The problem this project tries to mitigate is "portable" scripting for variety of operating systems (currently Linux distributions only) in the wild. While writing an "universal" script, one needs to take into account small or bigger differences among operating systems (like package installation tools, versions of utilities, expected directories for binaries, libraries, etc.).

The distgen project is thus something like database of OS differences together with convenience tool-set that allows you to instantiate valid script for particular distribution. The concept is to have template file (mostly raw jinja2 template) together with "declarative" spec file (YAML file) that fulfils the needs of particular template.

You can find distgen documentation at http://distgen.readthedocs.io.

Stable releases of distgen are available as RPMs in Fedora and EPEL repositories, and in pypi:

$ sudo dnf install distgen

$ pip install distgen

Development (git snapshot) RPMs are automatically built in Fedora Copr.

You can also run development version directly from git, simply use the dg shell wrapper available in this git root directory.

Typical example is the need to instantiate working FOO package oriented Dockerfiles for all supported Fedora/RHEL versions.

To achieve that goal with distgen, you need to write something like docker.tpl template and FOO.yaml spec file. If the system-default docker.tpl template is good enough, its enough to write proper spec file:

1. create FOO.yaml spec:

   $ cat FOO.yaml
   maintainer: John Doe <[email protected]>
   parts:
     pkginstall:
       data:
         - type: pkg
           action: install
           packages:
             - vim
     footer:
       cmd: ["vim"]
   

2. Run dg tool to generate Fedora 22 Dockerfile:

   $ dg --template docker.tpl \
        --spec FOO.yaml \
        --distro fedora-22-x86_64.yaml \
   > Dockerfile
   $ cat Dockerfile
   FROM index.docker.io/fedora:22
   MAINTAINER John Doe <[email protected]>
   
   ENV container="docker"
   
   RUN dnf -y --setopt=tsflags=nodocs install vim \
       && dnf -y --setopt=tsflags=nodocs clean all --enablerepo='*'
   
   CMD ["vim"]
   

3. Run dg tool again to generate RHEL 7 dockerfile:

   $ dg --template docker.tpl \
        --spec FOO.yaml \
        --distro rhel-7-x86_64.yaml \
   > Dockerfile
   $ cat Dockerfile
   FROM registry.access.redhat.com/rhel7
   MAINTAINER John Doe <[email protected]>
   
   ENV container="docker"
   
   RUN yum -y --setopt=tsflags=nodocs install vim \
       && yum -y --setopt=tsflags=nodocs clean all --enablerepo='*'
   
   CMD ["vim"]