Build a docker image with bash

README.md

Dockerfile as a bash script

A simple experiment.

By creating bash functions for common Dockerfile commands (e.g., RUN, COPY) you can sort of implement docker build as a bash script.

It's sort of like a cheap buildah knockoff.

It creates the image example:build.bash

Please feel free to ask questions or submit improvements.

build.bash

#!/bin/bash

set -eu

cmd=
cname=bob

colour() {
  tput bold
  tput smso
  tput setaf 2
  printf " %8s " "$1"
  shift
  tput rmso
  tput setaf 3
  printf " $*"
  tput sgr0
  echo
}

###
### Library of Dockerfile like methods
###

FROM() {
  colour FROM "$1"
  docker container rm -f "$cname" >/dev/null 2>&1 || :
  docker run -d -t --name="$cname" "$1" /bin/sh
}

RUN() {
  colour RUN "$@"
  docker exec -it "$cname" /bin/sh -c "$*"
}

CMD() {
  colour CMD "$@"
  cmd=$(python3 -c 'import json, sys; print((json.dumps(sys.argv[1:])))' "$@")
}

COMMIT() {
  colour COMMIT "${1:-}"
  local -a args=(commit)
  if [[ -n $cmd ]]; then
    args+=("--change=CMD ${cmd}")
  fi
  args+=("--author=Christian Holtje <https://docwhat.org>")
  args+=("--message=build.bash")
  args+=("$cname")
  if [[ -n ${1:-} ]]; then
    args+=("$1")
  fi

  docker "${args[@]}"
}

### The Dockerfile!

FROM ubuntu

CMD /bin/bash -l

RUN apt update -y
RUN apt install -y bash pigz
COMMIT

RUN id \> /root/my-id
RUN pigz -9 /root/my-id
COMMIT

RUN ls -al /bin

COMMIT example:build.bash

### Debugging info

colour SECTION "container"
docker container ls --filter=name="$cname"

# colour SECTION "image"
# docker image ls example:build.bash

colour SECTION "history"
docker image history example:build.bash

# colour SECTION "config"
# docker image inspect -f '{{ .Config | json }}' example:build.bash | jpp -c

# EOF