Build ARM Docker Containers on (x86 64 bit) Linux
EDIT: I have a much better cross-architecture build pipeline now
In preparation for the eventual shift to ARM that I will experience (whether directly or indirectly) with Apple shifting their Macbooks to ARM I needed a way to build my containers for ARM.
Prepare Your Linux Host: #
Configure Docker to Pull Multi-Architecture Images: #
After installing Docker on your host, enable experimental features to allow for you to pull containers that don’t match your architecture.
Add the following to /etc/docker/daemon.json
:
{
"experimental": true
}
Then restart the Docker service:
systemctl restart docker.service
To test, pull the arm version of the official Debian Docker image:
docker pull debian:stable --platform arm
stable: Pulling from library/debian
8889795e1736: Pull complete
Digest: sha256:281dabbeb55dd7fe6603c0afafdc1800ea4f4ab057516dfb629fe30eb642daf7
Status: Downloaded newer image for debian:stable
docker.io/library/debian:stable
Install Relevant Packages: #
In order to emulate ARM properly, we need to install two packages:
- qemu-user-binfmt
- qemu-user-static
Debian/Ubuntu derivatives:
apt-get update
apt-get install qemu-user-binfmt qemu-user-static -y
Arch Linux:
Use the following AUR packages:
Once the packages are installed, see if you can run the Debian arm image that we downloaded:
docker run -v /usr/bin/qemu-arm-static:/usr/bin/qemu-arm-static --platform arm --rm -ti debian:stable bash
root@25425d924f4a:/# arch
armv7l
Building ARM Containers: #
Let’s make a new directory for our test container image:
mkdir -p test-container && cd test-container
Now, let’s add the qemu-arm-static binary to that new directory (it will be copied to the container image):
cp /usr/bin/qemu-arm-static .
Now, in your Dockerfile you’ll just have to make sure the qemu-arm-static binary is added. For example:
FROM debian:stable
COPY qemu-arm-static /usr/bin/qemu-arm-static
CMD ["/bin/bash"]
Adding the qemu-arm-static binary will add about 4 MB of space to your container but will allow your ARM images to be able to run on any x86 Linux host with qemu-arm-static installed and configured.
When you build using that Dockerfile you should specify the platform, like so:
docker build heywoodlh/test-container:arm -f Dockerfile .
With the arm
tag you will have to specify that tag in order to use that image.
With the qemu-arm-static binary in /usr/bin/
you should be able to run the container on the Linux host with qemu-arm-static installed:
docker run -it --rm heywoodlh/test-container:arm bash
root@b80788989cff:/# arch
armv7l
linux docker container systems arm