Debian Testing Docker

Estimated reading time: 9 minutes

• A collection of common build dependencies used for installing various modules, e.g., gems.
• Debian and Ubuntu. Docker runs on: Ubuntu Xenial 16.04 LTS; Ubuntu Wily 15.10; Ubuntu Trusty 14.04 LTS; Ubuntu Precise 12.04 LTS; Debian testing stretch; Debian 8.0 Jessie; Debian 7.0 Wheezy (you must enable backports) Debian Wheezy. If so, you need to enable backports (if not, ignore this section).
• HASS.io on Ubuntu Server / Debian using Docker - Final Thoughts. Whether you use Home Assistant or HASS.io is your call. I am liking my move from Home Assistant to HASS.io on Docker. However, it certainly was not an easy move. I am pretty comfortable with Docker and Docker compose and I was cruising on my previous set up.
• Docker defines a format for bundling an application and all its dependencies into a single object called a container. This container can be transferred to any Docker-enabled machine. The container can be executed there with the guarantee that the execution environment exposed to the application is the same in development, testing, and production.

Does Docker run on Linux, macOS, and Windows?

In this guide, I'll discuss a step by step installation of Docker and Docker Compose on Debian 10 (Buster). Docker is the most popular and widely used container runtime. It enables you to package and run your applications in isolated containers in a single server or cluster of Linux servers orchestrated by Kubernetes and similar tools.

You can run both Linux and Windows programs and executables in Docker containers. The Docker platform runs natively on Linux (on x86-64, ARM and many other CPU architectures) and on Windows (x86-64).

Docker Inc. builds products that let you build and run containers on Linux, Windows and macOS.

What does Docker technology add to just plain LXC?

Docker technology is not a replacement for LXC. 'LXC' refers to capabilities ofthe Linux kernel (specifically namespaces and control groups) which allowsandboxing processes from one another, and controlling their resourceallocations. On top of this low-level foundation of kernel features, Dockeroffers a high-level tool with several powerful functionalities:

• Portable deployment across machines. Docker defines a format for bundling an application and all its dependencies into a single object called a container. This container can be transferred to any Docker-enabled machine. The container can be executed there with the guarantee that the execution environment exposed to the application is the same in development, testing, and production. LXC implements process sandboxing, which is an important pre-requisite for portable deployment, but is not sufficient for portable deployment. If you sent me a copy of your application installed in a custom LXC configuration, it would almost certainly not run on my machine the way it does on yours. The app you sent me is tied to your machine's specific configuration: networking, storage, logging, etc. Docker defines an abstraction for these machine-specific settings. The exact same Docker container can run - unchanged - on many different machines, with many different configurations.

• Application-centric. Docker is optimized for the deployment of applications, as opposed to machines. This is reflected in its API, user interface, design philosophy and documentation. By contrast, the lxc helper scripts focus on containers as lightweight machines - basically servers that boot faster and need less RAM. We think there's more to containers than just that.

• Automatic build. Docker includes a tool for developers to automatically assemble a container from their source code, with full control over application dependencies, build tools, packaging etc. They are free to use make, maven, chef, puppet, salt, Debian packages, RPMs, source tarballs, or any combination of the above, regardless of the configuration of the machines.

• Versioning. Docker includes git-like capabilities for tracking successive versions of a container, inspecting the diff between versions, committing new versions, rolling back etc. The history also includes how a container was assembled and by whom, so you get full traceability from the production server all the way back to the upstream developer. Docker also implements incremental uploads and downloads, similar to git pull, so new versions of a container can be transferred by only sending diffs.

• Component re-use. Any container can be used as a parent image tocreate more specialized components. This can be done manually or as part of anautomated build. For example you can prepare the ideal Python environment, anduse it as a base for 10 different applications. Your ideal PostgreSQL setup canbe re-used for all your future projects. And so on.

• Sharing. Docker has access to a public registry on DockerHub where thousands ofpeople have uploaded useful images: anything from Redis, CouchDB, PostgreSQL toIRC bouncers to Rails app servers to Hadoop to base images for various Linuxdistros. The registry also includes an official 'standardlibrary' of useful containers maintained by the Docker team. The registry itselfis open-source, so anyone can deploy their own registry to store and transferprivate containers, for internal server deployments for example.

• Tool ecosystem. Docker defines an API for automating and customizing the creation and deployment of containers. There are a huge number of tools integrating with Docker to extend its capabilities. PaaS-like deployment (Dokku, Deis, Flynn), multi-node orchestration (Maestro, Salt, Mesos, Openstack Nova), management dashboards (docker-ui, Openstack Horizon, Shipyard), configuration management (Chef, Puppet), continuous integration (Jenkins, Strider, Travis), etc. Docker is rapidly establishing itself as the standard for container-based tooling.

What is different between a Docker container and a VM?

There's a great StackOverflow answer showing the differences.

Do I lose my data when the container exits?

Not at all! Any data that your application writes to disk gets preserved in itscontainer until you explicitly delete the container. The file system for thecontainer persists even after the container halts.

How far do Docker containers scale?

Some of the largest server farms in the world today are based on containers.Large web deployments like Google and Twitter, and platform providers such asHeroku run on container technology, at a scale of hundreds ofthousands or even millions of containers.

How do I connect Docker containers?

Currently the recommended way to connect containers is via the Docker networkfeature. You can see details of how to work with Docker networks.

How do I run more than one process in a Docker container?

This approach is discouraged for most use cases. For maximum efficiency andisolation, each container should address one specific area of concern. However,if you need to run multiple services within a single container, seeRun multiple services in a container.

How do I report a security issue with Docker?

You can learn about the project's security policyhere and report security issues to thismailbox.

Why do I need to sign my commits to Docker with the DCO?

Read our blog post on the introduction of the DCO.

When building an image, should I prefer system libraries or bundled ones?

This is a summary of a discussion on the docker-dev mailing list.

Virtually all programs depend on third-party libraries. Most frequently, theyuse dynamic linking and some kind of package dependency, so that whenmultiple programs need the same library, it is installed only once.

Some programs, however, bundle their third-party libraries, because theyrely on very specific versions of those libraries. Docker run ansible playbook ubuntu.

When creating a Docker image, is it better to use the bundled libraries, orshould you build those programs so that they use the default system librariesinstead?

The key point about system libraries is not about saving disk or memory space.It is about security. All major distributions handle security seriously, byhaving dedicated security teams, following up closely with publishedvulnerabilities, and disclosing advisories themselves. (Look at the DebianSecurity Informationfor an example of those procedures.) Upstream developers, however, do not alwaysimplement similar practices.

Before setting up a Docker image to compile a program from source, if you wantto use bundled libraries, you should check if the upstream authors provide aconvenient way to announce security vulnerabilities, and if they update theirbundled libraries in a timely manner. If they don't, you are exposing yourself(and the users of your image) to security vulnerabilities.

Likewise, before using packages built by others, you should check if thechannels providing those packages implement similar security best practices.Downloading and installing an 'all-in-one' .deb or .rpm sounds great at first,except if you have no way to figure out that it contains a copy of the OpenSSLlibrary vulnerable to the Heartbleed bug.

Why is DEBIAN_FRONTEND=noninteractive discouraged in Dockerfiles?

When building Docker images on Debian and Ubuntu you may have seen errors like:

These errors don't stop the image from being built but inform you that theinstallation process tried to open a dialog box, but couldn't. Generally,these errors are safe to ignore.

Some people circumvent these errors by changing the DEBIAN_FRONTENDenvironment variable inside the Dockerfile using:

This prevents the installer from opening dialog boxes during installation whichstops the errors.

While this may sound like a good idea, it may have side effects. TheDEBIAN_FRONTEND environment variable is inherited by all images andcontainers built from your image, effectively changing their behavior. Peopleusing those images run into problems when installing softwareinteractively, because installers do not show any dialog boxes.

Because of this, and because setting DEBIAN_FRONTEND to noninteractive ismainly a ‘cosmetic' change, we discourage changing it.

If you really need to change its setting, make sure to change it back to itsdefault valueafterwards.

Why do I get Connection reset by peer when making a request to a service running in a container?

Typically, this message is returned if the service is already bound to yourlocalhost. As a result, requests coming to the container from outside aredropped. To correct this problem, change the service's configuration on yourlocalhost so that the service accepts requests from all IPs. If you aren't surehow to do this, check the documentation for your OS.

Why do I get Cannot connect to the Docker daemon. Is the docker daemon running on this host? when using docker-machine?

This error points out that the docker client cannot connect to the virtualmachine. This means that either the virtual machine that works underneathdocker-machine is not running or that the client doesn't correctly point atit.

To verify that the docker machine is running you can use the docker-machine lscommand and start it with docker-machine start if needed.

You need to tell Docker to talk to that machine. You can do this with thedocker-machine env command. For example,

Where can I find more answers?

You can find more answers on:

Estimated reading time: 10 minutes

To get started with Docker Engine on Debian, make sure youmeet the prerequisites, theninstall Docker.

Prerequisites

OS requirements

To install Docker Engine, you need the 64-bit version of one of these Debian orRaspbian versions:

• Debian Buster 10 (stable)
• Debian Stretch 9 / Raspbian Stretch

Docker Engine is supported on x86_64 (or amd64), armhf, and arm64 architectures.

Uninstall old versions

Older versions of Docker were called docker, docker.io, or docker-engine.If these are installed, uninstall them:

It's OK if apt-get reports that none of these packages are installed.

The contents of /var/lib/docker/, including images, containers, volumes, andnetworks, are preserved. The Docker Engine package is now called docker-ce.

Installation methods

You can install Docker Engine in different ways, depending on your needs:

• Most usersset up Docker's repositories and installfrom them, for ease of installation and upgrade tasks. This is therecommended approach, except for Raspbian.

• Some users download the DEB package andinstall it manually and manageupgrades completely manually. This is useful in situations such as installingDocker on air-gapped systems with no access to the internet.

• In testing and development environments, some users choose to use automatedconvenience scripts to install Docker.This is currently the only approach for Raspbian.

Install using the repository

Before you install Docker Engine for the first time on a new host machine, you needto set up the Docker repository. Afterward, you can install and update Dockerfrom the repository.

Debian Testing Docker Definition

Raspbian users cannot use this method!

For Raspbian, installing using the repository is not yet supported. You mustinstead use the convenience script.

Set up the repository

1. Update the apt package index and install packages to allow apt to use arepository over HTTPS:

2. Add Docker's official GPG key:

3. Use the following command to set up the stable repository. To add thenightly or test repository, add the word nightly or test (or both)after the word stable in the commands below. Learn about nightly and test Mac mojave dmg download. channels.

   Note: The lsb_release -cs sub-command below returns the name of yourDebian distribution, such as helium. Sometimes, in a distributionlike BunsenLabs Linux, you might need to change $(lsb_release -cs)to your parent Debian distribution. For example, if you are using BunsenLabs Linux Helium, you could use stretch. Docker does not offer any guarantees on untestedand unsupported Debian distributions.

Install Docker Engine

This procedure works for Debian on x86_64 / amd64, armhf, arm64, and Raspbian.

1. Update the apt package index, and install the latest version of DockerEngine and containerd, or go to the next step to install a specific version:

   Got multiple Docker repositories?

   If you have multiple Docker repositories enabled, installingor updating without specifying a version in the apt-get install orapt-get update command always installs the highest possible version,which may not be appropriate for your stability needs.

2. To install a specific version of Docker Engine, list the available versionsin the repo, then select and install:

   a. List the versions available in your repo:

   b. Install a specific version using the version string from the second column, for example, 5:18.09.1~3-0~debian-stretch .

3. Verify that Docker Engine is installed correctly by running the hello-worldimage.

   This command downloads a test image and runs it in a container. When thecontainer runs, it prints an informational message and exits.

Docker Engine is installed and running. The docker group is created but no usersare added to it. You need to use sudo to run Docker commands.Continue to Linux postinstall to allow non-privilegedusers to run Docker commands and for other optional configuration steps.

Upgrade Docker Engine

To upgrade Docker Engine, first run sudo apt-get update, then follow theinstallation instructions, choosing the newversion you want to install.

Install from a package

If you cannot use Docker's repository to install Docker Engine, you can download the.deb file for your release and install it manually. You need to downloada new file each time you want to upgrade Docker.

1. Go to https://download.docker.com/linux/debian/dists/,choose your Debian version, then browse to pool/stable/, choose amd64,armhf, or arm64, and download the .deb file for the Docker Engineversion you want to install.

   Note: To install a nightly or test (pre-release) package,change the word stable in the above URL to nightly or test.Learn about nightly and test channels.

2. Install Docker Engine, changing the path below to the path where you downloadedthe Docker package.

   The Docker daemon starts automatically.

3. Verify that Docker Engine is installed correctly by running the hello-worldimage.

   This command downloads a test image and runs it in a container. When thecontainer runs, it prints an informational message and exits.

Docker Engine is installed and running. The docker group is created but no usersare added to it. You need to use sudo to run Docker commands.Continue to Post-installation steps for Linux to allownon-privileged users to run Docker commands and for other optional configurationsteps.

Upgrade Docker Engine

To upgrade Docker Engine, download the newer package file and repeat theinstallation procedure, pointing to the new file.

Install using the convenience script

Docker provides convenience scripts at get.docker.comand test.docker.com for installing edge andtesting versions of Docker Engine - Community into development environments quickly andnon-interactively. The source code for the scripts is in thedocker-install repository.Using these scripts is not recommended for productionenvironments, and you should understand the potential risks before you usethem:

• The scripts require root or sudo privileges to run. Therefore,you should carefully examine and audit the scripts before running them.
• The scripts attempt to detect your Linux distribution and version andconfigure your package management system for you. In addition, the scripts donot allow you to customize any installation parameters. This may lead to anunsupported configuration, either from Docker's point of view or from your ownorganization's guidelines and standards.
• The scripts install all dependencies and recommendations of the packagemanager without asking for confirmation. This may install a large number ofpackages, depending on the current configuration of your host machine.
• The script does not provide options to specify which version of Docker to install,and installs the latest version that is released in the 'edge' channel.
• Do not use the convenience script if Docker has already been installed on thehost machine using another mechanism.

This example uses the script at get.docker.com toinstall the latest release of Docker Engine - Community on Linux. To install the latesttesting version, use test.docker.com instead. Ineach of the commands below, replace each occurrence of get with test.

Warning:

Always examine scripts downloaded from the internet beforerunning them locally.

If you would like to use Docker as a non-root user, you should now consideradding your user to the 'docker' group with something like:

Remember to log out and back in for this to take effect!

Warning:

Debian Testing Docker Ubuntu

Adding a user to the 'docker' group grants them the ability to run containerswhich can be used to obtain root privileges on the Docker host. Refer toDocker Daemon Attack Surfacefor more information.

Docker Engine - Community is installed. It starts automatically on DEB-based distributions. OnRPM-based distributions, you need to start it manually using the appropriatesystemctl or service command. As the message indicates, non-root users can'trun Docker commands by default.

Note:

To install Docker without root privileges, seeRun the Docker daemon as a non-root user (Rootless mode).

Upgrade Docker after using the convenience script

If you installed Docker using the convenience script, you should upgrade Dockerusing your package manager directly. There is no advantage to re-running theconvenience script, and it can cause issues if it attempts to re-addrepositories which have already been added to the host machine.

Uninstall Docker Engine

1. Uninstall the Docker Engine, CLI, and Containerd packages:

2. Images, containers, volumes, or customized configuration files on your hostare not automatically removed. To delete all images, containers, andvolumes:

You must delete any edited configuration files manually.

Next steps

• Continue to Post-installation steps for Linux.
• Review the topics in Develop with Docker to learn how to build new applications using Docker.

Debian Testing Docker Command