PostgreSQL 12 High Availability Cookbook - Third Edition

How to do it...

In addition to our usual pg-primary PostgreSQL server, we will also be using pg-primary2 for this recipe. Database data will remain in the /db/pgdata directory. A server named pg-shared will play the role of our shared database as well. Follow these steps as the postgres system user and postgres database user where indicated:

1. Use pg_basebackup executed from the pg-primary2 server to clone the data from pg-primary:

pg_basebackup -h pg-primary -D /db/pgdata

2. Create a file named recovery.conf in /db/pgdata on pg-primary2 with the following contents:

standby_mode = 'on' 
primary_conninfo = 'host=pg-primary user=postgres'  

3. Start PostgreSQL on pg-primary2:

sudo systemctl start postgresql@12-main

4. When ready to split the shards, ...