Install Server Instrumentation for Postgresql 8.4
To install Server Instrumentation for Postgresql 8.4 you may use the command line and type:
 sudo apt-get install postgresql-contrib

Run the adminpack.sql script,simply type:
 sudo -u postgres psql < /usr/share/postgresql/8.4/contrib/adminpack.sql

但是在9.1版本中找不到adminpack.sql.