[knot-dns-users] first time install got failed

Hi, My system is debian 6.0 (yes I know it's out of date). When I installed knot from source following the document, I got failed as below. How can I get continued? thanks. $ autoreconf -i -f libtoolize: putting auxiliary files in `.'. libtoolize: copying file `./ltmain.sh' libtoolize: putting macros in AC_CONFIG_MACRO_DIR, `m4'. libtoolize: copying file `m4/libtool.m4' libtoolize: copying file `m4/ltoptions.m4' libtoolize: copying file `m4/ltsugar.m4' libtoolize: copying file `m4/ltversion.m4' libtoolize: copying file `m4/lt~obsolete.m4' configure.ac:35: error: possibly undefined macro: AC_SUBST If this token and others are legitimate, please use m4_pattern_allow. See the Autoconf documentation. configure.ac:93: error: possibly undefined macro: AS_IF configure.ac:102: error: possibly undefined macro: AC_MSG_WARN configure.ac:122: error: possibly undefined macro: AC_DEFINE configure.ac:163: error: possibly undefined macro: AC_MSG_ERROR configure.ac:251: error: possibly undefined macro: AC_SEARCH_LIBS autoreconf: /usr/bin/autoconf failed with exit status: 1