/usr/share/texmf-texlive/tex/plain/plnfss/ 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/plnfss/MIKmathf.tex
/usr/share/texmf-texlive/tex/plain/plnfss/ams.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/il2cm.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/il2cmr.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/ly1lm.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/ot1cm.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/ot1cmr.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/ot4cm.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/plnfss.tex
/usr/share/texmf-texlive/tex/plain/plnfss/qxlm.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/t1lm.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/t5cm.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/t5cmr.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/t5lm.pfd
/usr/share/texmf-texlive/tex/plain/plnfss/ts1lm.pfd