Postgres Upgrade

Packages from Postgres

https://wiki.postgresql.org/wiki/Apt.

Upgrade in Place

I did this: https://gorails.com/guides/upgrading-postgresql-version-on-ubuntu-server.

I had 13 and 16 installed (for some reason), and the approach in the above link will upgrade to the newest installed version. Fortunately, skipping versions is supported by the upgrade (although internally I would guess it's just doing major version upgrade).

It worked within minutes, but then the apps couldn't connect. Changing the server to listen to all ports instead of just localhost fixed it, but the configuration for Postgres 12 was the same as the configuration for Postgres 16, so I wonder why it was working before.