Compiling Docker images for foreign architectures

Sometimes you would like to run anki-sync-server on a Raspberry Pi with ARM CPU, or on an older computer with i686 CPU on the board.

When starting the Docker container instance, you may encounter a message indicating an "exec format error".

This is likely due to the fact that you are trying to run a Docker image on an architecture it is not compatible with. Check the architecture of your CPU and check that you are using the appropriate Docker image.

lscpu

On GNU/Linux distributions, you can usually check your CPU architecture with lscpu.

If this image does not exist, you can usually easily create it, following the build instructions in the appropriate repository.

Building a Docker image

Most of the time you can build the Docker image by entering the directory that contains the Dockerfile and execute the command:

docker build -t container_name:tag .

For example:

docker build -t my-arm-build-of_anki-sync-server .

Always check the repository for special instructions first

Sometimes there is already a script supplied that prepares the repository first. If the README mentions one, use that, and modify it before running, accordingly.

For example, docker-anki-sync-server uses a separate build.sh, as it is mentioned in the README.

After creating the image, the result is going to be stored in the local Docker cache under the name and tag you specified, ready for use.

Publishing the image

If you wish to share your compiled image with others, the easiest way is to upload to DockerHub. After creating an account, you can attach your Docker installation to it with docker login.

Tag your existing image in the way you are going to upload it to DockerHub. Tagging means creating another alias for the same image in your local cache.

Listing your images

You can list the images and their tags in your local cache using docker image ls.

For example, if your username on DockerHub is yourdockerid, and you wish to upload the image under your account, you need to tag it first, then push it:

docker tag my-arm-build-of_anki-sync-server yourdockerid/yourreponame:arm64
docker tag my-arm-build-of_anki-sync-server yourdockerid/yourreponame:latest
docker push yourdockerid/yourreponame:arm64
docker push yourdockerid/yourreponame:latest

Share your image with us

We are happy to include your build of the image under the unofficial builds, here in this portal.