Create a container image for Docker-in-Docker
“Docker-in-docker” is an often useful technique to help running multiple instances of container clusters (e.g. swarm services, docker-compose) on the same container host. It consists of:
- A conventional container image with docker server daemon and client utilities.
- A privileged container running the image, which has its entrypoint script to start the nested docker server daemon.
- Other techniques applied optionally to enhance the server daemon performance.
Let’s build the container image. First, prepare a utility script called `modprobe`:
#!/bin/sh
set -eu
# “modprobe” without modprobe: https://twitter.com/lucabruno/status/902934379835662336
for module; do
if [ “${module#-}” = “$module” ]; then
ip link show “$module” >/dev/null 2>&1 || true
fi…
