text: DevStack is a set of scripts and utilities to quickly deploy an OpenStack cloud.
  
  # Goals
  
  * To quickly build dev OpenStack environments in a clean Ubuntu or Fedora environment
  * To describe working configurations of OpenStack (which code branches work together?  what do config files look like for those branches?)
  * To make it easier for developers to dive into OpenStack so that they can productively contribute without having to understand every part of the system at once
  * To make it easy to prototype cross-project features
  * To sanity-check OpenStack builds (used in gating commits to the primary repos)
  
  Read more at http://devstack.org (built from the gh-pages branch)
  
  IMPORTANT: Be sure to carefully read `stack.sh` and any other scripts you execute before you run them, as they install software and may alter your networking configuration.  We strongly recommend that you run `stack.sh` in a clean and disposable vm when you are first getting started.
  
  # Devstack on Xenserver
  
  If you would like to use Xenserver as the hypervisor, please refer to the instructions in `./tools/xen/README.md`.
  
  # Versions
  
  The devstack master branch generally points to trunk versions of OpenStack components.  For older, stable versions, look for branches named stable/[release] in the DevStack repo.  For example, you can do the following to create a diablo OpenStack cloud:
  
      git checkout stable/diablo
      ./stack.sh
  
  You can also pick specific OpenStack project releases by setting the appropriate `*_BRANCH` variables in `localrc` (look in `stackrc` for the default set).  Usually just before a release there will be milestone-proposed branches that need to be tested::
  
      GLANCE_REPO=https://github.com/openstack/glance.git
      GLANCE_BRANCH=milestone-proposed
  
  # Start A Dev Cloud
  
  Installing in a dedicated disposable vm is safer than installing on your dev machine!  To start a dev cloud:
  
      ./stack.sh
  
  When the script finishes executing, you should be able to access OpenStack endpoints, like so:
  
  * Horizon: http://myhost/
  * Keystone: http://myhost:5000/v2.0/
  
  We also provide an environment file that you can use to interact with your cloud via CLI:
  
      # source openrc file to load your environment with osapi and ec2 creds
      . openrc
      # list instances
      nova list
  
  If the EC2 API is your cup-o-tea, you can create credentials and use euca2ools:
  
      # source eucarc to generate EC2 credentials and set up the environment
      . eucarc
      # list instances using ec2 api
      euca-describe-instances
  
  # Customizing
  
  You can override environment variables used in `stack.sh` by creating file name `localrc`.  It is likely that you will need to do this to tweak your networking configuration should you need to access your cloud from a different host.
  
  # Database Backend
  
  Multiple database backends are available. The available databases are defined in the lib/databases directory.
  To choose a database backend, add a line to your `localrc` like:
  
      use_database postgresql
  
  By default, the mysql database backend is used.
  
  # RPC Backend
  
  Multiple RPC backends are available. Currently, this
  includes RabbitMQ (default), Qpid, and ZeroMQ. Your backend of
  choice may be selected via the `localrc`.
  
  Note that selecting more than one RPC backend will result in a failure.
  
  Example (ZeroMQ):
  
      ENABLED_SERVICES="$ENABLED_SERVICES,-rabbit,-qpid,zeromq"
  
  Example (Qpid):
  
      ENABLED_SERVICES="$ENABLED_SERVICES,-rabbit,-zeromq,qpid"
  
  # Swift
  
  Swift is not installed by default, you can enable easily by adding this to your `localrc`:
  
      enable_service swift
  
  If you want a minimal Swift install with only Swift and Keystone you can have this instead in your `localrc`:
  
      disable_all_services
      enable_service key mysql swift
  
  If you use Swift with Keystone, Swift will authenticate against it. You will need to make sure to use the Keystone URL to auth against.
  
  If you are enabling `swift3` in `ENABLED_SERVICES` devstack will install the swift3 middleware emulation. Swift will be configured to act as a S3 endpoint for Keystone so effectively replacing the `nova-objectstore`.
  
  Only Swift proxy server is launched in the screen session all other services are started in background and managed by `swift-init` tool.
  
  By default Swift will configure 3 replicas (and one spare) which could be IO intensive on a small vm, if you only want to do some quick testing of the API you can choose to only have one replica by customizing the variable `SWIFT_REPLICAS` in your `localrc`.
  