acbuild-template

Write declarative acbuild-scripts and build/install/run images from them without need of any auxiliary boilerplate code.

Motivation

I like that acbuild follows the unix-ideology to be flexible and composable tool. Unlike Dockerfile, acbuild can be built into scripts or makefiles to implement sophisticated image-bilding behaviour, such that would be impossible to make with Docker.

However, there are majority of cases, where just very simple behaviour is needed, e.g.: (1) get base image, (2) make some simple modification to it and (3) get the result.

In those cases the declarative nature of Dockerfiles seems to be superior to acbuild imperative approach. Dockerfile is all-in-one entity with simple syntax, which is self-explaining for reader. It is enough to look at Dockerfile to have a grasp of what is going on when image is built.

On the other hand, acbuild needs lots of auxilliary imperative scripting to execute. As a writer, I am to write some build scripts, or a makefile in which i should implement lots of things like build artifact management, version propagation etc. As a reader, I find it hard to read such implementations, since the code is split among multiple files.

I like the support for scripts added in the recent versions of acbuild, which allows to make more elegant build systems. But there are problems with scripts. For example, suppose i want to store version number only in one place in the project, to avoid mistakes when building releases. I store version number in my makefile, so i need some kind of templating to pass version number to script. Again i need boilerplate code.

acbuild-template implements simple idea of using variable placeholders instead of hard-coded values in acbuild scripts to make executing them more flexible.

Introduction

1. Write acbuild script named acbuild-script, using variable placeholders to identify values which can vary:

   begin --build-mode={{mode}}
   set-name example.com/nginx
   label add version 1.2.3
   run --insecure={{insecure}} --engine={{engine}} -- bash -c 'touch /var/lib/rpm/* && yum install nginx && yum clean all'
   set-exec -- nginx -g 'daemon off;'
   write --overwrite {{output}}
   

2. With a single command build/install image or run container from the script using default values, which acbuild-template substitutes for you:

   $ cd path/to/script
   $ acbuild-template build --print-name
   /tmp/tmp.duwasSaaLk/example_com_nginx-1.2.3-linux-amd64.aci
   $ acbuild-template install --print-hash
   sha512-0a1cb92dc276b0f9bedf87981e61ecde
   $ acbuild-template run
   ...
   

Of course, values can be customized, eg:

ACBUILD_RUN_INSECURE=true ACBUILD_RUN_ENGINE=chroot ACBUILD_IMAGE_BASE_DIR=/tmp/acbulid-cache acbuild-template run acbuild-script.template

Usage

From acbuild-template help:

Usage:
  acbuild-template [-i|--script <script>] \
    [apply [-o|--output <output>]] \
    [build [-o|--output <output>] [-s|--silent|-n|--print-name] \
    [sign  [-o|--output <output>] [-s|--silent|-n|--print-name] \
    [install [-s|--silent|-n|--print-hash]] \
    [upload upload (--repository|-r) <git-repo-url>] \
    [run <rkt image run parameters>]

Options:
  -h --help                print this message
  -n --print-name          print nothing except resulting image full name
  -n --print-hash          print nothing except installed image hash
  -i --script              input script template to process, default ./acbuild-script
  -o --output              if building, resulting image, if not harcoded in script
                           if signing, resulting signature, by default image with suffix '.asc'
  -s --silent              print nothing in case of success
  -n --print-name          like --silent, but print output filename
  -n --print-hash          print nothing except installed image hash

Environment:

  ACBUILD_SCRIPT           script to process (./acbuild-script by default)
  ACBUILD_IMAGE_DIR_NAME   directory to save resulting image
  ACBUILD_IMAGE_MODE       build mode, appc or oci
  ACBUILD_IMAGE_VERSION    label add os version (snapshot by default)
  ACBUILD_IMAGE_OS         label add os value (current by default)
  ACBUILD_IMAGE_ARCH       label add os value (current by arch)
  ACBUILD_IMAGE_EXT        image file extension, default aci  
  ACBUILD_RUN_INSECURE     run --insecure=value, defaul false
  ACBUILD_RUN_ENGINE       run --engine=value
  ACBUILD_IMAGE_BASE_NAME  image base file name, default {{name}}-{{version}}-{{os}}-{{arch}}.{{ext}}
  ACBUILD_IMAGE            image file full name
  ACBUILD_CACHE_DIR        directory to store temporary files
  
  ACBUILD_IMAGE_SIGNATURE  .asc-file to save image signature

  GPG                      gpg command, default gpg itself
  GPG_OPTS                 

  ACBUILD                  acbuild command, default acbuild itself
  ACBUILD_OPTS             

  RKT                      rkt command, default rkt itself
  RKT_OPTS                 
  RKT_FETCH_OPTS           
  RKT_RUN_OPTS