This morning in #chef someone had locked themselves out of their WebUI admin account, and wanted to know how to reset the password.

So long you have knife set up with an admin account locally, this should do the trick:

unless ARGV[0] && ARGV[1]
  puts "Usage: set_password.rb username password"
  exit 1
end

require 'chef'
require 'chef/config'
require 'chef/webui_user'

Chef::Config.from_file(File.expand_path("/.chef/knife.rb"))

user = Chef::WebUIUser.load(ARGV[0])
if user
  user.set_password(ARGV[1])
  user.save
else
  puts "Could not find user #{ARGV[0]}."
  exit 2
end

Put it in a file, and then run ruby set_password.rb admin newpassword. If it doesn’t say anything, it worked.