How to Change Extended Attributes of Files in Docker Images Across Different Architectures and Save Changes?

Question

I'm working with Docker images across different architectures (x86_64 and ARM). I need to change the extended attributes (xattrs) of some exacutable files within these Docker images and save these changes when I dont know what each image supports.

I am familiar with basic Docker operations like building, running, and committing containers. However, I am unsure how to handle extended attributes specifically and ensure compatibility across different architectures. Additionally, I can't just open the Docker container, change the extended attributes, and commit these changes because I am uncertain about which commands or scripts (such as Python scripts or attr commands) are supported within the container.

Could someone provide a detailed method or best practices to achieve this? Any example commands or scripts that can be used inside the container to handle extended attributes would be greatly appreciated!

I have tried to run a the docker with bash but some dockers do not support the attr commands. I have tried as well to create a python script which did not work as well as other dockers did not support the python script. What else can I do?

Answer 1

If you have access to the Dockerfiles themselves, you can make modifications to the Dockerfile to modify the extended attributes and ensure the build completes successfully. To ensure multi-arch compatibility for one Docker image, you can use the following methodology:

1. Create Two Unique Dockerfiles, one targeting x86 and the other targeting Arm.

Handle the extended attributes differently in each Dockerfile as needed.

2. Build the x86_64 Dockerfile on x86_64 hardware, and verify the image works as intended after building.

docker build -t my-image:amd64 .
docker push my-image:amd64

3. Build the Arm Dockerfile on Arm hardware, and verify the image works as intended after building.

docker build -t my-image:arm64 .
docker push my-image:arm64

4. Merge and Annotate the images using Docker Manifest (You can do this on either the x86 or Arm machine)

docker manifest create my-image:latest my-image:amd64 my-image:arm64
docker manifest annotate my-image:latest my-image:amd64 --os linux --arch amd64
docker manifest annotate my-image:latest my-image:arm64 --os linux --arch arm64
docker manifest push my-image:latest

At the end, you should have a my-image Docker image that works on both x86 and Arm hardware platforms, handling your extended attributes in architecture-specific ways as specified in your Dockerfiles.

An alternative is to use docker buildx, but you may run into issues with that multi-arch build process as you need to verify the extended attributes works directly on each machine's different architecture first. buildx builds multi-arch images from one machine.

To obtain an ARM machine for the build, you can select an Arm architecture machine on AWS or other cloud providers.

Hope this helps!