Docker

Christian Külker

0.1.2

2024-02-19

Introduction

Docker is an open source software mechanism for building, shipping, and running applications. Docker allows you to separate your software applications from your software infrastructure through an abstraction layer so you can deploy software in a generalized way. With Docker, you can manage your servers the same way you manage your applications. By taking advantage of Docker’s methods for rapidly shipping, testing, and deploying code, Docker promises to significantly reduce the time between writing code and running it on a server in a production environment.

Docker Engine can be installed in different ways:

  • Setup own Docker repository and install from them for the ease of installation and upgrade tasks. This is the recommended approach, except for Raspbian.
  • Download DEB packages and install them manually and manage upgrades completely manually. This gives full control on systems not connected to the internet.
  • In testing and development environments scripts can install Docker in one shot. This is currently the most used approach for Raspbian.

=> https://docs.docker.com/engine/install/debian/

Membership in the docker group is more dangerous than sudo, according to the Debian Wiki. This is due to the setUID root of the docker daemon and easy access to root. Access to docker commands therefore effectively grants root access. Therefore, do not add users to the docker group and use docker only with sudo.

Editions

Docker comes in editions.

  • ce: community edition
    • edge: monthly release
    • stable: quarterly release
  • ee: enterprise edition
    • quarterly release

Debian 11 on ARM

The docker.io package contains the daemon and client. From the package description:

“Using docker.io on non-amd64 hosts is not supported at this time. Please be careful when using it on anything besides amd64.”

Docker Repository

Docker is used through what is called a Docker repository. That is, you create a Docker repository before you install the Docker engine. After installation, this repository can be used to update Docker. Warning: Rasbian (or Debian for Arm?) users cannot use this method. Instead, they use a so-called “convenience script”, which can be obtained via a link. This method has not been tested.

Docker on Raspberry Pi 4 Debian 11 Bullseye

This works for Debian on x86_64 / amd64, armhf, arm64, and Raspbian and is a hello world example.

aptitude purge docker-ce docker-ce-cli containerd.io
aptitude install docker docker.io containerd runc
 # test docker installation
docker run hello-world
Unable to find image 'hello-world:latest' locally
latest: Pulling from library/hello-world
93288797bd35: Pull complete
Digest: sha256:cc15c5b292d8525effc0f89cb299f1804f3a725c8d05e158653a563f15e4f685
Status: Downloaded newer image for hello-world:latest

Hello from Docker!
This message shows that your installation appears to be working correctly.

To generate this message, Docker took the following steps:
 1. The Docker client contacted the Docker daemon.
 2. The Docker daemon pulled the "hello-world" image from the Docker Hub.
    (arm64v8)
 3. The Docker daemon created a new container from that image which runs the
    executable that produces the output you are currently reading.
 4. The Docker daemon streamed that output to the Docker client, which sent it
    to your terminal.

To try something more ambitious, you can run an Ubuntu container with:
 $ docker run -it ubuntu bash

Share images, automate workflows, and more with a free Docker ID:
 https://hub.docker.com/

For more examples and ideas, visit:
 https://docs.docker.com/get-started/

As root

export U=userid
aptitude install docker.io
root@w2:~# touch /var/run/docker.sock
root@w2:~# chown $U.$U /var/run/docker.so

As User

docker build --tag dh-venv-builder .
[...] (some minutes later)
Successfully built fba3ab967839
Successfully tagged dh-venv-builder:latest

docker run --rm dh-venv-builder tar -C /dpkg -c . | tar -C dist -xv
./
./dh-virtualenv_1.2.2-1~buster_all.deb
./dh-virtualenv_1.2.2-1~buster_amd64.buildinfo
./dh-virtualenv_1.2.2-1~buster_amd64.changes

Virtual Environment

aptitude install dh-virtualenv

Simple Docker Usage

List all containers

docker container ls
CONTAINER ID   IMAGE ...
419f0ee92d82   ...

Enter a container

docker exec -i -t 419f0ee92d82 bash

Leave a container with a bash shell

exit

History

Version Date Notes
0.1.2 2024-02-19 +Docker Repository, on Raspberry Pi4, Usage
0.1.1 2023-03-28 Improve writing, change cite format
0.1.0 2020-11-05 Initial release
  • Docker