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1. Docker Hello World Image Download
2. Download Hello World Docker Image Download
3. Download Hello World Docker Image File

Your Golang Docker image is available on your computer to run any time you want to. If you'd like to try modifying the program, feel free! Edit main.go and change the message to anything you like, for example. When you're ready to rebuild your container, run the docker image build -t hello. Mkdir hello–world cd hello–world. Create and edit a new YAML configuration file: sudo nano docker-compose.yml. YAML is a type of configuration file. This file will create a container named test-file based on the Hello World image on Docker Hub. Enter the following text into the editor.

So it turns out that the Moby Project has a shell script on the Moby GitHub account which can download images from Docker Hub in a format that can be imported into Docker: download-frozen-image-v2.sh; The usage syntax for the script is given by the following: download-frozen-image-v2.sh targetdir image:tag@digest. Sudo docker run -name helloWorld alpine echo hello If successful, the following should display: Unable to find image 'alpine:latest' locally latest: Pulling from library/alpine 0e: Pull complete Digest: sha256: Status: Downloaded newer image for alpine:latest hello.

Welcome to Docker Desktop! The Docker Desktop for Windows user manual provides information on how to configure and manage your Docker Desktop settings.

For information about Docker Desktop download, system requirements, and installation instructions, see Install Docker Desktop.

Settings

The Docker Desktop menu allows you to configure your Docker settings such as installation, updates, version channels, Docker Hub login,and more.

This section explains the configuration options accessible from the Settings dialog.

1. Open the Docker Desktop menu by clicking the Docker icon in the Notifications area (or System tray):

2. Select Settings to open the Settings dialog:

General

On the General tab of the Settings dialog, you can configure when to start and update Docker.

• Start Docker when you log in - Automatically start Docker Desktop upon Windows system login.

• Expose daemon on tcp://localhost:2375 without TLS - Click this option to enable legacy clients to connect to the Docker daemon. You must use this option with caution as exposing the daemon without TLS can result in remote code execution attacks.

• Send usage statistics - By default, Docker Desktop sends diagnostics,crash reports, and usage data. This information helps Docker improve andtroubleshoot the application. Clear the check box to opt out. Docker may periodically prompt you for more information.

Resources

The Resources tab allows you to configure CPU, memory, disk, proxies, network, and other resources. Different settings are available for configuration depending on whether you are using Linux containers in WSL 2 mode, Linux containers in Hyper-V mode, or Windows containers.

Advanced

Note

The Advanced tab is only available in Hyper-V mode, because in WSL 2 mode and Windows container mode these resources are managed by Windows. In WSL 2 mode, you can configure limits on the memory, CPU, and swap size allocatedto the WSL 2 utility VM.

Use the Advanced tab to limit resources available to Docker.

CPUs: By default, Docker Desktop is set to use half the number of processorsavailable on the host machine. To increase processing power, set this to ahigher number; to decrease, lower the number.

Memory: By default, Docker Desktop is set to use 2 GB runtime memory,allocated from the total available memory on your machine. To increase the RAM, set this to a higher number. To decrease it, lower the number.

Swap: Configure swap file size as needed. The default is 1 GB.

Disk image size: Specify the size of the disk image.

Disk image location: Specify the location of the Linux volume where containers and images are stored.

You can also move the disk image to a different location. If you attempt to move a disk image to a location that already has one, you get a prompt asking if you want to use the existing image or replace it.

File sharing

Note

The File sharing tab is only available in Hyper-V mode, because in WSL 2 mode and Windows container mode all files are automatically shared by Windows.

Use File sharing to allow local directories on Windows to be shared with Linux containers.This is especially useful forediting source code in an IDE on the host while running and testing the code in a container.Note that configuring file sharing is not necessary for Windows containers, only Linux containers. If a directory is not shared with a Linux container you may get file not found or cannot start service errors at runtime. See Volume mounting requires shared folders for Linux containers.

File share settings are:

• Add a Directory: Click + and navigate to the directory you want to add.

• Apply & Restart makes the directory available to containers using Docker’sbind mount (-v) feature.

Tips on shared folders, permissions, and volume mounts

• Share only the directories that you need with the container. File sharing introduces overhead as any changes to the files on the host need to be notified to the Linux VM. Sharing too many files can lead to high CPU load and slow filesystem performance.

• Shared folders are designed to allow application code to be edited on the host while being executed in containers. For non-code items such as cache directories or databases, the performance will be much better if they are stored in the Linux VM, using a data volume (named volume) or data container.

• Docker Desktop sets permissions to read/write/execute for users, groups and others 0777 or a+rwx.This is not configurable. See Permissions errors on data directories for shared volumes.

• Windows presents a case-insensitive view of the filesystem to applications while Linux is case-sensitive. On Linux it is possible to create 2 separate files: test and Test, while on Windows these filenames would actually refer to the same underlying file. This can lead to problems where an app works correctly on a developer Windows machine (where the file contents are shared) but fails when run in Linux in production (where the file contents are distinct). To avoid this, Docker Desktop insists that all shared files are accessed as their original case. Therefore if a file is created called test, it must be opened as test. Attempts to open Test will fail with “No such file or directory”. Similarly once a file called test is created, attempts to create a second file called Test will fail.

Shared folders on demand

You can share a folder “on demand” the first time a particular folder is used by a container.

If you run a Docker command from a shell with a volume mount (as shown in theexample below) or kick off a Compose file that includes volume mounts, you get apopup asking if you want to share the specified folder.

You can select to Share it, in which case it is added your Docker Desktop Shared Folders list and available tocontainers. Alternatively, you can opt not to share it by selecting Cancel.

Proxies

Docker Desktop lets you configure HTTP/HTTPS Proxy Settings andautomatically propagates these to Docker. For example, if you set your proxysettings to http://proxy.example.com, Docker uses this proxy when pulling containers.

Your proxy settings, however, will not be propagated into the containers you start.If you wish to set the proxy settings for your containers, you need to defineenvironment variables for them, just like you would do on Linux, for example:

For more information on setting environment variables for running containers,see Set environment variables.

Network

Note

The Network tab is not available in Windows container mode because networking is managed by Windows.

You can configure Docker Desktop networking to work on a virtual private network (VPN). Specify a network address translation (NAT) prefix and subnet mask to enable Internet connectivity.

DNS Server: You can configure the DNS server to use dynamic or static IP addressing.

Note

Some users reported problems connecting to Docker Hub on Docker Desktop. This would manifest as an error when trying to rundocker commands that pull images from Docker Hub that are not alreadydownloaded, such as a first time run of docker run hello-world. If youencounter this, reset the DNS server to use the Google DNS fixed address:8.8.8.8. For more information, seeNetworking issues in Troubleshooting.

Updating these settings requires a reconfiguration and reboot of the Linux VM.

WSL Integration

In WSL 2 mode, you can configure which WSL 2 distributions will have the Docker WSL integration.

By default, the integration will be enabled on your default WSL distribution. To change your default WSL distro, run wsl --set-default <distro name>. (For example, to set Ubuntu as your default WSL distro, run wsl --set-default ubuntu).

You can also select any additional distributions you would like to enable the WSL 2 integration on.

For more details on configuring Docker Desktop to use WSL 2, see Docker Desktop WSL 2 backend.

Docker Engine

The Docker Engine page allows you to configure the Docker daemon to determine how your containers run.

Type a JSON configuration file in the box to configure the daemon settings. For a full list of options, see the Docker Enginedockerd commandline reference.

Click Apply & Restart to save your settings and restart Docker Desktop.

Command Line

On the Command Line page, you can specify whether or not to enable experimental features.

You can toggle the experimental features on and off in Docker Desktop. If you toggle the experimental features off, Docker Desktop uses the current generally available release of Docker Engine.

Experimental features

Experimental features provide early access to future product functionality.These features are intended for testing and feedback only as they may changebetween releases without warning or can be removed entirely from a futurerelease. Experimental features must not be used in production environments.Docker does not offer support for experimental features.

For a list of current experimental features in the Docker CLI, see Docker CLI Experimental features.

Run docker version to verify whether you have enabled experimental features. Experimental modeis listed under Server data. If Experimental is true, then Docker isrunning in experimental mode, as shown here:

Kubernetes

Note

The Kubernetes tab is not available in Windows container mode.

Docker Desktop includes a standalone Kubernetes server that runs on your Windows machince, sothat you can test deploying your Docker workloads on Kubernetes. To enable Kubernetes support and install a standalone instance of Kubernetes running as a Docker container, select Enable Kubernetes.

For more information about using the Kubernetes integration with Docker Desktop, see Deploy on Kubernetes.

Reset

The Restart Docker Desktop and Reset to factory defaults options are now available on the Troubleshoot menu. For information, see Logs and Troubleshooting.

Troubleshoot

Visit our Logs and Troubleshooting guide for more details.

Log on to our Docker Desktop for Windows forum to get help from the community, review current user topics, or join a discussion.

Log on to Docker Desktop for Windows issues on GitHub to report bugs or problems and review community reported issues.

For information about providing feedback on the documentation or update it yourself, see Contribute to documentation.

Switch between Windows and Linux containers

From the Docker Desktop menu, you can toggle which daemon (Linux or Windows)the Docker CLI talks to. Select Switch to Windows containers to use Windowscontainers, or select Switch to Linux containers to use Linux containers(the default).

For more information on Windows containers, refer to the following documentation:

• Microsoft documentation on Windows containers.

• Build and Run Your First Windows Server Container (Blog Post)gives a quick tour of how to build and run native Docker Windows containers on Windows 10 and Windows Server 2016 evaluation releases.

• Getting Started with Windows Containers (Lab)shows you how to use the MusicStoreapplication with Windows containers. The MusicStore is a standard .NET application and,forked here to use containers, is a good example of a multi-container application.

• To understand how to connect to Windows containers from the local host, seeLimitations of Windows containers for localhost and published ports

Settings dialog changes with Windows containers

When you switch to Windows containers, the Settings dialog only shows those tabs that are active and apply to your Windows containers:

If you set proxies or daemon configuration in Windows containers mode, theseapply only on Windows containers. If you switch back to Linux containers,proxies and daemon configurations return to what you had set for Linuxcontainers. Your Windows container settings are retained and become availableagain when you switch back.

Dashboard

The Docker Desktop Dashboard enables you to interact with containers and applications and manage the lifecycle of your applications directly from your machine. The Dashboard UI shows all running, stopped, and started containers with their state. It provides an intuitive interface to perform common actions to inspect and manage containers and Docker Compose applications. For more information, see Docker Desktop Dashboard.

Docker Hello World Image Download

Docker Hub

Select Sign in /Create Docker ID from the Docker Desktop menu to access your Docker Hub account. Once logged in, you can access your Docker Hub repositories directly from the Docker Desktop menu.

For more information, refer to the following Docker Hub topics:

Two-factor authentication

Docker Desktop enables you to sign into Docker Hub using two-factor authentication. Two-factor authentication provides an extra layer of security when accessing your Docker Hub account.

You must enable two-factor authentication in Docker Hub before signing into your Docker Hub account through Docker Desktop. For instructions, see Enable two-factor authentication for Docker Hub.

After you have enabled two-factor authentication:

1. Go to the Docker Desktop menu and then select Sign in / Create Docker ID.

2. Enter your Docker ID and password and click Sign in.

3. After you have successfully signed in, Docker Desktop prompts you to enter the authentication code. Enter the six-digit code from your phone and then click Verify.

After you have successfully authenticated, you can access your organizations and repositories directly from the Docker Desktop menu.

Adding TLS certificates

You can add trusted Certificate Authorities (CAs) to your Docker daemon to verify registry server certificates, and client certificates, to authenticate to registries.

How do I add custom CA certificates?

Docker Desktop supports all trusted Certificate Authorities (CAs) (root orintermediate). Docker recognizes certs stored under Trust RootCertification Authorities or Intermediate Certification Authorities.

Docker Desktop creates a certificate bundle of all user-trusted CAs based onthe Windows certificate store, and appends it to Moby trusted certificates. Therefore, if an enterprise SSL certificate is trusted by the user on the host, it is trusted by Docker Desktop.

To learn more about how to install a CA root certificate for the registry, seeVerify repository client with certificatesin the Docker Engine topics.

How do I add client certificates?

You can add your client certificatesin ~/.docker/certs.d/<MyRegistry>:<Port>/client.cert and~/.docker/certs.d/<MyRegistry>:<Port>/client.key. You do not need to push your certificates with git commands.

When the Docker Desktop application starts, it copies the~/.docker/certs.d folder on your Windows system to the /etc/docker/certs.ddirectory on Moby (the Docker Desktop virtual machine running on Hyper-V).

You need to restart Docker Desktop after making any changes to the keychainor to the ~/.docker/certs.d directory in order for the changes to take effect.

The registry cannot be listed as an insecure registry (seeDocker Daemon). Docker Desktop ignorescertificates listed under insecure registries, and does not send clientcertificates. Commands like docker run that attempt to pull from the registryproduce error messages on the command line, as well as on the registry.

To learn more about how to set the client TLS certificate for verification, seeVerify repository client with certificatesin the Docker Engine topics.

Where to go next

• Try out the walkthrough at Get Started.

• Dig in deeper with Docker Labs example walkthroughs and source code.

• Refer to the Docker CLI Reference Guide.

There are many ways to optimize both the Docker build process and the resulting Docker images. This article explains how the Docker build process works and how to optimally create images for Windows containers.

Image layers in Docker build

Before you can optimize your Docker build, you'll need to know how Docker build works. During the Docker build process, a Dockerfile is consumed, and each actionable instruction is run, one-by-one, in its own temporary container. The result is a new image layer for each actionable instruction.

For example, the following sample Dockerfile uses the mcr.microsoft.com/windows/servercore:ltsc2019 base OS image, installs IIS, and then creates a simple website.

Download Hello World Docker Image Download

You might expect that this Dockerfile will produce an image with two layers, one for the container OS image, and a second that includes IIS and the website. However, the actual image has many layers, and each layer depends upon the one before it.

To make this clearer, let's run the docker history command against the image our sample Dockerfile made.

The output shows us that this image has four layers: the base layer and three additional layers that are mapped to each instruction in the Dockerfile. The bottom layer (6801d964fda5 in this example) represents the base OS image. One layer up is the IIS installation. The next layer includes the new website, and so on.

Dockerfiles can be written to minimize image layers, optimize build performance, and optimize accessibility through readability. Ultimately, there are many ways to complete the same image build task. Understanding how the Dockerfile's format affects build time and the image it creates improves the automation experience.

Optimize image size

Depending on your space requirements, image size can be an important factor when building Docker container images. Container images are moved between registries and host, exported and imported, and ultimately consume space. This section will tell you how to minimize image size during the Docker build process for Windows containers.

For additional information about Dockerfile best practices, see Best practices for writing Dockerfiles on Docker.com.

Group related actions

Because each RUN instruction creates a new layer in the container image, grouping actions into one RUN instruction can reduce the number of layers in a Dockerfile. While minimizing layers may not affect image size much, grouping related actions can, which will be seen in subsequent examples.

In this section, we'll compare two example Dockerfiles that do the same things. However, one Dockerfile has one instruction per action, while the other had its related actions grouped together.

The following ungrouped example Dockerfile downloads Python for Windows, installs it, and removes the downloaded setup file once installation is done. In this Dockerfile, each action is given its own RUN instruction.

The resulting image consists of three additional layers, one for each RUN instruction.

The second example is a Dockerfile that performs the exact same operation. However, all related actions have been grouped under a single RUN instruction. Each step in the RUN instruction is on a new line of the Dockerfile, while the ' character is used to line wrap.

The resulting image has only one additional layer for the RUN instruction.

Remove excess files

If there's a file in your Dockerfile, such as an installer, that you don't need after it's been used, you can remove it to reduce image size. This needs to occur in the same step in which the file was copied into the image layer. Doing so prevents the file from persisting in a lower-level image layer.

In the following example Dockerfile, the Python package is downloaded, executed, then removed. This is all completed in one RUN operation and results in a single image layer.

Optimize build speed

Multiple lines

You can split operations into multiple individual instructions to optimize Docker build speed. Multiple RUN operations increase caching effectiveness because individual layers are created for each RUN instruction. If an identical instruction was already run in a different Docker Build operation, this cached operation (image layer) is reused, resulting in decreased Docker build runtime.

In the following example, both Apache and the Visual Studio Redistribute packages are downloaded, installed, and then cleaned up by removing files that are no longer needed. This is all done with a single RUN instruction. If any of these actions are updated, all actions will rerun.

The resulting image has two layers, one for the base OS image, and one that contains all operations from the single RUN instruction.

By comparison, here are the same actions split into three RUN instructions. In this case, each RUN instruction is cached in a container image layer, and only those that have changed need to be rerun on subsequent Dockerfile builds.

The resulting image consists of four layers; one layer for the base OS image and each of the three RUN instructions. Because each RUN instruction ran in its own layer, any subsequent runs of this Dockerfile or identical set of instructions in a different Dockerfile will use cached image layers, reducing build time.

How you order the instructions is important when working with image caches, as you'll see in the next section.

Ordering instructions

A Dockerfile is processed from top to the bottom, each Instruction compared against cached layers. When an instruction is found without a cached layer, this instruction and all subsequent instructions are processed in new container image layers. Because of this, the order in which instructions are placed is important. Place instructions that will remain constant towards the top of the Dockerfile. Place instructions that may change towards the bottom of the Dockerfile. Doing so reduces the likelihood of negating existing cache.

The following examples show how Dockerfile instruction ordering can affect caching effectiveness. This simple example Dockerfile has four numbered folders.

The resulting image has five layers, one for the base OS image and each of the RUN instructions.

This next Dockerfile has now been slightly modified, with the third RUN instruction changed to a new file. When Docker build is run against this Dockerfile, the first three instructions, which are identical to those in the last example, use the cached image layers. However, because the changed RUN instruction isn't cached, a new layer is created for the changed instruction and all subsequent instructions.

Download Hello World Docker Image File

When you compare the image IDs of the new image to that in this section's first example, you'll notice that the first three layers from bottom to top are shared, but the fourth and fifth are unique.

Cosmetic optimization

Instruction case

Dockerfile instructions are not case-sensitive, but the convention is to use upper case. This improves readability by differentiating between the Instruction call and instruction operation. The following two examples compare an uncapitalized and capitalized Dockerfile.

The following is an uncapitalized Dockerfile:

The following is the same Dockerfile using upper-case:

Line wrapping

Long and complex operations can be separated onto multiple lines by the backslash character. The following Dockerfile installs the Visual Studio Redistributable package, removes the installer files, and then creates a configuration file. These three operations are all specified on one line.

The command can be broken up with backslashes so that each operation from the one RUN instruction is specified on its own line.

Further reading and references