$ cat work/buildkitd.toml
[registry."docker.io"]
  mirrors = ["m101-registry:5000"]
[registry."m101-registry:5000"]
  http = true
  insecure = true
[exit 0]

$ docker buildx create --name m101-builder --driver docker-container --driver-opt network=m101-net --buildkitd-config work/buildkitd.toml
m101-builder
[exit 0]