How to run docker in docker container

How do I run a docker instance from a DockerFile?

I finally figured out how to get docker up and running.

I linked it to a redis instance, cool.

This is from scratch and I assume that when I created the redis instance

it pulls the image from a remote repo?

NodeBB offers a Dockerfile https://github.com/NodeBB/NodeBB/blob/master/Dockerfile I am not really quite sure how to use it. I am assuming that I can somehow create a local environment by calling this Dockerfile on my remote.

Is this correct? If so how can I create the local instance pointing to the remote?

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While other answers were usable, this really helped me, so I am putting it also here.

Instead of specifying a context, you can pass a single Dockerfile in the URL or pipe the file in via STDIN. To pipe a Dockerfile from STDIN:

With Powershell on Windows, you can run:

When the build is done, run command:

You will see something like this:

Copy your actual IMAGE ID and then run

Where the number at the end is the actual Image ID from previous step

If you do not want to remember the image id, you can tag your image by

Which will tag your image as pavel/pavel-build

Как я запускал Докер внутри Докера и что из этого получилось

Всем привет! В своей предыдущей статье, я обещал рассказать про запуск Докера в Докере и о практических аспектах применения этого занятия. Настало время выполнить свое обещание. Опытный девопс, пожалуй, возразит, что тем кому нужен Докер внутри Докера, просто пробрасывают сокет Докер демона из хоста внутрь контейнера и этого хватит в 99% случаев. Но не спешите кидать в меня печеньки, ведь речь пойдет о реальном запуске Докера внутри Докера. У этого решения много возможных областей применения и об одном из них эта статья, так что усаживайтесь поудобнее и выпрямите руки перед собой.

Начало

Практика. Шишки

Я задался целью заставить контейнер работать так как мне было нужно и продолжал свои эксперименты, результатом которых стало несметное количество шишек. Итогом моего самоистязания стала следующий алгоритм:

Запускаем Докер контейнер в интерактивном режиме.

Обратите внимание на версию контейнера, шаг вправо или в лево и ваш ДинД превращается в тыкву. На самом деле, все ломается довольно часто с выходом новой версии.
Мы должны сразу попасть в шелл.

Пробуем узнать, какие контейнеры запущены (Ответ: никакие), но давайте выполним команду все-равно:

Вы будете немного удивлены, но оказывается Докер демон даже не запущен:

Давайте запустим его самостоятельно:

Еще одна неприятная неожиданность:

Устанавливаем пакеты iptables и bash (в баше всяко работать приятнее чем в sh):

Запускаем bash. Наконец-то мы снова в привычном шелле

попробуем запустить Докер еще раз:

Мы должны увидеть длинную простыню логов заканчивающуюся:

Нажимаем Enter. Мы снова в баше.

Начиная с этого момента мы можем пробовать запускать другие контейнеры внутри нашего Докер контейнера, но что если мы хотим поднять еще один Докер контейнер внутри нашего Докер контейнера или что-то пойдет не так и контейнер «вылетит»? Начинать все с начала.

Собственный DinD контейнер и новые эксперименты

Рабочее DinD решение дало мне возможность запускать Докер внутри Докера рекурсивно и проводить более смелые эксперименты.
Один такой (удачный) эксперимент с запуском MySQL и Nodejs я собираюсь сейчас описать.
Самые нетерпеливые могут посмотреть как это было здесь

Запускаем DinD в интерактивном режиме. В данной версии DinD нам нужно вручную замапить все порты которые могут использовать наши дочерние контейнеры (я над этим уже работаю)

Мы попадаем в баш, откуда можем сразу приступать к запуску дочерних контейнеров.

Подключаемся к базе данных так же как мы бы подключались к ней локально. Убеждаемся что все работает.

Запускаем второй контейнер:

Обратите внимание, что порт мапинг здесь будет именно 8080:8080, так как мы уже замапили порт 80 из хоста в родительский контейнер на порт 8080.

Идем на localhost в браузере, убеждаемся что сервер отвечает «Hello World!».

В моем случае эксперимент с вложенными Докер контейнерами оказался довольно положительным и я продолжу развивать проект и использовать его для стейджинга. Мне кажется, что это гораздо более легковесное решение чем тот же Kubernetes и Jenkins X. Но это мое субъективное мнение.

Я думаю, что для сегодняшней статьи — это все. В следующей статье я более подробно опишу эксперименты с рекурсивным запуском Докера в Докере и монтирование директорий вглубь вложенных контейнеров.

P.S. Если вы считаете данный проект полезным, то пожалуйста поставьте ему звездочку на ГитХабе, сделайте форк и расскажите друзьям.

Edit1 Исправил ошибки, сделал фокус на 2 видео

How To Run Docker in Docker Container [3 Easy Methods]

In this blog, I will walk you through the steps required to run docker in docker using three different methods.

Docker in Docker Use Cases

Here are a few use cases to run docker inside a docker container.

Table of Contents

Run Docker in a Docker Container

There are three ways to achieve docker in docker

Let’s have a look at each option in detail. Make sure you have docker installed in your host to try this setup.

Method 1: Docker in Docker Using [/var/run/docker.sock]

What is /var/run/docker.sock?

/var/run/docker.sock is the default Unix socket. Sockets are meant for communication between processes on the same host. Docker daemon by default listens to docker.sock. If you are on the same host where Docker daemon is running, you can use the / var/run/docker.sock to manage containers.

For example, if you run the following command, it would return the version of docker engine.

Now that you have a bit of understanding of what is docker.sock, let’s see how to run docker in docker using docker.sock

To run docker inside docker, all you have to do it just run docker with the default Unix socket docker.sock as a volume.

Now, from within the container, you should be able to execute docker commands for building and pushing images to the registry.

Here, the actual docker operations happen on the VM host running your base docker container rather than from within the container. Meaning, even though you are executing the docker commands from within the container, you are instructing the docker client to connect to the VM host docker-engine through docker.sock

To test his setup, use the official docker image from the docker hub. It has docker the docker binary in it.

Follow the steps given below to test the setup.

Step 1: Start Docker container in interactive mode mounting the docker.sock as volume. We will use the official docker image.

Step 2: Once you are inside the container, execute the following docker command.

Step 3: When you list the docker images, you should see the ubuntu image along with other docker images in your host VM.

Step 4: Now create a Dockerfile inside test directory.

Copy the following Dockerfile contents to test the image build from within the container.

How do I run a command on an already existing Docker container?

I see that the container has exited:

Now I would like to run occasional commands on the machine and exit. Just to get the response.

I tried to start the machine. I tried attaching. I thought I could call run with a container, but that does not seem to be allowed. Using start just seems to run and then exist quickly.

I’d like to get back into interactive mode after exiting.

But if I start it, it exits anyway. Catch 22. I can’t win.

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So now you can run any command in a running container just knowing its ID (or name):

Note that exec command works only on already running container. If the container is currently stopped, you need to first run it with the following command:

Your container will exit as the command you gave it will end. Use the following options to keep it live:

So your new run command is:

If you would like to attach to an already running container:

In these examples /bin/bash is used as the command.

So I think the answer is simpler than many misleading answers above.

To start an existing container which is stopped

To stop a running container

Then to login to the interactive shell of a container

To start an existing container and attach to it in one command

Beware, this will stop the container on exit. But in general, you need to start the container, attach and stop it after you are done.

To expand on katrmr’s answer, if the container is stopped and can’t be started due to an error, you’ll need to commit it to an image. Then you can launch bash in the new image:

Some of the answers here are misleading because they concern containers that are running, not stopped.

How To Use docker exec to Run Commands in a Docker Container

Introduction

Docker is a containerization tool that helps developers create and manage portable, consistent Linux containers.

When developing or deploying containers you’ll often need to look inside a running container to inspect its current state or debug a problem. To this end, Docker provides the docker exec command to run programs in containers that are already running.

In this tutorial we will learn about the docker exec command and how to use it to run commands and get an interactive shell in a running Docker container.

Prerequisites

For more information on using Docker without sudo access, please see the Executing the Docker Command Without Sudo section of our How To Install Docker tutorial.

Starting a Test Container

To use the docker exec command, you will need a running Docker container. If you don’t already have a container, start a test container with the following docker run command:

This command creates a new Docker container from the official alpine image. This is a popular Linux container image that uses Alpine Linux, a lightweight, minimal Linux distribution.

In the next step we’ll learn how to find the names of Docker containers. This will be useful if you already have a container you’re targeting, but you’re not sure what its name is.

Finding the Name of a Docker Container

We’ll need to provide docker exec with the name (or container ID) of the container we want to work with. We can find this information using the docker ps command:

This command lists all of the Docker containers running on the server, and provides some high-level information about them:

In this example, the container ID and name are highlighted. You may use either to tell docker exec which container to use.

If you’d like to rename your container, use the docker rename command:

Next, we’ll run through several examples of using docker exec to execute commands in a running Docker container.

Running an Interactive Shell in a Docker Container

This will run the sh shell in the specified container, giving you a basic shell prompt. To exit back out of the container, type exit then press ENTER :

Running a Non-interactive Command in a Docker Container

If you need to run a command inside a running Docker container, but don’t need any interactivity, use the docker exec command without any flags:

This command will run tail /var/log/date.log on the container-name container, and output the results. By default the tail command will print out the last ten lines of a file. If you’re running the demo container we set up in the first section, you will see something like this:

Running Commands in an Alternate Directory in a Docker Container

This example command sets the /tmp directory as the working directory, then runs the pwd command, which prints out the present working directory:

Running Commands as a Different User in a Docker Container

This will use the guest user to run the whoami command in the container. The whoami command prints out the current user’s username:

The whoami command confirms that the container’s current user is guest.

Passing Environment Variables into a Docker Container

First, make the file with a text editor. We’ll open a new file with nano here, but you can use any editor you’re comfortable with:

Write your KEY=value variables into the file, one per line, like the following:

The two variables in the file are set.

Common Errors

When using the docker exec command, you may encounter a few common errors:

The No such container error means the specified container does not exist, and may indicate a misspelled container name. Use docker ps to list out your running containers and double-check the name.

This not running message means that the container exists, but it is stopped. You can start the container with docker start container-name

The Container is paused error explains the problem fairly well. You need to unpause the container with docker unpause container-name before proceeding.

Conclusion

In this tutorial we learned how to execute commands in a running Docker container, along with some command line options available when doing so.

For more information on Docker in general, please see our Docker tag page, which has links to Docker tutorials, Docker-related Q&A pages, and more.

For help with installing Docker, take a look at How To Install and Use Docker on Ubuntu 20.04.

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