Docker images are essential components used for building Docker containers. Although closely related, there are major difference between Docker images and containers.

• Manually Download Docker Image Download
• Manual Download Docker Image
• Manually Download Docker Image File

Set the version number of my image name in my docker-compose file. If my image isn't built yet: run docker-compose build; Run docker-compose up -d; I didn't realize at the time, but docker-compose is smart enough to simply update my container to the new image with the one command, instead of having to bring it down first. Update Docker image. To update your Docker image and container, first download the latest version: docker pull hwdsl2/ipsec-vpn-server If the Docker image is already up to date, you should see: Status: Image is up to date for hwdsl2/ipsec-vpn-server:latest Otherwise, it will download the latest version. A docker image is the base of a container. These images are created by writing Dockerfiles, lists of instructions automatically executed for creating a specific Docker image. When building a Docker image, you want to make sure to keep it light. Avoiding large images speeds up building and deploying containers. Therefore, it is crucial to reduce.

A docker image is the base of a container. These images are created by writing Dockerfiles, lists of instructions automatically executed for creating a specific Docker image.

When building a Docker image, you want to make sure to keep it light. Avoiding large images speeds up building and deploying containers. Therefore, it is crucial to reduce the image size to a minimum.

Read on to learn how to keep your Docker images small.

To create a Docker image, you need a base on which you can install and add components, as needed. You can download an existing parent image and use it as the base of your own image or build one from scratch.

You install a variation of an operating system as the base of an image. The OS base can drastically impact the size of your final Docker image, which is why deciding on the right one plays a significant role.

Linux created a helpful alternative that is lightweight and has a minimal POSIX environment – Alpine. This Linux distribution image base is only 5 MB, built around musl libc and BusyBox.

Compared to other OS images, Alpine is much smaller in size. The most downloaded OS image, Ubuntu, is 188 MB, while Alpine is only 5 MB.

Excluding certain files that aren’t necessary for your image can help you reduce the image size. That is where the .dockerignore file comes in.

When building an image, you write a Dockerfile with specifications of what that image should look like.

When outlining the build context, it is important also to include a .dockerignore file and store it in the same folder as the Dockerfile.

This Docker feature is initiated with docker run. The system checks whether there is such a file and applies its exceptions and ignore rules. That way, you remove any irrelevant content from the built context.

Docker introduced the multi-stage feature in its 17.05 version. It allows users to divide the Dockerfile into multiple stages.

Each stage begins with a FROM instruction. The required artifact passes to the following stage, leaving behind content that you won’t need in the final image artifact.

Since the process only transfers the necessary components of the artifact, you don’t have to clean up manually after every instruction.

With the multi-stage feature, you avoid adding unnecessary layers, which has a considerable impact on the overall image size.

Avoid Adding Unnecessary Layers to Reduce Docker Image Size

A Docker image takes up more space with every layer you add to it. Therefore, the more layers you have, the more space the image requires.

Each RUN instruction in a Dockerfile adds a new layer to your image. That is why you should try to do file manipulation inside a single RUN command. Also, combine different commands into one instruction using the && option.

For instance, you can update the repository and install multiple packages in a single RUN instruction. To get a clear, comprehensive line, use the backslash () to type out the command in multiple lines.

Apart from updating and installing the packages, you should also clean up apt cache with && rm -rf /var/lib/apt/lists/* to save up some more space.

Beware of Updates and Unnecessary Packages and Dependencies

Another way to save space and keep your Docker image small is to ensure you are running the latest version of the platform you are building on.

By having the newest version, you avoid extensive updates that download countless rpm packages and take up a lot of space.

Note: If you need to update, make sure to clean up the rpm cache and add the dnf cleanall option: RUN dnf -y update && dnf clean all.

Installing a package also often includes downloading dependencies on which the software relies on. However, sometimes the download will also store packages that are not required but rather are recommended.

Such unwanted packages can add up and consume a lot of disk space. To download only the main dependencies, add the --no-install-recommends option to the install command.

For example:

Although this tip doesn’t affect the overall size of the Docker image, it does help with faster Docker builds.

Docker speeds up image building by locally caching existing layers of a Dockerfile and using it to rebuild images faster.

For example, imagine you have a simple Dockerfile consisting of three layers. Once you build an image from that file, the system automatically caches these three layers. The next time you build the image, it loads from the local cache.

If you decide to modify the image and change one of the layers, the cache won’t be used for anything after the modified layer.

We recommend ordering the instructions in a way that improved efficiency and utilizes the caching feature. Place instructions that are likely to change as low in the Dockerfile as possible.

Docker containers support the implementation of CI/CD in development. Image size and build efficiency are important factors when overseeing and working with the microservice architecture. This is why you should try to keep your Docker images small, by following the valuable advice outlined in this article.

Next you should also read

CMD is Docker instruction used if you need a default command which users can easily override. ENTRYPOINT is…

CentOS 8 does not provide official support for Docker. This article clearly shows you how to install a fully…

A Dockerfile offers a simpler and faster way of creating Docker images. They go through the script with all…

Docker allows users to create a container in which an application or process can run. In this guide, you will…

Estimated reading time: 14 minutes

Manually Download Docker Image Download

Welcome to Docker Desktop! The Docker Desktop for Mac 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.

Preferences

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

Choose the Docker menu > Preferences from themenu bar and configure the runtime options described below.

General

On the General tab, you can configure when to start and update Docker:

• Start Docker Desktop when you log in: Automatically starts Docker Desktop when you open your session.

• Include VM in Time Machine backups: Select this option to back up the Docker Desktop virtual machine. This option is disabled by default.

• Securely store Docker logins in macOS keychain: Docker Desktop stores your Docker login credentials in macOS keychain by default.

• Send usage statistics: Docker Desktop sends diagnostics, crash reports, and usage data. This information helps Docker improve and troubleshoot the application. Clear the check box to opt out.

Resources

The Resources tab allows you to configure CPU, memory, disk, proxies, network, and other resources.

Advanced

On the Advanced tab, you can limit resources available to Docker.

Advanced settings are:

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 Mac. 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.

Manual Download Docker 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

Use File sharing to allow local directories on the Mac 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.By default the /Users, /Volume, /private, /tmp and /var/folders directory are shared. If your project is outside this directory then it must be addedto the list. Otherwise you may get Mounts denied or cannot start service errors at runtime.

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.

• If you share the whole of your home directory into a container, MacOS may prompt you to give Docker access to personal areas of your home directory such as your Reminders or Downloads.

• By default, Mac file systems are case-insensitive while Linux is case-sensitive. On Linux, it is possible to create 2 separate files: test and Test, while on Mac these filenames would actually refer to the same underlying file. This can lead to problems where an app works correctly on a Mac (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 the error No such file or directory. Similarly, once a file called test is created, attempts to create a second file called Test will fail. For more information, see Volume mounting requires file sharing for any project directories outside of /Users.)

Proxies

Docker Desktop detects HTTP/HTTPS Proxy Settings from macOS and automaticallypropagates these to Docker. For example, if you set yourproxy settings to http://proxy.example.com, Docker uses this proxy whenpulling 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

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.

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

Manually Download Docker Image File

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

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.

You can see whether you are running experimental mode at the command line. IfExperimental is true, then Docker is running in experimental mode, as shownhere. (If false, Experimental mode is off.)

Kubernetes

Docker Desktop includes a standalone Kubernetes server that runs on your Mac, 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

Reset and Restart options

On Docker Desktop Mac, the Restart Docker Desktop, Reset to factory defaults, and other reset options are available from the Troubleshoot menu.

For information about the reset options, see Logs and Troubleshooting.

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 existing Docker Compose applications. For more information, see Docker Desktop Dashboard.

Add TLS certificates

You can add trusted Certificate Authorities (CAs) (used to verify registryserver certificates) and client certificates (used to authenticate toregistries) to your Docker daemon.

Add custom CA certificates (server side)

All trusted CAs (root or intermediate) are supported. Docker Desktop creates acertificate bundle of all user-trusted CAs based on the Mac Keychain, andappends it to Moby trusted certificates. So if an enterprise SSL certificate istrusted by the user on the host, it is trusted by Docker Desktop.

To manually add a custom, self-signed certificate, start by adding thecertificate to the macOS keychain, which is picked up by Docker Desktop. Here isan example:

Or, if you prefer to add the certificate to your own local keychain only (ratherthan for all users), run this command instead:

See also, Directory structures forcertificates.

Note: You need to restart Docker Desktop after making any changes to thekeychain or to the ~/.docker/certs.d directory in order for the changes totake effect.

For a complete explanation of how to do this, see the blog post AddingSelf-signed Registry Certs to Docker & Docker Desktop forMac.

Add client certificates

You can put your client certificates in~/.docker/certs.d/<MyRegistry>:<Port>/client.cert and~/.docker/certs.d/<MyRegistry>:<Port>/client.key.

When the Docker Desktop application starts, it copies the ~/.docker/certs.dfolder on your Mac to the /etc/docker/certs.d directory on Moby (the DockerDesktop xhyve virtual machine).

• 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 takeeffect.

• The registry cannot be listed as an insecure registry (see DockerEngine. Docker Desktop ignores certificates listedunder insecure registries, and does not send client certificates. Commandslike docker run that attempt to pull from the registry produce errormessages on the command line, as well as on the registry.

Directory structures for certificates

If you have this directory structure, you do not need to manually add the CAcertificate to your Mac OS system login:

The following further illustrates and explains a configuration with customcertificates:

You can also have this directory structure, as long as the CA certificate isalso in your keychain.

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

Install shell completion

Docker Desktop comes with scripts to enable completion for the docker and docker-compose commands. The completion scripts may befound inside Docker.app, in the Contents/Resources/etc/ directory and can beinstalled both in Bash and Zsh.

Bash

Bash has built-in support forcompletion To activate completion for Docker commands, these files need to becopied or symlinked to your bash_completion.d/ directory. For example, if youinstalled bash via Homebrew:

Add the following to your ~/.bash_profile:

OR

Zsh

In Zsh, the completionsystemtakes care of things. To activate completion for Docker commands,these files need to be copied or symlinked to your Zsh site-functions/directory. For example, if you installed Zsh via Homebrew:

Fish-Shell

Fish-shell also supports tab completion completionsystem. To activate completion for Docker commands,these files need to be copied or symlinked to your Fish-shell completions/directory.

Create the completions directory:

Now add fish completions from docker.

Give feedback and get help

To get help from the community, review current user topics, join or start adiscussion, log on to our Docker Desktop for Macforum.

To report bugs or problems, log on to Docker Desktop for Mac issues onGitHub,where you can review community reported issues, and file new ones. SeeLogs and Troubleshooting for more details.

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

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 and organizations 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.

Where to go next

• Try out the walkthrough at Get Started.

• Dig in deeper with Docker Labs examplewalkthroughs and source code.

• For a summary of Docker command line interface (CLI) commands, seeDocker CLI Reference Guide.

• Check out the blog post, What’s New in Docker 17.06 Community Edition(CE).