[luatex] \font primitive does not read otf file

[Petr Olsak]

Hello,

I am starting with LuaTeX and I have problem to find the relevant 
documentation about \font primitive. There is only one document

    http://www.luatex.org/talks/print-plain-tug-2009.pdf

page 7. It seems that the \font primitive works like in XeTeX. Thus I 
started with experiments:

    luatex -ini luatex.ini
    This is LuaTeX, Version beta-0.70.2-2012052410 (TeX Live 2012) (INITEX)
    (/usr/share/texmf-dist/tex/plain/config/luatex.ini
    (/usr/share/texmf/tex/generic/config/luatexiniconfig.tex)
    (/usr/share/texmf/tex/generic/config/luatex-unicode-letters.tex
    ...
    Beginning to dump on file luatex.fmt
    (format=luatex 2012.11.28)
    3439 strings using 12961 bytes
    ...
    No pages of output.
    Transcript written on luatex.log.

OK, the format luatex.fmt is generated. Then I prepared the following 
document pok.tex:

\font\aa="[lmroman10-regular]"
\aa  text
\end

Now, I run:

    luatex -fmt luatex pok
    This is LuaTeX, Version beta-0.70.2-2012052410 (TeX Live 2012)
    (./pok.tex
    ! Font \aa=[lmroman10-regular] not loadable: metric data not found or bad.
    <to be read again>
                       \aa
    l.2 \aa
             text
    ?

kpsewhich lmroman10-regular.otf says:

    /usr/share/texmf-dist/fonts/opentype/public/lm/lmroman10-regular.otf

The same experiment with XeTeX passes without problems.

What is wrong?

Thanks

Petr Olsak