This is the only way that security can be enforced and running processes can be properly controlled (e.g. Killing, handling stdin, stdout, exit-code, and so on). If course it would be pretty if this API could run inside Docker, but personally I don't mind to run it on the host directly. – barney765 Oct 28 '20 at 12:35. So, what is Docker? Docker is a special tool that’s designed especially for easier creation, deployment, and running Linux apps using “containers”. In Docker’s terms, “containers” are a pre-bundled environment where Linux apps can run in an expected and repeatable fashion. Docker-compose can be used to easily automate multi-container deployments. One of the most challenging tasks while running such deployments is separating data from software. While containers are ephemeral, user data needs to persist. A classic example, of this is when we try and run database container images.
$ docker run docker.io. My architecture is Linux buildkitsandbox 4.15.0-50-generic #54-Ubuntu SMP Mon May 6 18:46:08 UTC 2019 aarch64 Linux $ docker run docker.io. Docker run reference. Docker runs processes in isolated containers. A container is a process which runs on a host. The host may be local or remote. When an operator executes docker run, the container process that runs is isolated in that it has its own file system, its own networking, and its own isolated process tree separate from the host.
This blog post is the result of collaboration between Arm and Docker. Special thanks to Jason Andrews @ Arm for creating much of the original content.
Arm and Docker announced a strategic partnership earlier this year to unify software development and deployment across a diverse set of devices, from IoT endpoints to the edge of the network, and into the heart of the data center. Docker has simplified enterprise software development and deployment leading to true multi-platform portability and cost savings on Arm-based cloud instances. Even more exciting is how Docker is changing the way embedded software is being developed and deployed.
Traditionally embedded Linux software applications have been created by cross-compiling and copying files to an embedded target board. There are various methods to automate this process, but it has generally been unchanged since the 1990’s when non-x86 embedded possessors running Linux appeared. Docker stands to make the first significant change to the embedded Linux application developer’s workflow.
This article continues from Building Multi-Arch Images for Arm and x86 with Docker Desktop and shows the same capabilities in Linux. Although Windows and Mac support is great, the majority of software developers targeting embedded Linux systems also do their development work on Linux. The multi-architecture support in Docker also greatly simplifies embedded Linux application development and deployment.
If you are doing software development on x86 Linux machines and want to create Docker images that run on Arm servers or Arm embedded and IoT devices, this article will be helpful to understand the process and the different ways to do it.
Let’s see how to use Docker for Arm software development using the new buildx feature on Linux to create multi-architecture container images and run them. I’m using Ubuntu 18.04, but the same info applies to most any Linux distribution.
Install Docker
Installing Docker on Linux takes just a few commands. More installation info is available in the Docker Documentation.
If you already have an older version of Docker, make sure to uninstall it first. Using buildx requires Docker 19.03 and today the best way to get this is using the test instead of the stable version.
Add the current user to the docker group to avoid needing sudo to run the docker command:
Make sure to log out and back in again. Now test the install with a quick hello-world run.
Use the docker version command to check the running version:
Install buildx for multi-architecture image builds
There are three options to get buildx on Linux:
- Use buildx directly from the test channel version of Docker
- Download a binary release of buildx and copy it to the $HOME/.docker directory
- Download, build, and install buildx from github.com
Use buildx from Docker test channel
The test version of Docker already has buildx included. The only thing needed is to set the environment variable to enable experimental command line features.
Download a binary release
Another way to get buildx is to download a binary release from github and put in the .docker/cli-plugins directory.
For example, download the buildx for Linux amd64 with a browser from: https://github.com/docker/buildx/releases/tag/v0.2.0
Then copy it to the cli-plugins/ directory (create it first if necessary):
Download, build, and install buildx
Because buildx is a new command and documentation is still catching up, githubis a good place to read more information about how buildx works.
To get buildx from github use the commands:
To confirm buildx is now installed run the help and the version command.
Register Arm executables to run on x64 machines
Install the qemu instruction emulation to register Arm executables to run on the x86 machine. For best results, the latest qemu image should be used. If an older qemu is used some application may not work correctly on the x86 hardware.
To verify the qemu handlers are registered properly, run the following and make sure the first line of the output is “enabled”. Note that the handler registration doesn’t survive a reboot, but could be added to the system start-up scripts.
Create a multi-architecture build instance
Setup a new builder instance to create multi-architecture images.
Try buildx
There are multiple examples of buildx available, but here is a simple one for C programmers! Create a file named hello.c with this code:
Here is a Docker file to build and run it. Let’s get used to using multi-stage Docker files as it will be common for deploying embedded applications. Create a Dockerfile with the following:
Now, use buildx to build for multiple architectures and push to Docker hub.
Use docker login first if needed and substitute your own Hub account.
Run using the sha from the manifest and see the output from uname as armv7l, aarch64, and x86_64:
Run Docker On Linux
Next steps
Run Docker Linux On Windows Server
As we have seen, building multi-architecture containers can be created with buildx in the same way as with Docker Desktop for Mac and Windows. Give it a try for yourself and start making the transition to multi-architecture Docker images today.
Further Reading