Omnibus

Umbrella Project: Chef Foundation

Project State: Active

Issues Response Time Maximum: 14 days

Pull Request Response Time Maximum: 14 days

Easily create full-stack installers for your project across a variety of platforms.

Seth Chisamore and Christopher Maier of CHEF gave an introductory talk on Omnibus at ChefConf 2013, entitled Eat the Whole Bowl: Building a Full-Stack Installer with Omnibus:

• Slides

This project is managed by the CHEF Release Engineering team. For more information on the Release Engineering team's contribution, triage, and release process, please consult the CHEF Release Engineering OSS Management Guide.

Prerequisites

Omnibus is designed to run with a minimal set of prerequisites. You will need the following:

• Ruby 2.6+

Get Started

Omnibus provides both a DSL for defining Omnibus projects for your software, as well as a command-line tool for generating installer artifacts from that definition.

To get started, install Omnibus locally on your workstation.

$ gem install omnibus

You can now create an Omnibus project in your current directory by using the project generator feature.

$ omnibus new $MY_PROJECT_NAME

This will generate a complete project skeleton in the directory omnibus-$MY_PROJECT_NAME

By default this will make a directory called omnibus-$MY_PROJECT_NAME assuming you're keeping your omnibus config separate from the repo. However, keeping it in your repo is a common practice, so feel to rename this directory to omnibus and place it in the top level of your projects source repo.

$ cd omnibus-$MY_PROJECT_NAME
$ bundle install --binstubs

More details can be found in the generated project's README file.

Omnibus determines the platform for which to build an installer based on the platform it is currently running on. That is, you can only generate a .deb file on a Debian-based system. To alleviate this caveat, the generated project includes a Test Kitchen setup suitable for generating a series of Omnibus projects.

More documentation

• Building on Debian
• Building on OSX
• Building on RHEL
• Building on Windows
• Build Cache

Configuration DSL

Though the template project will build, it will not do anything exciting. For that, you need to use the Omnibus DSL to define the specifics of your application.

Config

If present, Omnibus will use a top-level configuration file named omnibus.rb at the root of your repository. This file is loaded at runtime and includes a number of configuration tunables. Here is an example:

# Build locally (instead of /var)
# -------------------------------
base_dir './local'

# Disable git caching
# ------------------------------
use_git_caching false

# Enable S3 asset caching
# ------------------------------
use_s3_caching true
s3_bucket      ENV['S3_BUCKET']

# There are three ways to authenticate to the S3 bucket

# 1. set `s3_access_key` and `s3_secret_key`
s3_access_key  ENV['S3_ACCESS_KEY']
s3_secret_key  ENV['S3_SECRET_KEY']

# 2. set `s3_profile` to use an AWS profile in the Shared Credentials files
#s3_profile    ENV['S3_PROFILE']

# 3. set `s3_iam_role_arn` to use an AWS IAM role
#s3_iam_role_arn    ENV['S3_IAM_ROLE_ARN']

For more information, please see the Config documentation.

You can tell Omnibus to load a different configuration file by passing the --config option to any command:

$ bin/omnibus --config /path/to/config.rb

Finally, you can override a specific configuration option at the command line using the --override flag. This takes ultimate precedence over any configuration file values:

$ bin/omnibus --override use_git_caching:false

Projects

A Project DSL file defines your actual application; this is the thing you are creating a full-stack installer for in the first place. It provides a means to define the dependencies of the project (again, as specified in Software DSL definition files), as well as ways to set installer package metadata.

All project definitions must be in the config/projects directory of your Omnibus repository.

name            "chef-full"
maintainer      "YOUR NAME"
homepage        "http://yoursite.com"

install_dir     "/opt/chef"
build_version   "0.10.8"
build_iteration 4

dependency "chef"

Some DSL methods available include:

By default a timestamp is appended to the build_version. You can turn this behavior off by setting append_timestamp to false in your omnibus.rb or using --override append_timestamp:false at the command line.

For more information, please see the Project documentation.

Software

Omnibus "software" files define individual software components that go into making your overall package. They are the building blocks of your application. The Software DSL provides a way to define where to retrieve the software sources, how to build them, and what dependencies they have. These dependencies are also defined in their own Software DSL files, thus forming the basis for a dependency-aware build ordering.

All Software definitions should go in the config/software directory of your Omnibus project repository.

Here is an example:

name "ruby"
default_version "1.9.2-p290"
source url: "http://ftp.ruby-lang.org/pub/ruby/1.9/ruby-#{version}.tar.gz",
       md5: "604da71839a6ae02b5b5b5e1b792d5eb"

dependency "zlib"
dependency "ncurses"
dependency "openssl"

relative_path "ruby-#{version}"

build do
  command "./configure"
  command "make"
  command "make install"
end

Some of the DSL methods available include:

For more DSL methods, please consult the Software documentation.

Additionally, there are a number of DSL methods available inside the build block:

For more DSL methods, please consult the Builder documentation.

You can support building multiple versions of the same software in the same software definition file using the version method and giving a block:

name "ruby"
default_version "1.9.2-p290"

version "1.9.2-p290" do
  source url: "http://ftp.ruby-lang.org/pub/ruby/1.9/ruby-#{version}.tar.gz",
         md5: "604da71839a6ae02b5b5b5e1b792d5eb"
end

version "2.1.1" do
  source url: "http://ftp.ruby-lang.org/pub/ruby/2.1/ruby-#{version}.tar.gz",
         md5: "e57fdbb8ed56e70c43f39c79da1654b2"
end

Since the software definitions are simply ruby code, you can conditionally execute anything by wrapping it with pure Ruby that tests for the version number.

Sharing software definitions

The easiest way to share organization-wide software is via bundler and Rubygems. For an example software repository, look at Chef's omnibus-software. For more information, please see the Rubygems documentation.

It is recommended you use bundler to pull down these gems (as bundler also permits pulling software directly from GitHub):

gem 'my-company-omnibus-software'
gem 'omnibus-software', github: 'my-company/omnibus-software'

Then add the name of the software to the list of software_gems in your Omnibus config:

software_gems %w(my-company-omnibus-software omnibus-software)

You may also specify local paths on disk (but be warned this may make sharing the project among teams difficult):

local_software_dirs %w(/path/to/software /other/path/to/software)

For all of these paths, order matters, so it is possible to depend on local software version while still retaining a remote software repo. Given the above example, Omnibus will search for a software definition named foo in this order:

$PWD/config/software/foo.rb
/path/to/software/config/software/foo.rb
/other/path/to/software/config/software/foo.rb
/Users/sethvargo/.gems/.../my-company-omnibus-software/config/software/foo.rb
/Users/sethvargo/.gems/.../omnibus-software/config/software/foo.rb

The first instance of foo.rb that is encountered will be used. Please note that local (vendored) softare definitions take precedence!

Building

Once you've created your package and software definitions you can build with:

./bin/omnibus build $MY_PACKAGE_NAME

However there are several caveats to be aware of:

1. You will almost certainly want to uncomment the base_dir in omnibus.rb, or at the very least change cache_dir and build_dir as otherwise it'll try to use /var/cache/omnibus and /opt/$MY_PROJECT_NAME, requiring root.
2. Update software dependencies listed in the project configuration in config/projects/$MY_PROJECT_NAME.rb. You can refer the software .rb files present in the config/software folder.
3. The install_dir specified in the project file typically requires root privilege at build time. Change it another location such as "/tmp/#{name}" to avoid running as root.
4. The default configuration created for you references a lot of things that are in the default config that come from the omnibus-software gem. So you want to use those you'll need to either uncomment it in the Gemfile, or fork it, and then reference your own
5. If this is a ruby project and you want binstubs in /opt/$project/bin, you will either need to use appbundler, or you will need to have a post install step to create those binstubs.
   • Side note, appbundler requires that you include your Gemfile and gemspec in your gem.
   • Also, needs to be in your Gemfile for you to use it, as it also must be in the resulting gem.
6. If you specify an override of the version of the ruby, you will also need to override rubygems and bundler to match the versions in that version of ruby or you'll get failures around bundler version mismatches.

The build command above will of course build on your local host thus being specific to the OS and base system you are on. But the skeleten setup by omnibus new already setup kitchen for you so that it's easy to build for a variety of OSes, See the README.md in your generated omnibus directory for details.

Version Manifest

Git-based software definitions may specify branches as their default_version. In this case, the exact git revision to use will be determined at build-time unless a project override (see below) or external version manifest is used. To generate a version manifest use the omnibus manifest command:

omnibus manifest PROJECT -l warn

This will output a JSON-formatted manifest containing the resolved version of every software definition.

Whitelisting Libraries

Sometimes a platform has libraries that need to be whitelisted so the healthcheck can pass. The whitelist found in the healthcheck code comprises the minimal required for successful builds on supported platforms.

To add your own whitelisted library, simply add a regex to your software definition in your omnibus project as follows:

whitelist_file /libpcrecpp\.so\..+/

It is typically a good idea to add a conditional to whitelist based on the specific platform that requires it.

Warning: You should only add libraries to the whitelist that are guaranteed to be on the system you install to; if a library comes from a non-default package you should instead build it into the package.

Changelog

STATUS: EXPERIMENTAL

omnibus changelog generate will generate a changelog for an omnibus project. This command currently assumes:

• A version-manifest.json file is checked into the project root
• The project is a git repository
• Each version is tagged with a SemVer compliant annotated tag
• Any git-based sources are checked out at ../COMPONENT_NAME
• Any commit message line prepended with ChangeLog-Entry: should be added to the changelog

These assumptions will change as we determine what works best for a number of our projects.

Caveats

Overrides

The project definitions can override specific software dependencies by passing in override to use the correct version:

name "chef-full"
# <snip>

# This will override the default version of "chef"
override :chef, version: "2.1.1"

dependency "chef"

The overridden version must be defined in the associated software!

Debugging

By default, Omnibus will log at the warn level. You can override this by passing the --log-level flag to your Omnibus call:

$ bin/omnibus build <project> --log-level info # or "debug"

Git caching

by default, Omnibus caches compiled software definitions, so n+1 Omnibus project builds are much faster. This functionality can be disabled by adding the following to your omnibus.rb:

use_git_caching false

Contributing

For information on contributing to this project see https://github.com/chef/chef/blob/master/CONTRIBUTING.md

License

Copyright 2012-2016 Chef Software, Inc.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.