[Dev-luatex] luatools --ini plain

This is something I don't understand. In the mk.pdf manual on luatex on page 21 there is the following example: luatools --ini plain Instead of the expected output 120,808 plain.fmt etc. I get an error: "There is no lua initialization file found. ..." Running "luatools --generate" does not help. There is a hint: "This file can be forced by the --progname directve, or specified with --luaname,..." How can I get a "lua initialization file" in order to not have the error. And how do I interpret the hint, as the text of the error message is too cryptic for me to understand. Hans van der Meer