Turtles docker image. Docker containers inside of docker containers recursively. A case of because I can, not because I should...

Dockerfile

FROM docker:dind as turtles
VOLUME ["/image"]
COPY ./turtles.sh /tmp
WORKDIR /tmp
ENTRYPOINT ["./turtles.sh"]
CMD ["turtle"]

run.sh

#!/bin/bash

docker build -t granthenke/turtles:latest .

# Setup: Save the image so it can be mounted as a volume
# This prevents downloading the image at each level.
mkdir image
docker save -o image/turtles.docker granthenke/turtles:latest
chmod 777 image/turtles.docker

# Run the turtles image and pass how deep you want to go...
docker run -it --rm --privileged -v $(pwd)/image:/image granthenke/turtles:latest turtle 3

turtles.sh

#!/bin/sh

if [ "$1" = "turtle" ]; then
  END=${2:-1}
  LAST=${3:-0}
  CUR=$(($LAST + 1))
  SIZE=${#CUR}
  LEFT=$(((6-$SIZE)/2))
  RIGHT=$((6-($LEFT+$SIZE)))

  printf "  _____     ____\n"
  printf "/      \  |  o |\n"
  printf "| " 
  printf "%*s%s%-*s" $LEFT "" "$CUR" $RIGHT ""
  printf "|/ ___\|\n"
  printf "|_________/\n"
  printf "|_|_| |_|_|\n"

  if [ $END -gt $CUR ]; then
    # Start the docker daemon.
    dockerd-entrypoint.sh >/dev/null 2>&1 &
    # Loop until the docker daemon is ready.
    until docker version >/dev/null 2>&1
    do
      sleep 1
    done
    # Copy the image into the container from the volume so it can be mounted again.
    mkdir /cimage 
    cp /image/turtles.docker /cimage/turtles.docker
    # Go deeper.
    docker load -q -i /cimage/turtles.docker >/dev/null 2>&1
    docker run -it --rm --privileged -v /cimage:/image -e LOG=file granthenke/turtles:latest turtle $END $CUR
  fi
  exit 0
fi

# Support calling anything else in the container.
exec "$@"