instalar postgis

Hola a todos. Estuve tratando de instalar postgis sobre postgresql
Instale postgresql desde el gestor de paquetes synaptic de la distribucion de debian.
al intentar instalar postgis me da el siguiente error:

casa:/home/usuario# psql -version
psql: FATAL: no existe la base de datos «root»
casa:/home/usuario# psql --version
psql (PostgreSQL) 8.1.11
incluye soporte para edición de línea de comandos
casa:/home/usuario# cd postgis-1.3.5
casa:/home/usuario/postgis-1.3.5# make # make install
./configure
checking for gcc... gcc
checking for C compiler default output file name... a.out
checking whether the C compiler works... yes
checking whether we are cross compiling... no
checking for suffix of executables...
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking for g++... g++
checking whether we are using the GNU C++ compiler... yes
checking whether g++ accepts -g... yes
checking whether ln -s works... yes
checking for iconv_open in -liconv... no
checking for libiconv_open in -liconv... no
checking for iconv_open in -lc... yes
checking how to run the C preprocessor... gcc -E
checking for grep that handles long lines and -e... /bin/grep
checking for egrep... /bin/grep -E
checking for ANSI C header files... yes
checking for sys/types.h... yes
checking for sys/stat.h... yes
checking for stdlib.h... yes
checking for string.h... yes
checking for memory.h... yes
checking for strings.h... yes
checking for inttypes.h... yes
checking for stdint.h... yes
checking for unistd.h... yes
checking iconv.h usability... yes
checking iconv.h presence... yes
checking for iconv.h... yes
checking build system type... x86_64-unknown-linux-gnu
checking host system type... x86_64-unknown-linux-gnu
checking for pg_config... no
configure: error: PostgreSQL is required by PostGIS
make: *** [config.status] Error 1
casa:/home/usuario/postgis-1.3.5

¿que me esta faltando para poder instalar postgis?

--
Z.M.