> db.getSiblingDB("$external").createUser({user:"fuu",pwd:"bar",roles:[]}) 2014-02-24T15:59:04.404-0500 Error: couldn't add user: User documents for users defined on '$external' must have 'credentials' field set to {external: true} at src/mongo/shell/db.js:1007 > db.getSiblingDB("$external").createUser({user:"fuu",pwd:"bar",roles:[],credentials:{external:true}}) 2014-02-24T15:59:11.985-0500 Error: couldn't add user: "credentials" is not a valid argument to createUser at src/mongo/shell/db.js:1007