PostgreSQL Replication Prerequisites

Replication / Guide 26 of 47 / Intermediate

• OSUbuntu 26.04 LTS
• PostgreSQL18.6-0ubuntu0.26.04.1
• ReplicationPhysical streaming, async, with slots
• TimeAbout 14 min

wal_level = replica and max_wal_senders = 10 are defaults, so a stock PostgreSQL is already able to feed a standby - unlike older versions where this section was mostly about turning things on.

This guide includes

Use this before creating a standby. This matters because four things have to be true first - and three of them already are, so the real work is a role, a rule and a slot.

• checking what is already true, which turns out to be most of it
• creating a role that can replicate and do nothing else
• adding a pg_hba rule for the replication pseudo-database
• creating a slot, so the primary keeps what the standby is going to need

Before you start

• A running primary, reachable on the network.

1. 1

   Check what is already true

2. 2

   Create a role that can replicate and nothing else

3. 3

   Add a pg_hba rule for the replication pseudo-database

4. 4

   Create a slot so the primary keeps what the standby needs

Official sources

• PostgreSQL 18 Documentation - High Availability and Replication
• PostgreSQL 18 Documentation - Setting Up a Standby Server
• PostgreSQL 18 Documentation - Replication Slots
• PostgreSQL 18 Documentation - pg_stat_replication
• PostgreSQL 18 Documentation - Failover and Timelines