Buildstep
Buildstep uses Docker and small buildpack scripts to build applications like Heroku. It was used by Dokku to create a 100-line Heroku clone. There are many open source Buildpack scripts for various languages like Java, Ruby, Erlang, PHP, etc.
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Eucalyptus
An open source software for building Amazon EC2-compatible private and hybrid cloud platforms
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Fog
The Ruby Cloud API library. Provides a Ruby API for interacting and managing many cloud providers, such as spinning up new instances, terminating old ones, attaching storage, etc. Currently supports more than 20 providers, including EC2, Rackspace, Brightbox, etc.
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Foreman
A complete lifecycle management tool for servers, both self-hosted and in the cloud. It allows you to create and manage instances, build and deploy images, view and audit hosts, and much more! It works with Puppet or Chef, and has multiple interaction facilities like a web frontend, CLI and a RESTful API.
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jclouds
A Java Library for controlling cloud resources, with various plugins for many popular cloud providers.
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Monit
An open source utility for managing and monitoring processes, programs, files, directories and filesystems
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SSH KeyBox
An open-source jump box solution with auditing capabilities
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