docker-build.sh

#!/bin/sh
# vim: set ft=sh fdm=manual ts=2 sw=2 sts=2 tw=85 et:

# ================================================
# Description: A docker build alternative impl, support squash and interactive build
# Usage:
#  $ docker-build -t foo:1.0.0 -f ./Dockerfile --no-cache (all of native build args)
#  -i interactive mode to maintain intermediate container
# Last Modified: Tue Dec 08, 2020 17:57
# Author: Allex Wang ([email protected])
# GistID: 0f2925a6140c67bf5379d1cddb748af4
# GistURL: https://gist.github.com/allex/0f2925a6140c67bf5379d1cddb748af4
# ================================================

set -euE -o pipefail

img_name=""
interactive=false

args=(" ")
while [ $# -gt 0 ]; do
  v=${2-}
  case "$1" in
    -t | --tag)
      img_name=$v
      shift
      ;;
    -i | --interactive)
      interactive=true
      ;;
    *)
      args+=("$1")
      ;;
  esac
  shift
done

[ -n "$img_name" ] || {
  echo >&2 "-t, --tag <img_name> Name and optionally a tag in the 'name:tag' format"
  exit 1
}

eval set -- "${args[@]}"


#### Build intermediate image
echo "Step 0: Build intermediate image"

tmp_img="tmp.$$"
{
  docker build -t $tmp_img "$@"
  echo " --> ${tmp_img}"
  trap '[ -n "$tmp_img" ] && docker rmi -f "$tmp_img" >/dev/null' 0 1 2 3 9 13 15
}


#### Squash image layers
echo "Step 1: Squash image layers"

intermediate_container=`docker run --net host --rm --entrypoint sh -id "$tmp_img" -l`
{
  echo " --> Running in ${intermediate_container:0:12}"
  while true; do docker inspect ${intermediate_container} -f '{{.Id}}' &>/dev/null && break; done

  if ${interactive}; then
    docker exec -it ${intermediate_container} sh -l || { echo >&2 "build abort."; exit 1; }
  fi
}


#### Export as dist image
echo "Step 2: Export intermediate container to image '${img_name}'"

{
  [ -n "${img_name}" ] || {
    read -p "Enter new image name (in the 'name:tag' format) " img_name || exit 1
  }

  cfg=`docker inspect --format='{{if .Config.Labels}}LABEL {{range $k, $v := .Config.Labels}}{{$k}}="{{$v}}" {{end}}{{end}}
{{range .Config.Env}}ENV {{println .}}{{end}}
CMD [{{range $i, $v := .Config.Cmd}}{{if $i}}, {{end}}"{{$v}}"{{end}}]
ENTRYPOINT [{{range $i, $v := .Config.Entrypoint}}{{if $i}}, {{end}}{{printf "\"%s\"" .}}{{end}}]
{{if .Config.Volumes}}VOLUME [{{$index := 0}}{{range $k, $v := .Config.Volumes}}{{if $index}}, {{else}}{{$index = 1}}{{end}}{{printf "\"%s\"" $k}}{{end}}]{{end}}
' "${tmp_img}"`

  cat <<DOC
 inspect image config:
 ~~~
 $cfg
 ~~~
DOC

  image_id=`docker export ${intermediate_container} | \
    docker import -m 'squash build' -c "$cfg" - ${img_name}`
  echo " --> ${image_id#*:}"
}

echo "Removing intermediate container ${intermediate_container:0:12}"
docker kill ${intermediate_container} >/dev/null
docker images |grep "<none>" |awk '{print $3}' |xargs -I{} docker rmi -f {} > /dev/null