Commands for installing postgis copied from How to compile PostGIS 2.0.1 on Ubuntu Server 12.04 (http://blog.mackerron.com/2012/06/01/postgis-2-ubuntu-12-04/)

install-postgis.sh

sudo /etc/init.d/postgresql stop
 
# PostGIS 1.5.2 and its dependencies were installed already, so I
# removed them
sudo aptitude remove postgis postgresql-9.1-postgis \
  libgdal1-dev libgdal1-1.7.0 gdal-bin python-gdal \
  libspatialite2 libspatialite3 libgeos-dev libgeos-c1
 
# install any missing prerequisites
sudo aptitude install build-essential checkinstall postgresql \
  postgresql-server-dev-9.1 libjson0-dev libxml2-dev libproj-dev \
  python2.7-dev swig
 
cd ~
mkdir -p src
 
# download and compile geos in /opt/geos
cd ~/src/
wget http://download.osgeo.org/geos/geos-3.3.5.tar.bz2
tar xvjf geos-3.3.5.tar.bz2
cd geos-3.3.5/
./configure --prefix=/opt/geos --enable-python
make -j2
sudo checkinstall  # uninstall with: dpkg -r geos
 
# download and compile gdal in /opt/gdal
cd ~/src/
wget http://download.osgeo.org/gdal/gdal-1.9.1.tar.gz
tar xvzf gdal-1.9.1.tar.gz
cd gdal-1.9.1/
./configure --prefix=/opt/gdal --with-geos=/opt/geos/bin/geos-config \
  --with-pg=/usr/lib/postgresql/9.1/bin/pg_config --with-python
make -j2
sudo checkinstall  # uninstall with: dpkg -r gdal
 
# download and compile postgis 2 in default location
cd ~/src/
wget http://www.postgis.org/download/postgis-2.0.1.tar.gz
tar xvzf postgis-2.0.1.tar.gz
cd postgis-2.0.1/
./configure --with-geosconfig=/opt/geos/bin/geos-config \
  --with-gdalconfig=/opt/gdal/bin/gdal-config
make -j2
sudo checkinstall  # uninstall with: dpkg -r postgis
 
# for command-line tools, append this line to .profile/.bashrc/etc.
export PATH=$PATH:/opt/geos/bin:/opt/gdal/bin
 
# so libraries are found, create /etc/ld.so.conf.d/geolibs.conf
# with these two lines:
/opt/geos/lib
/opt/gdal/lib
 
# then
sudo ldconfig
 
sudo /etc/init.d/postgresql start
 
# restore a pg_dump -Fc backup from an earlier PostGIS version
echo 'create database mydb;' | sudo -u postgres psql
echo 'create extension postgis; create extension postgis_topology;' \
  | sudo -u postgres psql -d mydb
/usr/share/postgresql/9.1/contrib/postgis-2.0/postgis_restore.pl \
  /path/to/mydb.dump \
  | sudo -u postgres psql -d mydb