Practical PostgreSQL

Initializing the Filesystem

Before you can create a database in a database cluster, the filesystem must first be initialized. There are two ways to initialize the filesystem for use with PostgreSQL; you may either use the initdb application to create an entirely new database cluster (as was used to prepare your initial database system, in Chapter 2), or you may use the initlocation application to prepare a secondary data directory.

A database cluster represents several associated databases. A single instance of the postmaster process can only access one database cluster at a time. Alternatively, through initlocation, you can create databases that are part of an existing cluster that just happen to be stored in another data directory.

The following sections cover these two applications.

Initializing a Database Cluster

Use the initdb program to create and initialize a new database cluster within your filesystem. Again, a database cluster is the framework upon which PostgreSQL databases are created. You should already have one cluster in the data directory which was initialized in Chapter 2.

You may use initdb to initialize a new data directory for a database cluster, and instruct postmaster to start up using that data cluster instead of the default.

Alternatively, you may have two postmaster processes running at the same time with different database clusters, provided that they are configured to listen on different ports.

After you use initdb to create a new database cluster, that new ...