PostGIS.SH

How to install PostGIS 2.1 on Ubuntu 12.04 LTS (precise) from source
Prerequisites

Several components are needed, which can either be built from source or installed from pre-built packages, as shown below.

Install prerequisite packages using:

sudo apt-get install build-essential postgresql-9.1 postgresql-server-dev-9.1 libxml2-dev python-all-dev libproj-dev libjson0-dev xsltproc docbook-xsl docbook-mathml
Build GEOS 3.4.x

PostGIS 2.1 is best used with GEOS >= 3.4 for several new features, however Ubuntu 12.04 LTS only has GEOS 3.2.2 available in packages, so it needs to be built from source.

There are multiple ways to build GEOS, but this is the simplest:

wget http://download.osgeo.org/geos/geos-3.4.2.tar.bz2
tar xfj geos-3.4.2.tar.bz2
cd geos-3.4.2
./configure
make
sudo make install
cd ..
Build GDAL 1.10.x

PostGIS 2.1 is best used with GDAL >= 1.8.0, however Ubuntu 12.04 LTS only has GDAL 1.7.3 available in packages, so it needs to be built from source.

There are multiple ways to build GDAL, but this is the simplest:

wget http://download.osgeo.org/gdal/1.10.1/gdal-1.10.1.tar.gz
tar xfz gdal-1.10.1.tar.gz
cd gdal-1.10.1
./configure --with-python
make
sudo make install
cd ..
Build PostGIS

wget http://download.osgeo.org/postgis/source/postgis-2.1.8.tar.gz
tar xfz postgis-2.1.8.tar.gz
cd postgis-2.1.8
A basic configuration for PostGIS 2.1, with raster and topology support:

./configure
make
sudo make install
sudo ldconfig
sudo make comments-install
Lastly, enable the command-line tools to work from your shell:

sudo ln -sf /usr/share/postgresql-common/pg_wrapper /usr/local/bin/shp2pgsql
sudo ln -sf /usr/share/postgresql-common/pg_wrapper /usr/local/bin/pgsql2shp
sudo ln -sf /usr/share/postgresql-common/pg_wrapper /usr/local/bin/raster2pgsql
Spatially enabling a database

Connect to your database using pgAdminIII or psql, and use the commands to add the PostgreSQL extensions. To add PostGIS with raster support:

CREATE EXTENSION postgis;
To add topology support, a second extension can be created on the database:

CREATE EXTENSION postgis_topology;