# Extras Hooks
 
 The `extras.d` directory contains project dispatch scripts that are called
 at specific times by `stack.sh`, `unstack.sh` and `clean.sh`.  These hooks are
 used to install, configure and start additional projects during a DevStack run
 without any modifications to the base DevStack scripts.
 
 When `stack.sh` reaches one of the hook points it sources the scripts in `extras.d`
 that end with `.sh`.  To control the order that the scripts are sourced their
 names start with a two digit sequence number.  DevStack reserves the sequence
 numbers 00 through 09 and 90 through 99 for its own use.
 

 The scripts are sourced at the beginning of each script that calls them. The
 entire `stack.sh` variable space is available.  The scripts are

 sourced with one or more arguments, the first of which defines the hook phase:
 

     override_defaults | source | stack | unstack | clean

     override_defaults: always called first in any of the scripts, used to
         override defaults (if need be) that are otherwise set in lib/* scripts
 
     source: called by stack.sh. Used to set the initial defaults in a lib/*
         script or similar

     stack: called by stack.sh.  There are four possible values for

         the second arg to distinguish the phase stack.sh is in:
 

         arg 2:  pre-install | install | post-config | extra

 
     unstack: called by unstack.sh
 
     clean: called by clean.sh.  Remember, clean.sh also calls unstack.sh
         so that work need not be repeated.

 
 The `stack` phase sub-phases are called from `stack.sh` in the following places:
 
     pre-install - After all system prerequisites have been installed but before any
         DevStack-specific services are installed (including database and rpc).
 
     install - After all OpenStack services have been installed and configured
         but before any OpenStack services have been started.  Changes to OpenStack
         service configurations should be done here.
 
     post-config - After OpenStack services have been initialized but still before
         they have been started. (This is probably mis-named, think of it as post-init.)
 
     extra - After everything is started.