Install DocBook SGML DTD by running the following commands: cp docbook.cat docbook.cat.orig && sed -e '/ISO 8879/d' docbook.cat.orig > docbook.cat && cp docbook.cat docbook.cat.orig && sed -e '/gml/d' docbook.cat.orig > docbook.cat && cp docbook.cat docbook.cat.orig && sed -e 's|DTDDECL "-//OASIS//DTD DocBook V&sgml-dtd-3-version;//EN"|SGMLDECL|g' \ docbook.cat.orig > docbook.cat && install -d /usr/share/sgml/docbook/sgml-dtd-&sgml-dtd-3-version; && chown -R root:root . && chmod -R 755 . && install docbook.cat /usr/share/sgml/docbook/sgml-dtd-&sgml-dtd-3-version;/catalog && cp -af *.dtd *.mod *.dcl /usr/share/sgml/docbook/sgml-dtd-&sgml-dtd-3-version; && install-catalog --add /etc/sgml/sgml-docbook-dtd-&sgml-dtd-3-version;.cat \ /usr/share/sgml/docbook/sgml-dtd-&sgml-dtd-3-version;/catalog && install-catalog --add /etc/sgml/sgml-docbook-dtd-&sgml-dtd-3-version;.cat \ /etc/sgml/sgml-docbook.cat