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A multi-dimensional docker build generator
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fish-pepper - Spicing1 up the ocean

fish-pepper is a multi-dimensional docker build generator . It allows you to create many similar Docker builds with the help of templates and building blocks. It allows for compositions of building blocks in addition to the usual Docker inheritance from base images.

For example consider a Java base image: Some users might require Java 7, some want Java 8. For running Microservices a JRE might be sufficient. In other use cases you need a full JDK. These four variants are all quite similar with respect to documentation, Dockerfiles and support files like startup scripts. Copy-and-paste might work but is not a good solution considering the image evolution over time or when introducing even more parameters.

With fish-pepper you can use flexible templates which are filled with variations of the base image (like 'version' : [ 'java7', 'java8'], 'type': ['jdk', 'jre']) and which will create multiple, similar Dockerfile builds. The example below dives into this in more details.

The generated build files can also be used directly to create the images with fish-pepper against a running Docker daemon or they can be used as the content for automated Docker Hub builds when checked in into Github.


fish-pepper can be installed as any other node.js application by calling npm:

npm -g install fish-pepper

It is recommended to install fish-pepper globally so that it is easily accessible from your build directories.

If you want to install the most current version, call npm from the project directory:

cd fish-pepper
npm -g install

If you are hitting Error: cannot open shared object file: No such file or directory, see issue #13.


Usage: fish-pepper [OPTION] <command>

Multidimensional Docker Build Generator

  -i, --image=ARG+    Images to create (e.g. "tomcat")
  -p, --param=ARG     Params to use for the build. Must be a comma separated list
  -a, --all           Process all parameters images
  -c, --connect       Docker URL (default: $DOCKER_HOST)
  -d, --dir=ARG       Directory holding the image definitions
  -n, --nocache       Don't cache when building images
  -e, --experimental  Include images which are marked as experimental
  -h, --help          display this help

The argument is interpreted as the command to perform. The following commands are supported:
    make  -- Create Docker build files from templates (default)
    build -- Build Docker images from generated build files. Implies 'make'

The configuration is taken from the file "fish-pepper.json" or "fish-pepper.yml" from the 
current directory or from the directory provided with the option '-d'. Alternatively the 
first parent directory containing one of the configuration files is used.


   # Find a 'fish-pepper.yml' in this or a parent directory and use
   # the images found there to create multiple Docker build directories.

   # Create all image families found in "example" directory
   fish-pepper -d example

   # Create only the image family "java" in "example" and build the images, too
   fish-pepper -d example -i java build


  • Make all docker builds and create the images with the Docker daemon running at $DOCKER_HOST:

      fish-pepper build
  • Create the image family "java" which can be found in the directory example:

      fish-pepper -d example -i java
  • Create only the image java-openjdk8-jre:

      fish-pepper -d example -i java -p openjdk8,jre
  • Asuming your current working directory is in examples/java/images/openjdk7/jdk and you call fish-pepper without arguments, only the Docker build for the image "java" with the parameter values "opendjk8" for the parameter "version", and "jre" for the parameter "type" is used ("version" and "type" are the parameter types as defined in fish-pepper.yml). This corresponds to

      fish-pepper -d example -i java -p openjdk7,jdk
  • Assume the same directory as above, but when you call fish-pepper -a then all images with all parameters are build nevertheless.

How it works


There are two kinds of configuration files:

  • A global configuration fish-pepper.yml global, image independent configuration, like a default Docker user name or the maintainer to use within the Dockerfile.
  • A per image family configuration images.yml which declares the parameterization of the images and image specific configuration.

The configuration can be given either in YAML syntax (with the file extensions .yml or .yaml) or in plain JSON (with extension .json).

Configuration within a fish-pepper section section in those files influence the behaviour of the image generation and the property names have a special meaning. All other configurations are mostly relevant for the templating.


The top-level configuration file is typically quite slim:

# Variable influencing the behaviour of fish-pepper are given in an extra object 'fish-pepper'
  # Registry for building the name when building images with '-b'. Can be omitted
  # in which case no registry is used
  registry: ""
  # A user which is used as default when no image stem is given
  repoUser: "fabric8"

  # Custom global variables useful in templates
  maintainer: ""

As mentioned above, the section fish-pepper has a special meaning. The following keys are used

  • registry - A default registry to use when creating images with fish-pepper -b
  • repoUser - A default repo user to use when creating images in build mode

These two parameters are used for calculating the base image name when doing a Docker build in build-mode. See below for how the name is calculated.

Any other key can be used by any image family. E.g. this is also perfect for defining a maintainer or global


For each image family found in a sub directory below the root directory where fish-pepper.yml is stored a dedicated configuration file images.yml is used. As the global config file, fish-pepper: blocks defined configuration values with a special meaning.

  • params defines the parameterization of the image family. See below.
  • name the name stem to use when building images with -b. If not given, the name is calculated as described in an extra section.

Parameters are a central concept of fish-pepper. They are used to fan-out a image family into multiple image builds. A parameter has a type (like 'version') and one or more possible values. For each value, a Docker build directory is created from the templates. The can be multiple parameter types, each with a dedicated set of possible values. The generated Docker build directories' hierarchy reflects the parameterization space: On the first directory level sub-directories are named like the values of the first parameter type, on the second level the directories are named after the values of the second parametere type and so on. See section How it works for an example layout. Note, that using multiple parameters can easily result in a multitude of Docker builds. So the set of possible parameters as well as their values should be chosen carefully.

fish-pepper will iterate over all parameter values and used dedicated, parameter value specific configurations for creating the template's context. This configuration is stored in a special config: object which looks like:

    - type1
    - type2

So, for each parameter type there's a set of config values. In the abstract example above, 6 (2 * 3) Docker build directories would be created, one for each permutation of parameter values. The ..... represent the specific configuration for this parameter values. The configuration of all select parameter values for a specific combination are merged into one single configuration which is used to fill in the template.

An example:

        version: "1.7"
          - "7u79"
      java: "java:7u79"
      fullVersion: "OpenJDK 1.7.0_79 (7u79-2.5.5-1~deb8u)"
        version: "1.8"
        - "8u45"
      java: "java:8u45"
      fullVersion: "OpenJDK 1.8.0_45 (1.8.0_45-internal-b14)"
      extension: "-jre"
      extension: "-jdk"

Here are two types with two values each, resulting in four Docker builds. For the build with version=openjdk7 and type=jre the template gets a template context which holds this information:

    java: "java:7u79"
    fullVersion: "OpenJDK 1.7.0_79 (7u79-2.5.5-1~deb8u)"
    extension: "-jre"
  version: "openjdk7"
  type: "jre"

As you can see, the parameter values are included, too. In the example above you can also see, that each parameter value's configuration can also contain a fish-pepper: section. As for the top-level fish-pepper: the properties specified here influence the behaviour of the build files generation.

The template context is described in detail in Template context.

  • experimental if set, this parameter value is considered to be experimental and the value will only be used when the command line option --experimental (or -e) is given.
  • version A paramer value specific version number which is used to generate the image name when building images with -b. See Image naming for details.
  • tags A list of tags which will be added to the created images in build mode.


Fish pepper templates are DoT.js templates. It is a fast template library which allows for the full expressiveness of JavaScript. Its a bit similar to JSP or PHP. The template syntax is described in detail [here] (section "Usage").

The most important directives are

  • {{= ... }} will evaluate the JavaScript within the parentheses and evaluate it as string which then is inserted literally into the text.

  • {{ ... }} will add the JavaScript code (which can be partially complete only) to the generated JavaScript rendering function. E.g.

      {{ images.forEach(function image) { }}
      * {{= }}
      {{ } }}

    will iterate over images (which needs to be initialized beforehand) and create a bullet list of the image names.

  • {{~ array :value:index}} can be used as shortcut for iteration over arrays. So, the example above can be written more elegantly with

      {{~ images :image:index}}
      * {{= }}
  • With {{? if-condition} ... {{?? else-if-conition}} ... {??} (else) ... {{?}} conditions can be build up easily:

      {{? images.length > 1 }}
        More than one image
      {{?? images.length == 1 }}
        Exactly one image 
        No image

Template context

All fish-pepper templates have access to the fish-pepper context object. This accessible as variable fp from within the templates.

The fp context has the following properties:

  • param is a map holding the current parameter values. As described in Configuration template are evaluated for every parameter values tuple. In each iteration the param property holds a map with the current parameter values. For the example above e.g when the current parameter values are version == "openjdk7" and type == "jdk" then fp.param is

        version: "openjdk7"
        type: "jdk"
  • config is an object which holds the configuration for the selected parameter values for the current template evaluation. E.g. assuming the example configuration given above, then when the template for the parameter values version == 'openjdk8' and type == 'jre' is used, then evaluated to java:8u45 and fp.config.type.extension to -jre. The general scheme is fp.config.parameter type which references to the currently active parameter's configuration.

  • All other properties defined in fish-pepper.yml and images.yml are directly accesible as properties from fp, so you can easily define image global and global global properties. Properties with the same name in images.yml take precedence over the properties in fish-pepper.yml.

  • block() is a function to use blocks

Examples of the context usage can be found in the templates used in the Java fish-pepper demo included in this repository.


One of the major features of fish-peppers are reusable blocks. These are reusable components which can be parameterized like any other template. A block itself can consist of two different kinds:

  • template snippets which will be inserted as a template fragment where referenced from within a template
  • files which are copied over into the Docker build direct.

These blocks can be defined locally or referenced remotely and a referenced by a unique ame. It is easy to share blocks across multiple image deinitions. The following two sections explain how to use blocks and how to create blocks.

Block usage

Defined Blocks can be referenced from within templates with a function on the template context.

{{= fp.block('version-info') }}

will refer to a block named "version-info". This block is processed as a template which receives the same context as the calling template. The processed content is the insert in place where the method is called.

Sub-snippets can be declared with an optional second argument:

{{= fp.block('version-info','java') }}

An (optional) third argument specifies additional processing instructions and additional arguments for the blocks as an JavaScript object:

{{= fp.block('version-info','java',{ "no-files": true, "copy-dir" :
"/usr/local/sti" }) }}

Processing instructions all start with fp-. The followin instructions are support:

  • fp-no-files : Don't copy over any files into the build directory

Block definitions

Blocks are stored in dedicated blocks/ directories. These will be looked up in multiple locations:

  • Top-level blocks/ directory where you global fish-pepper.yml resides. The blocks defined here are available across all defined images.
  • blocks/ directory on the image level where images.yml is located.
  • The location referenced in the blocks: sections in fish-pepper.yml.

There are two kind of blocks.

Simple blocks

Simple blocks are files within the blocks directory. They can have an arbitrary file extension which should match the content. The name before the extension defines the block name. E.g. a file in on of the blocks/ directories or in one of the locations referenced in the configuration will defined a block named "version-info" (and is probably written in markdown). This block can easily be referenced from within a template with {{= fp.block('version-info') }}. The text itself is a template, too and is processed before inserted.

The block itself can reference the fp context object as described in Templates. In addition is access to extra information which is available only for this block. This information is available as an object via the property fp.blockContext and has the following properties:

  • name : Name of the block
  • subname : Sub-snippet name (which is empty for simple blocks)
  • opts : Extra option given a third argument to the block call
Extended blocks

Extended blocks consist of multiple files which are stored within a directory in the blocks location. The name of the directory is also the block name. Any file within this directory defines a sub-snippet. The base filename of the sub snippets are the name of the sub-snippets, the extension can be anything. This directory can also contain a directory fp-files which holds files which should be copied over into a Docker build directory. This directory can hold other directories, which are deeply copied.

For example consider the following setup:

  +-- run-sh/
       +-- run-commands.dck
       +-- fp-files

This defines a block named run-sh with the template snippets run-commands.dck and The former holds the ADD command to put into the Dockerfile via {{= fp.block('run-sh','commands.dck')}}. This will also copy over all files in fp-files directory, in this case Alls files copied are also processed as templates. The contains the usage instructions which can be included in the README template with {{= fp.block('run-sh','',{ 'fp-no-files' : true }) }}. The third argument to this call indicates that no files should be copied in this case.

Remote Block definitions

Blocks can be also defined in a Git repository which must be accessible with https. These external references are defined in the main fish-pepper.yml configuration file in a dedicated blocks section.

For example

  - type: "git"
    url: ""
    path: "fish-pepper"

The blocks sections contains a list of external references. This external reference has a type (currently only git is supported), an access URL (https is mandatory for now). Optionally a path pointing in this Git Repo is provided. This directory is then used as a blocks directory as described above.

If type is omitted, the type is extracted from the url (i.e. if it ends with .git its of type "git"). If instead of an object a string is provided as block, this string is interpreted as URL. If no path is given, the defaul path fish-pepper is assumed. The example above hence can be written also as

  - ""

By default master is checked out, but this can be influenced either with a tag or branch property in which case the specific tag or branch is used.


For each parameter configuration default can be configured. Assume the following part of an images.yml:

# ....
      downloadUrl: "${JETTY_VERSION}/dist/jetty-distribution-${JETTY_VERSION}.tar.gz"
        jre8: "fabric8/java-centos-openjdk8-jre"
        jdk7: "fabric8/java-centos-openjdk7-jdk"
        version: "1.0.0"
      version: "9.3.2.v20150730"
      version: "8.1.17.v20150415"
      version: "7.6.17.v20150415"
# ...    

When iterating over the versions fp.config.version will also hold the properties downloadUrl and from which come from the default section if not overriden by a specfic version. The advantage is the you can avoid duplication of common parameter, the only drawback is that you can't have a parameter value of default.

File mappings

For more complex variations of Dockerfile which would lead into complicated Templates with a lof of conditionals it is possible to provide to use alternative templates based on parameter values.

This is best explained with an example: The project fabric8/base-images use fish pepper to generate a collection of base images, also for Jetty down to version 4. However the download process of the Jetty archives changes significantly when Jetty moved from Mortbay to Eclipse. So base images provides two different Dockerfile templates: One for Jetty 7 to 9 and one for Jetty 4 to 6

The relevant part in images.yml looks then like

# ...
      version: "9.3.2.v20150730"
      version: "8.1.17.v20150415"
      version: "7.6.17.v20150415"
      version: "6.1.18"
          __Dockerfile-456: "Dockerfile"
    # version 4 & 5 are similar

For Jetty version 6 there is a special section fish-pepper.mappings. This section contains an object which maps source files to its destination in the Docker build directory. In this example the template __Dockerfile-456 is copied over Dockerfile after it has been processed as a template. That way it is quite easy to create alternativs for certain template files.

Image naming

When using the build mode with -b, image names are calculated from various ways. The base name is taken from a when given in images.yml. If not the base is calculated as registry/userRepo/image, where registry and userRepo can be globally defined in fish-pepper.yml and image is the diretory name where images.yml is stored. registry and userRepo can be both left out.

From this base name the full name is calculated by appending the concrete parameter values with dashs (-). For example, when building an image for the param values version=openjdk7 and type=jre then image name will be java-openjdk7-jre, assuming that java is the base name as described above.

The image's tag is also calculated: Each param parameter value can have a version parameter in its fish-pepper section. For all parameter values this version are concatenaed with - to form an overall version number. When there is a top-level fish-pepper.buildVersion in the images file, then this will be appended, too. If no version is found at all latest is used.

In addition to this major tag more tags can be provided by the parameter values' configuration. Each tag creates an additional tag.

Sounds complicated ? Hopefully an example sheds some light on this. Consider the following images.yml for a java image family:

  # Two dimensional build: 1st dimension == version (7 or 8), 
  # 2nd dimension == type (jdk or jre)
      - "version"
      - "type"
    # Name stem to use for the images to create with -b (param value will be appended with -)
    name: "jolokia/fish-pepper-java"
    # Internal build number. Should be increased for each change
    build: 2

  # .......

  # Parameter specific configuration. For each type there is entry which holds all
  # possible values. This values are used to create the directory hierarchy and
  # also used within the image names.
        # The version is used in the tag
          version: "1.7"
          # Additional tags to add
            - "7u79"
        # ....
          version: "1.8"
          - "8u45"
          - "latest"
        # ....
        # ....
        # .... 

When using fish-pepper build with this image config you will get the following images (user and registry omitted):

  • java-openjdk7-jdk:1.7-jdk-2
  • java-openjdk7-jre:1.7-jre-2
  • java-openjdk8-jdk:1.8-jdk-2
  • java-openjdk8-jre:1.8-jre-2

and the additional tagged images:

  • java-openjdk7-jdk:7u79
  • java-openjdk7-jre:7u79
  • java-openjdk8-jdk:8u45, java-openjdk8-jdk:latest
  • java-openjdk8-jre:8u45, java-openjdk8-jre:latest

It is recommended to use and count up fish-pepper.buildVersion for any change in you build files.


A full featured example showing most of fish-pepper's possibilities can be found in the example directory which holds one configuration for building a agent-bond enabled Java image. The build it quite similar and we will build for OpenJDK 7 and 8 with a JDK and JRE, respectively.

All the configuration files are documented, so please have a look a them to see how the tepmplating works.

1: fish pepper is an ancient chili pepper variety coming from Baltimore and are famous for the ornamental qualities. They are not too hot and are ideal to spice up everything, even Docker builds :)

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