/usr/share/texmf-texlive/tex/plain/font-change/ is in texlive-plain-extra 2009-10ubuntu1.
This file is owned by root:root, with mode 0o755.
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/usr/share/texmf-texlive/tex/plain/font-change/font_antp_euler.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_antt.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_arev.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_bera_concrete.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_bera_euler.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_bera_fnc.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_bookman.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_century.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_charter.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_cm.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_cmbright.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_concrete.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_epigrafica_euler.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_epigrafica_palatino.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_iwona.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_kurier.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_palatino.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_times.tex
/usr/share/texmf-texlive/tex/plain/font-change/font_utopia.tex