This information is out-of-date. Please refer to the Learning Path Learn how to use Docker

Simple docker demos for Arm

Some ideas for working with Docker on the Arm architecture.

The example docker image is a simple C program (hello.c) which prints a message and the architecture (as reported by the Linux command: uname -a)

It also prints if it is a 32-bit application or a 64-bit application.

There are multiple ways to work with multi-architecture images.

Use buildx to emulate non-native architectures

build.sh: does everything on the local machine:

Create a buildx builder
Use the builder
Build for 3 target architectures on the local machine
Push the multi-arch image to Docker Hub

docker buildx create --name mybuilder
docker buildx use mybuilder
docker buildx build --platform linux/amd64,linux/arm64,linux/arm/v7 -t jasonrandrews/hello-world --push .

Edit build.sh and set HUBU to your Docker Hub username and try it:

./build.sh

Substitute your Docker Hub username and run the native image (automatically detected):

docker run --rm  jasonrandrews/hello-world

run.sh: Run a specific architecture, which may or may not be the native architecture:

docker run --rm  --platform linux/arm64 jasonrandrews/hello-world
docker run --rm  --platform linux/arm/v7 jasonrandrews/hello-world
docker run --rm  --platform linux/amd64 jasonrandrews/hello-world

Edit run.sh, substitute your Docker Hub username, and run all architectures.

./run.sh

This works well if the build process is mostly file copying and software installation. This does not work well if complex commands must be emulated, such as compiling a large C++ project.

Running non-native images shows it can be done, but not practical for real workloads.

Use a remote builder via ssh to build non-native architectures

Multi-arch images can be created without using buildx.

Edit remote-build.sh to fill in the username and IP address of a remote x86 machine which is accessible via ssh and has docker installed.

Create and use a remote context
Build for an architecture which is native to the remote machine
Push the resulting image to Docker Hub

docker context create remote --docker "host=ssh://ubuntu@IP"
docker context use remote
docker build --platform linux/amd64 -t jasonrandrews/hello-world:latest-amd64  .
docker push jasonrandrews/hello-world:latest-amd64

Edit remote-build.sh and change to your Docker Hub username to try it.

./remote-build.sh

The new image can be run on any x86 machine. This is not a multi-arch image.

docker run --rm jasonrandrews/hello-world:latest-amd64

On the local Arm machine build the Arm image.

docker context use default
docker build --platform linux/arm64 -t jasonrandrews/hello-world:latest-arm64  .
docker push jasonrandrews/hello-world:latest-arm64

Use docker manifest to create multi-arch images

To create a multi-arch image from multiple images use the docker manifest command.

This makes it easy to build and test images on their native architecture (without the complexity of buildx) and join them together into a single image.

Users will automatically get the right architecture when they run.

Create a manifest with a list of multiple images, each for a different archichitecture
Join them together into a single multi-arch image

docker manifest create jasonrandrews/hello-world:latest \
--amend jasonrandrews/hello-world:latest-arm64 \
--amend jasonrandrews/hello-world:latest-amd64
docker manifest push --purge jasonrandrews/hello-world:latest

jasonrandrews/arm-docker-demo

Simple docker demos for Arm

Use buildx to emulate non-native architectures

Use a remote builder via ssh to build non-native architectures

Use docker manifest to create multi-arch images