Deploying across multiple environments can be a daunting task, especially when it comes to ensuring that commonalities like IaaS properties and networking are common where they should be and specialized where they shouldn't.

An ideal deployment pipeline might look something like this:

Where sandbox is used to validate that deployments are sane, test stemcell upgrades, etc., preprod enables integration and acceptance testing, and prod is the thing that shouldn't break. For reasons of sanity, these environments should all be deployed on similar infrastructure, like Amazon EC2 or a hosted VMWare ESXi cluster.

Challenges arise when you need to make changes to the "common elements" of these different environments, like what AWS region the deployments should be done in, or what version of the BOSH release is being deployed. Without intense discipline, these different environments can easily drift, which may have disastrous consequences.

Genesis changes this by breaking up your BOSH configuration manifest along three logical strata: global, site and environment.

At the top, the most generic configuration is considered global. The general outline of your deployment, what jobs run on what instances, is specified here, and used everywhere. Defaults for job and global properties are defined here as well.

Beneath that, the site stratum defines the composition and configuration of your infrastructure. For example, if you are deploying on the Amazon AWS EC2 platform, you would set your S3/EC2 credentials, which AMI to use as a stemcell, etc. here.

At the lowest and most specific level, environment provides a place to set the networking for a single deployment, and override properties and scaling factors here. Your sandbox environment probably doesn't need to run as many instances as production, and they are most likely in different subnets.

Genesis combines these different levels of configuration to produce a single BOSH manifest for each environment, and uses a tool called spruce to handle overrides and references in a straightforward and predictable manner.

For more information, check out these fantastic Stark & Wayne blog articles about using Genesis in real world situations:

• Managing Multiple BOSH Environments with Genesis
• Standing up Vault with Genesis
• Using Genesis to Deploy Cloud Foundry

To install Genesis, you just need to put bin/genesis somewhere in your path and make it executable, like this:

curl https://raw.githubusercontent.com/starkandwayne/genesis/master/bin/genesis > ~/bin/genesis
chmod 0755 ~/bin/genesis

(assuming that ~/bin is in your $PATH, which it really ought to be)

If you have privileged access and wish to install Genesis for all users, you can put it in /usr/local/bin or /usr/bin