Estimated reading time: 9 minutes

Does Docker run on Linux, macOS, and Windows?

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 debian container

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. Docker is an application that simplifies the process of managing application processes in containers. In this tutorial, you'll install and use Docker Community Edition (CE) on Debian 10.

Docker cp /root/some-file.txt some-docker-container:/root This will copy the file some-file.txt in the directory /root on your host machine into the Docker container named some-docker-container into the directory /root. It is very close to the secure copy syntax. And as shown in the previous post, you can use it vice versa. Docker is a utility that lets you create a container for running applications. A Docker container is a fully-contained virtual machine. This guide will show you three methods to SSH into a Docker container and run commands. [email protected]:$ docker ps CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES 1bcf775d8cc7 ubuntu 'bash' 8 minutes ago Up About a minute container-2 94f92052f55f debian 'bash' 10 minutes ago Up 10 minutes container-1.

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.

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.

Docker Debian Container

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:

faq, questions, documentation, docker

This docker tutorial discusses methods to stop a single docker container, multiple docker containers or all running docker containers at once. You’ll also learn to gracefully stop a docker container.

To stop a docker container, all you have to do is to use the container ID or container name in the following fashion:

Docker Debian Container Bash

Docker

You may also use docker container stop container_id_or_name command but that’s one additional word in the command and it doesn’t provide any additional benefits so stick with docker stop.

But there is more to stopping a docker container that you should know, specially if you are a Docker beginner.

Debian Docker Container Location

Practical examples for stopping docker container

I’ll discuss various aspects around stopping a docker container in this tutorial:

  • Stop a docker container
  • Stop multiple docker containers at once
  • Stop all docker containers with a certain image
  • Stop all running docker containers at once
  • Gracefully stopping a docker container

Before you see that, you should know how to get the container name or ID.

You can list all the running docker containers with the docker ps command. Without any options, the docker ps command only shows the running containers.

The output also gives you the container name and container ID. You can use either of these two to stop a container.

Now let’s go about stopping containers.

1. Stop a docker container

To stop a specific container, use its ID or name with docker stop command:

The output should have been more descriptive but it just shows the container name or ID whichever you provided:

You can use the docker stop command on an already stopped container. It won’t throw any errors or a different output.

You can verify if the container has been stopped by using the docker ps -a command. The -a option shows all containers whether they are running or stopped.

If the status is Exited, it means the container is not running any more.

2. Stop multiple docker containers

You can stop multiple docker containers at once as well. You just have to provide the container names and IDs.

As previously, the output will simply show the name or ID of the containers:

Container

3. Stop all containers associated with an image

So far what you saw stopping containers by explicitely mentioning their name or ID.

What if you want to stop all running containers of a certain docker image? Imagine a scenario where you want to remove a docker image but you’ll have to stop all the associated running containers.

You may provide the container names or IDs one by one but that’s time consuming. What you can do is to filter all the running containers based on their base image.

Just replace the IMAGE_NAME by your docker image name and you should be able to stop all running containers associated with that image.

The option -q shows only the container ID. Thanks to the wonderful xargs command, these container IDs are piped to the docker stop as argument.

4. Stop all running docker containers

You may face a situation where you are required to stop all running containers. For example if you want to remove all containers in Docker, you should stop them beforehand.

To do that, you can use something similar to what you saw in the previous section. Just remove the image part.

5. Stop a container gracefully

To be honest, docker stops a container gracefully by default. When you use the docker stop command, it gives the container 10 seconds before forcefully killing it.

It doesn’t mean that it always takes 10 seconds to stop a container. It’s just that if the container is running some processes, it gets 10 seconds to stop the process and exit.

Docker stop command first sends the SIGTERM command. If the conainer is stopped in this period, it sends the SIGKILL command.

Macos installer (pkg) from apple's developer website. A process may ignore the SIGTERM but SIGKILL will kill the process immediately.

You may change this grace period of 10 seconds with the -t option. Suppose you want to wait 30 seconds before stopping the container:

In the end…

I think that this much information covers the topic very well. You know plenty of things about stopping a docker container.

Stay tuned for more docker tips and tutorials. If you have questions or suggestions, please let me know in the comment section.

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