When doing a PostgreSQL database server upgrade, you first need to backup all of the databases because the format changes from version to version.
Postgresql documentation states you need to run the command:
pg_dumpall > outputfile
I ran this, and received the error message:
pg_dumpall: could not connect to database "template1": FATAL: role "root" does not exist
So after some head scratching and googling without any results; I noticed that I had created a user for postgres; namely ‘postgres’. I sued to that user and ran the command – what do you know – it works fine! I’m glad that error message was so clear.
So, the thing that the documentation does not state – make sure you are running under the Postgresql user before running the backup command.