, click the Install button. Working with Docker Toolbox Let’s now look at how Docker Toolbox can be used to work with Docker containers on Windows. The first step is to launch the Docker Toolbox application for which the shortcut is created on the desktop when the installation of Docker toolbox is carried out. Next, you will see the configuration being carried out when Docker toolbox is launched. Once done, you will see Docker configured and launched. You will get an interactive shell for Docker. To test that Docker runs properly, we can use the Docker run command to download and run a simple HelloWorld Docker container. The working of the Docker run command is given below − docker run This command is used to run a command in a Docker container. Syntax docker run image Options Image − This is the name of the image which is used to run the container. Return Value The output will run the command in the desired container. Example sudo docker run hello-world This command will download the hello-world image, if it is not already present, and run the hello-world as a container. Output When we run the above command, we will get the following result − If you want to run the Ubuntu OS on Windows, you can download the Ubuntu Image using the following command − Docker run –it ubuntu bash Here you are telling Docker to run the command in the interactive mode via the –it option. In the output you can see that the Ubuntu image is downloaded and run and then you will be logged in as a root user in the Ubuntu container.

Docker – Compose Docker Compose is used to run multiple containers as a single service. For example, suppose you had an application which required NGNIX and MySQL, you could create one file which would start both the containers as a service without the need to start each one separately. In this chapter, we will see how to get started with Docker Compose. Then, we will look at how to get a simple service with MySQL and NGNIX up and running using Docker Compose. Docker Compose ─ Installation The following steps need to be followed to get Docker Compose up and running. Step 1 − Download the necessary files from github using the following command − curl -L “https://github.com/docker/compose/releases/download/1.10.0-rc2/dockercompose -$(uname -s) -$(uname -m)” -o /home/demo/docker-compose The above command will download the latest version of Docker Compose which at the time of writing this article is 1.10.0-rc2. It will then store it in the directory /home/demo/. Step 2 − Next, we need to provide execute privileges to the downloaded Docker Compose file, using the following command − chmod +x /home/demo/docker-compose We can then use the following command to see the compose version. Syntax docker-compose version Parameters version − This is used to specify that we want the details of the version of Docker Compose. Output The version details of Docker Compose will be displayed. Example The following example shows how to get the docker-compose version. sudo ./docker-compose -version Output You will then get the following output − Creating Your First Docker-Compose File Now let’s go ahead and create our first Docker Compose file. All Docker Compose files are YAML files. You can create one using the vim editor. So execute the following command to create the compose file − sudo vim docker-compose.yml Let’s take a close look at the various details of this file − The database and web keyword are used to define two separate services. One will be running our mysql database and the other will be our nginx web server. The image keyword is used to specify the image from dockerhub for our mysql and nginx containers For the database, we are using the ports keyword to mention the ports that need to be exposed for mysql. And then, we also specify the environment variables for mysql which are required to run mysql. Now let’s run our Docker Compose file using the following command − sudo ./docker-compose up This command will take the docker-compose.yml file in your local directory and start building the containers. Once executed, all the images will start downloading and the containers will start automatically. And when you do a docker ps, you can see that the containers are indeed up and running.

Docker – Images What are Docker Images? Docker images are self-contained templates that are used to build containers. They make use of a tiered file system to store data effectively. Each layer, which contains instructions such as downloading software packages or transferring configuration files, represents a particular phase in the image generation process. Only the updated layers need to be recreated and delivered, making layering an effective way to share and update images. A text file known as a Dockerfile forms the basis of a Docker image. The instructions for creating the image layer by layer are contained in this file. In most cases, an instruction begins with a term such as “FROM” to identify the base image, which is usually a minimal Linux distribution. Commands such as “RUN” are then used to carry out particular operations within a layer. As a result, the environment inside the container can be managed precisely. Docker images are read-only templates, so any changes you make to the running program happen inside a container, not to the image itself. By doing this, a clear division is maintained between the runtime state (container) and the application definition (image). In addition, since new versions may be made with targeted modifications without affecting already-existing containers, image versioning and maintenance are made simpler. Key Components and Concepts of Docker Images Here are a few key components that makeup Docker Images. Layers Docker images consist of several layers. Every layer denotes a collection of filesystem modifications. Each Dockerfile instruction adds a layer on top of the previous one while building a Docker image. Layers are unchangeable once they are produced, which makes them immutable. Because of its immutability, Docker can effectively reuse layers during image builds and deploys, which speeds up build times and uses less disk space. Base Image The foundation upon which your customized Docker image is built is a base image. Usually, it has the bare minimum runtime environment and operating system needed to complete your application. Base images from CentOS, Ubuntu, Debian, and Alpine Linux are frequently used. For compatibility and to minimize image size, selecting the appropriate foundation image is crucial. Dockerfile Dockerfile is a text document with a set of instructions for creating a Docker image. These instructions describe how to create the basic image, add files and directories, install dependencies, adjust settings, and define the container”s entry point. By specifying the build process in a Dockerfile, you can automate and replicate the image creation process, assuring consistency across environments. Image Registry Docker images can be stored in either public or private registries, such as Azure Container Registry (ACR), Google Container Registry (GCR), Amazon Elastic Container Registry (ECR), and Docker Hub. Registries offer a centralized area for managing, sharing, and distributing Docker images. They also provide image scanning for security flaws, versioning, and access control. Tagging A repository name and a tag combine to form a unique identification for Docker images. Tags are used to distinguish between various image versions. When no tag is given, Docker uses the “latest” tag by default. To maintain reproducibility and track image versions, it is recommended to utilize semantic versioning or other relevant tags. Image Pulling and Pushing The docker pull command can be used to download Docker images to a local system from a registry. Similarly, the docker push command can be used to push images from a local machine to a registry. This enables you to distribute your images to various environments or share them with others. Layer Caching For performance optimization, Docker uses layer caching while building images. When you construct an image, Docker leverages previously built cached layers if the associated Dockerfile instructions haven”t changed. This drastically cuts down on build times, particularly for big projects with intricate dependencies. Useful Docker Image Commands Now that we have discussed what Docker Images are, let’s have a look at the basic and most useful Docker Image commands that you will use very frequently. Listing all Docker Images To see a list of all the Docker images that are present on your local computer, you can use the “docker images” command. It gives important details like the size, creation time, image ID, tag, and repository name. Using this command, you may quickly see which images are available to run containers on your system. $ docker images If you want to just display the Image IDs, you can use the “–quiet” flag. $ docker image ls -q Pulling Docker Images To download Docker images to your local computer from a registry, use the Docker pull command. Docker will automatically pull the “latest” version of the image if no tag is specified. Before launching containers based on images, this command is necessary to fetch images from public or private registries. $ docker pull ubuntu:20.04 Building Docker Images from Dockerfile The docker build command creates a Docker image from a Dockerfile placed at the provided path. During the build process, Docker follows the instructions in the Dockerfile to generate layers and assemble the final image. This command is essential for creating customized images that are tailored to your application”s specific needs. Dockerfile # Use a base image from Docker Hub FROM alpine:3.14 # Set the working directory inside the container WORKDIR /app # Copy the application files from the host machine to the container COPY . . # Expose a port for the application (optional) EXPOSE 8080 # Define the command to run when the container starts CMD [“./myapp”] For the above Dockerfile, you can build an image using the below command. $ docker build -t myapp:latest . Tagging Docker Images The docker tag command creates a new tag for an existing Docker image. Tags allow you to label and reference multiple versions of an image. This command is frequently used before uploading an image to a registry under a different tag. $ docker tag myapp:latest myrepo/myapp:v1.0 Pushing Docker Images The docker push command transfers a Docker image from your local machine to a registry, such as Docker

Docker Tutorial Table of content Docker Tutorial What is Docker? Traditional Deployment vs Docker Deployment Docker Developers in Demand: Job Opportunities Salary Expectations Who Uses Docker? Docker and Beyond: Building a Strong Resume Why Should You Learn Docker? Features and Characteristics of Docker Careers for Docker Developers Prerequisites to Learn Docker Target Audience Frequently Asked Questions About Docker Docker Questions & Answers PDF Version Quick Guide Resources Job Search Discussion Docker Tutorial Docker is an open-source platform that has completely changed the way we develop, deploy, and use apps. The application development lifecycle is a dynamic process, and developers are always looking for ways to make it more efficient. Docker enables developers to package their work and all of its dependencies into standardized units called containers by utilizing containerization technology. By separating apps from the underlying infrastructure, these lightweight containers provide reliable performance and functionality in a variety of environments. Because of this, Docker is a game-changer for developers because it frees them up to concentrate on creating amazing software rather than handling difficult infrastructure. Regardless of your level of experience, Docker provides an extensive feature set and a strong toolset that can greatly enhance your development process. In this tutorial, we will provide you with a thorough understanding of Docker, going over its main features, advantages, and ways to use it to develop, launch, and distribute apps more quickly and easily. What is Docker? Docker is a platform that is based on the idea of software containers. The code, libraries, system tools, and configurations required to run an application are all included in these self-contained containers. Consider a shipping container; it can easily be moved between different sites and accommodates all of your belongings, including clothing and furnishings. In the same manner, Docker containers, independent of the underlying operating system, encompass all the requirements of an application. This guarantees consistency in behavior and gets rid of compatibility problems that sometimes arise with traditional deployments. Technically, Docker does this by using the virtualization capabilities of the operating system”s kernel. Containers are lightweight and extremely portable since they share the host”s operating system kernel, unlike virtual machines that mimic full hardware systems. Developers may create, manage, and launch these containers in a variety of environments, from local development workstations to cloud-based production servers, with the help of Docker”s suite of tools and APIs. Traditional Deployment vs Docker Deployment Let”s look at a web application that was created using a particular Python version and a few third-party libraries. The required Python version, libraries, and environment configuration would need to be manually installed to deploy this application on a new server. It is necessary to repeat this procedure on each server, which can be laborious and prone to errors. This is where Docker excels. Developers can use Docker to generate a container image that contains the application code together with all of its dependencies (particular libraries and versions of Python) and any setups that the system may require. After that, this image may be quickly installed on any host that has Docker installed. By providing the container with an isolated environment, the Docker engine prevents problems with other programs or libraries on the host system. This saves developers a great deal of time and work because it not only makes deployment simpler but also ensures consistent behavior across all settings. Docker Developers in Demand: Job Opportunities The expertise in Docker is becoming increasingly valuable in today”s IT environment. The need for engineers with the skills to plan, create, and supervise Dockerized applications has increased significantly as a result of containerization. As more businesses adopt containerization due to its scalability and efficiency advantages, this trend is anticipated to continue. Salary Expectations Competitive salaries are expected for Docker developers, based on several job sites and salary reports. The location, type of work, and experience levels can all affect average pay. Senior developers with a lot of expertise can earn wages above $150,000, while entry-level jobs might start anywhere from $70,000 to $90,000 per year. Who Uses Docker? The use of Docker is widespread in many industries. Docker is being used by businesses of all kinds, from startups to established corporations, to IT behemoths like Google and Netflix. Here are a few examples − Technology Companies − Docker integration is offered by cloud providers such as Microsoft Azure, Google Cloud Platform (GCP), Amazon Web Services (AWS), and others, which makes it an ideal choice for businesses developing cloud-native applications. FinTech − Due to Docker”s security and dependability when developing financial apps, financial institutions are using it more and more. E-commerce − Docker is perfect for e-commerce platforms that manage large levels of traffic since it can scale quickly and meet scalability requirements. Media & Entertainment − Businesses in this industry use Docker to handle workflows related to media processing and content delivery networks. Docker and Beyond: Building a Strong Resume Although knowledge of Docker provides a solid basis, being proficient in supplementary technologies can greatly improve your CV and increase your marketability. Here are some crucial points to think about − Tools for DevOps − Knowledge of tools for DevOps, such as Kubernetes, which facilitates the large-scale orchestration of containerized deployments, is a beneficial addition. Cloud Platforms − Your ability to use Docker in cloud environments is demonstrated by your familiarity with popular cloud platforms like as AWS, Azure, or GCP. Programming Languages − You will stand out if you have strong proficiency in the widely used Python, Java, or Go programming languages, which are utilized to create Dockerized apps. Infrastructure Automation − Your ability to automate infrastructure provisioning and configuration in conjunction with Docker deployments is demonstrated by your familiarity with tools such as Terraform or Ansible. Your resume may make a big impression and put you in the best possible position to succeed in the competitive job market for Docker developers if you combine your Docker expertise with these complementary skills. Why Should You Learn Docker? Being ahead of the

Docker – Hub ”; Previous Next What is Docker Hub? Docker Hub is a cloud-based repository service that allows users to store, share, and manage Docker container images. It is offered by Docker. Developers can package their apps and dependencies into lightweight, portable containers using the widely used Docker platform. Applications can then be deployed and scaled more easily since these containers can operate consistently in various environments. Fundamentally, Docker Hub is a central location where Docker users can find, share, and work together on containerized applications. Databases, web servers, programming languages, and a plethora of other software and services are all provided by the extensive library of pre-built Docker images that it hosts. With a single command, users can find images based on particular criteria, like functionality, operating system version, or search terms, and then pull those images into their local environment. Features and Benefits of Docker Hub Docker Hub is a cloud-based repository service offered by Docker that has a plethora of features. These features are designed to make the creation, implementation, and administration of containerized applications easier. Docker Hub, the global hub for Docker users, promotes productivity, guarantees security, and eases collaboration across the container lifecycle. Here are a few features and benefits of Docker Hub. Centralized Repository − Docker Hub allows you to search, access, and share containerized apps and services. It acts as a single source of truth thanks to the central repository for Docker container images. Vast Library of Images − It provides access to a huge library of pre-built Docker images. This includes popular web servers, databases, programming languages, and frameworks, among other software and services. You don”t have to start from scratch. You can just find and select images based on your unique requirements in this vast collection. Open Collaboration − Docker Hub promotes an environment of open collaboration. It allows developers to share their own Docker images with the community. You can build upon and improve each other”s work. This promotes knowledge sharing and speeds up development cycles. Automation Tools − It offers tools for automating the build, test, and deployment of Docker images. This includes functions like integration with CI/CD pipelines for smooth continuous integration and delivery workflows. Moreover, it provides support for automated builds, which start builds automatically whenever changes are pushed to a repository. Versioning and Tagging − Docker Hub allows the versioning and tagging of Docker images. This simplifies the management and tracking of various iterations of a service or application over time. This makes it easier to roll back to earlier versions if necessary and guarantees consistency and reproducibility across various environments. Access Control and Permissions − Docker Hub has some powerful features for managing access control and permissions. This allows businesses to regulate who can view, edit, and share Docker images. This is especially beneficial for teams working on confidential or proprietary applications as it helps guarantee the security and integrity of containerized deployments. Scalability and Performance − Docker Hub, a cloud-based service, provides high-performance infrastructure and scalability for hosting and distributing Docker images. This guarantees dependable and quick access to container images irrespective of the repository”s size or level of popularity. Integration with Docker Ecosystem − It offers a unified platform for developing, launching, and overseeing containerized applications from development to production. It does this by integrating seamlessly with the larger Docker ecosystem, which includes Docker Engine, Docker Compose, and Docker Swarm. How to Create a Docker Hub Repository? It’s quite easy and simple to create a Docker Hub repository. Here”s a basic guide − Step 1: Sign in to Docker Hub Visit https://hub.docker.com/ to create a Docker Hub account and sign in using your credentials. Step 2: Create a New Repository After you have completed the signup process, you will be directed to your Docker Hub dashboard. You can manage your repositories, images, and account settings here. To create a new repository, click on “Repositories” in the menu bar and then click on the “Create Repository” button in the upper right corner of the dashboard. Step 3: Choose Repository Visibility and Details Here, you can provide the repository name, details, and visibility of the repository. Public repositories are visible to everyone. On the other hand, private repositories restrict access to authorized users only. Step 4: Save and Create the Repository You can click the “Create” or “Save” button to create your repository. Once the repository is created, you can access it from your Docker Hub dashboard. You can configure the builds, webhooks, tags, and other setting here. How to Push or Pull Images from Docker Hub? You can use the Docker commands to push and pull Docker images to and from a Docker Hub repository. Here”s how you can do it − Pushing Images to Docker Hub In this section, let”s see how you can push images to Docker Hub − Step 1: Tag Your Image Before you push an image to Docker Hub, you should ensure that it is properly tagged with the repository name and version. Here, we will use a “hello-world” image from the Docker Hub public repository for reference. You can tag an image using the following command − $ docker pull hello-world $ docker images $ docker tag <image_id> <username/repository_name:tag> Step 2: Log in to Docker Hub Before you can pull or push images from your private repository, you have to log in to Docker Hub using the command line. You can use the docker login command to authenticate with Docker Hub using your Docker Hub username and password. $ docker login Step 3: Push the Image Now that you have logged in, you can use the docker push command to push

How to Install Docker on Linux? ”; Previous Next Docker has transformed the software development industry completely by allowing programmers to bundle their apps and all of their dependencies into small, lightweight units known as containers. By separating apps from the underlying operating system, these containers provide reliable performance and easy deployment in a variety of environments. If you”re a Linux user hoping to take advantage of containerization, this chapter is the perfect place to be. You will be able to install Docker on your Linux system using various ways that will be explained in this detailed guide. We will provide detailed instructions according to your requirements, regardless of whether you like to use pre-built packages, download DEB files, or make use of handy installation scripts. We will discuss in detail, the following approaches to installing Docker on Linux − Install using the apt repository Install from a package Install using the convenience script So, let’s understand these approaches to install Docker on Ubuntu. Prerequisites to Install Docker on Linux Make sure your Linux system satisfies the prerequisites before starting the Docker installation process. This will ensure that the Docker installation is done smoothly and in the best way. Use a 64-bit Architecture − Docker works best in a 64-bit setting. You can use the “uname -m” command in your terminal to confirm the architecture of your system. It will be difficult to install Docker directly if your system is 32-bit. However, alternative solutions are available on the internet for particular use cases. Use Kernel Version 3.10 or Higher − A stable Linux kernel is required for Docker to work as expected and in the best way. You can verify that the kernel version you”re using is 3.10 or higher. You can do so using the “uname -r” command in your terminal. This will give you the version of your kernel. You may check the documentation for your distribution to determine the best course of action if you need an update. Package Management − The approach to installing Docker largely depends on the package manager for your Linux distribution. APT (Ubuntu/Debian) and Yum (Red Hat/CentOS) are two popular examples. It’s always good to follow the installation guidelines unique to your distribution if you are familiar with these distributions. In this chapter, we will discuss the approaches for Ubuntu. Similar commands can be used for other Linux distributions depending on their package managers. Additional Considerations Virtualization Support − You should ensure that your system is compatible with the hardware virtualization technologies such as KVM for better performance. This is especially important when executing specific containerized apps. Sudo Access − Almost all the installation techniques require sudo access, so make sure you have that handy. Once you meet these requirements, you are in a good position to install Docker in the best possible way on your Linux machine. In the following section, we”ll explore the different installation techniques, so stay tuned! Installing Docker using APT Repository Before installing a Docker Engine on a new host for the first time, it’s important to set up the Docker repository. After that, you can easily install or update Docker from that repository. To set up the Docker’s apt repository, you can use the below set of commands. $ sudo apt-get update $ sudo apt-get install ca-certificates curl $ sudo install -m 0755 -d /etc/apt/keyrings $ sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc $ sudo chmod a+r /etc/apt/keyrings/docker.asc The next step is to add the repository to Apt sources. echo “deb [arch=$(dpkg –print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu $(. /etc/os-release && echo “$VERSION_CODENAME”) stable” | sudo tee /etc/apt/sources.list.d/docker.list > /dev/null sudo apt-get update Note − If you are using another derivative of Ubuntu such as Linux Mint or others, you may need to replace VERSION_CODENAME with UBUNTU_CODENAME in the above command. The next step is to install the Docker packages. To install the latest version, you can run the below commands − $ sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin After you have completed the installation, you can verify the installation is successful by running the hello-world image. $ sudo docker run hello-world The above command downloads the hello-world image from the Docker repository and runs a container associated with it. It prints a message and exits. This verifies the successful installation of the Docker engine on your Ubuntu host. Instead of installing the latest version, you can also install a specific version of the Docker engine using the below set of commands. The first command lists the available Docker versions for Ubuntu. # List the available versions: apt-cache madison docker-ce | awk ”{ print $3 }” Then you can set the desired version in a variable and install it using the below commands. $ VERSION_STRING=5:26.1.1-1~ubuntu.22.04~jammy $ sudo apt-get install docker-ce=$VERSION_STRING docker-ce-cli=$VERSION_STRING containerd.io docker-buildx-plugin docker-compose-plugin Installing Docker From a Package Instead of installing Docker from the APT repository, you can also manually download the deb files for the specific release versions and install them. But in this case, if you want to upgrade the Docker engine versions, you will have to do it manually. Visit https://download.docker.com/linux/ubuntu/dists/. Then, select the version of Ubuntu from this list. Then, go to the path – pool/stable and select the architecture of your Linux host (amd64, armhf, arm64, or s390x). After that, you need to download the following deb files. containerd.io_<version>_<arch>.deb docker-ce_<version>_<arch>.deb docker-ce-cli_<version>_<arch>.deb docker-buildx-plugin_<version>_<arch>.deb docker-compose-plugin_<version>_<arch>.deb After downloading these, you can install these packages using the following command. This will also start the Docker daemon automatically. $ sudo dpkg -i ./containerd.io_<version>_<arch>.deb

How to Setup Alpine in Docker Containers? ”; Previous Next Alpine Linux, often referred to simply as Alpine, is a security-oriented, lightweight Linux distribution based on musl libc and BusyBox. It has a remarkably small size, typically ranging from a few megabytes to tens of megabytes. This makes it an ideal OS candidate for containerized environments where resource optimization is important. Alpine is the most popular base image for Docker containers. It offers a clean slate for developers to build and deploy their applications. Its minimalist design ensures a reduced attack surface, enhancing security posture. Moreover, its efficient resource utilization helps in faster container start times and optimized performance. You can set up and start Docker containers with Alpine Linux in 2 easy ways − By pulling an Alpine Image from Dockerhub and running a container. By specifying Alpine base images and other instructions in Dockerfile to build Docker images. In this chapter, we will discuss how to set up Alpine Linux as a base image for Docker containers with the help of step-by-step processes, commands, and examples. How to Create Docker Containers with Alpine Linux? Let’s understand how to quickly pull an Alpine Linux Docker image from Dockerhub and run a container associated with it. Step 1: Pull the Alpine Linux Image Let’s start by pulling the Alpine Linux image from Docker Hub using the following command − docker pull alpine On running this command, it downloads the latest version of the Alpine Linux image to your local machine. Step 2: Run a Docker Container Once you have pulled the Alpine image, you can run a Docker container based on it using the following command − docker run -it –name my-alpine-container alpine This command will create and start a new Docker container named `my-alpine-container` based on the `alpine` image. The `-it` flags will allocate a pseudo-TTY and keep STDIN open even if not attached. This allows you to interact with the container. Step 3: Access the Bash Shell Now, that you are inside the Alpine Linux container, you can access the Bash shell by simply typing − /bin/sh This will launch the Bash shell within the container and allow you to execute commands and interact with the Alpine environment. Step 4: Verify the Operating System Once you”re in the Bash shell, you can verify the operating system of the container. You can do this by running the following command − cat /etc/os-release This will display information about the operating system, including its name, version, and other details. Step 5: Exit and Remove the Container Once you”re done, you can exit the Bash shell by typing `exit`. If you want to remove the container, you use the Docker rm command. docker rm my-alpine-container How to Create Alpine Linux Docker Containers using Dockerfile? Here’s a step-by-step guide on how to create a Dockerfile that uses an Alpine Linux base image. Step 1: Create a Dockerfile Create a new file named `Dockerfile` in your project directory. This file will contain the instructions for building your Alpine Linux Docker container. # Use the Alpine Linux base image FROM alpine:latest # Update package repositories and install necessary packages RUN apk update && apk upgrade && apk add –no-cache bash # Set a working directory inside the container WORKDIR /app # Copy your application files into the container COPY . . # Define the command to run your application CMD [“bash”] `FROM alpine:latest` − This line specifies the base image to be pulled, in this case, the latest version of Alpine Linux. `RUN apk update && apk upgrade && apk add –no-cache bash` − Here, we update the package repositories and install Bash, which is often useful for debugging and running scripts inside the container. `WORKDIR /app` − This command is used to set the working directory inside the container to `/app`. `COPY . .` − This command is used to copy the contents of your current directory (where the Dockerfile is located) into the `/app` working directory inside the container. `CMD [“bash”]` − This specifies the default command to run when the container starts, in this case, it starts a Bash shell. Step 2: Build the Docker Image Next, you can open a terminal or command prompt, navigate to the directory containing your Dockerfile, and run the following command to build the Docker image − docker build -t my-alpine-container . This command builds an image and tags the built image with the name `my-alpine-container` for easier reference. Step 3: Run the Docker Container Once you have built the Docker image, you can run a container for that image using the following command − docker run -it my-alpine-container This command runs the container in interactive mode and attaches your terminal to the container”s stdin, stdout, and stderr. You have to specify the name of the Docker image you built in the previous step. Now that your container is up and running, you can verify the OS of the container. For this, you need to access the bash of the container. To do so, you can use the Docker exec command below. docker exec -it <container_id_or_name> /bin/bash You can verify that everything is working correctly by running commands like `ls` to list files or `cat /etc/os-release` to display information about the operating system. Conclusion To sum up, Alpine Linux OS images are one of the most popular base images for Docker containers. They offer lightweight and efficient solutions for deploying applications in containerized environments. You can directly pull an Alpine Docker base image from Dockerhub and start the container. You

Docker – Quick Guide ”; Previous Next Docker – Overview Docker is a container management service. The keywords of Docker are develop, ship and run anywhere. The whole idea of Docker is for developers to easily develop applications, ship them into containers which can then be deployed anywhere. The initial release of Docker was in March 2013 and since then, it has become the buzzword for modern world development, especially in the face of Agile-based projects. Features of Docker Docker has the ability to reduce the size of development by providing a smaller footprint of the operating system via containers. With containers, it becomes easier for teams across different units, such as development, QA and Operations to work seamlessly across applications. You can deploy Docker containers anywhere, on any physical and virtual machines and even on the cloud. Since Docker containers are pretty lightweight, they are very easily scalable. Components of Docker Docker has the following components Docker for Mac − It allows one to run Docker containers on the Mac OS. Docker for Linux − It allows one to run Docker containers on the Linux OS. Docker for Windows − It allows one to run Docker containers on the Windows OS. Docker Engine − It is used for building Docker images and creating Docker containers. Docker Hub − This is the registry which is used to host various Docker images. Docker Compose − This is used to define applications using multiple Docker containers. We will discuss all these components in detail in the subsequent chapters. The official site for Docker is https://www.docker.com/ The site has all information and documentation about the Docker software. It also has the download links for various operating systems. Installing Docker on Linux To start the installation of Docker, we are going to use an Ubuntu instance. You can use Oracle Virtual Box to setup a virtual Linux instance, in case you don’t have it already. The following screenshot shows a simple Ubuntu server which has been installed on Oracle Virtual Box. There is an OS user named demo which has been defined on the system having entire root access to the sever. To install Docker, we need to follow the steps given below. Step 1 − Before installing Docker, you first have to ensure that you have the right Linux kernel version running. Docker is only designed to run on Linux kernel version 3.8 and higher. We can do this by running the following command. uname This method returns the system information about the Linux system. Syntax uname -a Options a − This is used to ensure that the system information is returned. Return Value This method returns the following information on the Linux system − kernel name node name kernel release kernel version machine processor hardware platform operating system Example uname –a Output When we run above command, we will get the following result − From the output, we can see that the Linux kernel version is 4.2.0-27 which is higher than version 3.8, so we are good to go. Step 2 − You need to update the OS with the latest packages, which can be done via the following command − apt-get This method installs packages from the Internet on to the Linux system. Syntax sudo apt-get update Options sudo − The sudo command is used to ensure that the command runs with root access. update − The update option is used ensure that all packages are updated on the Linux system. Return Value None Example sudo apt-get update Output When we run the above command, we will get the following result − This command will connect to the internet and download the latest system packages for Ubuntu. Step 3 − The next step is to install the necessary certificates that will be required to work with the Docker site later on to download the necessary Docker packages. It can be done with the following command. sudo apt-get install apt-transport-https ca-certificates Step 4 − The next step is to add the new GPG key. This key is required to ensure that all data is encrypted when downloading the necessary packages for Docker. The following command will download the key with the ID 58118E89F3A912897C070ADBF76221572C52609D from the keyserver hkp://ha.pool.sks-keyservers.net:80 and adds it to the adv keychain. Please note that this particular key is required to download the necessary Docker packages. Step 5 − Next, depending on the version of Ubuntu you have, you will need to add the relevant site to the docker.list for the apt package manager, so that it will be able to detect the Docker packages from the Docker site and download them accordingly. Precise 12.04 (LTS) ─ deb https://apt.dockerproject.org/repoubuntu-precise main Trusty 14.04 (LTS) ─ deb https://apt.dockerproject.org/repo/ ubuntu-trusty main Wily 15.10 ─ deb https://apt.dockerproject.org/repo ubuntu-wily main Xenial 16.04 (LTS) – https://apt.dockerproject.org/repo ubuntu-xenial main Since our OS is Ubuntu 14.04, we will use the Repository name as “deb https://apt.dockerproject.org/repoubuntu-trusty main”. And then, we will need to add this repository to the docker.list as mentioned above. echo “deb https://apt.dockerproject.org/repo ubuntu-trusty main” | sudo tee /etc/apt/sources.list.d/docker.list Step 6 − Next, we issue the apt-get update command to update the packages on the Ubuntu system. Step 7 − If you want to verify that the package manager is pointing to the right repository, you can do it by issuing the apt-cache command. apt-cache policy docker-engine In the output, you will get the link to https://apt.dockerproject.org/repo/ Step 8 − Issue the apt-get update command to ensure all the packages on the local system are up to date. Step 9 − For Ubuntu Trusty, Wily, and Xenial, we have to install the linux-image-extra-* kernel packages, which allows one to use the aufs storage driver. This driver is used by the newer versions of Docker. It can be done by using the following command. sudo apt-get install linux-image-extra-$(uname -r) linux-image-extra-virtual Step 10 − The final step is to install Docker and we can do this with the following command − sudo apt-get install –y

Discuss Docker ”; Previous Next This tutorial explains the various aspects of the Docker Container service. Starting with the basics of Docker which focuses on the installation and configuration of Docker, it gradually moves on to advanced topics such as Networking and Registries. The last few chapters of this tutorial cover the development aspects of Docker and how you can get up and running on the development environments using Docker Containers. Print Page Previous Next Advertisements ”;