The master password is the password of openERP application. 

this one way to set the master password manually by edit the openerp-server.conf:

[options]
; This is the password that allows database operations:
; admin_passwd = master_password_here
db_host = x.x.x.x
db_port = False
db_user = openerp
db_password = openerp
addons_path = D:\.....\openerp-7.0\openerp\addons