external_pid_file

external_pid_file — Writes the postmaster PID to the specified file. Observed in PG9.0–19 Beta 3; its last measured boot default is not set in PG19 Beta 3, with postmaster context. This is a beta-snapshot fact and can change before PostgreSQL 19 GA.

Note

Fact — official short description: “Writes the postmaster PID to the specified file.”

Identity

Type , Valuestring: Upstream pg_settings type
Context , Valuepostmaster: Requires a server restart
Unit , Value—: Raw unit
Range , Value—: Raw limits in the last observed version
Enum values , Value—: — for non-enum types
Category , ValueFile Locations: Upstream classification
Latest boot value , Value—: not set

Lifecycle

Fact	Value
First observed	PG9.0 (research boundary)
Present in	PG9.0–19 Beta 3
Removed in	No
Introduction commit	Not asserted: predates the PG9.0 research boundary
Commit date	—
Discussion	—

Default history

Measured PG9.0–19 Beta 3 boot defaults
Versions	Raw `boot_val`	Unit	Human value
PG9.0–19 Beta 3	—	—	not set

How it works

Writes the postmaster PID to the specified file. The value is fixed when the server starts, so changing it requires a restart.

At startup PostgreSQL writes the postmaster PID to this additional path for external service tooling. postmaster.pid in the data directory remains authoritative for server internals, and the external file must not be used as the sole proof that a process is the intended cluster.

Monitor and change external_pid_file together with allow_alter_system, config_file, data_directory. 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.

Tuning advice

Tip

Advice. These are workload-specific starting points and must be validated with measurements.

Workload	Guidance
OLTP	external_pid_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.
OLAP	Follow the OLTP rule, and for separate mounts also verify boot ordering, backup coverage, and path consistency on failover nodes.
Small nodes	The default co-located layout is simplest. Split paths only for a concrete backup, packaging, or permission-isolation benefit.

Pigsty

Values use the fixed 8-vCPU, 32-GiB, 100-GiB SSD fixture and render the current Pigsty templates for PG19 Beta 3; this does not assert current Pigsty support for that historical or beta release.

Template	Effective value	Versus upstream boot	Source expression
OLTP	Unmodified	—	—
OLAP	Unmodified	—	—
CRIT	Unmodified	—	—
TINY	Unmodified	—	—

Caution

Advice — pending human review. Fact from the current Pigsty template projection: OLTP: PG9.0–19 Beta 3 unmodified; OLAP: PG9.0–19 Beta 3 unmodified; CRIT: PG9.0–19 Beta 3 unmodified; TINY: PG9.0–19 Beta 3 unmodified. No Pigsty-specific rationale is inferred from an absent override.

Common pitfalls

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.

allow_alter_system · config_file · data_directory · hba_file · ident_file · extension_destdir