First follow the steps for getting started with derby-auth.
Next require the module in server/index.js:
var gravatar = ;
Add gravatar after derby-auth middleware:
// derby-auth middleware// gravatar middleware
A user's gravatar data is stored in "users.*.auth.local.gravatar". Each gravatar object contains a hash property that can be used to generate a gravatar image url
If a user has a profile then their profile data will also be stored in the gravatar object.
*Note: For whatever reason, secondary gravatar accounts do not return profile data.