If you specify -X f or more likely -X s, that will cause pg_basebackup to include the WAL files that were written after you started the operation. Since you're setting up a replica, use the -X s option as that's for streaming.
I ran pg_basebackup with -X s and it finished in the middle of the night last night. I would now like to make the switch, but what's the best way to copy over the records that have been inserted since the backup stopped?
The -Xs option just keeps the WAL files that were written during the backup run so that if you restore it, it's brought back up to a consistent state at the point when the backup itself finished.
If you want to be able to bring up a slave from a backup at any point after that backup was complete, you have to keep all the WAL files that have been written since then. This is what is called Point-In-Time Recovery (PITR). I highly recommend you read up on the docs for how WAL files in postgres work and how to use them with backups and slaves. I think that is a key point your missing in understanding how to get a streaming slave set up and working.
Ok, that was a misunderstanding on my part. I had understood that with the -Xs option pg_basebackup would stay online and keep streaming the WAL files until it was turned off. Thanks for the clarification, but on a related note, that would be a really nice feature that would make doing this sort of replication a lot easier.
That feature does currently exist, it's just not part of pg_basebackup, which is why I recommended that you read up on the documentation for PITR in postgres.
I have run into another issue now though. I'm trying to start up the server after running pg_basebackup and it keeps timing out. Do I have something setup incorrectly? Or what is causing this issue?
It's probably replaying the WAL files to bring itself into a consistent state. If you're using the service options of the OS to start/stop the database it may have a timeout period shorter than the replay takes. I know that is an issue on debian/ubuntu sometimes. Monitor the postgres log files themselves to see where things are at and give it a few minutes to start up and see how it goes. If it's unable to start at all, the log files will tell you that as well.
