I have a cron job that backs up my PG databases and emails them to me everynight. Today I wanted to upgrade my PostgreSQL 8.3 databases to PG 8.4 so I made a few modifications to my script so that I could dump out my PG data, and then restore it under PG 8.4. In case you are wondering I am doing this because Ubuntu Lucid now ships with PG 8.4 (yay!). I also made the script generate another script to restore the databases. So basically the procedure is to run the script below on your 8.3 cluster, shut that down and bring up your 8.4 cluster, and then restore your databases into that. Here follows my little script:

Mas:

http://linfiniti.com/2010/05/automated-backup-of-multiple-postgresqlpostgis-databases/