Dockerfile: create and mount disk image during build

Question

I am trying to build and mount a custom disk image during the Dockerfile build process:

FROM ubuntu:16.04
RUN dd if=/dev/zero of=foo.img count=500 bs=1M
RUN mkfs.ext4 foo.img
RUN mkdir -p /media/ext4disk
RUN mount -t ext4 foo.img /media/ext4disk

Running docker build, I get the following error message on the last command: mount failed: Unknown error -1.

Is there any way to achieve what I want to do?

user_565319 · Answer

Seems like you can now run "insecure" in build mode:

Check docs: https://github.com/docker/buildx/blob/master/README.md#--allowentitlement

docker buildx create --use --name insecure-builder --buildkitd-flags '--allow-insecure-entitlement security.insecure'
docker buildx build --allow security.insecure -t my-image:latest .

Dockerfile: create and mount disk image during build

2 Answers