config_file

Definition PG 18 manual

Specifies the main server configuration file (customarily called postgresql.conf). This parameter can only be set on the postgres command line.

How it works

Sets the server's main configuration file. The value is fixed when the server starts, so changing it requires a restart.

PostgreSQL determines this path before reading the main configuration, so config_file itself can only be supplied on the postgres command line. Includes are resolved by the chosen configuration, while data_directory may point somewhere else.

Monitor and change config_file together with allow_alter_system, data_directory, hba_file. Validate on the relevant server role and real workload, then use its postmaster context to choose session change, reload, or restart; a historical boot default is not the current effective value.

Operational considerations

Missing directory traversal, read, or write permission for the service account.

Confusing restart requirements for a path with reload behavior of the selected file contents.

Omitting the path on a failover node or from backup inventory.

Using a relative path that depends on an unstable working directory.

Workload guidance

OLAP: Follow the OLTP rule, and for separate mounts also verify boot ordering, backup coverage, and path consistency on failover nodes.

OLTP: config_file is deployment topology, not workload tuning. Use an absolute path, least privilege, and atomic configuration rollout; verify access as the postgres service account before restart/reload.

SMALL: The default co-located layout is simplest. Split paths only for a concrete backup, packaging, or permission-isolation benefit.