Full Backup
You must be logged in as a superuser to preform any backups and the file must be created with a sql extension.
pg_dumpall > backupfile.sql
pg_dumpall backs up all databases, users and permissions. This is good for small databases .
Incremental Backup
To make incremental backups you need to create a base backup
pg_dump db > backupfile.sql
pg_dump only backs up one database at a time and does not save the users or permissions. Restoring from pg_dump requires that you have a base backup set in before you can restore otherwise you will get errors when you restore.
-Fc
To create custom backups in file format tar or dump.
Restoring Database
There are several ways to restore a database.
psql < backupfile.sql
...
Database Commands
\l
List of all databases, owners and access privileges.
\du
List of roles, attributes and Group affiliation.
\d
List of all tables.
TBC by Roderick
References
http://www.postgresql.org/docs/8.1/static/backup.html - not too clear, for example how do I specify a user?
http://www.thegeekstuff.com/2009/01/how-to-backup-and-restore-postgres-database-using-pg_dump-and-psql/ - looks promising, syntax looks very different from official manual though.
Also, there is a backup interface via the gui... figure out how to get the command line equivalent. It worked well enough for my 52MB database. Just took a while as it went over the network (gui ran from a client machine).