Using buildx from Docker makes it super easy building images for multiple architectures.
I will be building a fluent-bit docker image for ARMv7 on a AMD64 platform.
Install Buildx
First installing buildx on our build server:
$ sudo apt install qemu-user -y
$ wget https://github.com/docker/buildx/releases/download/v0.4.2/buildx-v0.4.2.linux-amd64
$ mkdir ~/.docker/cli-plugins
$ mv buildx-v0.4.2.linux-amd64 .docker/cli-plugins/docker-buildx
$ chmod a+x ~/.docker/cli-plugins/docker-buildx
Making sure we can use the binary:
$ docker buildx
Usage: docker buildx [OPTIONS] COMMAND
Create a Build Instance
Create a new build instance which we will be using:
$ docker run --rm --privileged multiarch/qemu-user-static --reset -p yes
$ docker buildx create --name newbuilder
$ docker buildx use newbuilder
$ docker buildx inspect --bootstrap
Build for ARM
In this example we will be building a docker image for armv7 of the loki fluent-bit plugin.
Get the source:
$ git clone https://github.com/grafana/loki
Login to your docker registry:
$ docker login
Then build using the --platform linux/arm/v7 flag:
$ docker buildx build -f cmd/fluent-bit/Dockerfile --push --platform linux/arm/v7 --tag pistacks/fluent-bit-plugin-loki:armv7-latest .
Once everything goes according to plan you should have an image for armv7 in your docker registry available.