The original how-to is available here: http://geonetwork-opensource.org/documentation/how-to/installation-on-ubuntu

It is assumed that Ubuntu is installed and configured.

Java 6

1. Install Java 6 (JDK)

 sudo apt-get install sun-java6-jdk

2. Set Java 6 as the default installation

 sudo update-java-alternatives -s java-6-sun

Tomcat

1. Install Tomcat.

 sudo apt-get install tomcat5.5

2. Configure Tomcat.

 sudo vi /etc/default/tomcat5.5

Ensure the following lines are present (and uncommented):

 JAVA_HOME=/usr/lib/jvm/java-6-sun
 TOMCAT5_SECURITY=no

3. Restart Tomcat.

 sudo /etc/init.d/tomcat5.5 restart

PostgreSQL

1. Install PostgreSQL server, clients and languages. 

    It may be worth looking more closely at this, as it likely installs more than you need.

 sudo apt-get install postgresql-.*-8.2

2. Initialize and run instance.

 sudo mkdir /var/pg_data
 sudo chown postgres:postgres /var/pg_data
 su postgres
 /usr/lib/postgresql/8.2/bin/initdb /var/pg_data
 /usr/lib/postgresql/8.2/bin/pg_ctl -D /var/pg_data -l /var/log/pg_logs/pg.log start
 exit

3. Create GeoNetwork user and database.

 createuser -SDRlP -U postgres geonetwork
 createdb -O geonetwork geonetwork

GeoNetwork

1. Download and install GeoNetwork.

    This downloads from my sourceforge mirror.  Substitute a more appropriate one if you aren't in Australia.

 wget http://optusnet.dl.sourceforge.net/sourceforge/geonetwork/geonetwork-install-2.1.0.jar
 sudo java -jar geonetwork-install-2.1.0.jar

1. click Next

2. Read and accept licence

3. Use default location (/usr/local/geonetwork), click Next

4. Install Core and GeoServer Map Server

5. Await installation

6. Do not install sample metadata

7. Install shortcuts

8. Ignore getting started

9. Done

2. Configure Tomcat server.

 sudo vi /usr/share/tomcat5.5/conf/server.xml

1. Within the Host element, add:

 <Context path="/geonetwork" 
          docBase="/usr/local/geonetwork/web/geonetwork/" 
          crossContext="false" 
          debug="0" 
          reloadable="false" />
 <Context path="/intermap"
          docBase="/usr/local/geonetwork/web/intermap/"
          crossContext="false"
          debug="0"
          reloadable="false" />

2. Update permissions

 sudo chown -R tomcat55 /usr/local/geonetwork/web*

3. Restart tomcat

 sudo /etc/init.d/tomcat5.5 restart

Apache

1. Install Apache and mod_jk (to integrate Tomcat).

 sudo apt-get install apache2 libapache2-mod-jk

2. Configure jk.

 sudo vi /etc/apache2/mods-available/jk.conf

          Add the lines:

 JkWorkersFile  /etc/apache2/workers.properties
 JkLogFile      /var/log/apache2/mod_jk.log
 JkShmFile      /var/log/apache2/mod_jk.shm
 JkLogLevel     /info

3. Configure workers.

 sudo vi /etc/apache2/workers.properties

          Add the lines:

 worker.list=worker1
 worker.worker1.type=ajp13
 worker.worker1.host=localhost
 worker.worker1.port=8009

4. Enable mod_jk

 sudo a2dismod jk
 sudo a2enmod jk

5. Create site configuration

 sudo vi /etc/apache2/sites-available/geonetwork

 <IfModule mod_jk.c>
     Alias /geonetwork /usr/local/geonetwork/web/
     JkMount /geonetwork/* worker1
     Alias /intermap /usr/local/geonetwork/web/
     JkMount /intermap/* worker1
     Alias /geoserver /usr/local/geonetwork/web/
     JkMount /geoserver/* worker1
 </IfModule>

6. Enable site

 sudo a2ensite geonetwork

7. Restart Apache

 sudo /etc/init.d/apache2 force-reload

Configure GeoNetwork

1. Run GAST

 sudo java -jar /usr/local/geonetwork/gast/gast.jar

2. Configure DBMS

1. Select Configuration->DBMS from the left menu

2. Select PostgreSQL from the DBMS list

3. Enter the following options:

 Server   localhost
 Port     5432
 Database geonetwork
 Username geonetwork
 Password gn

4. Select Save

3. Setup Database

1. Select Database->Setup from left menu

2. Click Setup

3. Click Yes to erase current database (make sure it's empty)

4. Ignore cyclic reference warning

4. Close GAST

5. Check GeoNetwork site

 http://localhost/geonetwork